EP1044265A1 - Adn codant un polypeptide gaba br2 et ses utilisations - Google Patents

Adn codant un polypeptide gaba br2 et ses utilisations

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Publication number
EP1044265A1
EP1044265A1 EP99943972A EP99943972A EP1044265A1 EP 1044265 A1 EP1044265 A1 EP 1044265A1 EP 99943972 A EP99943972 A EP 99943972A EP 99943972 A EP99943972 A EP 99943972A EP 1044265 A1 EP1044265 A1 EP 1044265A1
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EP
European Patent Office
Prior art keywords
gaba
receptor
polypeptide
cell
nucleic acid
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP99943972A
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German (de)
English (en)
Other versions
EP1044265A4 (fr
Inventor
Kenneth A. Jones
Thomas M. Laz
Beth Borowsky
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Synaptic Pharmaceutical Corp
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Synaptic Pharmaceutical Corp
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Publication date
Priority claimed from PCT/US1998/022033 external-priority patent/WO1999020751A1/fr
Priority claimed from US09/211,755 external-priority patent/US20020045742A1/en
Application filed by Synaptic Pharmaceutical Corp filed Critical Synaptic Pharmaceutical Corp
Publication of EP1044265A1 publication Critical patent/EP1044265A1/fr
Publication of EP1044265A4 publication Critical patent/EP1044265A4/fr
Withdrawn legal-status Critical Current

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Definitions

  • GABA Gamma amino butyric acid
  • GABA B receptors were initially discriminated by their sensitivity to the drug baclofen (Bowery, 1993) . This and their dependency on G-proteins for effector coupling distinguishes them from the ion channel -forming GABA and GABA. receptors.
  • Principle molecular targets of GABA receptor activation are Ca ++ and K + channels whose gating is directly modulated by the liberation of G-protein that follows the binding of the neurotransmitter to its receptor (Misgeld et al . 1995; Krapivinsky et al . , 1995a).
  • GABA B receptors operate mechanistically as other G-protein coupled receptors (GPCRs) , such as dopamine D2 , serotonin 5HTla, neuropeptide Y and opiate receptors, that are also negatively coupled to adenylyl cyclase activity (North, 1989) .
  • GPCRs G-protein coupled receptors
  • Stimulation of GABA ⁇ receptors inhibits release of neurotransmitters such as glutamate, GABA, somatostatin, and acetylcholine by modulation of Ca ++ and K + channels at presynaptic nerve terminals.
  • GABA ⁇ receptors also mediate a powerful postsynaptic hyperpolarization of neuronal cell bodies via the opening of G-protein-gated inwardly rectifying K * channels (GIRK) (Kofuji et al . 1996) .
  • GABA B receptors are widely distributed throughout the central nervous system. Receptor autoradiography and binding studies show that receptors are found in relatively high abundance in nearly all areas of the brain including cerebral cortex, hippocampus, cerebellum, basal ganglia, thalamus, and spinal cord (Bowery et al . 1987) . In the periphery, GABA and GABA ⁇ receptors are found in pancreatic islets, autonomic ganglia, guinea-pig ileum, lung, oviduct, and urinary bladder (Giotti et al . 1983; Erdo et al . 1984; Santicioli et al . 1986; Sawynok, 1986; Hills et al . 1989; Chapman et al . 1993).
  • baclofen has been used as an anti-spastic agent for the past 25 years.
  • baclofen has a spinal site of action that most likely involves the depression of mono-and polysynaptic reflexes.
  • baclofen has antinociceptive properties that are attributed to the inhibition of release of excitatory neurotransmitters glutamate and substance P from primary sensory afferent terminals (Dirig and Yaksh, 1978; Sawynok, 1987; Malcangio et al . , 1991).
  • the presence of GABA ⁇ receptors in intestine, lung and urinary bladder indicates a possible therapeutic role for diseases associated with these peripheral tissues.
  • baclofen is currently used for treatment of bladder-urethral dissynergia (Leyson et al . , 1980) .
  • Selective GABA g receptor agonists may also prove useful for the treatment of incontinence by reducing the feeling of bladder fullness (Taylor and Bates, 1979) .
  • GABA ⁇ agonists also may be useful as antitussive agents and for the treatment of asthma (Luzzi et al . , 1987; Bolser et al . , 1993).
  • GABA B receptors have been implicated in absence seizure activity in the neocortex and with presynaptic depression of excitatory transmission in the spinal cord.
  • GABA acting through GABA ⁇ receptors, can inhibit the release of GABA, glutamate, and somatostatin in rat cerebrocortical synaptosomes depolarized with KC1.
  • somatostatin release is inhibited by baclofen and this effect is antagonized by phaclofen and CGP35348.
  • Glutamate release is similarly affected except that the potency of phaclofen to block inhibition is considerably lower than that for release of somatostatin.
  • a third receptor subtype, the cortical GABA autoreceptor has been defined based on an insensitivity to CGP35348, although this potency difference is not seen in a cortical slice preparation ( aldmeier et al . 1994) .
  • the GABA autoreceptor is insensitive to baclofen, but sensitive to 3APPA and block by CGP35348.
  • baclofen is active at the GABA g receptor modulating glutamate release. Differences in the sensitivities of presynaptic receptors controlling release of GABA and glutamate in the spinal cord may importantly contribute to the therapeutic action of baclofen as an antispastic agent (Bonanno, Raiteri, 1993) .
  • GABA ⁇ Rla a polypeptide that binds radiolabelled GABA ⁇ receptor antagonists in transfected cells.
  • the predicted amino acid sequence displays homology with the metabotropic glutamate receptor gene family which includes eight members and a Ca ++ -sensing receptor. Included in this homology is a large N-terminal domain that contains two lobes with structural similarity to the amino acid binding sites of bacterial proteins.
  • a second polypeptide, GABA ⁇ Rlb presumably a splice variant, differs from GABA ⁇ Rla in that the N-terminal 147 amino acids are replaced by 18 different residues in the predicted mature protein after signal peptide cleavage.
  • the pharmacological profile of the cloned GABA ⁇ Rl polypeptide is similar in some respects to that of native receptors isolated from rat cerebral cortex, but there are important differences.
  • IC 50 s are nearly identical to those at native receptors.
  • IC 50 s for agonists and some low affinity antagonists display large rightward shifts relative to their displacement curves in native tissue.
  • both splice variants of the polypeptide couple poorly to intracellular effectors such as inhibition of adenylyl cyclase and, against expectations, fail completely to stimulate GIRK currents in oocytes (Kaupmann et al . 1997b) .
  • the poor binding affinity of agonists and weak or non-existent activation of effectors may not be adequately explained by inappropriate G-protein coupling in the heterologous expression system used.
  • This invention is directed to an isolated nucleic acid encoding a GABA g R2 polypeptide.
  • This invention is further directed to a purified GABA ⁇ R2 protein.
  • This invention is further directed to a vector comprising the above-identified nucleic acid.
  • This invention is further directed to a above- identified vector, wherein the vector is a plasmid.
  • This invention is directed to a method of detecting a nucleic acid encoding a GABA ⁇ R2 polypeptide, which comprises contacting the nucleic acid with a probe comprising at least 15 nucleotides, which probe specifically hybridizes with the nucleic acid encoding the GABA ⁇ R2 polypeptide, wherein the probe has a unique sequence, which sequence is present within one of the two strands of the nucleic acid encoding the GABA ⁇ R2 polypeptide contained in plasmid BO-55, and detecting hybridization of the probe to the nucleic acid.
  • This invention is further directed to a method of detecting a nucleic acid encoding a GABA ⁇ R2 polypeptide, which comprises contacting the nucleic acid with a probe comprising at least 15 nucleotides, which probe specifically hybridizes with the nucleic acid encoding the
  • GABA-R2 polypeptide wherein the probe has a unique sequence, which sequence is present within (a) the nucleic acid sequence shown in Figures 22A-22D (SEQ ID NO: 46) or (b) the reverse complement to the nucleic acid sequence shown in Figures 22A-22D (SEQ ID NO: 46) , and detecting hybridization of the probe to the nucleic acid.
  • This invention is further directed to a method of detecting a nucleic acid encoding a GABA ⁇ R2 polypeptide, which comprises contacting the nucleic acid with a probe comprising at least 15 nucleotides, which probe specifically hybridizes with the nucleic acid encoding the GABA-R2 polypeptide, wherein the probe has a unique sequence, which sequence is present within one of the two strands of the nucleic acid encoding the GABA ⁇ R2 polypeptide contained in plasmid pEXJT3T7-hGABAB2 , and detecting hybridization of the probe to the nucleic acid.
  • This invention is further directed to a method of detecting a nucleic acid encoding a GABA ⁇ R2 polypeptide, which comprises contacting the nucleic acid with a probe comprising at least 15 nucleotides, which probe specifically hybridizes with the nucleic acid encoding the GABA ⁇ R2 polypeptide, wherein the probe has a unique sequence, which sequence is present within (a) the nucleic acid sequence shown in Figures 3A-3D (SEQ ID NO: 3) or (b) the reverse complement to the nucleic acid sequence shown in Figures 3A-3D (SEQ ID NO: 3) , and detecting hybridization of the probe to the nucleic acid.
  • This invention is further directed to a method of detecting a nucleic acid encoding a GABA ⁇ R2 polypeptide, which comprises contacting the nucleic acid with a probe comprising a nucleic acid of at least 15 nucleotides which is complementary to the antisense sequence of a unique segment of the sequence of the nucleic acid encoding the GABA ⁇ R2 polypeptide, and detecting hybridization of the probe to the nucleic acid.
  • This invention is directed to an isolated antibody capable of binding to a GABA ⁇ R2 polypeptide encoded by the above- identified nucleic acid.
  • This invention is further directed to an antibody capable of competitively inhibiting the binding of the above- identified antibody to a GABA ⁇ R2 polypeptide.
  • This invention is further directed to a pharmaceutical composition which comprises an amount of the above- identified antibody effective to block binding of a ligand to the GABA ⁇ R2 polypeptide and a pharmaceutically acceptable carrier.
  • This invention is directed to a transgenic, nonhuman mammal expressing DNA encoding a GABA ⁇ R2 polypeptide.
  • This invention is further directed to a transgenic, nonhuman mammal comprising a homologous recombination knockout of the native GABA ⁇ R2 polypeptide.
  • This invention is further directed to a transgenic, nonhuman mammal whose genome comprises antisense DNA complementary to DNA encoding an above-identified GABA ⁇ R2 polypeptide so placed as to be transcribed into antisense mRNA which is complementary to mRNA encoding such GABA ⁇ R2 polypeptide and which hybridizes to such mRNA encoding such GABA ⁇ R2 polypeptide, thereby reducing its translation.
  • This invention is directed to a method of detecting the presence of a GABA ⁇ R2 polypeptide on the surface of a cell which comprises contacting the cell with the above- identified antibody under conditions permitting binding of the antibody to the polypeptide, detecting the presence of the antibody bound to the cell, and thereby detecting the presence of a GABA ⁇ R2 polypeptide on the surface of the cell.
  • This invention is further directed to a method of preparing the purified GABA ⁇ R2 polypeptide which comprises:
  • This invention is further directed to a method of preparing the purified GABA g R2 polypeptide which comprises:
  • This invention is directed to a GABA ⁇ Rl/R2 receptor comprising two polypeptides, one of which is a GABA ⁇ R2 polypeptide and another of which is a GABA ⁇ Rl polypeptide.
  • This invention is directed to a method of forming a GABA ⁇ Rl/R2 receptor which comprises inducing cells to express both a GABA ⁇ Rl polypeptide and a GABA ⁇ R2 polypeptide .
  • This invention is directed to an antibody capable of binding to a GABA ⁇ Rl/R2 receptor, wherein the GABA ⁇ R2 polypeptide is encoded by the above- identified nucleic acid.
  • This invention is further directed to an antibody capable of competitively inhibiting the binding of the above- identified antibody to a GABA ⁇ Rl/R2 receptor.
  • This invention is directed to a pharmaceutical composition which comprises an amount of the above-identified antibody effective to block binding of a ligand to the GABA ⁇ Rl/R2 receptor and a pharmaceutically acceptable carrier.
  • This invention is directed to a transgenic, nonhuman mammal expressing a GABA ⁇ Rl/R2 receptor, which is not naturally expressed by the mammal.
  • This invention is further directed to a transgenic, nonhuman mammal comprising a homologous recombination knockout of the native GABA ⁇ Rl/R2 receptor.
  • This invention is directed to a method of detecting the presence of a GABA ⁇ Rl/R2 receptor on the surface of a cell which comprises contacting the cell with the above- identified antibody under conditions permitting binding of the antibody to the receptor, detecting the presence of the antibody bound to the cell, and thereby detecting the presence of a GABA ⁇ Rl/R2 receptor on the surface of the cell.
  • This invention is directed to a method of determining the physiological effects of varying levels of activity of GABA ⁇ Rl/R2 receptors which comprises producing an above- identified transgenic nonhuman mammal whose levels of GABA ⁇ Rl/R2 receptor activity vary due to the presence of an inducible promoter which regulates GABA ⁇ Rl/R2 receptor expression.
  • This invention is directed to a cell which expresses on its surface a mammalian GABA ⁇ Rl/R2 receptor that is not naturally expressed on the surface of such cell.
  • This invention is directed to a process for identifying a chemical compound which specifically binds to a GABA ⁇ Rl/R2 receptor which comprises contacting cells containing nucleic acid encoding and expressing on their cell surface -lithe GABA ⁇ Rl/R2 receptor, wherein such cells do not normally express the GABA ⁇ Rl/R2 receptor, with the compound under conditions suitable for binding, and detecting specific binding of the chemical compound to the GABA ⁇ Rl/R2 receptor.
  • This invention is directed to a process for identifying a chemical compound which specifically binds to a GABA ⁇ Rl/R2 receptor which comprises contacting a membrane fraction from a cell extract of cells containing nucleic acid encoding and expressing on their cell surface the GABA ⁇ Rl/R2 receptor, wherein such cells do not normally express the GABA g Rl/R2 receptor, with the compound under conditions suitable for binding, and detecting specific binding of the chemical compound to the GABA ⁇ Rl/R2 receptor.
  • This invention is directed to a process involving competitive binding for identifying a chemical compound which specifically binds to a GABA ⁇ Rl/R2 receptor which comprises separately contacting cells expressing on their cell surface the GABA ⁇ Rl/R2 receptor, wherein such cells do not normally express the GABA ⁇ Rl/R2 receptor, with both the chemical compound and a second chemical compound known to bind to the receptor, and with only the second chemical compound, under conditions suitable for binding of both compounds, and detecting specific binding of the chemical compound to the GABA g Rl/R2 receptor, a decrease in the binding of the second chemical compound to the GABA ⁇ Rl/R2 receptor in the presence of the chemical compound indicating that the chemical compound binds to the GABA ⁇ Rl/R2 receptor.
  • This invention is directed to a process involving competitive binding for identifying a chemical compound which specifically binds to a human GABA ⁇ Rl/R2 receptor which comprises separately contacting a membrane fraction from a cell extract of cells expressing on their cell surface the GABA ⁇ Rl/R2 receptor, wherein such cells do not normally express the GABA ⁇ Rl/R2 receptor, with both the chemical compound and a second chemical compound known to bind to the receptor, and with only the second chemical compound, under conditions suitable for binding of both compounds, and detecting specific binding of the chemical compound to the GABA g Rl/R2 receptor, a decrease in the binding of the second chemical compound to the GABA ⁇ Rl/R2 receptor in the presence of the chemical compound indicating that the chemical compound binds to the GABA ⁇ Rl/R2 receptor.
  • This invention is directed to a method of screening a plurality of chemical compounds not known to bind to a GABA ⁇ Rl/R2 receptor to identify a compound which specifically binds to the GABA ⁇ Rl/R2 receptor, which comprises
  • step (b) contacting the same cells as in step (a) with the plurality of compounds not known to bind specifically to the GABA ⁇ Rl/R2 receptor, under conditions permitting binding of compounds known to bind the GABA ⁇ Rl/R2 receptor;
  • This invention is directed to a method of screening a plurality of chemical compounds not known to bind to a GABA ⁇ Rl/R2 receptor to identify a compound which specifically binds to the GABA ⁇ Rl/R2 receptor, which comprises
  • step (b) contacting the same membrane fraction as in step (a) with the plurality of compounds not known to bind specifically to the GABA ⁇ Rl/R2 receptor, under conditions permitting binding of compounds known to bind the GABA ⁇ Rl/R2 receptor;
  • This invention is directed to a process for determining whether a chemical compound is a GABA ⁇ Rl/R2 receptor agonist which comprises contacting cells with the compound under conditions permitting the activation of the GABA ⁇ Rl/R2 receptor, and detecting an increase in GABA ⁇ Rl/R2 receptor activity, so as to thereby determine whether the compound is a GABA ⁇ Rl/R2 receptor agonist .
  • This invention is directed to a process for determining whether a chemical compound is a GABA ⁇ Rl/R2 receptor antagonist which comprises contacting cells containing nucleic acid encoding and expressing on their cell surface the GABA ⁇ Rl/R2 receptor, wherein such cells do not normally express the GABA g Rl/R2 receptor, with the compound in the presence of a known GABA ⁇ Rl/R2 receptor agonist, under conditions permitting the activation of the GABA ⁇ Rl/R2 receptor, and detecting a decrease in GABA ⁇ Rl/R2 receptor activity, so as to thereby determine whether the compound is a GABA ⁇ Rl/R2 receptor antagonist.
  • This invention is directed to a process for determining whether a chemical compound activates a GABA ⁇ Rl/R2 receptor, which comprises contacting cells producing a second messenger response and expressing on their cell surface the GABA ⁇ Rl/R2 receptor, wherein such cells do not normally express the GABA B R1/R2 receptor, with the chemical compound under conditions suitable for activation of the
  • GABA ⁇ Rl/R2 receptor measuring the second messenger response in the presence and in the absence of the chemical compound, a change in the second messenger response in the presence of the chemical compound indicating that the compound activates the GABA ⁇ Rl/R2 receptor.
  • This invention is directed to a process for determining whether a chemical compound inhibits activation of a GABA ⁇ Rl/R2 receptor, which comprises separately contacting cells producing a second messenger response and expressing on their cell surface the GABA ⁇ Rl/R2 receptor, wherein such cells do not normally express the GABA ⁇ Rl/R2 receptor, with both the chemical compound and a second chemical compound known to activate the GABA g Rl/R2 receptor, and with only the second chemical compound, under conditions suitable for activation of the GABA ⁇ Rl/R2 receptor, and measuring the second messenger response in the presence of only the second chemical compound and in the presence of both the second chemical compound and the chemical compound, a smaller change in the second messenger response in the presence of both the chemical compound and the second chemical compound than in the presence of only the second chemical compound indicating that the chemical compound inhibits activation of the GABA ⁇ Rl/R2 receptor.
  • This invention is directed to a method of screening a plurality of chemical compounds not known to activate a
  • GABA ⁇ Rl/R2 receptor to identify a compound which activates the GABA ⁇ Rl/R2 receptor which comprises:
  • This invention is directed to a method of screening a plurality of chemical compounds not known to inhibit the activation of a GABA ⁇ Rl/R2 receptor to identify a compound which inhibits the activation of the GABA ⁇ Rl/R2 receptor, which comprises:
  • This invention is directed to a process for determining whether a chemical compound is a GABA ⁇ Rl/R2 receptor agonist, which comprises preparing a membrane fraction from cells which comprise nucleic acid encoding and expressing on their cell surface the GABA g Rl/R2 receptor, wherein such cells do not normally express the GABA ⁇ Rl/R2 receptor, separately contacting the membrane fraction with both the chemical compound and GTPyS, and with only GTPyS, under conditions permitting the activation of the GABA g Rl/R2 receptor, and detecting GTPyS binding to the membrane fraction, an increase in GTPyS binding in the presence of the compound indicating that the chemical compound activates the GABA ⁇ Rl/R2 receptor.
  • This invention is directed to aprocess for determining whether a chemical compound is a GABA ⁇ Rl/R2 receptor antagonist, which comprises preparing a membrane fraction from cells which comprise nucleic acid encoding and expressing on their cell surface the GABA ⁇ Rl/R2 receptor, wherein such cells do not normally express the GABA ⁇ Rl/R2 receptor, separately contacting the membrane fraction with the chemical compound, GTPyS and a second chemical compound known to activate the GABA ⁇ Rl/R2 receptor, with GTPyS and only the second compound, and with GTPyS alone, under conditions permitting the activation of the GABA ⁇ Rl/R2 receptor, detecting GTPyS binding to each membrane fraction, and comparing the increase in GTPyS binding in the presence of the compound and the second compound relative to the binding of GTPyS alone, to the increase in GTPyS binding in the presence of the second chemical compound known to activate the GABA ⁇ Rl/R2 receptor relative to the binding of GTPyS alone, a smaller increase in
  • This invention is directed to a method of treating spasticity in a subject which comprises administering to the subject an amount of a compound which is an agonist of a GABA ⁇ Rl/R2 receptor effective to treat spasticity in the subject .
  • This invention is directed to a method of treating asthma in a subject which comprises administering to the subject an amount of a compound which is a GABA ⁇ Rl/R2 receptor agonist effective to treat asthma in the subject.
  • This invention is directed to a method of treating incontinence in a subject which comprises administering to the subject an amount of a compound which is a GABA ⁇ Rl/R2 receptor agonist effective to treat incontinence in the subject.
  • This invention is directed to a method of decreasing nociception in a subject which comprises administering to the subject an amount of a compound which is a GABA ⁇ Rl/R2 receptor agonist effective to decrease nociception in the subject .
  • This invention is directed to a use of a GABA ⁇ R2 agonist as an antitussive agent which comprises administering to the subject an amount of a compound which is a GABA ⁇ Rl/R2 receptor agonist effective as an antitussive agent in the subject .
  • This invention is directed to a method of treating drug addiction in a subject which comprises administering to the subject an amount of a compound which is a GABA ⁇ Rl/R2 receptor agonist effective to treat drug addiction in the subject .
  • This invention is directed to a method of treating Alzheimer's disease in a subject which comprises administering to the subject an amount of a compound which is a GABA ⁇ Rl/R2 receptor antagonist effective to treat Alzheimer's disease in the subject.
  • This invention is directed to a peptide selected from the group consisting of : a) P L Y S I L S A L T I L G M I M A S A F L F F N I K N; (SEQ ID NO:48) b) L I I L G G L S Y A S I F L F G L D G S F V S E K T; (SEQ ID NO: 49) c) C T V R T I L T V G Y T T A F G A M F A K T R; (SEQ ID NO:50) d) Q K L L V I V G G M L L I D L C I L I C W Q; (SEQ ID NO: 51) e) M T I W L G I V Y A Y K G L L M L F G C F L A ; (SEQ ID NO: 52) f) A L N D S K Y I G M S V Y N V G I M C I I G A A V;
  • This invention is directed to a compound that prevents the formation of a GABA ⁇ Rl/R2 receptor complex.
  • this invention provides a process for making a composition of matter which specifically binds to a GABA ⁇ Rl/R2 receptor which comprises identifying a chemical compound using any of the processes described herein for identifying a compound which binds to and/or activates or inhibits activation of a GABA ⁇ Rl/R2 receptor and then synthesizing the chemical compund or a novel structural and functional analog or homolog thereof.
  • This invention furhter provides a process for preparing a pharmaceutical composition which comprises admixing a pharmaceutically acceptable carrier and a pharmaceutically acceptable amount of a chemical compound identified by any of the processes described herein for identifying a compound which binds to and/or activates or inhibits activation of a GABA ⁇ Rl/R2 receptor or a novel structural and functional analog or homolog thereof .
  • Figures 1A-1E Nucleotide coding sequence of the human GABA ⁇ R2 polypeptide (SEQ ID NO: 1), with partial 5' and 3' untranslated sequences. Two possible start (ATG) codons are underlined as well as the stop codon (TAA) .
  • Figures 2A-2D Deduced amino acid sequence of the human GABA ⁇ R2 polypeptide (SEQ ID NO: 2) encoded by the nucleotide sequence shown in Figures 1A-1E.
  • Figures 3A-3D Nucleotide coding sequence of the rat GABA B R2 polypeptide (SEQ ID NO : 3) . Start (ATG) and stop (TAG) codons are underlined.
  • Figures 4A-4D Deduced amino acid sequence of the rat GABA ⁇ R2 polypeptide (SEQ ID NO: 4) encoded by the nucleotide sequence shown in Figures 3A-3D.
  • Figures 5A-5D Amino acid sequence of the human GABA ⁇ R2 polypeptide (SEQ ID NO: 2) with brackets above the sequence showing the boundaries of seven (7) putative transmembrane domains, numbered consecutively from I to VII.
  • Figures 6A-6B Measurement of EC 50 for GABA in a cumulative concentration response assay in oocytes expressing GABA ⁇ Rlb/GABA ⁇ R2 + GIRKs .
  • Figure 6A Electrophysiological trace from a voltage clamped oocyte showing increasing inward currents evoked successively by concentrations of GABA ranging from 0.03 to 30 ⁇ M. Numbers over bars indicate concentration of GABA in ⁇ M. hK is 49 mM external K + .
  • Figure 6B Averaged responses from 3-6 oocytes plotted vs . concentration of GABA results in an EC 50 value of 1.76 ⁇ M. For each oocyte, currents were normalized to the maximum response at 30 ⁇ M.
  • FIG. 8 Current voltage relationship for the current activated by GABA in oocytes expressing GABA ⁇ Rlb/GABA ⁇ R2 + GIRKs. Voltage ramps (50 mV/s) from -140 to +40 mV were applied in the presence of GABA (in hK) and again in the presence of GABA + 100 ⁇ M Ba ++ to block inward rectifier current. The resulting traces were subtracted (GABA alone - GABA + Ba ++ ) to yield the Ba ++ -sensitive portion of the GABA-stimulated current. As expected for GIRK current, the current displays steep inward rectification and reverses near the predicted equilibrium potential for K + (-23 mV in hK) .
  • FIGs 9A-9B Electrophysiological responses under voltage clamp conditions to GABA in an HEK-293 cell transiently transfected with GABA B Rlb/GABA g R2 + GIRKs.
  • a second GABA-evoked current is abolished by the selective antagonist CGP55845. After a 1 minute wash period GABA-responsivity returns.
  • Figure 10 Alignment of amino acids predicted for rat GABA ⁇ R2 and rat GABA g Rl (SEQ ID NO: 55) . Horizontal bars indicate TM regions.
  • FIGS 11A-11D Photomicrographs showing the regional distribution of the GABA ⁇ Rl (A,C) and GABA ⁇ R2 (B,D) mRNAs in representative coronal rat brain sections.
  • Figures 13A-13B Figure 13A: Response to GABA (100 ⁇ M) from oocyte expressing GABA ⁇ Rl, GABA ⁇ R2 , and GIRKs (lower trace) . Similar oocyte pretreated 6 h earlier with pertussis toxin (2 ng injected; upper trace) .
  • Figure 13B Summary of mean response amplitudes from oocytes expressing various combinations of GABA ⁇ Rl and GABA ⁇ R2 plus GIRKs. Responses are to 100 ⁇ M GABA (solid bars) or 100 ⁇ M baclofen (open bar) . Number of observations are in parenthesis .
  • Figure 14A Response to GABA or baclofen (100 ⁇ M in 25 mM K + ) in HEK293 cells expressing GIRKs along with GABA B Rlb, GABA ⁇ R2 , or both.
  • Figure 14B Summary of mean response amplitudes from HEK293 cells co-transfected with various combinations and ratios of cDNA. To prepare different ratios of GABA g Rlb : GABA ⁇ R2 the most abundant cDNA was held constant at 0.6 ⁇ g/dish and the other cDNA was reduced by a factor of 10 or 100. Responses are to 100 ⁇ M GABA. Number of observations are shown in parenthesis.
  • Figures 15A-15B Figure 15A: Agonist concentration-effect curves for 3-APMPA in oocytes (open triangle) , GABA in oocytes (open circle) and HEK293 cells (solid circle) , and baclofen in oocytes (open square) .
  • Figure 15B Right-ward shifts in the GABA concentration-response curve (solid circle) caused by CGP55845 at 50 nM (open triangle) and CGP54626 at 5 ⁇ M (open circle) . Each point is the average response from 4-6 oocytes.
  • Figures 17A-17D Co-localization of GABA ⁇ Rl and GABA g R2 in HEK293 cells by dual wavelength scanning confocal microscopy.
  • Figure 17A Green channel showing GABA ⁇ Rl RGS6xH
  • FIG. 17A Dual channel image of the same cell reveals a predominant yellow hue caused by the co-localization of fluorescent tags for GABA g Rl RGS6xH and GABA ⁇ R2 HA .
  • Figure 17D Dual wavelength image, of cell expressing GABA ⁇ R2 HA (red) and NPY Y5 Flag (green) . Note the low degree of spatial overlap of the two polypeptides.
  • Figures 18A-18C Identification of GABA ⁇ Rl and GABA ⁇ R2 in cell lysates and immunoprecipitates .
  • Figure 18A Detection of GABA ⁇ Rl RGS6xH in whole cell extracts from cells expressing either or both polypeptides. Proteins labeled with anti-His or anti-HA, migrate as monomeric and dimeric forms.
  • Figure 18B Detection of GABA ⁇ R2 HA in whole cell extracts from cells expressing either or both. Labels over lanes denote which polypeptides were transfected. Proteins labeled with anti-His or anti-HA, migrate as monomeric and dimeric forms.
  • Figure 18C Co-immunoprecipitation of
  • GABA ⁇ Rl RGS6xH and GABA ⁇ R2 HA were immunoprecipitated (IP) with anti-HA or anti-His antibodies, subjected to SDS-PAGE, blotted, and probed for the presence of the HA epitope. Note that in anti-His immunoprecipitated material, HA immunoreactivity appears only in the lane from cells expressing both proteins.
  • FIG. 19 Rostro-caudal distribution of the GABA D DR2 mRNA in coronal rat brain sections (A-F) and spinal cord (G) .
  • Figure 20 (A) Detection of Na+/K+ ATPase by anti-alpha 1 subunit antibodies in membrane fractions enriched in (P1 + ) or depleted of (P2) plasma membranes (50 :g protein/lane) .
  • FIG. 21 Photomicrographs showing the regional distribution of GABA g R2 (A,C) and GABA ⁇ Rlb (B,D) mRNAs in pairs of adjacent coronal rat brain sections. Arrow heads identify Purkinje cell layer in cerebellum (A,B) . High magnification views of hippocampal CA3 region showing both transcripts in cells from alternate sections (C,D) . Arrows mark individual cells. Hybridization of GABA ⁇ R2 (E) and GABA B Rlb (F) transcripts in large cells of mesencephalic trigeminal nucleus.
  • Figure 22A-22D Nucleotide coding sequence of the human GABA B R2 polypeptide (SEQ ID NO: 46) . Start (ATG) and stop (TAA) codons are underlined.
  • GABA B R2 polypeptide (SEQ ID No: 47) encoded by the nucleotide sequence shown in Figures 22A-22D.
  • Figure 24 Acidification responses from CHO cells expressing GABA ⁇ Rlb/GABA ⁇ R2 from human and rat.
  • Figure 25 FLIPR responses to increasing concentrations of the GABA ⁇ agonist 3-APMPA from individual wells of COS-7 cells transfected with GABA ⁇ Rl , GABA ⁇ R2 , and Go! /13 .
  • 7-TM spanning protein or a 7-TM protein indicates a protein presumed to have seven transmembrane regions which cross the cellular membrane band on its amino acid sequence.
  • the mammalian GABA ⁇ Rl/R2 receptor is understood to include rat-rat polypeptides (i.e. rat GABA g Rl and rat GABA g R2 polypeptides) , rat-human polypeptides (i.e. either rat GABA g Rl and human GABA ⁇ R2 polypeptides or human GABA ⁇ Rl and rat GABA ⁇ R2 polypeptides), or human-human polypeptides (i.e. human GABA g Rl and human GABA ⁇ R2 polypeptides) .
  • rat-rat polypeptides i.e. rat GABA g Rl and rat GABA g R2 polypeptides
  • rat-human polypeptides i.e. either rat GABA g Rl and human GABA ⁇ R2 polypeptides or human GABA ⁇ Rl and rat GABA ⁇ R2 polypeptides
  • human-human polypeptides i.e.
  • This invention is directed to an isolated nucleic acid encoding a GABA g R2 polypeptide.
  • the nucleic acid is DNA. In another embodiment, the DNA is cDNA. In another embodiment, the DNA is genomic DNA. In another embodiment, the nucleic acid is RNA. In another embodiment, the nucleic acid encodes a mammalian GABA ⁇ R2 polypeptide. In another embodiment, the nucleic acid encodes a rat GABA ⁇ R2 polypeptide. In another embodiment, the nucleic acid encodes a human GABA ⁇ R2 polypeptide.
  • the nucleic acid encodes a polypeptide characterized by an amino acid sequence in the transmembrane regions which has an identity of 90% or higher to the amino acid sequence in the transmembrane regions of the human GABA ⁇ R2 polypeptide shown in Figures 5A- 5D .
  • the nucleic acid encodes a mammalian GABA g R2 polypeptide which has substantially the same amino acid sequence as does the GABA ⁇ R2 polypeptide encoded by the plasmid BO-55 (ATCC Accession No. 209104) .
  • the nucleic acid encodes a rat GABA ⁇ R2 polypeptide which has an amino acid sequence encoded by the plasmid BO-55 (ATCC Accession No. 209104) .
  • nucleic acid encodes a rat GABA ⁇ R2 polypeptide having substantially the same amino acid sequence as the amino acid sequence shown in Figures 4A-4D (SEQ ID NO: 4) .
  • nucleic acid encodes a rat GABA ⁇ R2 polypeptide having the amino acid sequence shown in Figures 4A-4D (SEQ ID NO : 4) .
  • the nucleic acid encodes a mammalian GABA g R2 polypeptide which has substantially the same amino acid sequence as does the GABA ⁇ R2 polypeptide encoded by the plasmid pEXJT3T7-hGABAB2 (ATCC Accession No. 203515) .
  • the nucleic acid encodes a human GABA ⁇ R2 polypeptide which has an amino acid sequence encoded by the plasmid pEXJT3T7-hGABAB2 (ATCC Accession No. 203515) .
  • the human GABA ⁇ R2 polypeptide has a sequence, which sequence comprises substantially the same amino acid sequence as the sequence shown in Figures 23A- 23D (SEQ ID NO: 47) .
  • the human GABA ⁇ R2 polypeptide has a sequence, which sequence comprises the sequence shown in Figures 23A-23D (SEQ ID NO: 47) .
  • This application further supports an isolated nucleic acid encoding a GABA ⁇ R2 polypeptide, the amino acid sequence of which is encoded by the nucleotide sequence set forth in either the Figures 22A-22D and 3A-3D.
  • human GABA ⁇ R2 polypeptide described herein exhibits 38% amino acid identity with the GABA ⁇ Rla polypeptide, while the rat GABA ⁇ R2 polypeptide described herein exhibits 98% identity with the human GABA B R2 polypeptide .
  • the ATG encoding the methionine at position 16 is surrounded by flanking sequences which correspond to the well-known Kozak consensus sequence for translation initiation (Kozak, 1989 and Kozak, 1991) , thus the sequence from amino acid 16 through amino acid 898 is believed to be the most likely polypeptide expressed by the nucleic acid.
  • flanking sequences which correspond to the well-known Kozak consensus sequence for translation initiation (Kozak, 1989 and Kozak, 1991) , thus the sequence from amino acid 16 through amino acid 898 is believed to be the most likely polypeptide expressed by the nucleic acid.
  • Neither the ATG encoding methionine 1 nor the ATG encoding methionine 19 has the Kozak flanking sequences; however, it is to be understood that the present invention provides a GABA ⁇ R2 polypeptide having any one of the three possible starting methionines .
  • This invention provides a splice variant of the polypeptides disclosed herein. This invention further provides for alternate translation initiation sites and alternately spliced or edited variants of nucleic acids encoding rat and human polypeptides of this invention.
  • This invention also encompasses DNAs and cDNAs which encode amino acid sequences which differ from those of the polypeptides of this invention, but which should not produce phenotypic changes.
  • this invention also encompasses DNAs, cDNAs, and RNAs which hybridize to the DNA, cDNA, and RNA of the subject invention.
  • nucleic acids of the subject invention also include nucleic acid molecules coding for polypeptide analogs, fragments or derivatives of antigenic polypeptides which differ from naturally-occurring forms in terms of the identity or location of one or more amino acid residues
  • substitution analogs containing less than all of the residues specified for the protein, substitution analogs wherein one or more residues specified are replaced by other residues and addition analogs where in one or more amino acid residues is added to a terminal or medial portion of the polypeptides and which share some or all properties of naturally-occurring forms.
  • These molecules include: the incorporation of codons "preferred" for expression by selected non-mammalian hosts; the provision of sites for cleavage by restriction endonuclease enzymes; and the provision of additional initial, terminal or intermediate DNA sequences that facilitate construction of readily expressed vectors.
  • modified polypeptides of this invention may be transfected into cells either transiently or stably using methods well-known in the art, examples of which are disclosed herein.
  • This invention also provides for binding assays using the modified polypeptides, in which the polypeptide is expressed either transiently or in stable cell lines.
  • This invention further provides for a compound identified using a modified polypeptide in a binding assay such as the binding assays described herein.
  • nucleic acids described and claimed herein are useful for the information which they provide concerning the amino acid sequence of the polypeptide and as products for the large scale synthesis of the polypeptide by a variety of recombinant techniques.
  • the nucleic acid molecule is useful for generating new cloning and expression vectors, transformed and transfected prokaryotic and eukaryotic host cells, and new and useful methods for cultured growth of such host cells capable of expression of the polypeptide and related products.
  • Suitable vectors comprise, but are not limited to, a plasmid or a virus. These vectors may be transformed into a suitable host cell to form a host cell expression system for the production of a GABA ⁇ R2 polypeptide.
  • Suitable host cells include, for example, neuronal cells such as the glial cell line C6, a Xenopus cell such as an oocyte or melanophore cell, as well as numerous mammalian cells and non-neuronal cells.
  • This invention further provides for any vector or plasmid which comprises modified untranslated sequences, which are beneficial for expression in desired host cells or for use in binding or functional assays.
  • a vector or plasmid with untranslated sequences of varying lengths may express differing amounts of the polypeptide depending upon the host cell used.
  • the vector or plasmid comprises the coding sequence of the polypeptide and the regulatory elements necessary for expression in the host cell .
  • the phrase “specifically hybridizing” means the ability of a nucleic acid molecule to recognize a nucleic acid sequence complementary to its own and to form double-helical segments through hydrogen bonding between complementary base pairs.
  • complementary is used in its usual sense in the art, i.e., G and C are complementary and A is complementary to T (or U in RNA) , such that two strands of nucleic acid are “complementary” only if every base matches the opposing base exactly.
  • This invention is directed to a purified GABA ⁇ R2 protein.
  • This invention is directed to a vector comprising a above- identified nucleic acid.
  • the vector is adapted for expression in a bacterial cell which comprises the regulatory elements necessary for expression of the nucleic acid in the bacterial cell operatively linked to the nucleic acid encoding a GABA g R2 polypeptide so as to permit expression thereof .
  • the vector is adapted for expression in an amphibian cell which comprises the regulatory elements necessary for expression of the nucleic acid in the amphibian cell operatively linked to the nucleic acid encoding a GABA ⁇ R2 polypeptide so as to permit expression thereof.
  • the vector is adapted for expression in a yeast cell which comprises the regulatory elements necessary for expression of the nucleic acid in the yeast cell operatively linked to the nucleic acid encoding a GABA ⁇ R2 polypeptide so as to permit expression thereof .
  • the vector is adapted for expression in an insect cell which comprises the regulatory elements necessary for expression of the nucleic acid in the insect cell operatively linked to the nucleic acid encoding the GABA ⁇ R2 polypeptide so as to permit expression thereof.
  • the vector is a baculovirus
  • the vector is adapted for expression in a mammalian cell which comprises the regulatory elements necessary for expression of the nucleic acid in the mammalian cell operatively linked to the nucleic acid encoding a GABA ⁇ R2 polypeptide so as to permit expression thereof.
  • the vector is a plasmid.
  • the plasmid is designated BO-55 (ATCC Accession No. 209104) .
  • the plasmid is designated pEXJT3T7-hGABAB2 (ATCC Accession No. 203515) .
  • This invention provides a plasmid designated pEXJT3T7- hGABAB2 (ATCC Accession No. 203515) which comprises the regulatory elements necessary for expression of DNA in a mammalian cell operatively linked to DNA encoding the human polypeptide so as to permit expression thereof.
  • This plasmid (pEXJT3T7-hGABAB2) was deposited on December 9, 1998, with the American Type Culture Collection (ATCC) , 10801 University Boulevard., Manassas, Virginia 20110-2209, U.S.A. under the provisions of the Budapest Treaty for the International Recognition of the Deposit of Microorganisms for the Purposes of Patent Procedure and was accorded ATCC Accession No. 203515.
  • ATCC American Type Culture Collection
  • This invention provides a plasmid designated BO-55 (ATCC Accession No. 209104) which comprises the regulatory elements necessary for expression of DNA in a mammalian cell operatively linked to DNA encoding the rat polypeptide so as to permit expression thereof.
  • This plasmid (BO-55) was deposited on June 10, 1997, with the American Type Culture Collection (ATCC) , 12301
  • Nucleic acid probe technology is well known to those skilled in the art who will readily appreciate that such probes may vary greatly in length and may be labeled with a detectable label, such as a radioisotope or fluorescent dye, to facilitate detection of the probe.
  • DNA probe molecules may be produced by insertion of a DNA molecule which encodes the polypeptides of this invention into suitable vectors, such as plasmids or bacteriophages, followed by transforming into suitable bacterial host cells, replication in the transformed bacterial host cells and harvesting of the DNA probes, using methods well known in the art. Alternatively, probes may be generated chemically from DNA synthesizers.
  • RNA probes may be generated by inserting the DNA molecule which encodes the polypeptides of this invention downstream of a bacteriophage promoter such as T3 , T7 or SP6. Large amounts of RNA probe may be produced by incubating the labeled nucleotides with the linearized fragment where it contains an upstream promoter in the presence of the appropriate RNA polymerase .
  • This invention is directed to a method of detecting a nucleic acid encoding a GABA ⁇ R2 polypeptide, which comprises contacting the nucleic acid with a probe comprising at least 15 nucleotides, which probe specifically hybridizes with the nucleic acid encoding the GABA ⁇ R2 polypeptide, wherein the probe has a unique sequence, which sequence is present within one of the two strands of the nucleic acid encoding the GABA ⁇ R2 polypeptide contained in plasmid BO-55, and detecting hybridization of the probe to the nucleic acid.
  • This invention is directed to a method of detecting a nucleic acid encoding a GABA ⁇ R2 polypeptide, which comprises contacting the nucleic acid with a probe comprising at least 15 nucleotides, which probe specifically hybridizes with the nucleic acid encoding the GABA ⁇ R2 polypeptide, wherein the probe has a unique sequence, which sequence is present within (a) the nucleic acid sequence shown in Figures 22A-22D (SEQ ID NO: 46) or (b) the reverse complement to the nucleic acid sequence shown in Figures 22A-22D (SEQ ID NO: 46) , and detecting hybridization of the probe to the nucleic acid.
  • This invention is directed to a method of detecting a nucleic acid encoding a GABA ⁇ R2 polypeptide, which comprises contacting the nucleic acid with a probe comprising at least 15 nucleotides, which probe specifically hybridizes with the nucleic acid encoding the GABA ⁇ R2 polypeptide, wherein the probe has a unique sequence, which sequence is present within one of the two strands of the nucleic acid encoding the GABA ⁇ R2 polypeptide contained in plasmid pEXJT3T7-hGABAB2 and detecting hybridization of the probe to the nucleic acid.
  • This invention is directed to a method of detecting a nucleic acid encoding a GABA ⁇ R2 polypeptide, which comprises contacting the nucleic acid with a probe comprising at least 15 nucleotides, which probe specifically hybridizes with the nucleic acid encoding the GABA ⁇ R2 polypeptide, wherein the probe has a unique sequence, which sequence is present within (a) the nucleic acid sequence shown in Figures 3A-3D (SEQ ID NO: 3) or (b) the reverse complement to the nucleic acid sequence shown in Figures 3A-3D (SEQ ID NO: 3), and detecting hybridization of the probe to the nucleic acid.
  • the nucleic acid is DNA.
  • the nucleic acid is RNA.
  • the probe comprises at least 15 nucleotides complementary to a unique segment of the sequence of the nucleic acid molecule encoding the GABA ⁇ R2 polypeptide .
  • This invention is directed to a method of detecting a nucleic acid encoding a GABA ⁇ R2 polypeptide, which comprises contacting the nucleic acid with a probe comprising a nucleic acid of at least 15 nucleotides which is complementary to the antisense sequence of a unique segment of the sequence of the nucleic acid encoding the GABA ⁇ R2 polypeptide, and detecting hybridization of the probe to the nucleic acid.
  • This invention is directed to a method of inhibiting translation of mRNA encoding a GABA ⁇ R2 polypeptide which comprises contacting such mRNA with an antisense oligonucleotide having a sequence capable of specifically hybridizing to the above- identified mRNA, so as to prevent translation of the mRNA.
  • This invention is directed to a method of inhibiting translation of mRNA encoding a GABA ⁇ R2 polypeptide which comprises contacting such mRNA with an antisense oligonucleotide having a sequence capable of specifically hybridizing to the above- identified genomic DNA.
  • the oligonucleotide comprises chemically modified nucleotides or nucleotide analogues.
  • the isolated antibody is capable of binding to a GABA ⁇ R2 polypeptide encoded by an above- identified nucleic acid.
  • the GABA ⁇ R2 polypeptide is a human GABA B R2 polypeptide.
  • This invention is directed to an antibody capable of competitively inhibiting the binding of an above- identified antibody to a GABA ⁇ R2 polypeptide.
  • the antibody is a monoclonal antibody.
  • the monoclonal antibody is directed to an epitope of a GABA ⁇ R2 polypeptide present on the surface of a GABA ⁇ R2 polypeptide expressing cell.
  • the oligonucleotide is coupled to a substance which inactivates mRNA.
  • the substance which inactivates mRNA is a ribozyme.
  • This invention is directed to a pharmaceutical composition which comprises an amount of an above-identified antibody effective to block binding of a ligand to the GABA ⁇ R2 polypeptide and a pharmaceutically acceptable carrier.
  • pharmaceutically acceptable carriers means any of the standard pharmaceutically acceptable carriers. Examples include, but are not limited to, phosphate buffered saline, physiological saline, water and emulsions, such as oil/water emulsions.
  • Animal model systems which elucidate the physiological and behavioral roles of the polypeptides of this invention are produced by creating transgenic animals in which the activity of the polypeptide is either increased or decreased, or the amino acid sequence of the expressed polypeptide is altered, by a variety of techniques.
  • these techniques include, but are not limited to: 1) Insertion of normal or mutant versions of DNA encoding the polypeptide, by microinjection, electroporation, retroviral transfection or other means well known to those skilled in the art, into appropriate fertilized embryos in order to produce a transgenic animal or 2) Homologous recombination of mutant or normal, human or animal versions of these genes with the native gene locus in transgenic animals to alter the regulation of expression or the structure of these polypeptide sequences.
  • homologous recombination is well known in the art. It replaces the native gene with the inserted gene and so is useful for producing an animal that cannot express native polypeptides but does express, for example, an inserted mutant polypeptide, which has replaced the native polypeptide in the animal's genome by recombination, resulting in underexpression of the transporter. Microinjection adds genes to the genome, but does not remove them, and so is useful for producing an animal which expresses its own and added polypeptides, resulting in overexpression of the polypeptides.
  • transgenic animal One means available for producing a transgenic animal, with a mouse as an example, is as follows: Female mice are mated, and the resulting fertilized eggs are dissected out of their oviducts. The eggs are stored in an appropriate medium such as M2 medium. DNA or cDNA encoding a polypeptide of this invention is purified from a vector by methods well known in the art. Inducible promoters may be fused with the coding region of the DNA to provide an experimental means to regulate expression of the trans-gene. Alternatively, or in addition, tissue specific regulatory elements may be fused with the coding region to permit tissue-specific expression of the transgene.
  • microinjection needle which may be made from capillary tubing using a pipet puller
  • the egg to be injected is put in a depression slide.
  • the needle is inserted into the pronucleus of the egg, and the DNA solution is injected.
  • the injected egg is then transferred into the oviduct of a pseudopregnant mouse (a mouse stimulated by the appropriate hormones to maintain pregnancy but which is not actually pregnant) , where it proceeds to the uterus, implants, and develops to term.
  • pseudopregnant mouse a mouse stimulated by the appropriate hormones to maintain pregnancy but which is not actually pregnant
  • This invention is directed to a transgenic, nonhuman mammal expressing DNA encoding a GABA ⁇ R2 polypeptide.
  • This invention is directed to a transgenic, nonhuman mammal comprising a homologous recombination knockout of the native GABA g R2 polypeptide.
  • This invention is further directed to a transgenic, nonhuman mammal whose genome comprises antisense DNA complementary to DNA encoding a GABA B R2 polypeptide so placed as to be transcribed into antisense mRNA which is complementary to mRNA encoding such GABA ⁇ R2 polypeptide and which hybridizes to such mRNA encoding such GABA ⁇ R2 polypeptide, thereby reducing its translation.
  • This invention is directed to an above-identified transgenic, nonhuman mammal, wherein the DNA encoding the GABA ⁇ R2 polypeptide additionally comprises an inducible promoter.
  • This invention is directed to an above-identified transgenic, nonhuman mammal, wherein the DNA encoding the GABA ⁇ R2 polypeptide additionally comprises tissue specific regulatory elements .
  • This invention is directed to an above- identified transgenic, nonhuman mammal, wherein the transgenic, nonhuman mammal is a mouse.
  • This invention is directed to method of detecting the presence of a GABA ⁇ R2 polypeptide on the surface of a cell which comprises contacting the cell with an above- identified antibody under conditions permitting binding of the antibody to the polypeptide, detecting the presence of the antibody bound to the cell, and thereby detecting the presence of a GABA ⁇ R2 polypeptide on the surface of the cell.
  • This invention is directed to a method of preparing a purified GABA g R2 polypeptide which comprises: a. inducing cells to express a GABA g R2 polypeptide;
  • This invention is directed to a method of preparing the purified GABA g R2 polypeptide which comprises:
  • This invention is directed to a GABA ⁇ Rl/R2 receptor comprising two polypeptides, one of which is a GABA .2 polypeptide and another of which is a GABA ⁇ Rl polypeptide.
  • This invention is directed to a method of forming a GABA ⁇ Rl/R2 receptor which comprises inducing cells to express both a GABA ⁇ Rl polypeptide and a GABA ⁇ R2 polypeptide.
  • GABA g Rl as used in this application could be GABA g Rla or GABA ⁇ Rlb.
  • the observation that at least two variants of the GABA g Rl polypeptide exist raises the possibility that GABA ⁇ R2 splice variants may exist or that there may exist introns in coding or non-coding regions of the genes encoding the GABA ⁇ R2 polypeptides.
  • spliced form(s) of mRNA may encode additional amino acids either upstream of the currently defined starting methionine or within the coding region.
  • the existence and use of alternative exons is possible, whereby the mRNA may encode different amino acids within the region comprising the exon.
  • single amino acid substitutions may arise via the mechanism of RNA editing such that the amino acid sequence of the expressed protein is different than that encoded by the original gene (Burns et al . , 1996; Chu et al . , 1996) .
  • Such variants may exhibit pharmacologic properties differing from the polypeptide encoded by the original gene.
  • GPCR G-protein coupled receptor
  • the activity of a G-protein coupled receptor typically is measured using any of a variety of functional assays in which activation of the receptor in question results in an observable change in the level of some second messenger system, including but not limited to adenylate cyclase, calcium mobilization, arachidonic acid release, ion channel activity, inositol phospholipid hydrolysis or guanylyl cyclase.
  • Heterologous expression systems utilizing appropriate host cells to express the nucleic acids of the subject invention are used to obtain the desired second messenger coupling. Receptor activity may also be assayed in an oocyte expression system.
  • GABA ⁇ R2 When GABA ⁇ R2 is co-expressed with GABA ⁇ Rl , are similar to the pharmacologic properties of the GABA ⁇ receptor observed using tissues.
  • applicants will refer to the product of the heterologous coexpression of GABA ⁇ R2 and GABA B R1 as the "GABA ⁇ Rl/R2 receptor.”
  • a cell expressing nucleic acid encoding a GABA ⁇ Rl/R2 receptor is to be understood to refer to a cell expressing both nucleic acid encoding a GABA ⁇ Rl polypeptide and nucleic acid encoding a GABA ⁇ R2 polypeptide.
  • GABA B R1 can be either GABA ⁇ Rla or GABA ⁇ Rlb.
  • This invention is directed to an antibody capable of binding to a GABA ⁇ Rl/R2 receptor, wherein the GABA ⁇ R2 polypeptide is encoded by an above-identified nucleic acid.
  • This invention is directed to an above-identified antibody, wherein the GABA ⁇ R2 polypeptide is a human GABA ⁇ R2 polypeptide.
  • This invention is directed to an antibody capable of competitively inhibiting the binding of an above- identified antibody to a GABA ⁇ Rl/R2 receptor.
  • the antibody is a monoclonal antibody.
  • This invention is directed to an above-identified monoclonal antibody directed to an epitope of a GABA ⁇ Rl/R2 receptor present on the surface of a GABA ⁇ Rl/R2 polypeptide expressing cell.
  • This invention is directed to a pharmaceutical composition which comprises an amount of an above-identified antibody effective to block binding of a ligand to the GABA ⁇ Rl/R2 receptor and a pharmaceutically acceptable carrier.
  • This invention is directed to a transgenic, nonhuman mammal expressing a GABA ⁇ Rl/R2 receptor, which is not naturally expressed by the mammal.
  • This invention is directed to a transgenic, nonhuman mammal comprising a homologous recombination knockout of the native GABA g Rl/R2 receptor.
  • the transgenic nonhuman mammal is a mouse .
  • This invention is directed to a method of detecting the presence of a GABA ⁇ Rl/R2 receptor on the surface of a cell which comprises contacting the cell with an above- identified antibody under conditions permitting binding of the antibody to the receptor, detecting the presence of the antibody bound to the cell, and thereby detecting the presence of a GABA ⁇ Rl/R2 receptor on the surface of the cell.
  • This invention is directed to a method of determining the physiological effects of varying levels of activity of GABA ⁇ Rl/R2 receptors which comprises producing an above- identified transgenic nonhuman mammal whose levels of
  • GABA ⁇ Rl/R2 receptor activity vary due to the presence of an inducible promoter which regulates GABA ⁇ Rl/R2 receptor expression.
  • This invention is directed to a method of determining the physiological effects of varying levels of activity of GABA ⁇ Rl/R2 receptors which comprises producing a panel of above-identified transgenic nonhuman mammals, each expressing a different amount of GABA ⁇ Rl/R2 receptor.
  • This invention is directed to a method for identifying an antagonist capable of alleviating an abnormality, by decreasing the activity of a GABA ⁇ Rl/R2 receptor comprising administering a compound to a above-identified transgenic nonhuman mammal, and determining whether the compound alleviates the physical and behavioral abnormalities displayed by the transgenic, nonhuman mammal, the alleviation of the abnormality identifying the compound as the antagonist .
  • This invention is directed to an antagonist identified by an above- identified method.
  • This invention is directed to a pharmaceutical composition comprising an above-identified antagonist and a pharmaceutically acceptable carrier.
  • This invention is directed to a method of treating an abnormality in a subject wherein the abnormality is alleviated by decreasing the activity of a GABA ⁇ Rl/R2 receptor which comprises administering to a subject an effective amount of an above-identified pharmaceutical composition, thereby treating the abnormality.
  • This invention is directed to a method for identifying an agonist capable of alleviating an abnormality, by increasing the activity of a GABA ⁇ Rl/R2 receptor comprising administering a compound to an above-identified transgenic nonhuman mammal , and determining whether the compound alleviates the physical and behavioral abnormalities displayed by the transgenic, nonhuman mammal, the alleviation of the abnormality identifying the compound as the agonist.
  • This invention is directed to an agonist identified by an above-identified method.
  • This invention is directed to a pharmaceutical composition
  • a pharmaceutical composition comprising an above- identified agonist and a pharmaceutically acceptable carrier.
  • This invention is directed to a method for treating an abnormality in a subject wherein the abnormality is alleviated by increasing the activity of a GABA ⁇ Rl/R2 receptor which comprises administering to a subject an effective amount of an above-identified pharmaceutical composition, thereby treating the abnormality.
  • This invention is directed to a cell which expresses on its surface a mammalian GABA ⁇ Rl/R2 receptor that is not naturally expressed on the surface of such cell .
  • This invention is directed to a cell, wherein the mammalian GABA ⁇ Rl/R2 receptor comprises two polypeptides, one of which is a GABA ⁇ R2 polypeptide and another of which is a GABA ⁇ Rl polypeptide.
  • This invention is directed to a process for identifying a chemical compound which specifically binds to a GABA ⁇ Rl/R2 receptor which comprises contacting cells containing nucleic acid encoding and expressing on their cell surface the GABA ⁇ Rl/R2 receptor, wherein such cells do not normally express the GABA ⁇ Rl/R2 receptor, with the compound under conditions suitable for binding, and detecting specific binding of the chemical compound to the GABA ⁇ Rl/R2 receptor.
  • This invention is directed to a process for identifying a chemical compound which specifically binds to a GABA ⁇ Rl/R2 receptor which comprises contacting a membrane fraction from a cell extract of cells containing nucleic acid encoding and expressing on their cell surface the
  • GABA B Rl/R2 receptor wherein such cells do not normally express the GABA ⁇ Rl/R2 receptor, with the compound under conditions suitable for binding, and detecting specific binding of the chemical compound to the GABA ⁇ Rl/R2 receptor.
  • the GABA ⁇ Rl/R2 receptor is a mammalian GABA g Rl/R2 receptor.
  • the GABA ⁇ Rl/R2 receptor comprises a
  • GABA ⁇ R2 polypeptide which has substantially the same amino acid sequence as that encoded by the plasmid BO-55 (ATCC Accession No. 209104) .
  • the GABA ⁇ Rl/R2 receptor comprises a GABA ⁇ R2 polypeptide which has substantially the same sequence as the amino acid sequence shown in Figures 23A- 23D (SEQ ID NO: 47) .
  • the GABA ⁇ Rl/R2 receptor comprises a GABA ⁇ R2 polypeptide which has the amino acid sequence shown in Figures 23A-23D (SEQ ID NO: 47) .
  • the GABA ⁇ Rl/R2 receptor comprises a GABA ⁇ R2 polypeptide which has substantially the same amino acid sequence as that encoded by the plasmid pEXJT3T7- hGABAB2 (ATCC Accession No. 203515) .
  • the GABA ⁇ Rl/R2 receptor comprises a GABA B R2 polypeptide which has substantially the same amino acid sequence as the sequence shown in Figures 23A-23D (SEQ ID NO: 47) .
  • the GABA ⁇ Rl/R2 receptor comprises a GABA ⁇ R2 polypeptide which has the sequence shown in Figures 23A-23D (SEQ ID NO: 47) .
  • the compound is not previously known to bind to a GABA ⁇ Rl/R2 receptor.
  • This invention is directed to a compound identified by an above-identified process.
  • the cell is an insect cell.
  • the cell is a mammalian cell.
  • the cell is nonneuronal in origin.
  • the nonneuronal cell is a COS-7 cell, 293 human embryonic kidney cell, a CHO cell, a NIH- 3T3 cell a mouse Yl cell or LM(tk-) cell.
  • the compound is not previously known to bind to a GABA ⁇ Rl/R2 receptor.
  • This invention is directed to a compound identified by an above-identified process.
  • This invention is directed to a process involving competitive binding for identifying a chemical compound which specifically binds to a GABA ⁇ Rl/R2 receptor which comprises separately contacting cells expressing on their cell surface the GABA B R1/R2 receptor, wherein such cells do not normally express the GABA ⁇ Rl/R2 receptor, with both the chemical compound and a second chemical compound known to bind to the receptor, and with only the second chemical compound, under conditions suitable for binding of both compounds, and detecting specific binding of the chemical compound to the GABA ⁇ Rl/R2 receptor, a decrease in the binding of the second chemical compound to the GABA ⁇ Rl/R2 receptor in the presence of the chemical compound indicating that the chemical compound binds to the GABA B R1/R2 receptor.
  • This invention is directed to a process involving competitive binding for identifying a chemical compound which specifically binds to a human GABA ⁇ Rl/R2 receptor which comprises separately contacting a membrane fraction from a cell extract of cells expressing on their cell surface the GABA ⁇ Rl/R2 receptor, wherein such cells do not normally express the GABA ⁇ Rl/R2 receptor, with both the chemical compound and a second chemical compound known to bind to the receptor, and with only the second chemical compound, under conditions suitable for binding of both compounds, and detecting specific binding of the chemical compound to the GABA ⁇ Rl/R2 receptor, a decrease in the binding of the second chemical compound to the GABA ⁇ Rl/R2 receptor in the presence of the chemical compound indicating that the chemical compound binds to the GABA B R1/R2 receptor.
  • the GABA ⁇ Rl/R2 receptor is a mammalian GABA B R1/R2 receptor.
  • the GABA ⁇ Rl/R2 receptor comprises a GABA ⁇ R2 polypeptide which has substantially the same amino acid sequence as that encoded by plasmid BO-55 (ATCC Accession No. 209104) .
  • the GABA ⁇ Rl/R2 receptor comprises a GABA ⁇ R2 polypeptide which has substantially the same amino acid sequence as that shown in Figures 23A-23D (SEQ ID NO: 47) .
  • the GABA ⁇ Rl/R2 receptor comprises a GABA ⁇ R2 polypeptide which has the amino acid sequence shown in Figures 23A-23D (SEQ ID NO: 47) .
  • the GABA ⁇ Rl/R2 receptor comprises a GABA ⁇ R2 polypeptide which has substantially the same amino acid sequence as that encoded by plasmid pEXJT3T7-hGABAB2 (ATCC Accession No. 203515) .
  • the GABA ⁇ Rl/R2 receptor comprises a GABA ⁇ R2 polypeptide which has substantially the same amino acid sequence as the sequence shown in Figures 23A-23D (SEQ ID NO: 47) .
  • the GABA ⁇ Rl/R2 receptor comprises a GABA ⁇ R2 polypeptide which has the sequence shown in Figures 23A-23D (SEQ ID NO: 47) .
  • the cell is an insect cell.
  • the cell is a mammalian cell.
  • the cell is nonneuronal in origin.
  • the nonneuronal cell is a COS-7 cell, 293 human embryonic kidney cell, a CHO cell, a NIH- 3T3 cell a mouse Yl cell or LM(tk-) cell.
  • the compound is not previously known to bind to a GABA ⁇ Rl/R2 receptor.
  • This invention is directed to a compound identified by an above-identified process.
  • This invention is directed to a method of screening a plurality of chemical compounds not known to bind to a GABA ⁇ Rl/R2 receptor to identify a compound which specifically binds to the GABA ⁇ Rl/R2 receptor, which comprises
  • step (b) contacting the same cells as in step (a) with the plurality of compounds not known to bind specifically to the GABA ⁇ Rl/R2 receptor, under conditions permitting binding of compounds known to bind the GABA ⁇ Rl/R2 receptor;
  • This invention is directed to a method of screening a plurality of chemical compounds not known to bind to a GABA ⁇ Rl/R2 receptor to identify a compound which specifically binds to the GABA ⁇ Rl/R2 receptor, which comprises
  • step (b) contacting the same membrane fraction as in step (a) with the plurality of compounds not known to bind specifically to the GABA ⁇ Rl/R2 receptor, under conditions permitting binding of compounds known to bind the GABA ⁇ Rl/R2 receptor;
  • the GABA B R1/R2 receptor is a mammalian GABA ⁇ Rl/R2 receptor.
  • the cell is a mammalian cell.
  • the mammalian cell is non-neuronal in origin.
  • the non-neuronal cell is a COS-7 cell, a 293 human embryonic kidney cell, a LM(tk-) cell, a CHO cell, a mouse Yl cell or an NIH-3T3 cell.
  • This invention is directed to a process for determining whether a chemical compound is a GABA ⁇ Rl/R2 receptor agonist which comprises contacting cells with the compound under conditions permitting the activation of the GABA ⁇ Rl/R2 receptor, and detecting an increase in GABA ⁇ Rl/R2 receptor activity, so as to thereby determine whether the compound is a GABA ⁇ Rl/R2 receptor agonist.
  • This invention is directed to a process for determining whether a chemical compound is a GABA ⁇ Rl/R2 receptor antagonist which comprises contacting cells containing nucleic acid encoding and expressing on their cell surface the GABA ⁇ Rl/R2 receptor, wherein such cells do not normally express the GABA ⁇ Rl/R2 receptor, with the compound in the presence of a known GABA-R1/R2 receptor agonist, under conditions permitting the activation of the GABA B R1/R2 receptor, and detecting a decrease in GABA ⁇ Rl/R2 receptor activity, so as to thereby determine whether the compound is a GABA ⁇ Rl/R2 receptor antagonist.
  • the cells additionally express nucleic acid encoding GIRK1 and GIRK4.
  • the GABA ⁇ R2 receptor is a mammalian GABA B R2 receptor.
  • This invention is directd to a pharmaceutical composition which comprises an amount of a GABA ⁇ Rl/R2 receptor agonist determined to be an agonist by an above-identified process effective to increase activity of a GABA ⁇ Rl/R2 receptor and a pharmaceutically acceptable carrier.
  • This invention is directed to a pharmaceutical, wherein the GABA ⁇ Rl/R2 receptor agonist was not previously known.
  • This invention is directed to a pharmaceutical composition which comprises an amount of a GABA ⁇ Rl/R2 receptor antagonist determined to be an antagonist an above- identified process effective to reduce activity of a GABA B R1/R2 receptor and a pharmaceutically acceptable carrier.
  • This invention is directed to a pharmaceutical composition, wherein the GABA ⁇ Rl/R2 receptor antagonist was not previously known.
  • This invention is directed to a process for determining whether a chemical compound activates a GABA ⁇ Rl/R2 receptor, which comprises contacting cells producing a second messenger response and expressing on their cell surface the GABA ⁇ Rl/R2 receptor, wherein such cells do not normally express the GABA ⁇ Rl/R2 receptor, with the chemical compound under conditions suitable for activation of the GABA ⁇ Rl/R2 receptor, and measuring the second messenger response in the presence and in the absence of the chemical compound, a change in the second messenger response in the presence of the chemical compound indicating that the compound activates the GABA ⁇ Rl/R2 receptor.
  • the second messenger response comprises potassium channel activation and the change in second messenger is an increase in the level of potassium current .
  • This invention is directed to a process for determining whether a chemical compound inhibits activation of a GABA ⁇ Rl/R2 receptor, which comprises separately contacting cells producing a second messenger response and expressing on their cell surface the GABA ⁇ Rl/R2 receptor, wherein such cells do not normally express the GABA ⁇ Rl/R2 receptor, with both the chemical compound and a second chemical compound known to activate the GABA ⁇ Rl/R2 receptor, and with only the second chemical compound, under conditions suitable for activation of the GABA ⁇ Rl/R2 receptor, and measuring the second messenger response in the presence of only the second chemical compound and in the presence of both the second chemical compound and the chemical compound, a smaller change in the second messenger response in the presence of both the chemical compound and the second chemical compound than in the presence of only the second chemical compound indicating that the chemical compound inhibits activation of the GABA ⁇ Rl/R2 receptor.
  • the second messenger response comprises potassium channel activation and the change in second messenger response is a smaller increase in the level of inward potassium current in the presence of both the chemical compound and the second chemical compound than in the presence of only the second chemical compound.
  • the GABA ⁇ Rl/R2 receptor comprises a
  • GABA ⁇ R2 polypeptide which has substantially the same amino acid sequence as that encoded by the plasmid BO-55 (ATCC Accession No. 209104) .
  • the GABA ⁇ Rl/R2 receptor comprises a GABA ⁇ R2 polypeptide which has substantially the same amino acid sequence as that shown in Figures 4A-4D (SEQ ID NO: 4) .
  • the GABA ⁇ Rl/R2 receptor comprises a GABA ⁇ R2 polypeptide which has substantially the same amino acid sequence as that shown in Figures 23A-23D (SEQ ID NO: 47) .
  • the GABA ⁇ Rl/R2 receptor comprises a GABA ⁇ R2 polypeptide which has the sequence, shown in Figures 23A-23D (SEQ ID NO: 47) .
  • the GABA ⁇ Rl/R2 receptor comprises a GABA ⁇ R2 polypeptide which has substantially the same amino acid sequence as that encoded by the plasmid pEXJT3T7- hGABAB2 (ATCC Accession No. 203515) .
  • This invention is directed to an above- identified process, wherein the cell is an insect cell.
  • This invention is directed to an above- identified process, wherein the cell is a mammalian cell.
  • the mammalian cell is nonneuronal in origin.
  • the nonneuronal cell is a COS-7 cell, CHO cell, 293 human embryonic kidney cell, NIH-3T3 cell or LM(tk-) cell.
  • the compound was not previously known to activate or inhibit a GABA ⁇ Rl/R2 receptor.
  • This invention is directed to a compound determined by an above- identified process.
  • This invention is directed to a pharmaceutical composition which comprises an amount of a GABA ⁇ Rl/R2 receptor agonist determined by an above- identified process effective to increase activity of a GABA ⁇ Rl/R2 receptor and a pharmaceutically acceptable carrier.
  • the GABA ⁇ Rl/R2 receptor agonist was not previously known.
  • This invention is directed to a pharmaceutical composition which comprises an amount of a GABA ⁇ Rl/R2 receptor antagonist determined by an above-identified process effective to reduce activity of a GABA ⁇ Rl/R2 receptor and a pharmaceutically acceptable carrier.
  • the GABA ⁇ Rl/R2 receptor antagonist was not previously known.
  • This invention is directed to method of screening a plurality of chemical compounds not known to activate a GABA ⁇ Rl/R2 receptor to identify a compound which activates the GABA ⁇ Rl/R2 receptor which comprises:
  • the cells express nucleic acid encoding GIRK1 and GIRK4.
  • the GABA ⁇ Rl/R2 receptor is a mammalian GABA g Rl/R2 receptor.
  • This invention is directed to a method of screening a plurality of chemical compounds not known to inhibit the activation of a GABA ⁇ Rl/R2 receptor to identify a compound which inhibits the activation of the GABA ⁇ Rl/R2 receptor, which comprises:
  • GABA g Rl/R2 receptor is reduced in the presence of the plurality of compounds, relative to the activation of the GABA ⁇ Rl/R2 receptor in the absence of the plurality of compounds, and if it is reduced;
  • GABA g Rl/R2 receptor GABA g Rl/R2 receptor.
  • the cells express nucleic acid encoding GIRK1 and GIRK4.
  • the GABA ⁇ Rl/R2 receptor is a mammalian GABA g Rl/R2 receptor.
  • the cell is a mammalian cell.
  • the mammalian cell is non-neuronal in origin.
  • the non-neuronal cell is a COS-7 cell, a 293 human embryonic kidney cell, a LM(tk-) cell or an NIH-3T3 cell.
  • This invention is directed to a pharmaceutical composition
  • a pharmaceutical composition comprising a compound identified by an above-identified method, effective to increase GABA ⁇ Rl/R2 receptor activity and a pharmaceutically acceptable carrier.
  • This invention is directed to a pharmaceutical composition
  • a pharmaceutical composition comprising a compound identified by an above-identified method, effective to decrease GABA ⁇ Rl/R2 receptor activity and a pharmaceutically acceptable carrier.
  • This invention is directed to a process for determining whether a chemical compound is a GABA ⁇ Rl/R2 receptor agonist, which comprises preparing a membrane fraction from cells which comprise nucleic acid encoding and expressing on their cell surface the GABA ⁇ Rl/R2 receptor, wherein such cells do not normally express the GABA ⁇ Rl/R2 receptor, separately contacting the membrane fraction with both the chemical compound and GTPyS, and with only GTPyS, under conditions permitting the activation of the GABA ⁇ Rl/R2 receptor, and detecting GTPyS binding to the membrane fraction, an increase in GTPyS binding in the presence of the compound indicating that the chemical compound activates the GABA g Rl/R2 receptor.
  • This invention is directed to a process for determining whether a chemical compound is a GABA g Rl/R2 receptor antagonist, which comprises preparing a membrane fraction from cells which comprise nucleic acid encoding and expressing on their cell surface the GABA ⁇ Rl/R2 receptor, wherein such cells do not normally express the GABA ⁇ Rl/R2 receptor, separately contacting the membrane fraction with the chemical compound, GTPyS and a second chemical compound known to activate the GABA ⁇ Rl/R2 receptor, with GTPyS and only the second compound, and with GTPyS alone, under conditions permitting the activation of the
  • GABA ⁇ Rl/R2 receptor detecting GTPyS binding to each membrane fraction, and comparing the increase in GTPyS binding in the presence of the compound and the second compound relative to the binding of GTPyS alone, to the increase in GTPyS binding in the presence of the second chemical compound known to activate the GABA ⁇ Rl/R2 receptor relative to the binding of GTPyS alone, a smaller increase in GTPyS binding in the presence of the compound and the second compound indicating that the compound is a GABA 8 R1/R2 receptor antagonist.
  • the GABA ⁇ R2 receptor is a mammalian GABA ⁇ R2 receptor .
  • the GABA ⁇ Rl/R2 receptor comprises a GABA ⁇ R2 polypeptide which has substantially the same amino acid sequence as that encoded by the plasmid BO-55 (ATCC Accession No. 209104) .
  • the GABA ⁇ Rl/R2 receptor comprises a GABA ⁇ R2 polypeptide which has substantially the same amino acid sequence as that shown in Figures 4A-4D (SEQ ID NO: 4) .
  • the GABA ⁇ Rl/R2 receptor comprises a GABA ⁇ R2 polypeptide which has substantially the same amino acid sequence as that encoded by the plasmid pEXJT3T7- hGABAB2 (ATCC Accession No. 203515) .
  • the GABA ⁇ Rl/R2 receptor comprises a GABA ⁇ R2 polypeptide which has substantially the same amino acid sequence as that shown in Figures 23A-23D (SEQ ID NO: 47) .
  • the GABA ⁇ Rl/R2 receptor comprises a GABA ⁇ R2 polypeptide which has the sequence shown in Figures 23A-23D (SEQ ID NO: 47) .
  • the cell is an insect cell.
  • the cell is a mammalian cell.
  • the mammalian cell is nonneuronal in origin.
  • the nonneuronal cell is a COS-7 cell, CHO cell, 293 human embryonic kidney cell, NIH-3T3 cell or LM(tk-) cell.
  • the compound was not previously known to be an agonist or antagonist of a GABA ⁇ Rl/R2 receptor.
  • This invention is directed to a compound determined to be an agonist or antagonist of a GABA ⁇ Rl/R2 receptor by an above-identified process.
  • This invention is directed to a method of treating spasticity in a subject which comprises administering to the subject an amount of a compound which is an agonist of a GABA ⁇ Rl/R2 receptor effective to treat spasticity in the subject .
  • This invention is directed to a method of treating asthma in a subject which comprises administering to the subject an amount of a compound which is a GABA ⁇ Rl/R2 receptor agonist effective to treat asthma in the subject.
  • This invention is directed to a method of treating incontinence in a subject which comprises administering to the subject an amount of a compound which is a GABA ⁇ Rl/R2 receptor agonist effective to treat incontinence in the subject.
  • This invention is directed to method of decreasing nociception in a subject which comprises administering to the subject an amount of a compound which is a GABA ⁇ Rl/R2 receptor agonist effective to decrease nociception in the subject .
  • This invention is directed to a use of a GABA..R2 agonist as an antitussive agent which comprises administering to the subject an amount of a compound which is a GABA g Rl/R2 receptor agonist effective as an antitussive agent in the subject .
  • This invention is directed to a method of treating drug addiction in a subject which comprises administering to the subject an amount of a compound which is a GABA g Rl/R2 receptor agonist effective to treat drug addiction in the subject .
  • This invention directed to a method of treating Alzheimer's disease in a subject which comprises administering to the subject an amount of a compound which is a GABA ⁇ Rl/R2 receptor antagonist effective to treat Alzheimer's disease in the subject.
  • This invention is directed to a peptide selected from the group consisting of: a) P L Y S I L S A L T I L G M I M A S A F L F F N I
  • This invention is directed to a compound that prevents the formation of a GABA ⁇ Rl/R2 receptor complex.
  • Transmembrane peptides derived from GABA ⁇ R2 sequences may modulate the functional activity of GABA ⁇ Rl/R2 receptors.
  • One mode of action involves the destruction of the
  • GABA g Rl/R2 receptor complex via competitive displacement of the GABA ⁇ R2 polypeptide subunit by the peptide upon binding to the GABA ⁇ Rl polypeptide subunit.
  • the peptides may be synthesized using standard solid phase F-moc peptide synthesis protocol using an Advanced Chemtech 396 Automated Peptide Synthesizer.
  • GABA ⁇ subtypes in hypothalamus and caudate putamen are predicted due to the under-representation of GABA ⁇ R2 hybridization signals.
  • GABA ⁇ R2 polypeptides may be identified by using GABA ⁇ R2 polypeptides in co- immunoprecipitation experiments.
  • This invention provides a process for making a composition of matter which specifically binds to a GABA ⁇ Rl/R2 receptor which comprises identifying a chemical compound using any of the processes descirbed herein for identifying a compound which binds to and/or activates or inhibits activation of a GABA ⁇ Rl/R2 receptor and then synthesizing the chemical compound or a novel structural and functional analog or homolog thereof .
  • the GABA ⁇ Rl/R2 receptor is a human GABA g Rl/R2 receptor.
  • This invention further provides a process for preparing a pharmaceutical composition which comprises admixing a pharmaceutically acceptable carrier and a pharmaceutically acceptable amount of a chemical compound identified by any of the processes described herein for identifying a compound which binds to and/or activates or inhibits activation of a GABA ⁇ Rl/R2 receptor or a novel structural and functional analog or homolog thereof.
  • the GABA ⁇ Rl/R2 receptor is a human GABA ⁇ Rl/R2 receptor.
  • the gene for a targeted receptor subtype is cloned, it is placed into a recipient cell which then expressses the targeted receptor subtype on its surface.
  • This cell which expresses a single population of the targeted human receptor subtype, is then propagated resulting in the establishment of a cell line.
  • This cell line which constitutes a drug discovery system, is used in two different types of assays: binding assays and functional assays. In binding assays, the affinity of a compound for both the receptor subtype that is the target of a particular drug discovery program and other receptor subtypes that could be associated with side effects are measured.
  • the data obtained from binding assays also enable chemists to design compounds toward or away from one or more of the relevant subtypes, as appropriate, for optimal therapeutic efficacy.
  • functional assays the nature of the response of the receptor subtype to the compound is determined. Data from the functional assays show whether the compound is acting to inhibit or enhance the activity of the receptor subtype, thus enabling pharmacologists to evaluate compounds rapidly at their ultimate human receptor subtypes targets permitting chemists to rationally design drugs that will be more effective and have fewer or substantially less severe side effects than existing drugs.
  • Combinatorial chemistry involves automated synthesis of a variety of novel compounds by assembling them using different combinations of chemical building blocks.
  • the use of combinatorial chemistry greatly accelerates the process of generating compounds.
  • the resulting arrays of compounds are called libraries and are used to screen for compounds (lead compounds) that demonstrate a sufficient level of activity at receptors of interest.
  • Using combinatorial chemistry it is possible to synthesize focused libraries of compounds anticiapted to be highly biased toward the receptor target of interest .
  • DNA sequences were determined using an ABI PRISM 377 DNA Sequencer (Perkin-Elmer, Foster City, CA) according to the manufacturer's instructions.
  • nucleotide sequences of the hybridization probes are shown below:
  • T-891 5'-AGGGATGCTTTCCTATGCTTCCATATTTCTCTTTGGCCTTGATGG-3' (SEQ ID NO: 5) Nucleotides 1449-1493 of TL-267, forward strand.
  • T--892 5'-CAATGTGCAGTTCTGCATCGTGGCTCTGGTCATCATCTTCTGCAG-3' (SEQ ID NO: 6) Nucleotides 2022-2066 of TL-267, forward strand.
  • PCR Methodology PCR reactions were carried out using a PE 9600 (Perkin- Elmer) PCR cycler in 20 ⁇ L volumes using Expand Long Template Polymerase (Boehringer-Mannheim) and the manufacturer's buffer 1 for internal PCR primers or manufacturer's buffer 2 for vector-anchored PCR. Reactions were run using a program consisting of 35 cycles of 94 °C for 30 sec, 68°C for 20 sec, and 72°C for 1 min, with a pre-incubation at 95°C for 5 min and post-incubation hold at 4°C.
  • T-94 5'-CTTCTAGGCCTGTACGGAAGTGTT-3' (SEQ ID NO : 7); vector, forward primer.
  • T-95 5'-GTTGTGGTTTGTCCAAACTCATCAAT-3' (Seq. ID No . 8); vector, reverse primer.
  • T-887 5'-GGGATGAGTGTCTACAACGTGGGG-3' (SEQ ID NO : 9) ; nucleotides 1948-1971 of TL-267, forward primer.
  • T-888 5'-TGCGTTGCTGCATCTGGGTTTGTTCT-3' (SEQ ID NO : 10); nucleotides 2138-2113 of TL-267, reverse primer.
  • T-889 5'-ATCTCCCTACCTCTCTACAGCATCCT-3' (SEQ ID NO : 11); nucleotides 1300-1325 of TL-267, forward primer.
  • T-890 5'-CAGGTCCTGACGGTGCAAAGTGTTTC-3' (SEQ ID NO: 12); nucleotides 1544-1519 of TL-267, reverse primer.
  • T-921 5'-TGACGCAAGACGTTCAGAGGTTCTCT-3' (SEQ ID NO: 13); nucleotides 473-498 of TL-267, forward primer.
  • T-922 5'-TGTAGCCTTCCATGGCAGCAAGCAGA-3' (SEQ ID NO : 14); nucleotides 814-789 of TL-267, reverse primer.
  • T-923 5'-AGAGAACCTCTGAACGTCTTGCGTCA-3' (SEQ ID NO : 15); nucleotides 498-473 of TL-267, reverse primer.
  • T-935 5'-GGCTCTGTTGTGTTCCACTGTAGCTG-3' (SEQ ID NO: 16); nucleotides 2483-2458 of TL-267, reverse primer.
  • T-938 5'-TCATGCCGCTCACCAAGGAGGTGGCC-3' (SEQ ID NO: 17); nucleotides 53 to 78 of TL-267, forward primer.
  • T-939 5'-GGCCACCTCCTTGGTGAGCGGCATGA-3' (SEQ ID NO: 18); nucleotides 78 to 53 of TL-267, reverse primer.
  • T-947 5'-TGAGTGAGCAGAGTCCAGAGCCGT-3' (SEQ ID NO : 19); nucleotides -68 to -45 of TL-267, forward primer.
  • T-948 5'-ATGGATGGGAGGTAGGCGTGGTGGAG-3' (SEQ ID NO: 20); nucleotides 2591-2566 of TL-267, reverse primer.
  • RNA was prepared by a modification of the guanidine thiocyanate method, from 6 grams of human hippocampus.
  • Poly A + RNA was purified with a FastTrack kit (Invitrogen Corp. , San Diego, CA) .
  • Double stranded (ds) cDNA was synthesized from 4 ⁇ g of poly A + RNA according to G ⁇ bler and Hoffman (1983) , except that ligase was omitted in the second strand cDNA synthesis.
  • the resulting DS cDNA was ligated to BstxI/EcoRI adaptors (Invitrogen Corp.), the excess of adaptors was removed by exclusion chromatography.
  • High molecular weight fractions were ligated in pcEXV.BS (An Okayama and Berg expression vector) cut by Bstxl as described by Aruffo and Seed (1987) .
  • the ligated DNA was electroporated in E. coli MC 1061 (Gene Pulser, Biorad). A total of 2.2 x 10 6 independent clones with an insert mean size of approximately 3 kb was generated.
  • the library was plated on Petri dishes (Ampicillin selection) in pools of 0.4 to 1.2 x 10 4 independent clones.
  • T07621 and Z43654 Two entries, T07621 and Z43654, had probability scores that suggested significant amino acid homology to the GABA ⁇ Rla polypeptide.
  • T07621 had sequence homology from the beginning of the first transmembrane domain to the beginning of third transmembrane domain of the GABA g Rla polypeptide.
  • Z43654 had sequence homology from the sixth transmembrane domain to the seventh transmembrane domain of the GABA ⁇ Rla polypeptide.
  • the sequence documentation for T07621 and Z43654 was retrieved with Entrez (NCBI) and neither sequence was annotated as having homology to any 7-TM spanning protein.
  • T07621 and Z43654 are part of the same sequence.
  • a series of PCR reactions were carried out on human hippocampus DNA with multiple primer sets: primer set T-887/T-888 designed to Z43654 sequence; primer set T-889/T-890 designed to the T07621 sequence; and primer set T-889/T-888 designed to the forward strand of T07621 and the reverse stand of Z43654.
  • the PCR products was loaded on duplicate lanes of an agarose gel and the DNA was southern blotted to a Zeta-Probe membrane (Bio-Rad, CA) . The regions of the membrane corresponding to the individual lanes on the gel were cut to produce membrane strips that contained duplicate samples of the DNA.
  • T-891 a probe specific for the T07621 sequence.
  • Another set of membranes was hybridized with T-892, a probe specific to the Z43654 sequence.
  • the membrane from primer set T-887/T-888 hybridized with probe T-892 for the Z43654 sequence.
  • the membrane from primer set T-889/T-890 hybridized with probe T-891 for the T07621 sequence.
  • the membrane from primer set T889/T-888 hybridized with both the T-891 and T-892 probes .
  • T-888/T-889 was used to identify the bacterial pools that contained a portion of the novel receptor.
  • Vector-anchored PCR was carried out on the positive pools to determine which pool contained the longest cDNA insert .
  • Four primer sets were used for the vector-anchored PCR: T-94/T-888, T- 94/T889, T-95/T888, and T-95/T889.
  • Pool 365 was identified having the longest cDNA inset and the plasmid was sib selected (McCormick, 1987) .
  • the nucleotide sequence of clone 365-9-7-4, designated TL-260 was translated into amino acids and compared to the amino acid sequence of the rat GABA g Rla polypeptide. Relative the rat GABA g Rla amino acid sequence, TL-260 was truncated at the amino terminus .
  • a set of PCR primers (T-921/T-922) was made to the 5' region of TL-260 and was used to re-screen the bacterial pools of the human hippocampus library for the missing segment of the novel clone.
  • Vector-anchored PCR was carried out on the positive pools to determine which pool contained the longest cDNA insert.
  • Four primer sets were used for the vector-anchored PCR: T-94/T-921, T-94/T922, T-95/T921, and T-95/T-922. Pool 299 contained the most 5' sequence .
  • a PCR product derived from the primer set T-94/T-923 was isolated (T-261) and sequenced.
  • the putative amino acids derived from TL-261 were compared to the rat GABA-.R1 sequence.
  • TL-261 contained an initiation codon but didn't contain a stop codon upstream of the initiation codon.
  • a set of PCR primers (T-938/T-935) was made to the 5' region of TL-261 and was used to re-screen the bacterial pools of the human hippocampus library for additional sequence.
  • Vector-anchored PCR was carried out on the positive pools to determine which pool contained the longest cDNA insert .
  • Four primer sets were used for the vector-anchored PCR: T-94/T-938, T-94/T939, T-95/T938, and T-95/T-939.
  • a PCR product derived from primer set T-95/T- 939 was isolated (T-261a) and sequenced. The putative amino acids derived from T-261a were compared to the rat GABA-1 amino acid sequence.
  • T-261a contained an initiation codon and an in-frame upstream stop codon.
  • pool 389 contained the longest cDNA insert. This pool was sib selected with the primer set T-947/T-935. The resulting plasmid, 389-20- 29-2, was designated TL-266 and was sequenced.
  • GABA-.R2 polypeptide in expression vector A Cla-I-Xba-I fragment from TL-266 was subcloned into the expression vector pEXJ.HRT3T7 and designated TL-267.
  • This plasmid (TL-267) was deposited on June 10, 1997, with the American Type Culture Collection (ATCC) , 12301 Parklawn Drive, Rockville, Maryland 20852, U.S.A. under the provisions of the Budapest Treaty for the International Recognition of the Deposit of Microorganisms for the Purposes of Patent Procedure and was accorded ATCC Accession No. 209103.
  • PCR product cDNA from rat hippocampus and rat cerebellum were amplified in 50 ⁇ L PCR reaction mixtures using the Expand Long Template PCR System (as supplied and described by the manufacturer, Boehringer Mannheim) using a program consisting of 40 cycles of 94°C for 1 min, 50°C for 2 min, and 68 °C for 2 min, with a pre- and post-incubation of 95 °C for 5 min and 68 °C for 7 min, respectively.
  • PCR primers for rat GABA ⁇ R2 were designed against the human GABA g R2 sequence: BB 257, forward primer in the first transmembrane domain, and BB 258, reverse primer in the seventh transmembrane domain.
  • the single 780 bp fragment from both rat hippocampus and rat cerebellum were isolated from a 1% agarose gel, purified using a GENECLEAN III kit (BIO 101, Vista, CA) and sequenced using AmpliTaq DNA Polymerase, FS (Perkin Elmer) .
  • the sequence was run on an ABI PRISM 377 DNA Sequencer and analyzed using the Wisconsin Package (GCG, Genetics Computer Group, Madison, WI) . This sequence was used to design PCR primers for the rat GABA ⁇ R2 gene.
  • RNA was purified from rat hypothalamic RNA (Clontech) using a FastTrack kit (Invitrogen, Corp.).
  • DS- cDNA was synthesized from 5 ⁇ g of poly A+ RNA according to Gubler and Hoffman (1983) with minor modifications.
  • the resulting cDNA was ligated to BstXI adaptors (Invitrogen, Corp.) And the excess adapters removed by exclusion column chromatography.
  • the conditions for PCR were 1 min at 94°C, 4 min at 68°C for 40 cycles, with a pre- and post -incubation of 5 min at 95°C and 7 min at 68°C, respectively.
  • positive pools were screened by PCR using the vector primers BB172 or BB173, and a gene-specific primer BB265 or BB266.
  • One positive primary pool, 1-47 was subdivided into 24 pools of 1000 clones, and grown in LB medium overnight. Two ⁇ L of cultures were screened by PCR using primers BB172 and BB266. One positive subpool , 1-47-4 was subdivided into 10 pools of 200 clones and plated on agar plates (ampicillin selection) . Colonies were transferred to nitrocellulose membranes (Schleicher and Schuell, Keene, NH) , denatured in 0.4 N NaOH, 1.5 M NaCl, renatured in 1M Tris, 1.5 M NaCl, and UV cross-linked.
  • Filters were hybridized overnight at 40 °C in a buffer containing 50 % formamide, 0.12 M Na 2 HP0 4 (pH7.2), 0.25M NaCl, 7%SDS, 25 mg/L ssDNA and 10 6 cpm/mL of a cDNA probe corresponding to transmembrane domains 1 to 7 of rat GABA ⁇ R2 , labeled with [ 32 P] dCTP (3000Ci/mmol, NEN) using a random prime labeling kit (Boehringer Mannheim) . Filters were washed lx 5 min then 2x 20 min at room temperature in 2x SSC, 0.1%SDS then 3x 20 min at 50° in 0.
  • Transformants were screened by PCR using the primers BB56 and BB268 under the following conditions: 30 sec at 94°C, 2.5 min at 68°C for 32 cycles, with a pre- and post-incubation of 5 min at 95°C and 3 min at 68°C respectively.
  • One transformant in the correct orientation was amplified overnight in 100 ml TB media and processed for plasmid purification using a standard alkaline lysis miniprep procedure followed by a PEG precipitation.
  • This plasmid was designated B055 and sequenced using AmpliTaq DNA Polymerase, FS (Perkin Elmer) .
  • Plasmid BO-55 was deposited with the ATCC on June 10, 1997, and was accorded ATCC Accession No. 209104. The sequence of BO-55 was determined using an ABI PRISM 377 DNA Sequencer and analyzed using the Wisconsin Package (GCG, Genetics Computer Group, Madison, WI) .
  • the gene encoding the rat GABA ⁇ Rlb polypeptide was obtained by screening the same rat hypothalamic library used for
  • GABA ⁇ R2 with primers based on the original publication of the clone by Kaupmann, et al . , 1997.
  • a partial clone lacking the first 55 nucleotides was identified and ligated to a PCR fragment containing the missing base pairs to obtain the full length clone.
  • a restriction fragment containing the entire coding region of GABA ⁇ Rlb was subcloned into the mammalian expression vector pEXJ.T7 and designated "B058".
  • a rat GABA ⁇ la polypeptide clone was obtained by ligating a restriction fragment of the GABA ⁇ lb clone, which contained the common region of the GABA ⁇ l gene, to a PCR product containing the GABA ⁇ la-specific 5' end.
  • tissue Prior to hybridization, the tissues were fixed in 4% paraformaldehyde/PBS pH 7.4 followed by two washes in PBS (Specialty Media, Lavallette, NJ) . Tissues were then treated in 5 mM dithiothreitol , rinsed in DEPC-treated
  • Oligonucleotide probes MJ79/80, corresponding to nucleotides 354-398 and MJ109/110, corresponding to nucleotides 952-991 of the rat GABA ⁇ R2 cDNA, MJ94/95, corresponding to nucleotides 151-193 of the human GABA ⁇ Rla cDNA, and MJ83/84, corresponding to nucleotides 34-71 of the rat GABA ⁇ Rlb cDNA were used to characterize the distribution of each polypeptides's respective mRNA.
  • the oligonucleotides were synthesized using an Expedite
  • oligonucleotides are: For rat GABA ⁇ R2 Sense probe, MJ79:
  • Probes were 3'-end labeled with t 35 S] dATP (1200Ci/mmol , NEN, Boston, MA) to a specific activity of 10 9 dpm/ ⁇ g using terminal deoxynucleotidyl transferase (Pharmacia, Piscataway, NJ) . In situ hybridization was done with modification of the method described by Durkin, M, et al , 1995 ⁇ .
  • the labeling reaction was carried out as outlined in the DIG/Genius System, (Boehringer Mannheim, Indianapolis, IN) . Conditions used in ISHH with digoxigenin-labeled probes are the same as described above.
  • the sections were rinsed in buffer 1, washing buffer (0.1 M Tris-HCl pH 7.5/0.15 M NaCl), pre-incubated in Blocking Solution (Buffer 1 , 0.1% Triton-X and 2% normal sheep serum) for 30 minutes and then incubated for 2 hours in Blocking Solution containing anti-digoxigenin- AP Fab fragment (Boehringer Mannheim) at 1:500 dilution followed by two 10 minute washes in Buffer 1.
  • washing buffer 0.1 M Tris-HCl pH 7.5/0.15 M NaCl
  • Blocking Solution Buffer 1 , 0.1% Triton-X and 2% normal sheep serum
  • Detection Buffer 0.1M Tris-HCl pH 9.5/0.15M NaCl/0.05 M MgCl 2
  • Detection Buffer containing 0.5 mM NBT, 0.1 mM BCIP, and 1 mM levamisole.
  • slides were dipped in dH 2 0 and coverslipped using aqua mount.
  • Probe specificity was established by performing in situ hybridization on HEK293 cells transiently transfected with eukaryotic expression vectors containing the rat GABA ⁇ Rlb and human GABA ⁇ Rla DNA or no insert for transfection. Furthermore, two pairs of hybridization probes, sense and antisense, that were targeted to different segments of the GABA ⁇ R2 mRNA were used for cells and rat tissues.
  • the strength of the hybridization signal obtained in various region of the rat brain was graded as weak (+) , moderate (++) , heavy (+++) or intense (++++) . These were qualitative evaluations for each of the polypeptide mRNA distributions based on the relative optical density on the autoradiographic film and on the relative number of silver grains observed over individual cells at the microscopic level .
  • COS- 7 cells are grown on 150 mm plates in DMEM with supplements (Dulbecco's Modified Eagle Medium with 10% bovine calf serum, 4 mM glutamine, 100 units/mL penicillin/100 ⁇ g/mL streptomycin) at 37°C, 5% C0 2 . Stock plates of COS-7 cells are trypsinized and split 1:6 every 3-4 days.
  • supplements Dulbecco's Modified Eagle Medium with 10% bovine calf serum, 4 mM glutamine, 100 units/mL penicillin/100 ⁇ g/mL streptomycin
  • Human embryonic kidney 293 cells are grown on 150 mm plates in DMEM with supplements (10% bovine calf serum, 4 mM glutamine, 100 units/mL penicillin/lOO ⁇ g/mL streptomycin) at 37°C, 5% C0 2 . Stock plates of 293 cells are trypsinized and split 1:6 every 3-4 days.
  • Mouse fibroblast LM(tk-) cells are grown on 150 mm plates in D-MEM with supplements (Dulbecco's Modified Eagle Medium with 10% bovine calf serum, 4 mM glutamine, 100 units/mL penicillin/100 ⁇ g/mL streptomycin) at 37°C, 5% C0 2 .
  • Stock plates of LM(tk-) cells are trypsinized and split 1:10 every 3-4 days.
  • CHO cells Chinese hamster ovary (CHO) cells are grown on 150 mm plates in HAM's F-12 medium with supplements (10% bovine calf serum, 4 mM L-glutamine and 100 units/mL penicillin/100 ug/mL streptomycin) at 37°C, 5% C02. Stock plates of CHO cells are trypsinized and split 1:8 every 3- 4 days .
  • Mouse embryonic fibroblast NIH-3T3 cells are grown on 150 mm plates in Dulbecco's Modified Eagle Medium (DMEM) with supplements (10% bovine calf serum, 4 mM glutamine, 100 units/mL penicillin/100 ⁇ g/mL streptomycin) at 37°C, 5% C02. Stock plates of NIH-3T3 cells are trypsinized and split 1:15 every 3-4 days.
  • DMEM Dulbecco's Modified Eagle Medium
  • Sf9 and Sf21 cells are grown in monolayers on 150 mm tissue culture dishes in TMN-FH media supplemented with 10% fetal calf serum, at 27°C, no C0 2 .
  • High Five insect cells are grown on 150 mm tissue culture dishes in Ex-Cell 400TM medium supplemented with L-Glutamine, also at 27°C, no C0 2 .
  • LM(tk-) cells stably transfected with the DNA encoding the polypeptides disclosed herein may be routinely converted from an adherent monolayer to a viable suspension.
  • Adherent cells are harvested with trypsin at the point of confluence, resuspended in a minimal volume of complete DMEM for a cell count, and further diluted to a concentration of 10 6 cells/mL in suspension media (10% bovine calf serum, 10% 10X Medium 199 (Gibco) , 9 mM NaHC0 3 , 25 mM glucose, 2 mM L-glutamine, 100 units/mL penicillin/100 ⁇ g/mL streptomycin, and 0.05% methyl cellulose) . Cell suspensions are maintained in a shaking incubator at 37°C, 5% C0 2 for 24 hours. Membranes harvested from cells grown in this manner may be stored as large, uniform batches in liquid nitrogen.
  • cells may be returned to adherent cell culture in complete DMEM by distribution into 96-well microtiter plates coated with poly-D-lysine (0.01 mg/mL) followed by incubation at 37°C, 5% C0 2 for 24 hours.
  • the coding region of DNA encoding the polypeptides disclosed herein may be subcloned into pBlueBacIII into existing restriction sites, or sites engineered into sequences 5' and 3' to the coding region of the polypeptides.
  • 0.5 ⁇ g of viral DNA (BaculoGold) and 3 ⁇ g of DNA construct encoding a polypeptide may be co-transfected into 2 x 10° Spodoptera frugiperda insect Sf9 cells by the calcium phosphate co- precipitation method, as outlined in by Pharmingen (in "Baculovirus Expression Vector System: Procedures and
  • the supernatant of the co-transfection plate may be collected by centrifugation and the recombinant virus plaque purified.
  • the procedure to infect cells with virus, to prepare stocks of virus and to titer the virus stocks are as described in Pharmingen's manual .
  • DNA encoding the polypeptides disclosed herein may be co- transfected with a G-418 resistant gene into the human embryonic kidney 293 cell line by a calcium phosphate transfection method (Cullen, 1987) . Stably transfected cells are selected with G-418.
  • Transfected cells from culture flasks were scraped into 5 mL of Tris-HCl, 5mM EDTA, pH 7.5, and lysed by sonication.
  • the cell lysates were centrifuged at 1000 rpm for 5 min. at 4°C, and the supernatant was centrifuged at 30,000 x g for 20 min. at 4°C.
  • the pellet was suspended in binding buffer (50 mM Tris-HCl, 2.5 mM CaCl 2 at pH 7.5 supplemented with 0.1% BSA, 2 ⁇ g/mL aprotinin, 0.5mg/mL leupeptin, and lO ⁇ g/mL phosphoramidon) .
  • Optimal membrane suspension dilutions defined as the protein concentration required to bind less than 10% of the added labeled compound (typically a radiolabeled compound) , were added to 96-well polypropylene microtiter plates containing labeled compound, unlabeled compounds (i.e., displacing ligand in an equilibrium competition binding assay) and binding buffer to a final volume of 250 ⁇ L.
  • labeled compound typically a radiolabeled compound
  • the binding affinities of the different compounds were determined in equilibrium competition binding assays, using labeled compound, such as 1 nM [ 3 H] - CGP54626, in the presence of ten to twelve different concentrations of the displacing ligand (s).
  • labeled compound such as 1 nM [ 3 H] - CGP54626, in the presence of ten to twelve different concentrations of the displacing ligand (s).
  • Some examples of displacing ligands included GABA, baclofen, 3APMPA, phaclofen, CGP54626, and CGP55845.
  • Mixtures of several unlabeled test compounds may also be used in competition binding assays, to determine whether one of the mixture component compounds binds to the polypeptide or receptor.
  • Binding reaction mixtures were incubated for 1 hr at 30°C, and the reaction was stopped by filtration through GF/B filters treated with 0.5% polyethyleneimine, using a cell harvester.
  • the labeled compound was a radiolabeled compound
  • the amount of bound compound was evaluated by gamma counting (for 1 5 I) or scintillation counting (for 3 H) .
  • Data were analyzed by a computerized non-linear regression program. Non-specific binding was defined as the amount of radioactivity remaining after incubation of membrane protein in the presence of excess unlabeled compound. Protein concentration may be measured by the Bradford method using Bio-Rad Reagent, with bovine serum albumin as a standard.
  • Cyclic AMP (cAMP) formation assay The receptor-mediated inhibition of cyclic AMP (cAMP) formation may be assayed in transfected cells expressing the mammalian receptors described herein.
  • Cells are plated in 96-well plates and incubated in Dulbecco's phosphate buffered saline (PBS) supplemented with 10 mM HEPES, 5mM theophylline, 2 ⁇ g/ml aprotinin, 0.5 mg/ml leupeptin, and 10 ⁇ g/ml phosphoramidon for 20 min at 37 "C, in 5% C0 2 .
  • Test compounds are added and incubated for an additional 10 min at 37 * C.
  • the medium is then aspirated and the reaction stopped by the addition of 100 mM HCl.
  • the plates are stored at 4'C for 15 min, and the cAMP content in the stopping solution measured by radioimmunoassay . Radioactivity may be quantified using a gamma counter equipped with data reduction software.
  • Chimeric G-proteins were constructed using standard mutagenesis methods (Conklin et al . , 1993). Two chimeras were constructed. The first comprises the entire coding region of human Ga with the exception of the final 3' 15 nucleotides which encode the C-terminal 5 amino acids of G ⁇ ---. The second also comprises the entire coding region of human Go; with the exception of the final 3' 15 nucleotides which encode the C-terminal 5 amino acids of G ⁇ z . Sequences of both chimeric G-protein genes were verified by nucleotide sequencing. For the purposes of expression in oocytes, synthetic mRNA transcripts of each gene were synthesized using the T7 polymerase.
  • Phosphoinositide Assay The agonist activities of GABA-B agonists were assayed by measuring their ability to generate phosphoinositide production in COS-7 cells transfected transiently with GABA B R1, GABA ⁇ R2, and chimeric G ⁇ Alternatively, COS-7 cells are transfected transiently with GABA g Rl , GABA ⁇ R2 , and other chimeric G-protein alpha subunits such as Got /i2 , Go; /i3 , or G ⁇ /0 . Cells were plated in 96-well plates and grown to confluence.
  • the growth medium was changed to 100 ⁇ l of medium containing 1% serum and 0.5 ⁇ Ci l "3 Hl myo-inositol, and the plates were incubated overnight in a C0 2 incubator (5% C0 2 at 37°C) .
  • the medium was removed and replaced by 200 ⁇ l of PBS containing 10 mM LiCl, and the cells were equilibrated with the new medium for 20 min.
  • IP inositol -phosphate
  • the contents of the wells were then transferred to a Multiscreen HV filter plate (Millipore) containing Dowex AG1-X8 (200-400 mesh, formate form) .
  • the filter plates were prepared adding 100 ⁇ l of Dowex AG1-X8 suspension
  • Oocyte expression Female Xenopus laevis (Xenopus-1, Ann Arbor, MI) are anesthetized in 0.2% tricain (3-aminobenzoic acid ethyl ester, Sigma Chemical Corp.) and a portion of ovary is removed using aseptic technique (Quick and Lester, 1994) .
  • Oocytes are defolliculated using 3 mg/ml collagenase (Worthington Biochemical Corp., Freehold, NJ) in a solution containing 87.5 mM NaCl, 2 mM KCl, 2 mM MgCl 2 and 5 mM HEPES, pH 7.5.
  • Oocytes are injected (Nanoject, Drummond Scientific, Broomall, PA) with 50-70 nl mRNA prepared as described below. After injection of mRNA, oocytes are incubated at 17 degrees for 3-8 days.
  • RNAs are prepared by transcription from: (1) , linearized DNA plasmids containing the complete coding region of the gene, or (2), templates generated by PCR incorporating a
  • T7 promoter and a poly A + tail. From either source, DNA is transcribed into mRNA using the T7 polymerase ("Message Machine", Ambion) .
  • the transcription template for the rat GABA ⁇ Rlb gene was prepared by PCR amplification of the plasmid B058 using the primers MJ23 and MJ47 (see below) .
  • the template for the rat GABA ⁇ R2 gene was made by linearization of the plasmid B056, rat GABA ⁇ R2 insert from B055 in the expression vector pEXJ.T7, with NotI.
  • GIRK1 and GIRK4 G-protein inwardly rectifying K + channels 1 and 4
  • GIRKs G-protein inwardly rectifying K + channels 1 and 4
  • Dual electrode voltage clamp (“GeneClamp”, Axon Instruments Inc., Foster City, CA) is performed using 3 M KCl-filled glass microelectrodes having resistances of 1-3 Mohms .
  • oocytes are voltage clamped at a holding potential of -80 mV.
  • oocytes are bathed in continuously flowing (1-3 ml/min) medium containing 96 mM NaCl, 2 mM KCl, 1.8 mM CaCl 2 , 1 mM MgCl 2 , and 5 mM HEPES, pH 7.5 (ND96), or elevated K + containing 49 M KCl, 49 mM NaCl, 1.8 mM CaCl 2 , 2 mM MgCl 2 , and 5 mM HEPES, pH 7.5 (hK) .
  • Drugs are applied either by local perfusion from a 10 ⁇ l glass capillary tube fixed at a distance of 0.5 mm from the oocyte, or for calculation of steady-state EC 50 s, by switching from a series of gravity fed perfusion lines. Experiments are carried out at room temperature. All values are expressed as mean +/- standard error of the mean.
  • HEK-293 cells were maintained in Dulbecco's modified Eagle medium (DMEM) plus 10% (v/v) bovine calf serum, 2% L-glutamine, 50 U/ml penicillin, and 50 ⁇ g/ml streptomycin and were incubated at 37° C in a humidified 5% C0 2 atmosphere.
  • DMEM Dulbecco's modified Eagle medium
  • Cells were harvested twice each week by treatment with 0.25% trypsin/1 mM EDTA in Hank's Salts and re-seeded at 20% of their original density either into 75 cm 2 flasks (for passaging) or into 35 mm tissue culture dishes (for transfection and electrophysiology experiments) .
  • HEK-293 cells 40% - 80% confluent, were co-transfected with various combinations of 0.6 ug each of the following plasmids: pGreen Lantern-1 (Gibco/BRL, Gaithersburg, MD) , human GIRK1 (JS1800) , human GIRK4 (JS1741) , rat GABA D Rlb (B058) , and rat GABA ⁇ R2 (B055) .
  • Cells were transiently transfected using the Superfect Transfection Reagent from Qiagen (Valencia, CA) according to the manufacturer's instructions.
  • GIRK currents were recorded in elevated K + solution containing 25 iTiM K + and a correspondingly lower concentration of Na + .
  • Voltage clamp recordings were made with an EPC-9 amplifier using Pulse+PulseFit software (HEKA Elektronik) . Series resistances were kept below 10 Mohm and no attempt was made to provide series resistance compensation. Currents were low-pass filtered at 1 kHz and digitized at a rate of 5 kHz. Unless otherwise noted, experiments were performed at room temperature on cells voltage clamped at a holding potential of -70 mV.
  • Application of agonists was realized using a gravity- fed, perfusion system consisting of six concentrically arranged microcapillary tubes (Jones et al . 1997) . The time to complete solution exchange was about 100 ms . The bath was constantly perfused at a low rate with control solution.
  • GABA g Rl, GABA ⁇ R2 or the combination were transiently expressed in CHO-K1 cells by liposome mediated transfection according to the manufacturer's recommendations ( "LipofectAMINE” , GibcoBRL, Bethesda, MD) , and maintained in Ham's F-12 medium with 10% bovine serum. Cells were prepared for microphysiometric recording as previously described (Salon, J. A., et al . , 1995). On the day of the experiment the cell capsules were transferred to the microphysiometer and allowed to equilibrate in recording media (low buffer RPMI 1640, no bicarbonate, no serum, Molecular Devices Corp.), during which a baseline was established.
  • recording media low buffer RPMI 1640, no bicarbonate, no serum, Molecular Devices Corp.
  • the recording paradigm consisted of a 100 ml/min flow rate and a 30 s flow interruption during which the rate measurement was taken. Challenges involved an 80 s drug exposure just prior to the first post -challenge rate measurement being taken, followed by two additional pump cycles. Acidification rates reported are expressed as a percentage increase of the peak response over the baseline rate observed just prior to challenge.
  • N-terminal deletion experiments were performed on the GABA ⁇ R2-HA construct (see below) . All such deletion mutants caused a complete disruption of receptor activity as assessed by the measurement of GIRK currents in transfected HEK293 cells.
  • wildtype GABA ⁇ R2-HA was digested with Bglll restriction enzyme and religated.
  • the Bglll deletion mutant (M118) lacks 257 amino acids at the N-terminus, corresponding to positions 226-482.
  • M118 was found to be expressed on the cell surface, similarly to the wildtype GABA ⁇ R2-HA, yet when co-expressed with GABA ⁇ Rl did not produce GIRK activation with 100 ⁇ M GABA.
  • the N- terminal region comprising amino acids 226-482 is critically important either for dimer formation, ligand binding or conformational changes associated with signal transduction.
  • Mouse monoclonal anti-RGS (Qiagen) and mouse anti-FLAG (Boehringer-Mannheim) were labeled with FITC-conjugated goat anti-mouse antibodies.
  • Rat monoclonal anti -HA (Boehringer-Mannheim) was visualized with TRITC-conjugated rabbit anti-irat antibodies. Fluorescent images were obtained with a Zeiss LSM 410 confocal microscope using a lOOx oil-immersion objective .
  • HEK293 cells Forty-eight hours following transient transfection HEK293 cells were solubilized in lysis buffer containing (in mM) : 50 Tris/Cl pH 7.4, 300 NaCl, 1.5 MgCl 2 , 1 CaCl 2 , protease inhibitors (Boehringer Mannheim tablets), 1% Triton X-100, and 10% glycerol. 1-2 mg of protein was immunoprecipitated overnight at 4° C with either 0.5 ⁇ g rat monoclonal anti-HA antibody or 0.5 ⁇ g mouse monoclonal anti-4xHis antibody (Qiagen) . Immune complexes were bound to 20 ⁇ l Protein-A agarose (Research Diagnostics, Inc.) for 2 h at RT.
  • Protein-A pellets were washed twice with buffer containing Triton-X-100, then once without, and eluted with 80 ⁇ l Laemmli sample buffer containing 2% (w/v) SDS and 20 mM DTT. After heating for 3 min. at 70° C, 20 ⁇ l IP samples or 20 ⁇ g total protein was subjected to SDS-PAGE followed by Western blotting with either anti-HA or anti-4xHis antibody, followed by sheep anti-rat (Amersham) or goat anti -mouse (RDI) HRP-linked secondary antibodies, respectively. Proteins were visualized with enhanced chemiluminescent substrates (Pierce) .
  • material for immunoprecipitations was obtained by sucrose gradient fractionation of the PI pellet as described by Graham (Graham, 1984) .
  • Na + /K + ATPase in the P1+ and P2 (primarily microsomal and vesicular (Graham, 1984)) fractions was quantified by fluorescence detection of anti-alpha 1 subunit antibody (Research Diagnostics, Inc., clone 9A-5) on a phosphor imager (Molecular Dynamics) .
  • ATPase in P1+ fractions used for immunoprecipitations was found to be enriched >50 fold compared to P2 fractions.
  • the rat GABA ⁇ Rla amino acid sequence (Kaupmann et al . (1997) Nature 386:239) was used as a query to search the EST division of GenBank with BLAST.
  • Two entries, T07621 and Z43654 had probability scores that suggested significant amino acid homology to the GABA ⁇ Rla polypeptide.
  • T07621 had sequence homology from the beginning of the first transmembrane domain to the beginning of third transmembrane domain of the GABA ⁇ Rla polypeptide.
  • Z43654 had sequence homology from the sixth transmembrane domain to the seventh transmembrane domain of the GABA ⁇ Rla polypeptide.
  • the sequence documentation for T07621 and Z43654 was retrieved with Entrez (NCBI) and neither sequence was annotated as having homology to any 7-TM spanning protein.
  • the longest open reading frame encodes an 898 amino acid protein with 38% amino acid identity to the rat GABA ⁇ Rla polypeptide.
  • Hydropathy plots of the predicted amino acid sequence reveal seven hydrophobic regions that may represent transmembrane domains (TMs, data not shown) , typical of the G protein-coupled receptor superfamily.
  • TMs transmembrane domains
  • GABA ⁇ R2 exhibits 45% amino acid identity with the rat GABA g Rla polypeptide.
  • the amino terminus of TL-266 has amino acid homology to the bacterial periplasmic binding protein, a common feature of the metabotropic receptors (O'Hara et al . (1993) Neuron 11:41-52) .
  • rat GABA ⁇ R2 clone pools of a rat hypothalamic cDNA library were screened by PCR using primers BB265 and BB266. A 440 base pair fragment was amplified from 44 out of 47 pools.
  • Vector-anchored PCR was performed to identify pools with the largest insert size.
  • One positive primary pool, 1-47 was subdivided into 24 pools of 1000 individual clones and screened by vector-anchored PCR. Seven positive subpools were identified and one, 1-47-4, was subdivided into 10 pools of 200 clones, plated onto agar plates, and screened by southern analysis. Four closely clustering colonies that appeared positive were rescreened individually by vector- anchored PCR.
  • B054 One positive colony, 1-47-4-2, designated B054, was amplified as a single rat GABA ⁇ R2 clone. Since vector-anchored PCR revealed that B054 was in the wrong orientation for expression, the insert was isolated by restriction digest and subcloned into the expression vector pEXJ. A transformant in the correct orientation was identified by vector-anchored PCR, and designated BO- 55 .
  • BO-55 contains a 2.82 kB open reading frame and encodes a polypeptide of 940 amino acids.
  • the nucleotide sequence of BO-55 is 89% identical to TL-267 in the coding region, with an overall amino acid identity of 98%.
  • the proposed signal peptide cleavage site is between amino acids 40 and 41 (Nielsen et al . , 1997).
  • GABA ⁇ R2 contains a large N-terminal extracellular domain having regions of homology to bacterial periplasmic binding proteins .
  • the specificity of the hybridization of the GABA ⁇ R2 probe was verified by performing in situ hybridization on transiently transfected HEK293 cells as described in Methods. The results indicate that hybridization to each of the individual GABA ⁇ polypeptides was specific only to the HEK293 cells transfected with each respective cDNA.
  • in situ hybridization on rat brain sections was performed using two hybridization probes targeted to different segments of the GABA ⁇ R2 mRNA. In each case the pattern and intensity of labeling was identical in all regions of the rat CNS . Nonspecific hybridization signal was determined using the sense probes and was indistinguishable from background.
  • GABA ⁇ R2 mRNA in the rat brain was determined by in situ hybridization. By light microscopy the silver grains were determined to be distributed over neuronal profiles. The results suggest that the mRNA for GABA ⁇ R2 is widely distributed throughout the rat CNS in addition to several sensory ganglia ( Figures 19H-I) . However, expression levels in the brain were not uniform with several regions exhibiting higher levels of expression such as the medial habenula, CA3 region of the hippocampus, piriform cortex, and cerebellar
  • Purkinje cells ( Figures 19A-F) . Moderate expression levels were observed in the ventral pallidum, septum, thalamus, CAI region of the hippocampus, and geniculate nuclei ( Figures 19C,D,E) . Lower expression of GABA exert DR2 mRNA was seen in the hypothalamus, mesencephalon, and several brainstem nuclei ( Figures 19D,F). GABAergic neurons and terminals are likewise widely distributed in the CNS (Mugnaini, E., et al . , 1985). and the distribution of the GABA ⁇ R2 mRNA correlates well with the distribution of GABAergic neurons.
  • GABA ⁇ Rlb mRNA did occur in vivo in neurons .
  • colocalization was observed in cells of the medial habenula, hippocampus, and the cerebellar Purkinje cells.
  • the Purkinje cells of the cerebellum contained message for only GABA ⁇ R2 and GABA g Rlb and not the GABA ⁇ Rla. Additionally, all three subtypes appear to be distributed throughout the gray matter of the spinal cord in all levels of the spinal cord.
  • GIRK inwardly rectifying K + channels
  • GABA and baclofen evoked sustained currents of similar magnitude (Fig. 13B) .
  • Others have reported similar results with GABA ⁇ Rl Karl (Kaupmann, K. et al . , 1997a; Kaupmann, K. , et al . , 1997b).
  • Table lb Magnitude of GIRK currents stimulated by GABA in oocytes and HEK-293 cells expressing GIRKl and GIRK4 and various combinations of rat GABA ⁇ Rl and rat GABA ⁇ R2.
  • n 4-6 oocytes.
  • GABA-induced currents were mediated by GIRK channels included: 1) dependency on elevated external K + , 2) strong inward rectification of the current-voltage (I/V) relation, 3) reversal potential (-23.3 mV) close to the predicted equilibrium potential for K + (-23 mV) , and 4) sensitivity to block by 100 ⁇ M Ba ++ ( Figure 8) .
  • GABA ⁇ Rlb and GABA ⁇ R2 are also required for expression of functional GABA ⁇ receptors in mammalian cells.
  • voltage clamp recordings were obtained from HEK-293 cells transiently transfected with various combinations of each gene along with GIRKs.
  • GIRKs we transiently co-transfected CHO cells with GABA ⁇ Rl and GABA ⁇ R2 and measured agonist -evoked extracellular acidification using a microphysiometer .
  • Baclofen stimulated a 9-fold increase in acidification rate (Fig 16) which was blocked by 100 nM CGP55845 and by pretreatment with PTX (not shown) .
  • This response was absent in cells expressing either protein alone. Since GIRK activity is undetectable in wild-type CHO cells (Krapivinsky, G., et al . , 1995b) we conclude that GIRK expression is not a prerequisite for signal generation by
  • Chimeric G-proteins have been used to "switch" the coupling pathway of a GPCR from one that normally inhibits adenylyl cyclase to one that activates phospholipase C (Conklin et al . , 1993) .
  • a Go; /]3 chimera to obtain Ca ++ - induced Cl " responses in oocytes.
  • Oocytes were injected with GABA ⁇ Rl and GABA ⁇ R2 mRNAs as previously described. 2-3 days later oocytes were injected again with 50 pg of G ⁇ .. 3 mRNA and recorded under voltage clamp conditions.
  • GABA g agonists also resulted in concentration-dependent stimulation of phosphoinositide production in COS-7 cells transfected transiently with GABA ⁇ Rl , GABA ⁇ R2 , and the chimeric G-protein Ga /z .
  • GABA B R2 co-associate in a heteromeric complex
  • we performed immunoprecipitations using membrane fractions enriched in plasma membrane as determined by the presence of Na + /K + ATPase (Figure 20A) .
  • GABA ⁇ R2 HA was detected in material immunoprecipitated using antibodies specific for the GABA ⁇ Rl RGS6xH protein ( Figure 2OB) .
  • This result confirms that both GABA ⁇ Rl and GABA ⁇ R2 are correctly targeted to the plasma membrane of HEK293 cells, and that the two proteins exist in a heteromeric complex, perhaps as heterodimers, on the membrane surface.
  • GABA ⁇ R2 (1.09 ⁇ M) and human GABA ⁇ Rl/rat GABA ⁇ R2 (1.08 ⁇ M) .
  • human GABA ⁇ receptor is formed by subunits composed of GABA g Rl and GABA ⁇ R2.
  • the cells were grown under controlled conditions for 24 h, at which time they were re-seeded into poly-D- lysine coated 96 well plates (Biocoat, VWR #62406-036) at a density of 50000 cells/well, and grown for another 24 h.
  • the medium was aspirated and 100 ⁇ l of loading buffer (Hank's buffer containing 20 mM HEPES, 1% FBS, 2.5 mM probenecid, and 4 ⁇ M Fluo-3 AM; F1241 Molecular Probes, Eugene, OR) was added to each well.
  • the cells were then incubated for 1 h at 37°C in an atmosphere of 5% C0 2
  • the cells were then washed 3x with assay buffer (Hank's buffer containing 20 mM HEPES and 2.5 mM probenecid) at room temperature. The cells were left in a final volume of 150 assay buffer.
  • test compounds were added from drug plates in 50 ⁇ l volumes via the FLIPR instrument (Molecular Devices, Sunnyvale, Ca) in a volume of 50 ⁇ l .
  • Receptor-mediated increases in intracellular Ca + concentration were recorded as flourescent units.
  • responses above background were plotted versus agonist concentration to give final concentration effect curves.
  • Concentration-effect curves were analyzed by non- linear regression analysis to derive agonist potencies .
  • the GABA B agonist 3-APMPA evoked concentration dependent increases in intracellular Ca + concentration in COS-7 cells transfected with GABA g Rl, GABA ⁇ R2 , and Got 13 .
  • the potency derived for 3-APMPA in this assay was 6.85 (pEC 50 ) .
  • GABA ⁇ Rl A gene has been cloned that shows 38% overall identity at the amino acid level with the recently cloned GABA ⁇ Rl polypeptide. Important predicted features of the new gene product include 7 transmembrane spanning regions, and a large extracellular N-terminal domain. Like the GABA ⁇ Rl gene product, GABA ⁇ R2 by itself does not promote the activation of cellular effectors such as GIRKs. When co- expressed together, however, the two permit a GABA ⁇ receptor phenotype that is quite similar to that found in the brain.
  • the functional attributes of this reconstituted receptor include: 1) robust stimulation of a physiological effector (GIRKs) , 2) EC 50 s for GABA and baclofen in the same range as for GABA ⁇ receptors previously studied in the CNS, 3) antagonism by the high affinity selective antagonist CGP55845, and 4) inhibition of receptor function by pertussis toxin. These attributes are not observed when either GABA ⁇ Rl or GABA ⁇ R2 is expressed alone.
  • GIRKs physiological effector
  • GABA g Rl and GABA ⁇ R2 associate as subunits to produce a single pharmacologically and functionally defined receptor. Consistent with this view, double labeling in situ hybridization experiments provided evidence that GABA ⁇ Rl and GABA g R2 mRNAs are co-expressed in individual neurons and populations of neurons in several regions of the nervous system including hippocampal pyramidal cells (Fig. 21), cerebellar Purkinje cells (Fig. 12A,B) and sensory neurons in mesencephalic trigeminal nucleus (Fig. 21) and dorsal root ganglia.
  • GABA ⁇ Rl and R2 transcripts predicts that GABA ⁇ receptors on these cells are comprised of GABA ⁇ Rl/R2 heteromers .
  • Other as yet unidentified GABA ⁇ receptor homologues may associate elsewhere to produce novel subtypes.
  • the low level of expression of GABA ⁇ R2 mRNA relative to GABA ⁇ Rl in caudate putamen and hypothalamus raises the possibility that other GABA B receptor homologues may associate with GABA ⁇ Rl to produce novel subtypes in these regions.
  • Conclusive evidence that functional GABA B receptors exist in vivo as multimers will await immunofluorescence studies with specific antibodies.
  • Useful parallels may be drawn from other classes of receptors where heterodimeric structures are well-known.
  • the NMDA (glutamate) receptor is comprised of two principal subunits, neither of which alone permits all of the native features of the receptor (see Wisden and Seeburg, 1993) .
  • GABA ⁇ receptors may be comprised similarly of two (or more) peptide subunits, such as GABA ⁇ Rl and GABA ⁇ R2 , that form a quaternary structure having appropriate binding sites for agonist and G-protein.
  • GABA g R2 A role for GABA g R2 in modulating sensory information is suggested by in situ hybridization histochemistry which revealed the expression of GABA ⁇ R2 mRNA in relay nuclei of several sensory pathways.
  • GABA g R2 appears to be in a position to modulate excitatory glutamatergic projections from the olfactory bulb and retina
  • GABA ⁇ R2 mRNA was observed in the target regions of projection fibers from the main olfactory bulb, including the olfactory tubercle, piriform and entorhinal cortices and from the retina, for instance the superior colliculus ( Figures 19A,B; Table 3) .
  • nociceptive information might be indicated not only by the presence of GABA ⁇ R2 transcripts in somatic sensory neurons of the trigeminal and dorsal root ganglia ( Figures 19H-I) but also by being present in the target regions of nociceptive primary afferent fibers, including the superficial layers of the spinal trigeminal nucleus and dorsal horn of the spinal cord ( Figures 19F- G) .
  • GABA ⁇ R2 has been shown to be in a position to potentially modulate the influence of excitatory glutamatergic nociceptive primary afferents.
  • GABA B R2 may be able to influence various sensory modalities. Expression levels appeared to be higher in the ganglion cells of the dorsal root with light to moderate expression in the trigeminal ganglia.
  • GABA ⁇ R2 mRNA was likewise observed to be expressed in the vestibular nuclei which are target regions of inhibitory GABAergic Purkinje cells and also in the Purkinje cells themselves, suggesting that GABA ⁇ R2 may be important in the mediation of planned movements (Figure 19F) .
  • GABA ⁇ R2 transcripts throughout the telencephalon indicate a potential modulatory role in the processing of somatosensory and limbic system (entorhinal cortex) information, in addition to modulating visual (parietal cortex) and auditory stimuli (temporal cortex) as well as cognition. Furthermore, modulation of patterns of integrated behaviors, such as defense, ingestion, aggression, reproduction and learning could also be attributed to this receptor owing to its expression in the amygdala (Table 3) .
  • the high levels of expression in the thalamus suggest a possible regulatory role in the transmission of somatosensory (nociceptive) information to the cortex and the exchange of information between the forebrain and midbrain limbic system (schiula) .
  • GABA ⁇ R2 mRNA The presence of GABA ⁇ R2 mRNA in the hypothalamus indicates a likely modulatory role in food intake, reproduction, the expression of emotion and possibly neuroendocrine regulation (Figure 19D) .
  • a role in the mediation of memory acquisition and learning may be suggested by the presence of the GABA g R2 transcript throughout all regions of the hippocampus and the entorhinal cortex ( Figure 19D) .
  • the strength of the hybridization signal for each of the respective mRNAs obtained in various regions of the rat brain was graded as weak (+) , moderate (++), heavy (+++) or intense (++++) and is relative to the individual polypeptides.
  • a potential GABA ⁇ agonist application may in antinociception.
  • the inhibitory effects of GABA and GABAniz agonists are thought to be predominantly a presynaptic mechanism on excitation-induced impulses in high threshold Ad and C fibers on primary afferents. This effect can be blocked by GABA g antagonists (Hao,J-H., et al . , 1994).
  • GABA g antagonists Hao,J-H., et al . , 1994.
  • Baclofen's spinal cord analgesic effects have been well documented in the rat, though it has not been as effective in human.
  • baclofen has been successful in the treatment of trigeminal neuralgia in human.
  • GABA agonists may have some potential in the treatment of cocaine addiction.
  • a role for the action of psychostimulants in the mesoaccumbens dopamine system is well established.
  • the ventral pallidum receives a GABAergic projection from the nucleus accumbens and both regions contain GABA ⁇ R2 transcripts.
  • GABA receptors were shown to have an inhibitory effect on dopamine release in the ventral pallidum. Phaclofen acting at these receptors resulted in increased dopamine release and baclofen was shown to attenuate the reinforcing effects of cocaine. (Roberts, D. C. S., et al.,1996; Morgan, A. E. et al . )
  • GABA ⁇ agonists there is a potential application for GABA ⁇ agonists in the treatment of bladder dysfunction.
  • Baclofen has been used in the treatment of detrussor hyperreflexia through inhibition of contractile responses.
  • GABA B agonists there is also the possibility for a central site.
  • the pontine micturition center in the brainstem is involved in mediating the spinal reflex pathway, via Onuf's nucleus in the sacral spinal cord.
  • Support for possible application of GABA ⁇ agonists in the treatment of bladder dysfunction may be augmented by presence of GABA ⁇ R2 mRNA in the various nuclei involved in the control of the lower urinary tract f unction .
  • GABA ⁇ antagonists may have a potential application in the treatment of Alzheimer's Disease.
  • the blockade of GABA D receptors might lead to signal amplification and improvement m cognitive functions resulting from an increased excitability of cortical neurons via amplification of the acetycholme signal.
  • memory may be enhanced by GABA ⁇ antagonists which have been shown to suppress late IPSPs, thus facilitating long- term potentiation m the hippocampus (see Table 3) .
  • CGP36742 a GABA ⁇ antagonist, has been shown to improve learning performance aged rats as well as the performance of rhesus monkeys in conditioned spatial color task. (Mondado ⁇ , C. et al . , 1993).
  • the significance of the GABA ⁇ Rl/R2 receptor in cognitive functioning might be indicated by the presence of GABA ⁇ R2 mRNA the cerebral cortex and its codist ⁇ bution in the ventral forebra with cortically projecting cholinergic neurons as well as its localization in the pyramidal cells in all regions of Ammon's horn and dentate gyrus m the hippocampus.
  • G-protein-gated atrial K channel 1 ⁇ is a heteromultimer of two inwardly rectifying K channel proteins. (1995b) _Nature 374:135- 141. Lacey, M.G., Mercuri, N.B., North, R.A. (1988) On the potassium conductance increase activated by GABAB and dopamine D2 receptors in rat substantia nigra neurones. J Physiol (Lond) 401:437-53:437-453.
  • G protein-coupled inwardly rectifying K+ channels mediate postsynaptic but not presynaptic transmitter actions in hippocampal neurons [Published erratum appears in Neuron 1997 Oct. 19(4) : following 945] , (1997)_Neuron 19, 687-695.
  • Metabotropic glutamate receptor 5 is a disulfide-linked dimer. J. Biol. Chem. 271:28612-28616.

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  • Peptides Or Proteins (AREA)
  • Micro-Organisms Or Cultivation Processes Thereof (AREA)

Abstract

La présente invention concerne des acides nucléiques isolés codant un polypeptide GABABR2 mammifère, une protéine GABABR2 isolée, des vecteurs comprenant un acide nucléique isolé codant des polypeptides GABABR2 mammifères, des cellules exprimant des récepteurs de GABABR1/R2 mammifères, des anticorps dirigés contre un épitope sur des polypeptides GABABR2 mammifères ou des récepteurs de GABABR1/R2 mammifères, des sondes d'acide nucléique utilisées pour détecter des acides nucléiques codant des polypeptides GABABR2 mammifères, des oligonucléotides antisens complémentaires aux séquences uniques d'acides nucléiques codant des polypeptides GABABR1/R2 mammifères, des animaux transgéniques exprimant des récepteurs de GABABR1/R2 mammifères normaux ou mutants, ainsi que des procédés de criblage de composés agissant comme agonistes ou antagonistes des récepteurs de GABABR1/R2 mammifères.
EP19990943972 1998-08-27 1999-08-27 Adn codant un polypeptide gaba br2 et ses utilisations Withdrawn EP1044265A4 (fr)

Applications Claiming Priority (9)

Application Number Priority Date Filing Date Title
US14176098A 1998-08-27 1998-08-27
US141760 1998-08-27
PCT/US1998/022033 WO1999020751A1 (fr) 1997-10-17 1998-10-16 Adn codant un polypeptide gababr2 et ses utilisations
WOPCT/US98/22033 1998-10-16
US18666498A 1998-11-04 1998-11-04
US186664 1998-11-04
US211755 1998-12-15
US09/211,755 US20020045742A1 (en) 1998-12-15 1998-12-15 Dna encoding a gaba b r2 polypeptide and uses thereof
PCT/US1999/019651 WO2000012692A1 (fr) 1998-08-27 1999-08-27 Adn codant un polypeptide gababr2 et ses utilisations

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999040114A1 (fr) * 1998-02-05 1999-08-12 Merck & Co., Inc. Nouvelles sequences d'adn codant le recepteur gaba¿b?
WO1999051636A2 (fr) * 1998-04-03 1999-10-14 Nps Pharmaceuticals, Inc. Recepteur gaba b
WO1999061606A1 (fr) * 1998-05-29 1999-12-02 The Government Of The United States As Represented By The Secretary, Department Of Health And Human Services RECEPTEURS MAMMALIENS gb2 ET GABA¿B?
WO2000014222A2 (fr) * 1998-09-07 2000-03-16 Glaxo Group Limited Sous-types gabab-r1c et gabab-r2 du recepteur gabab et leurs heterodimeres

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999040114A1 (fr) * 1998-02-05 1999-08-12 Merck & Co., Inc. Nouvelles sequences d'adn codant le recepteur gaba¿b?
WO1999051636A2 (fr) * 1998-04-03 1999-10-14 Nps Pharmaceuticals, Inc. Recepteur gaba b
WO1999061606A1 (fr) * 1998-05-29 1999-12-02 The Government Of The United States As Represented By The Secretary, Department Of Health And Human Services RECEPTEURS MAMMALIENS gb2 ET GABA¿B?
WO2000014222A2 (fr) * 1998-09-07 2000-03-16 Glaxo Group Limited Sous-types gabab-r1c et gabab-r2 du recepteur gabab et leurs heterodimeres

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of WO0012692A1 *

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EP1044265A4 (fr) 2002-10-29

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