WO1995029234A1 - Human gamma 3 gaba-a receptor subunit and stably co-transfected cell lines - Google Patents
Human gamma 3 gaba-a receptor subunit and stably co-transfected cell lines Download PDFInfo
- Publication number
- WO1995029234A1 WO1995029234A1 PCT/GB1995/000834 GB9500834W WO9529234A1 WO 1995029234 A1 WO1995029234 A1 WO 1995029234A1 GB 9500834 W GB9500834 W GB 9500834W WO 9529234 A1 WO9529234 A1 WO 9529234A1
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- subunit
- human
- leu
- receptor
- gabaa receptor
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07K—PEPTIDES
- C07K14/00—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof
- C07K14/435—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from animals; from humans
- C07K14/705—Receptors; Cell surface antigens; Cell surface determinants
- C07K14/70571—Receptors; Cell surface antigens; Cell surface determinants for neuromediators, e.g. serotonin receptor, dopamine receptor
Definitions
- This invention concerns the cloning of a novel cDNA 5 sequence encoding a particular subunit of the human GABA ⁇ receptor.
- the invention relates to a stable cell line capable of expressing said cDNA and to the use of the cell line in a screening technique for the design and development of subtype-specific medicaments.
- GABA Gamma-amino butyric acid
- This receptor comprises a multimeric protein of molecular size 230-270 kDa with specific binding sites for a variety of drugs including benzodiazepines, barbiturates and ⁇ -carbolines, in addition to sites for the 5 agonist ligand GABA (for reviews see Stephenson, Biochem. J., 1988, 249. 21; Olsen and Tobin, Faseb J., 1990, 4, 1469; and Sieghart, Trends in Pharmacol. Sci., 1989, 10, 407).
- the present invention accordingly provides, in a first aspect, a DNA molecule encoding the 73 subunit of the human GABAA receptor comprising all or a portion of the sequence depicted in Figure 2, or a m lified human sequence.
- the sequencing of the novel cDNA molecule in accordance with the invention can conveniently be carried out by the standard procedure described in accompanying Example 1; or may be accomplished by alternative molecular cloning techniques which are well known in the art, such as those described by Maniatis et al. in Molecular Cloning, A Laboratory Manual, Cold Spring Harbor Press, New York, 2nd edition, 1989.
- the invention provides a recombinant expression vector comprising the nucleotide sequence of the GABAA receptor 73 subunit together w h additional sequences capable of directing the synthesis of the said GABAA receptor 73 subunit in cultures of stably co-transfected eukaryotic cells.
- expression vectors refers to DNA sequences that are required for the transcription of cloned copies of recombinant DNA sequences or genes and the translation of their mRNAs in an appropriate host.
- Such vectors can be used to express eukaryotic genes in a variety of hosts such as bacteria, blue-green algae, yeast cells, insect cells, plant cells and animal cells. Specifically designed vectors allow the shuttling of DNA between bacteria-yeast, bacteria-plant or bacteria-animal cells.
- An appropriately constructed expression vector should contain: an origin of replication for autonomous replication in host cells, selective markers, a limited number of useful restriction enzyme sites, a high copy number, and strong promoters.
- a promoter is defined as a DNA sequence that directs RNA polymerase to bind to DNA and to initiate RNA synthesis.
- a strong promoter is one which causes mRNAs to be initiated at high frequency.
- Expression vectors may include, but are not limited to, cloning vectors, modified cloning vectors, specifically designed plasmids or viruses.
- Cloning vector refers to a DNA molecule, usually a small plasmid or bacteriophage DNA capable of self- replication in a host organism, and used to introduce a fragment of foreign DNA into a host cell.
- the foreign DNA combined with the vector DNA constitutes a recombinant DNA molecule which is derived from recombinant technology.
- Cloning vectors may include plasmids, bacteriophages, viruses and cosmids.
- the recombinant expression vector in accordance with the invention may be prepared by inserting the nucleotide sequence of the GABAA Y3 subunit into a suitable precursor expression vector (hereinafter referred to as the "precursor vector") using conventional recombinant DNA methodology known from the art.
- the precursor vector may be obtained commercially, or constructed by standard techniques from known expression vectors.
- the precursor vector suitably contains a selection marker, typically an antibiotic resistance gene, such as the neomycin or ampicillin resistance gene.
- the precursor vector preferably contains a neomycin resistance gene, adjacent the SV40 early splicing and polyadenylation region; an ampicillin resistance gene; and an origin of replication, e.g. pBR322 ori.
- the vector also preferably contains an inducible promoter, such as MMTV-LTR (inducible with dexamethasone) or metallothionin (inducible with zinc), so that transcription can be controlled in the cell line of this invention.
- an inducible promoter such as MMTV-LTR (inducible with dexamethasone) or metallothionin (inducible with zinc), so that transcription can be controlled in the cell line of this invention. This reduces or avoids any problem of toxicity in the cells because of the chloride channel intrinsic to the GABAA receptor.
- precursor vector pMAMneo available from Clontech Laboratories Inc. (Lee et al, Nature, 1981, 294. 228; and Sardet et al, Cell, 1989, 56, 271).
- precursor vector pMSGneo can be constructed from the vectors pMSG and pSV2neo.
- the recombinant expression vector of the present invention is then produced by cloning the GABAA receptor 73 subunit cDNA in .he above precursor vector.
- the receptor subunit cDNA is subcloned from the vector in which it is harboured, and Hgated into a * estriction enzyme site, e.g. the HindHI site, in the polylinker of the precursor vector, for example pMAMneo or pMSGneo, by standard cloning methodology known from the art, and in particular by techniques analogous to those described herein.
- a stably co-transfected eukaryotic cell line capable of expressing a GABAA receptor, which receptor comprises at least one alpha, one beta and the 73 subunit. This is achieved by co-transfecting cells with three expression vectors, each harbouring cDNAs encoding for an ⁇ , ⁇ or 73 GABAA receptor subunit.
- the present invention provides a process for the preparation of a eukaryotic cell line capable of expressing a GABAA receptor, which comprises stably co-transfecting a eukaryotic host cell with at least three expression vectors, one such vector harbouring the cDNA sequence encoding for an alpha, another such vector harbouring the cDNA sequence encoding for a beta, and a third such vector harbouring the cDNA sequence encoding for the 73 GABAA receptor subunit.
- the stable cell-line which is established expresses an 0 ⁇ 73 GABAA receptor.
- Each receptor thereby expressed, comprising a unique combination of ⁇ , ⁇ and 73 subunits, will be referred to hereinafter as a
- GABAA receptor "subunit combination”. Pharmacological and electrophysiological data confirm that the recombinant ⁇ y3 receptor expressed by the cells of the present invention has the properties expected of a native GABAA receptor.
- the GABAA receptor may be accomplished by a variety of different promoter-expression systems in a variety of different host cells.
- the eukaryotic host cells suitably include yeast, insect and mammalian cells.
- the eukaryotic cells which can provide the host for the expression of the receptor are mammalian cells.
- Suitable host cells include rodent fibroblast fines, for example mouse Ltk", Chinese hamster ovary (CHO) and baby hamster kidney (BHK); HeLa; and HEK293 cells. It is necessary to incorporate at least one ⁇ , one ⁇ and the 73 subunit into the cell line in order to produce the required receptor.
- benzodiazepines represent one class of drugs which act upon the GABAA receptor.
- the presence of an ⁇ j subunit is specific for a class of benzodiazepines having the pharmacology designated BZj; whereas ct2 to 015 define diffe ⁇ " ⁇ !t pharmacological profiles, broadly designated as BZ2.
- the type ..- ⁇ subunit is not critical in defining the class of benzodiazepine, although a ⁇ subunit is required.
- the 73 subunit is also important in defining BZ selectivity. It is likely that differentiation between ⁇ subunit selectivity is conferred by the 73 subunit.
- a library of cell lines each with a different combination of subunits.
- Preferred subunit combinations include: ct2 ⁇ i73 and 0 ⁇ 173, and in particular 0 ⁇ 373.
- cell lines containing other subunit combinations such as oq ⁇ ] 2; ⁇ l ⁇ 2Y2; «2 ⁇ ; c i 2 ⁇ i72; ⁇ 4 ⁇ lY2; ⁇ r ⁇ ⁇ 6 ⁇ lY2; and ⁇ l ⁇ lY2L-
- three such vectors will be necessary, one containing an ⁇ subunit, one containing a ⁇ subunit, and the third containing the 73 subunit.
- Cells are then co-transfected with the desired combination of three expression vectors.
- a small percentage of the host cells takes up the recombinant DNA. In a small percentage of those, the DNA will integrate into the host cell chromosome.
- the neomycin resistance gene will have been incorporated into these host cells, they can be selected by isolating the individual clones which will grow in the presence of neomycin. Each such clone is then tested to identify those which will produce the receptor. This is achieved by inducing the production, for example with dexamethasone, and then detecting the presence of receptor by means of radioligand binding.
- the present invention provides protein preparations of GABAA receptor subunit combinations, especially human
- GABAA receptor subunit combinations comprising the human 73 GABAA receptor subunit derived from cultures of stably transfected eukaryotic cells.
- the invention also provides preparations of membranes containing subunit combinations of the GABAA receptor, especially human GABAA receptor subunit combinations, comprising the human 73 GABAA receptor subunit derived from cultures of stably transfected eukaryotic cells.
- the invention provides cell membranes containing a human GABAA receptor consisting of an C 73 subunit combination isolated from stably transfected mouse Ltk" fibroblast cells, most especially an 0 ⁇ 373 subunit combination.
- the cell fine, and the membrane preparations therefrom, according to the present invention have utility in screening and design of drugs which act upon the GABAA receptor, for example benzodiazepines, barbiturates, ⁇ -carbolines and neurosteroids.
- the present invention accordingly provides the use of the cell fine described above, and membrane preparations derived therefrom, in screening for and designing medicaments which act upon the GABAA receptor.
- the present invention accordingly provides the use of the cell fine described above, and membrane preparations derived therefrom, in screening for and designing medicaments which act upon the GABAA receptor.
- molecules capable of interacting selectively with GABAA receptors made up of varying subunit combinations are molecules capable of interacting selectively with GABAA receptors made up of varying subunit combinations.
- the cell line in accordance with the present invention, and the membrane preparations derived therefrom provide ideal systems for the study of structure
- cDNAs were cloned from human foetal brain cDNA libraries. All cDNA libraries were constructed in the lambdaZAP vector, and were purchased from Stratagene (San Diego, California). For screening, the cDNA libraries were plated according to the manufacturer's instructions, at 40,000 pfu per 137 mm plate. Filter lifts were taken using Hybond N filters (Amersham) according to the manufacturer's instructions.
- a rat 73 cDNA probe was first generated by PCR using oligonucleotide primers derived from the rat 73 sequence (Knoflach et al,
- a 1250bp PCR product was obtained which when digested with Hind III was cut into 2 pieces of 900bp and 350bp in size.
- the 900bp fragment was subcloned into the Hind III site of pBluescript SK-(Stratagene) and its identity confirmed by DNA sequencing using standard techniques and the Sequensase II enzyme (United States Biochemicals).
- a human foetal brain cDNA Hbrary was screened using 32p labelled rat 73 900bp DNA as described above. A single cDNA clone was obtained. Sequence analysis was performed, using an Appfied Biosystems 373 A DNA sequencer and dye terminator chemistry according to the manufacturers' instructions.
- This cDNA lacked both the 5' and 3' ends of the coding region. These were subsequently obtained by anchored PCR. For the 3' end, a sense oHgonucleotide derived from sequence near the 3' end of the truncated cDNA clone
- SEQ. ID. NO.: 3 was used in conjunction with an oHgonucleotide "anchor" primer derived from the T7 primer sequence of the pBluescript vector
- Incubations were terminated by filtration through GF/B filters (Brandel, Gathersberg, MD) on a Tomtech ceU harvester, foUowed by three washes in ice-cold assay buffer. After drying, filter-retained radioactivity was measured by Hquid scintillation counting.
- a ceU Hne prepared as described in Example 2 expressed approximately 80fmol [3H]Rol5-1788 binding sites/mg protein foUowing a 5-day induction of receptor expression.
- the expression of human 0:5, ⁇ 3 and 73 mRNA transcripts was confirmed by isolation of mRNA, cDNA synthesis and PCR using subunit specific oHgonucleotide primers in a conventional manner. Scatchard analysis of saturation binding curves for
- [8H]Rol5-1788 was performed for membrane preparations from two cell Hnes expressing the 0 ⁇ 373 subunit combination according to the present invention, giving the foUowing KD values (mean ⁇ SEM): 0.32 ⁇ 0.06nM and 0.63 ⁇ 0.11nM.
- TCC TCA AGA TGG ATT CCT GAG CGA ATA AGC CTA CAA GCC CCT TCC AAC 1157 Ser Ser Arg Trp He Pro Glu Arg He Ser Leu Gin Ala Pro Ser Asn 360 365 370 375
- TGT AAA TCA GGA TCC TGG AGG AAA GGG CGT ATT CAC ATA GAC ATC TTG 1349 Cys Lys Ser Gly Ser Trp Arg Lys Gly Arg He His He Asp He Leu 425 430 435
- MOLECULE TYPE protein
Abstract
Description
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Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP7527433A JPH10500007A (en) | 1994-04-22 | 1995-04-12 | Human γ lower 3 GABA lower A receptor subunit and stably co-transfected cell line |
EP95915245A EP0756626A1 (en) | 1994-04-22 | 1995-04-12 | Human gamma 3 gaba-a receptor subunit and stably co-transfected cell lines |
Applications Claiming Priority (2)
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GB9408064.5 | 1994-04-22 | ||
GB9408064A GB9408064D0 (en) | 1994-04-22 | 1994-04-22 | Nucleic acids |
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WO1995029234A1 true WO1995029234A1 (en) | 1995-11-02 |
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PCT/GB1995/000834 WO1995029234A1 (en) | 1994-04-22 | 1995-04-12 | Human gamma 3 gaba-a receptor subunit and stably co-transfected cell lines |
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EP (1) | EP0756626A1 (en) |
JP (1) | JPH10500007A (en) |
CA (1) | CA2188258A1 (en) |
GB (1) | GB9408064D0 (en) |
WO (1) | WO1995029234A1 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1998011885A1 (en) * | 1996-09-18 | 1998-03-26 | Astra Aktiebolag | Reflux inhibitors |
WO1998049293A1 (en) * | 1997-04-25 | 1998-11-05 | Merck Sharp & Dohme Limited | Human theta subunit of the gaba-a receptor |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1992022652A1 (en) * | 1991-06-11 | 1992-12-23 | Merck Sharp & Dohme Limited | GABA-A RECEPTOR SUBUNITS (α-2, α-3, α-5, α-6, β-2) AND TRANSFECTED CELLS EXPRESSING THEM |
-
1994
- 1994-04-22 GB GB9408064A patent/GB9408064D0/en active Pending
-
1995
- 1995-04-12 EP EP95915245A patent/EP0756626A1/en not_active Withdrawn
- 1995-04-12 WO PCT/GB1995/000834 patent/WO1995029234A1/en not_active Application Discontinuation
- 1995-04-12 JP JP7527433A patent/JPH10500007A/en active Pending
- 1995-04-12 CA CA 2188258 patent/CA2188258A1/en not_active Abandoned
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1992022652A1 (en) * | 1991-06-11 | 1992-12-23 | Merck Sharp & Dohme Limited | GABA-A RECEPTOR SUBUNITS (α-2, α-3, α-5, α-6, β-2) AND TRANSFECTED CELLS EXPRESSING THEM |
Non-Patent Citations (2)
Title |
---|
HERB A;WISDEN W;LUDDENS H;PUIA G;VICINI S;SEEBURG PH;: "The third gamma subunit of the gamma-aminobutyric acid type A receptor family.", PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF USA, vol. 89, WASHINGTON US, pages 1433 - 1437 * |
KNOFLACH F;RHYNER T;VILLA M;KELLENBERGER S;DRESCHER U;MALHERBE P;SIGEL E;MOHLER H: "The gamma 3-subunit of the GABAA-receptor confers sensitivity to benzodiazepine receptor ligands", FEBS LETTERS, vol. 293, no. 1,2, AMSTERDAM NL, pages 191 - 194 * |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1998011885A1 (en) * | 1996-09-18 | 1998-03-26 | Astra Aktiebolag | Reflux inhibitors |
US6117908A (en) * | 1996-09-18 | 2000-09-12 | Astra Aktiebolag | Use of GABAB receptor agonists as reflux inhibitors |
US6664069B1 (en) | 1996-09-18 | 2003-12-16 | Astrazeneca Ab | Use of GABAB receptor agonists in the screening of compounds which are reflux inhibitors |
CZ299997B6 (en) * | 1996-09-18 | 2009-01-14 | Astrazeneca Ab | Reflux inhibitors |
WO1998049293A1 (en) * | 1997-04-25 | 1998-11-05 | Merck Sharp & Dohme Limited | Human theta subunit of the gaba-a receptor |
US6555341B1 (en) | 1997-04-25 | 2003-04-29 | Merck Sharp & Dohme Ltd. | Human theta subunit of the GABAa receptor |
Also Published As
Publication number | Publication date |
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CA2188258A1 (en) | 1995-11-02 |
EP0756626A1 (en) | 1997-02-05 |
GB9408064D0 (en) | 1994-06-15 |
JPH10500007A (en) | 1998-01-06 |
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