EP1220912A2 - Menschliche membranproteine - Google Patents
Menschliche membranproteineInfo
- Publication number
- EP1220912A2 EP1220912A2 EP00967218A EP00967218A EP1220912A2 EP 1220912 A2 EP1220912 A2 EP 1220912A2 EP 00967218 A EP00967218 A EP 00967218A EP 00967218 A EP00967218 A EP 00967218A EP 1220912 A2 EP1220912 A2 EP 1220912A2
- Authority
- EP
- European Patent Office
- Prior art keywords
- ngpcr
- seq
- amino acid
- gene
- nucleotide sequence
- 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.)
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Classifications
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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
- C07K14/72—Receptors; Cell surface antigens; Cell surface determinants for hormones
- C07K14/723—G protein coupled receptor, e.g. TSHR-thyrotropin-receptor, LH/hCG receptor, FSH receptor
Definitions
- the present invention relates to the discovery, identification and characterization of novel human polynucleotides that encode membrane associated proteins and receptors.
- the invention encompasses the described polynucleotides, host cell expression systems, the encoded proteins, fusion proteins, polypeptides and peptides, antibodies to the encoded proteins and peptides, and genetically engineered animals that lack the disclosed genes, or over express the disclosed genes, or antagonists and agonists of the proteins, and other compounds that modulate the expression or activity of the proteins encoded by the disclosed genes that can be used for diagnosis, drug screening, clinical trial monitoring, and/or the treatment of physiological or behavioral disorders.
- Membrane receptor proteins are integral components of the mechanisms through which cells sense their surroundings as well as maintain cellular homeostasis and function. Accordingly, membrane receptor proteins are often involved in signal transduction pathways that control cell physiology, chemical communication, and gene expression. A particularly relevant class of membrane receptors are those typically characterized by the presence of 7 conserved transmembrane domains that are interconnected by nonconserved hydrophilic loops. Such, “7TM receptors” include a superfamily of receptors known as G-protein coupled receptors (GPCRs) . GPCRs are typically involved in signal transduction pathways involving G-proteins or PPG proteins. As such, the GPCR family includes many receptors that are known to serve as drug targets for therapeutic agents.
- GPCRs G-protein coupled receptors
- the present invention relates to the discovery, identification and characterization of nucleotides that encode novel GPCRs, and the corresponding novel GPCR (NGPCR) amino acid sequences.
- NGPCR novel GPCR
- the NGPCRs described for the first time herein, are transmembrane proteins that span the cellular membrane and are involved in signal transduction after ligand binding.
- the described NGPCRs have structural motifs found in the 7TM receptor family. Expression of the described NGPCRs can be detected in adipose and lymph node cells, among others.
- Certain novel human GPCRs described herein encode proteins of 528, 464, 451, 414, 384, 185, 474, 410, 397, 360, 330 and 131 amino acids in length (see SEQ ID NOS: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, and 24 respectively).
- the described NGPCRs have a characteristic leader sequence, and contain the characteristic multiple transmembrane regions (of about 20-30 amino acids) , as well as several predicted cytoplasmic domains.
- clones displaying splice and other polymorphisms clones were identified that indicate that 3' truncated versions of the described NGPCRs exist.
- a ES cell clone has been produced that contains a mutated, or "knockout”, allele of the murine homolog of the described NGPCR(s). Additionally contemplated are "knockout” ES cells that have been produced using conventional methods (see, for example, PCT Applic. No. PCT/US98/03243 , filed February 20, 1998, herein incorporated by reference) . Accordingly, an additional aspect of the present invention includes knockout cells and animals having genetically engineered mutations in the gene encoding the presently described NGPCRs .
- the invention encompasses the nucleotides presented in the Sequence Listing, host cells expressing such nucleotides, and the expression products of such nucleotides, and: (a) nucleotides that encode mammalian homologs of the described NGPCRs, including the specifically described human NGPCRs, and the human NGPCR gene products; (b) nucleotides that encode one or more portions of the NGPCRs that correspond to functional domains, and the polypeptide products specified by such nucleotide sequences, including but not limited to the novel regions of the described extracellular domain (s) (ECD), one or more transmembrane domain (s) (TM) first disclosed herein, and the cytoplasmic domain (s) (CD); (c) isolated nucleotides that encode mutants, engineered or naturally occurring, of the described NGPCRs in which all or a part of at least one of the domains is deleted or altered, and the polypeptide products specified by such nucleotide sequences, including but not limited to
- the invention also encompasses agonists and antagonists of the NGPCRs, including small molecules, large molecules, mutant NGPCR proteins, or portions thereof that compete with the native NGPCR, and antibodies, as well as nucleotide sequences that can be used to inhibit the expression of the described NGPCR (e . g. , antisense and ribozyme molecules, and gene or regulatory sequence replacement constructs) or to enhance the expression of the described NGPCR gene ( e . g. , expression constructs that place the described gene under the control of a strong promoter system) , and transgenic animals that express a NGPCR transgene or "knock-outs" that do not express functional NGPCR.
- nucleotide sequences that can be used to inhibit the expression of the described NGPCR (e . g. , antisense and ribozyme molecules, and gene or regulatory sequence replacement constructs) or to enhance the expression of the described NGPCR gene (e . g. , expression constructs that place the described
- the present invention also relates to methods for the use of the described NGPCR gene and/or NGPCR gene products for the identification of compounds that modulate, i.e., act as agonists or antagonists, of NGPCR gene expression and or NGPCR gene product activity.
- Such compounds can be used as therapeutic agents for the treatment of various symptomatic representations of biological disorders or imbalances .
- the human NGPCRs are novel receptor proteins that are expressed, inter alia , in adipose and lymph node cells.
- the NGPCRs are transmembrane proteins that fall within the 7TM family of receptors.
- signal transduction is triggered when a ligand binds to the receptor. Interfering with the binding of the natural ligand, or neutralizing or removing the ligand, or interference with its binding to a NGPCR will effect NGPCR mediated signal transduction.
- 7TM, and particularly GPCR proteins have been subjected to intense scientific/commercial scrutiny (see, for example, U.S. Applic. Ser. Nos.
- the invention encompasses the use of the described NGPCR nucleotides, NGPCR proteins and peptides, as well as antibodies, preferably humanized monoclonal antibodies, or binding fragments, domains, or fusion proteins thereof, to the NGPCRs (which can, for example, act as NGPCR agonists or antagonists) , antagonists that inhibit receptor activity or expression, or agonists that activate receptor activity or increase its expression in the diagnosis and treatment of disease .
- NGPCR polypeptides or peptides corresponding to functional domains of NGPCR e . g. , ECD, TM or CD
- mutated, truncated or deleted NGPCRs e . g. , NGPCRs missing one or more functional domains or portions thereof, such as, ⁇ ECD, ⁇ TM and/or ⁇ CD
- NGPCR fusion proteins e . g.
- NGPCR or a functional domain of a NGPCR, such as the ECD, fused to an unrelated protein or peptide such as an imrrvunoglobulin constant region, i.e., IgFc) , nucleotide sequences encoding such products, and host cell expression systems that can produce such NGPCR products.
- the invention also encompasses antibodies and anti- idiotypic antibodies (including Fab fragments) , antagonists and agonists of the NGPCR, as well as compounds or nucleotide constructs that inhibit expression of a NGPCR gene (transcription factor inhibitors, antisense and ribozyme molecules, or gene or regulatory sequence replacement constructs), or promote expression of NGPCR ( e . g. , expression constructs in which NGPCR coding sequences are operatively associated with expression control elements such as promoters, promoter/enhancers, etc.) .
- the invention also relates to host cells and animals genetically engineered to express the human
- NGPCRs or mutants thereof or to inhibit or "knock-out" expression of the animal's endogenous NGPCR genes.
- the NGPCR proteins or peptides, NGPCR fusion proteins, NGPCR nucleotide sequences, antibodies, antagonists and agonists can be useful for the detection of mutant NGPCRs or inappropriately expressed NGPCRs for the diagnosis of disease.
- the NGPCR proteins or peptides, NGPCR fusion proteins, NGPCR nucleotide sequences, host cell expression systems, antibodies, antagonists, agonists and genetically engineered cells and animals can be used for screening for drugs (or high throughput screening of combinatorial libraries) effective in the treatment of the symptomatic or phenotypic manifestations of perturbing the normal function of NGPCR in the body.
- the use of engineered host cells and/or animals may offer an advantage in that such systems allow not only for the identification of compounds that bind to an ECD of a NGPCR, but can also identify compounds that affect the signal transduced by an activated NGPCR.
- NGPCR protein products especially soluble derivatives such as peptides corresponding to the NGPCR ECD, or truncated polypeptides lacking one or more TM domains
- fusion protein products especially NGPCR-Ig fusion proteins, i . e . , fusions of a NGPCR, or a domain of a NGPCR, e . g. , ECD,
- ⁇ TM to an IgFc antibodies and anti-idiotypic antibodies (including Fab fragments) , antagonists or agonists (including compounds that modulate signal transduction which may act on downstream targets in a NGPCR-mediated signal transduction pathway) can be used for therapy of such diseases.
- the administration of an effective amount of soluble NGPCR ECD, ⁇ TM, or an ECD-IgFc fusion protein or an anti- idiotypic antibody (or its Fab) that mimics the NGPCR ECD would "mop up” or “neutralize” the endogenous NGPCR ligand, and prevent or reduce binding and receptor activation.
- Nucleotide constructs encoding such NGPCR products can be used to genetically engineer host cells to express such products in vivo; these genetically engineered cells function as "bioreactors" in the body delivering a continuous supply of a NGPCR, a NGPCR peptide, soluble ECD or ⁇ TM or a NGPCR fusion protein that will "mop up” or neutralize a NGPCR ligand.
- Nucleotide constructs encoding functional NGPCRs, mutant NGPCRs, as well as antisense and ribozyme molecules can be used in "gene therapy” approaches for the modulation of NGPCR expression.
- the invention also encompasses pharmaceutical formulations and methods for treating biological disorders.
- the cDNA sequences and deduced amino acid sequences of certain described human NGPCRs are presented in the Sequence Listing .
- the NGPCRs of the present invention include: (a) the human DNA sequences presented in the Sequence Listing and additionally contemplate any nucleotide sequence encoding a contiguous and functional NGPCR open reading frame (ORF) that hybridizes to a complement of the DNA sequences presented in the Sequence Listing under highly stringent conditions, e . g.
- polynucleotides encoding NGPCR ORFs or their functional equivalents, encoded by polynucleotide sequences that are about 99, 95, 90, or about 85 percent similar to corresponding regions of SEQ ID NO : 1 (as measured by BLAST sequence comparison analysis using, for example, the GCG sequence analysis package using default parameters) .
- the invention also includes nucleic acid molecules, preferably DNA molecules, that hybridize to, and are therefore the complements of, the described NGPCR nucleotide sequences.
- Such hybridization conditions may be highly stringent or less highly stringent, as described above.
- the nucleic acid molecules are deoxyoligonucleotides ("DNA oligos")
- DNA oligos deoxyoligonucleotides
- such molecules can be used in conjunction with the polymerase chain reaction
- oligonucleotides can be used singly or in chip format as hybridization probes.
- a series of the described NGPCR oligonucleotide sequences, or the complements thereof, can be used to represent all or a portion of the described NGPCRs.
- the oligonucleotides typically between about 16 to about 40 (or any whole number within the stated range) nucleotides in length may partially overlap each other and/or the NGPCR sequence may be represented using oligonucleotides that do not overlap.
- the described NGPCR polynucleotide sequences shall typically comprise at least about two or three distinct oligonucleotide sequences of at least about 18 nucleotides in length that are each first disclosed in the described Sequence Listing.
- Such oligonucleotide sequences may begin at any nucleotide present within a sequence in the Sequence Listing and proceed in either a sense (5'-to-3') orientation vis-a-vis the described sequence or in an antisense orientation.
- highly stringent conditions may refer, e . g.
- the described oligonucleotides may encode or act as NGPCR antisense molecules, useful, for example, in NGPCR gene regulation (for and/or as antisense primers in amplification reactions of NGPCR gene nucleic acid sequences) .
- NGPCR gene regulation such techniques can be used to regulate biological functions.
- sequences may be used as part of ribozyme and/or triple helix sequences, also useful for NGPCR gene regulation.
- the antisense oligonucleotides may comprise at least one modified base moiety which is selected from the group including but not limited to 5-fluorouracil , 5-bromouracil , 5-chlorouracil , 5-iodouracil , hypoxanthine, xantine, 4-acetylcytosine, 5- (carboxyhydroxylmethyl) uracil, 5 -carboxymethylaminomethyl -2 -1hiouridine ,
- 2-thiouracil 3- (3-amino-3-N-2-carboxypropyl) uracil, (acp3)w, and 2 , 6-diaminopurine .
- the antisense oligonucleotide may also comprise at least one modified sugar moiety selected from the group including but not limited to arabinose, 2-fluoroarabinose, xylulose, and hexose .
- the antisense oligonucleotide comprises at least one modified phosphate backbone selected from the group consisting of a phosphorothioate, a phosphorodithioate, a phosphoramidothioate, a phosphoramidate, a phosphordiamidate, a methylphosphonate, an alkyl phosphotriester, and a formacetal or analog thereof.
- the antisense oligonucleotide is an ⁇ -anomeric oligonucleotide.
- An ⁇ -anomeric oligonucleotide forms specific double-stranded hybrids with complementary RNA in which, contrary to the usual ⁇ -units, the strands run parallel to each other (Gautier et al . , 1987,
- the oligonucleotide is a 2'-0- methylribonucleotide (Inoue et al . , 1987, Nucl. Acids Res. 15:6131-6148), or a chimeric RNA-DNA analogue (Inoue et al . ,
- Oligonucleotides of the invention may be synthesized by standard methods known in the art, e.g. by use of an automated
- DNA synthesizer such as are commercially available from Biosearch, Applied Biosystems, etc.
- phosphorothioate oligonucleotides may be synthesized by the method of Stein et al . (1988, Nucl. Acids Res. 15:3209), methylphosphonate oligonucleotides can be prepared by use of controlled pore glass polymer supports (Sarin et al . , 1988,
- suitably labeled NGPCR nucleotide probes may be used to screen a human genomic library using appropriately stringent conditions or by PCR.
- the identification and characterization of human genomic clones is helpful for identifying polymorphisms, determining the genomic structure of a given locus/allele, and designing diagnostic tests.
- sequences derived from regions adjacent to the intron/exon boundaries of the human gene can be used to design primers for use in amplification assays to detect mutations within the exons, introns, splice sites ( e . g. , splice acceptor and/or donor sites), etc., that can be used in diagnostics and pharmacogenomics .
- a NGPCR gene homolog may be isolated from nucleic acid of the organism of interest by performing PCR using two degenerate oligonucleotide primer pools designed on the basis of amino acid sequences within the NGPCR gene product disclosed herein.
- the template for the reaction may be total RNA, mRNA, and/or cDNA obtained by reverse transcription of mRNA prepared from, for example, human or non-human cell lines or tissue known or suspected to express a NGPCR gene allele.
- the PCR product may be subcloned and sequenced to ensure that the amplified sequences represent the sequence of the desired NGPCR gene.
- the PCR fragment may then be used to isolate a full length cDNA clone by a variety of methods.
- the amplified fragment may be labeled and used to screen a cDNA library, such as a bacteriophage cDNA library.
- the labeled fragment may be used to isolate genomic clones via the screening of a genomic library.
- RNA may be isolated, following standard procedures, from an appropriate cellular or tissue source (i.e., one known, or suspected, to express a
- NGPCR gene such as, for example, brain tissue
- a reverse transcription (RT) reaction may be performed on the RNA using an oligonucleotide primer specific for the most 5 ' end of the amplified fragment for the priming of first strand synthesis.
- the resulting RNA/DNA hybrid may then be "tailed" using a standard terminal transferase reaction, the hybrid may be digested with RNase H, and second strand synthesis may then be primed with a complementary primer.
- cDNA sequences upstream of the amplified fragment may easily be isolated.
- a cDNA of a mutant NGPCR gene can be isolated, for example, by using PCR.
- the first cDNA strand may be synthesized by hybridizing an oligo-dT oligonucleotide to mRNA isolated from tissue known or suspected to be expressed in an individual putatively carrying a mutant NGPCR allele, and by extending the new strand with reverse transcriptase .
- the second strand of the cDNA is then synthesized using an oligonucleotide that hybridizes specifically to the 5' end of the normal gene.
- the product is then amplified via PCR, optionally cloned into a suitable vector, and subjected to DNA sequence analysis through methods well known to those of skill in the art.
- DNA sequence analysis By comparing the DNA sequence of the mutant NGPCR allele to that of the normal NGPCR allele, the mutation (s) responsible for the loss or alteration of function of the mutant NGPCR gene product can be ascertained.
- a genomic library can be constructed using DNA obtained from an individual suspected of or known to carry the mutant NGPCR allele, or a cDNA library can be constructed using RNA from a tissue known, or suspected, to express the mutant NGPCR allele.
- a normal NGPCR gene, or any suitable fragment thereof, can then be labeled and used as a probe to identify the corresponding mutant NGPCR allele in such libraries.
- Clones containing the mutant NGPCR gene sequences can then be purified and subjected to sequence analysis according to methods well known to those of skill in the art.
- an expression library can be constructed utilizing cDNA synthesized from, for example, RNA isolated from a tissue known, or suspected, to express a mutant NGPCR allele in an individual suspected of or known to carry such a mutant allele.
- gene products made by the putatively mutant tissue may be expressed and screened using standard antibody screening techniques in conjunction with antibodies raised against the normal NGPCR gene product, as described, below, in Section 5.3.
- For screening techniques see, for example, Harlow, E. and Lane, eds., 1988, "Antibodies: A Laboratory Manual", Cold Spring Harbor Press, Cold Spring Harbor)
- screening can be accomplished by screening with labeled NGPCR fusion proteins, such as, for example, AP-
- NGPCR or NGPCR-AP fusion proteins are likely to cross-react with the mutant NGPCR gene product.
- Library clones detected via their reaction with such labeled antibodies can be purified and subjected to sequence analysis according to methods well known to those of skill in the art.
- the invention also encompasses nucleotide sequences that encode mutant NGPCRs, peptide fragments of the NGPCRs, truncated NGPCRs, and NGPCR fusion proteins.
- mutant NGPCRs include, but are not limited to, nucleotide sequences encoding mutant NGPCRs described below; polypeptides or peptides corresponding to one or more ECD, TM and/or CD domains of the NGPCR or portions of these domains; truncated NGPCRs in which one or two of the domains is deleted, e . g. , a soluble NGPCR lacking the TM or both the TM and CD regions, or a truncated, nonfunctional NGPCR lacking all or a portion of the CD region.
- Nucleotides encoding fusion proteins may include, but are not limited to, full length NGPCR sequences, truncated NGPCRs, or nucleotides encoding peptide fragments of NGPCR fused to an unrelated protein or peptide, such as for example, a transmembrane sequence, which anchors the NGPCR ECD to the cell membrane; an IgFc domain which increases the stability and half life of the resulting fusion protein ( e . g. , NGPCR-Ig) in the bloodstream; or an enzyme, fluorescent protein, luminescent protein which can be used as a marker.
- the invention also encompasses (a) DNA vectors that contain any of the foregoing NGPCR coding sequences and/or their complements ( i . e . , antisense); (b) DNA expression vectors that contain any of the foregoing NGPCR coding sequences operatively associated with a regulatory element that directs the expression of the coding sequences; and (c) genetically engineered host cells that contain any of the foregoing NGPCR coding sequences operatively associated with a regulatory element that directs the expression of the coding sequences in the host cell.
- regulatory elements include but are not limited to inducible and non- inducible promoters, enhancers, operators and other elements known to those skilled in the art that drive and regulate expression.
- Such regulatory elements include but are not limited to the cytomegalovirus hCMV immediate early gene, regulatable, viral (particularly retroviral LTR) promoters, the early or late promoters of SV40 adenovirus, the lac system, the trp system, the TAC system, the TRC system, the major operator and promoter regions of phage A, the control regions of fd coat protein, the promoter for 3-phosphoglycerate kinase (PGK) , the promoters of acid phosphatase, and the promoters of the yeast ⁇ -mating factors.
- PGK 3-phosphoglycerate kinase
- NGPCR proteins, polypeptides and peptide fragments, mutated, truncated or deleted forms of the NGPCR and/or NGPCR fusion proteins can be prepared for a variety of uses, including but not limited to the generation of antibodies, as reagents in diagnostic assays, the identification of other cellular gene products related to a NGPCR, as reagents in assays for screening for compounds that can be used as pharmaceutical reagents useful in the therapeutic treatment of mental, biological, or medical disorders and disease.
- the Sequence Listing discloses the amino acid sequences encoded by certain described NGPCR genes .
- the NGPCRs have initiator methionines in DNA sequence contexts consistent with translation initiation sites, followed by hydrophobic signal sequences typical of membrane associated proteins.
- the sequence data presented herein indicate that alternatively spliced forms of the NGPCRs exist (which may or may not be tissue specific) . Additionally, analysis has revealed several polymorphisms in the described NGPCR sequences. At position 846 of, for example, SEQ ID NO:l, a silent C to T transition, or vice-versa, can be present, and an A to G transitions was detected in the 5' UTR of the described sequences.
- NGPCR amino acid sequences of the invention include the nucleotide and amino acid sequences presented in the
- any NGPCR protein encoded by the NGPCR nucleotide sequences described above are within the scope of the invention, as are any novel polynucleotide sequences encoding all or any novel portion of an amino acid sequence presented in the Sequence Listing.
- the degenerate nature of the genetic code is well known, and, accordingly, each amino acid presented in the Sequence Listing, is generically representative of the well known nucleic acid "triplet" codon, or in many cases codons, that can encode the amino acid.
- amino acid sequences presented in the Sequence Listing when taken together with the genetic code (see, for example, Table 4-1 at page 109 of "Molecular Cell Biology", 1986, J. Darnell et al . eds., Scientific American Books, New York, NY, herein incorporated by reference) are generically representative of all the various permutations and combinations of nucleic acid sequences that can encode such amino acid sequences.
- the invention also encompasses proteins that are functionally equivalent to the NGPCR encoded by the described nucleotide sequences as judged by any of a number of criteria, including but not limited to the ability to bind a ligand for a NGPCR and the ability to effect an identical or complementary signal transduction pathway; a change in cellular metabolism (e . g. , ion flux, tyrosine phosphorylation, etc.); or a change in phenotype when the NGPCR equivalent is present in an appropriate cell type (such as the amelioration, prevention or delay of a biochemical, biophysical, or overt phenotype).
- proteins that are functionally equivalent to the NGPCR encoded by the described nucleotide sequences as judged by any of a number of criteria, including but not limited to the ability to bind a ligand for a NGPCR and the ability to effect an identical or complementary signal transduction pathway; a change in cellular metabolism (e . g. , ion flux, t
- Such functionally equivalent NGPCR proteins include but are not limited to, additions or substitutions of amino acid residues within the amino acid sequence encoded by the NGPCR nucleotide sequences described above but which result in a silent change, thus producing a functionally equivalent gene product.
- Amino acid substitutions according to certain embodiments may be made on the basis of similarity in polarity, charge, solubility, hydrophobicity, hydrophilicity, and/or the amphipathic nature of the residues involved.
- nonpolar (hydrophobic) amino acids include alanine, leucine, isoleucine, valine, proline, phenylalanine, tryptophan, and methionine;
- polar neutral amino acids include glycine, serine, threonine, cysteine, tyrosine, asparagine, and glutamine;
- positively charged (basic) amino acids include arginine, lysine, and histidine; and negatively charged (acidic) amino acids include aspartic acid and glutamic acid.
- site-directed mutations of the NGPCR coding sequence can be engineered (using site-directed mutagenesis techniques well known to those skilled in the art) to generate mutant NGPCRs with increased function, e . g. , higher binding affinity for the target ligand, and/or greater signaling capacity; or decreased function, and/or decreased signal transduction capacity.
- One starting point for such analysis is by aligning the disclosed human sequences with corresponding gene/protein sequences from, for example, other mammals in order to identify amino acid sequence motifs that are conserved between different species.
- Non-conservative changes can be engineered at variable positions to alter function, signal transduction capability, or both.
- deletion or non-conservative alterations of the conserved regions i.e., identical amino acids
- deletion or non-conservative alterations substitutions or insertions of the various conserved transmembrane domains.
- NGPCR coding sequence can be made to generate NGPCRs that are better suited for expression, scale up, etc. in the host cells chosen.
- cysteine residues can be deleted or substituted with another amino acid in order to eliminate disulfide bridges; N- linked glycosylation sites can be altered or eliminated to achieve, for example, expression of a homogeneous product that is more easily recovered and purified from yeast hosts which are known to hyperglycosylate N-linked sites.
- Peptides corresponding to one or more domains of the NGPCR e.g., ECD, TM, CD, etc.
- truncated or deleted NGPCRs e.g., ECD, TM, CD, etc.
- NGPCR in which a ECD, TM and/or CD is deleted
- fusion proteins in which a full length NGPCR, a NGPCR peptide, or truncated NGPCR is fused to an unrelated protein, are also within the scope of the invention and can be designed on the basis of the presently disclosed NGPCR nucleotide and
- fusion proteins include but are not limited to IgFc fusions which stabilize the NGPCR protein or peptide and prolong half-life in vivo; or fusions to any amino acid sequence that allows the fusion protein to be anchored to the cell membrane, allowing an ECD to be exhibited on the cell surface; or fusions to an enzyme, fluorescent protein, or luminescent protein which provide a marker function.
- NGPCR polypeptides and peptides can be chemically synthesized (e.g., see Creighton, 1983, Proteins:
- RNA corresponding to all or a portion of a transcript encoded by a NGPCR can be advantageously produced by recombinant DNA technology using techniques well known in the art for expressing nucleic acid containing NGPCR gene sequences and/or coding sequences .
- Such methods can be used to construct expression vectors containing presently described NGPCR nucleotide sequences and appropriate transcriptional and translational control signals. These methods include, for example, in vi tro recombinant DNA techniques, synthetic techniques, and in vivo genetic recombination. See, for example, the techniques described in Sambrook et al . , 1989, supra , and Ausubel et al . , 1989, supra .
- NGPCR nucleotide sequence may be chemically synthesized using, for example, synthesizers. See, for example, the techniques described in "Oligonucleotide Synthesis", 1984, Gait, M.J. ed. , IRL Press, Oxford, which is incorporated by reference herein in its entirety.
- NGPCR nucleotide sequences of the invention A variety of host-expression vector systems may be utilized to express the NGPCR nucleotide sequences of the invention.
- NGPCR peptide or polypeptide is a soluble derivative (e.g., NGPCR peptides corresponding to an
- ECD truncated or deleted NGPCR in which a TM and/or CD are deleted
- the peptide or polypeptide can be recovered from the culture, i.e., from the host cell in cases where the NGPCR peptide or polypeptide is not secreted, and from the culture media in cases where the NGPCR peptide or polypeptide is secreted by the cells.
- expression systems also encompass engineered host cells that express a NGPCR, or functional equivalent, in si tu, i . e . , anchored in the cell membrane. Purification or enrichment of NGPCR from such expression systems can be accomplished using appropriate detergents and lipid micelles and methods well known to those skilled in the art.
- engineered host cells themselves may be used in situations where it is important not only to retain the structural and functional characteristics of the NGPCR, but to assess biological activity, e.g., in drug screening assays .
- the expression systems that may be used for purposes of the invention include but are not limited to microorganisms such as bacteria (e.g., E. coli , B . subtilis) transformed with recombinant bacteriophage DNA, plasmid DNA or cosmid DNA expression vectors containing NGPCR nucleotide sequences; yeast (e.g., Saccharomyces , Pichia) transformed with recombinant yeast expression vectors containing NGPCR nucleotide sequences; insect cell systems infected with recombinant virus expression vectors (e.g., baculovirus) containing NGPCR sequences; plant cell systems infected with recombinant virus expression vectors (e.g., cauliflower mosaic virus, CaMV; tobacco mosaic virus, TMV) or transformed with recombinant plasmid expression vectors (e.g., Ti plasmid) containing NGPCR nucleotide sequences; or mammalian cell systems (e.g., COS,
- a number of expression vectors may be advantageously selected depending upon the use intended for the NGPCR gene product being expressed. For example, when a large quantity of such a protein is to be produced, for the generation of pharmaceutical compositions of NGPCR protein or for raising antibodies to a NGPCR protein, for example, vectors that direct the expression of high levels of fusion protein products that are readily purified may be desirable.
- vectors include, but are not limited, to the E . coli expression vector pUR278 (Ruther et al . , 1983, EMBO J.
- pGEX vectors may also be used to express foreign polypeptides as fusion proteins with glutathione S-transferase (GST) .
- GST glutathione S-transferase
- fusion proteins are soluble and can easily be purified from lysed cells by adsorption to glutathione-agarose beads followed by elution in the presence of free glutathione.
- the PGEX vectors are designed to include thrombin or factor Xa protease cleavage sites so that the cloned target gene product can be released from the GST moiety.
- Autographa calif ornica nuclear polyhidrosis virus (AcNPV) is used as a vector to express foreign genes.
- the virus grows in Spodoptera frugiperda cells.
- a NGPCR gene coding sequence may be cloned individually into non-essential regions (for example the polyhedrin gene) of the virus and placed under control of an AcNPV promoter (for example the polyhedrin promoter) .
- Successful insertion of NGPCR gene coding sequence will result in inactivation of the polyhedrin gene and production of non- occluded recombinant virus (i.e., virus lacking the proteinaceous coat coded for by the polyhedrin gene) .
- Patent No. 4,215,051 Japanese Patent No. 4,215,051
- a number of viral -based expression systems may be utilized.
- the NGPCR nucleotide sequence of interest may be ligated to an adenovirus transcription/translation control complex, e.g., the late promoter and tripartite leader sequence.
- This chimeric gene may then be inserted in the adenovirus genome by in vitro or in vivo recombination. Insertion in a non- essential region of the viral genome (e.g., region El or E3) will result in a recombinant virus that is viable and capable of expressing a NGPCR gene product in infected hosts (e. g. ,
- Specific initiation signals may also be required for efficient translation of inserted NGPCR nucleotide sequences. These signals include the ATG initiation codon and adjacent sequences. In cases where an entire NGPCR gene or cDNA, including its own initiation codon and adjacent sequences, is inserted into the appropriate expression vector, no additional translational control signals may be needed. However, in cases where only a portion of a NGPCR coding sequence is inserted, exogenous translational control signals, including, perhaps, the ATG initiation codon, typically are provided. Furthermore, the initiation codon typically must be in phase with the reading frame of the desired coding sequence to ensure translation of the entire insert.
- exogenous translational control signals and initiation codons can be of a variety of origins, both natural and synthetic.
- the efficiency of expression may be enhanced by the inclusion of appropriate transcription enhancer elements, transcription terminators, etc. (See Bittner et al . , 1987, Methods in
- a host cell strain may be chosen that modulates the expression of the inserted sequences, or modifies and processes the gene product in the specific fashion desired. Such modifications (e.g., glycosylation) and processing (e.g., cleavage) of protein products may be important for the function of the protein.
- Different host cells have characteristic and specific mechanisms for the post-translational processing and modification of proteins and gene products. Appropriate cell lines or host systems can be chosen to ensure the correct modification and processing of the foreign protein expressed.
- eukaryotic host cells which possess the cellular machinery for proper processing of the primary transcript, glycosylation, and phosphorylation of the gene product may be used.
- mammalian host cells include, but are not limited to, CHO, VERO, BHK, HeLa, COS, MDCK, 293, 3T3, and WI38 cell lines.
- cell lines which stably express the NGPCR sequences described above may be engineered.
- host cells can be transformed with DNA controlled by appropriate expression control elements (e.g., promoter, enhancer sequences, transcription terminators, polyadenylation sites, etc.), and a selectable marker.
- appropriate expression control elements e.g., promoter, enhancer sequences, transcription terminators, polyadenylation sites, etc.
- engineered cells may be allowed to grow for 1-2 days in an enriched media, and then are switched to a selective media.
- the selectable marker in the recombinant plasmid confers resistance to the selection and allows cells to stably integrate the plasmid into their chromosomes and grow to form foci which in turn can be cloned and expanded into cell lines.
- This method may advantageously be used to engineer cell lines which express the NGPCR gene product. Such engineered cell lines may be particularly useful in screening and evaluation of compounds that affect the endogenous activity of the NGPCR gene product .
- a number of selection systems may be used, including but not limited to the herpes simplex virus thymidine kinase (Wigler, et al . , 1977, Cell 11:223), hypoxanthine-guanine phosphoribosyltransferase (Szybalska & Szybalski, 1962, Proc . Natl. Acad. Sci. USA 48:2026), and adenine phosphoribosyltransferase (Lowy, et al . , 1980, Cell 22:817) genes can be employed in tk " , hgprt " or aprt cells, respectively. Also, antimetabolite resistance can be used as the basis of selection for the following genes: dhfr, which confers resistance to methotrexate (Wigler, et al . , 1980,
- any fusion protein may be readily purified by utilizing an antibody specific for the fusion protein being expressed.
- a system described by Janknecht et al allows for the ready purification of non-denatured fusion proteins expressed in human cell lines (Janknecht, et al . ,
- NGPCR gene products can also be expressed in transgenic animals.
- Animals of any species including, but not limited to, worms, mice, rats, rabbits, guinea pigs, rodents, pigs, micro-pigs, birds, goats, farm animals, and non-human primates, e.g., baboons, monkeys, and chimpanzees may be used to generate NGPCR transgenic animals.
- Any technique known m the art may be used to introduce a NGPCR transgene into animals to produce the founder lines of transgenic animals.
- Such techniques include, but are not limited to pronuclear microin ⁇ ection (Hoppe, P.C. and Wagner, T.E., 1989, U.S. Pat. No. 4,873,191); retrovirus mediated gene transfer into germ lines (Van der Putten et al . , 1985, Proc.
- the present invention provides for transgenic animals that carry the NGPCR transgene m all their cells, as well as animals which carry the transgene m some, but not all their cells, i.e., mosaic animals or somatic cell transgenic animals.
- the transgene may be integrated as a single transgene or in concatamers, e.g., head-to-head tandems or head-to-tail tandems.
- the transgene may also be selectively introduced into and activated m a particular cell type by following, for example, the teaching of Lasko et al . , 1992,
- NGPCR transgene be integrated into the chromosomal site of the endogenous NGPCR gene
- gene targeting is preferred. Briefly, when such a technique is to be utilized, vectors containing some nucleotide sequences homologous to the endogenous NGPCR gene are designed for the purpose of integrating, via homologous recombination with chromosomal sequences, into and disrupting the function of the nucleotide sequence of the endogenous NGPCR gene ( i . e . ,
- the transgene can also be selectively introduced into a particular cell type, thus inactivating the endogenous NGPCR gene in only that cell type, by following, for example, the teaching of Gu et al . , 1994, Science, 265:103-106.
- the regulatory sequences required for such a cell -type specific inactivation will depend upon the particular cell type of interest, and will be apparent to those of skill in the art.
- the expression of the recombinant NGPCR gene may be assayed utilizing standard techniques. Initial screening may be accomplished by Southern blot analysis or PCR techniques to analyze animal tissues to assay whether integration of the transgene has taken place. The level of mRNA expression of the transgene in the tissues of the transgenic animals may also be assessed using techniques which include but are not limited to Northern blot analysis of tissue samples obtained from the animal, in si tu hybridization analysis, and RT-PCR.
- Samples of NGPCR gene-expressing tissue may also be evaluated immunocytochemically using antibodies specific for the NGPCR transgene product .
- Antibodies that specifically recognize one or more epitopes of a NGPCR, or epitopes of conserved variants of a NGPCR, or peptide fragments of a NGPCR are also encompassed by the invention.
- Such antibodies include but are not limited to polyclonal antibodies, monoclonal antibodies (mAbs), humanized or chimeric antibodies, single chain antibodies, Fab fragments, F(ab') 2 fragments, fragments produced by a Fab expression library, anti-idiotypic (anti-Id) antibodies, and epitope-binding fragments of any of the above.
- the antibodies of the invention may be used, for example, in the detection of NGPCR in a biological sample and may, therefore, be utilized as part of a diagnostic or prognostic technique whereby patients may be tested for abnormal amounts of NGPCR.
- Such antibodies may also be utilized in conjunction with, for example, compound screening schemes, as described, below, in Section 5.5, for the evaluation of the effect of test compounds on expression and/or activity of a NGPCR gene product.
- Such antibodies can be used in conjunction gene therapy to, for example, evaluate the normal and/or engineered NGPCR-expressing cells prior to their introduction into the patient.
- Such antibodies may additionally be used as a method for the inhibition of abnormal NGPCR activity.
- such antibodies may, therefore, be utilized as part of weight disorder treatment methods.
- various host animals may be immunized by injection with the NGPCR, an NGPCR peptide (e.g., one corresponding to a functional domain of the receptor, such as an ECD, TM or CD) , truncated NGPCR polypeptides (NGPCR in which one or more domains, e.g., a TM or CD, has been deleted) , functional equivalents of the NGPCR or mutants of the NGPCR.
- Such host animals may include but are not limited to rabbits, mice, and rats, to name but a few.
- adjuvants may be used to increase the immunological response, depending on the host species, including but not limited to Freund ' s (complete and incomplete), mineral gels such as aluminum hydroxide, surface active substances such as lysolecithin, pluronic polyols, polyanions, peptides, oil emulsions, keyhole limpet hemocyanin, dinitrophenol , and potentially useful human adjuvants such as BCG (bacille Calmette-Guerin) and Corynebacterium parvum.
- BCG Bacille Calmette-Guerin
- Monoclonal antibodies which are homogeneous populations of antibodies to a particular antigen, may be obtained by any technique which provides for the production of antibody molecules by continuous cell lines in culture. These include, but are not limited to, the hybridoma technique of Kohler and Milstein, (1975, Nature 256:495-497; and U.S. Patent No.
- Such antibodies may be of any immunoglobulin class including IgG, IgM, IgE, IgA, IgD and any subclass thereof .
- the hybridoma producing the mAb of this invention may be cultivated in vitro or in vivo. Production of high titers of mAbs in vivo makes this the presently preferred method of production.
- a chimeric antibody is a molecule in which different portions are derived from different animal species, such as those having a variable region derived from a murine mAb and a human immunoglobulin constant region.
- techniques described for the production of single chain antibodies U.S. Patent 4,946,778; Bird, 1988, Science 242:423-426; Huston et al . , 1988, Proc. Natl. Acad.
- Single chain antibodies are formed by linking the heavy and light chain fragments of the Fv region via an amino acid bridge, resulting in a single chain polypeptide .
- Antibody fragments which recognize specific epitopes may be generated by known techniques.
- such fragments include but are not limited to: the F(ab') 2 fragments which can be produced by pepsin digestion of the antibody molecule and the Fab fragments which can be generated by reducing the disulfide bridges of the F(ab') 2 fragments.
- Fab expression libraries may be constructed (Huse et al . , 1989,
- Antibodies to a NGPCR can, in turn, be utilized to generate anti-idiotype antibodies that "mimic" a given NGPCR, using techniques well known to those skilled in the art.
- antibodies which bind to a NGPCR ECD and competitively inhibit the binding of a ligand of NGPCR can be used to generate anti- idiotypes that "mimic" a NGPCR ECD and, therefore, bind and neutralize a ligand.
- Such neutralizing anti-idiotypes or Fab fragments of such anti-idiotypes can be used in therapeutic regimens involving the NGPCR signaling pathway.
- such reagents may be used, for example, for: (1) the detection of the presence of NGPCR gene mutations, or the detection of either over- or under-expression of NGPCR mRNA relative to a given phenotype; (2) the detection of either an over- or an under-abundance of NGPCR gene product relative to a given phenotype; and (3) the detection of perturbations or abnormalities in the signal transduction pathway mediated by NGPCR.
- the methods described herein may be performed, for example, by utilizing pre-packaged diagnostic kits comprising at least one specific NGPCR nucleotide sequence or NGPCR antibody reagent described herein, which may be conveniently used, e.g., in clinical settings, to diagnose patients exhibiting body weight disorder abnormalities.
- any nucleated cell can be used as a starting source for genomic nucleic acid.
- any cell type or tissue in which the NGPCR gene is expressed such as, for example, stomach or brain cells can be utilized.
- NGPCR GENES AND TRANSCRIPTS Mutations within a NGPCR gene can be detected by utilizing a number of techniques. Nucleic acid from any nucleated cell can be used as the starting point for such assay techniques, and may be isolated according to standard nucleic acid preparation procedures which are well known to those of skill in the art.
- DNA may be used in hybridization or amplification assays of biological samples to detect abnormalities involving NGPCR gene structure, including point mutations, insertions, deletions and chromosomal rearrangements.
- assays may include, but are not limited to, Southern analyses, single stranded conformational polymorphism analyses (SSCP) , and PCR analyses .
- Such diagnostic methods for the detection of NGPCR gene- specific mutations can involve for example, contacting and incubating nucleic acids including recombinant DNA molecules, cloned genes or degenerate variants thereof, obtained from a sample, e.g., derived from a patient sample or other appropriate cellular source, with one or more labeled nucleic acid reagents including recombinant DNA molecules, cloned genes or degenerate variants thereof, as described in Section 5.1, under conditions favorable for the specific annealing of these reagents to their complementary sequences within a given NGPCR gene.
- the lengths of these nucleic acid reagents are at least 15 to 30 nucleotides.
- nucleic acid:NGPCR molecule hybrid After incubation, all non-annealed nucleic acids are removed from the nucleic acid:NGPCR molecule hybrid. The presence of nucleic acids which have hybridized, if any such molecules exist, is then detected. Using such a detection scheme, the nucleic acid from the cell type or tissue of interest can be immobilized, for example, to a solid support such as a membrane, or a plastic surface such as that on a microtiter plate or polystyrene beads. In this case, after incubation, non- annealed, labeled nucleic acid reagents of the type described in Section 5.1 are easily removed.
- NGPCR gene sequences to which the nucleic acid reagents have annealed can be compared to the annealing pattern expected from a normal NGPCR gene sequence in order to determine whether a NGPCR gene mutation is present.
- Alternative diagnostic methods for the detection of NGPCR gene specific nucleic acid molecules, in patient samples or other appropriate cell sources may involve their amplification, e.g., by PCR (the experimental embodiment set forth in Mullis, K.B., 1987, U.S. Patent No. 4,683,202), followed by the detection of the amplified molecules using techniques well known to those of skill in the art.
- the resulting amplified sequences can be compared to those which would be expected if the nucleic acid being amplified contained only normal copies of a NGPCR gene in order to determine whether a NGPCR gene mutation exists.
- genotyping techniques can be performed to identify individuals carrying NGPCR gene mutations. Such techniques include, for example, the use of restriction fragment length polymorphisms (RFLPs) , which involve sequence variations in one of the recognition sites for the specific restriction enzyme used.
- RFLPs restriction fragment length polymorphisms
- Caskey et al . (U.S. Pat. No. 5,364,759, which is incorporated herein by reference in its entirety) describe a DNA profiling assay for detecting short tri and tetra nucleotide repeat sequences.
- the process includes extracting the DNA of interest, such as the NGPCR gene, amplifying the extracted DNA, and labeling the repeat sequences to form a genotypic map of the individual's DNA.
- the level of NGPCR gene expression can also be assayed by detecting and measuring NGPCR transcription.
- RNA from a cell type or tissue known, or suspected to express the NGPCR gene, such as brain may be isolated and tested utilizing hybridization or PCR techniques such as are described, above.
- the isolated cells can be derived from cell culture or from a patient.
- the analysis of cells taken from culture may be a necessary step in the assessment of cells to be used as part of a cell-based gene therapy technique or, alternatively, to test the effect of compounds on the expression of the NGPCR gene.
- analyses may reveal both quantitative and qualitative aspects of the expression pattern of the NGPCR gene, including activation or inactivation of NGPCR gene expression.
- cDNAs are synthesized from the RNAs of interest (e.g., by reverse transcription of the RNA molecule into cDNA) .
- a sequence within the cDNA is then used as the template for a nucleic acid amplification reaction, such as a PCR amplification reaction, or the like.
- the nucleic acid reagents used as synthesis initiation reagents (e.g., primers) in the reverse transcription and nucleic acid amplification steps of this method can be chosen from among the NGPCR nucleic acid reagents described in Section 5.1.
- the preferred lengths of such nucleic acid reagents are at least 9-30 nucleotides.
- the nucleic acid amplification may be performed using radioactively or non- radioactively labeled nucleotides.
- enough amplified product may be made such that the product may be visualized by standard ethidium bromide staining, by utilizing any other suitable nucleic acid staining method, or by sequencing.
- NGPCR gene expression assays in si tu" , i . e . , directly upon tissue sections (fixed and/or frozen) of patient tissue obtained from biopsies or resections, such that no nucleic acid purification is necessary.
- Nucleic acid reagents such as those described in Section 5.1 may be used as probes and/or primers for such in situ procedures (See, for example, Nuovo, G.J., 1992, “PCR In Situ Hybridization: Protocols And Applications", Raven Press, NY) .
- Standard Northern analysis can be performed to determine the level of mRNA expression of the NGPCR gene.
- NGPCR GENE PRODUCTS Antibodies directed against wild type or mutant NGPCR gene products or conserved variants or peptide fragments thereof, which are discussed, above, in Section 5.3, may also be used as diagnostics and prognostics, as described herein. Such diagnostic methods, may be used to detect abnormalities in the level of NGPCR gene expression, or abnormalities in the structure and/or temporal, tissue, cellular, or subcellular location of the NGPCR, and may be performed in vivo or in vitro, such as, for example, on biopsy tissue.
- antibodies directed to epitopes of the NGPCR ECD can be used in vivo to detect the pattern and level of expression of the NGPCR in the body.
- Such antibodies can be labeled, e.g., with a radio-opaque or other appropriate compound and injected into a subject in order to visualize binding to the NGPCR expressed in the body using methods such as X-rays, CAT-scans, or MRI .
- Labeled antibody fragments e.g., the Fab or single chain antibody comprising the smallest portion of the antigen binding region, are preferred for this purpose to promote crossing the blood-brain barrier and permit labeling NGPCRs expressed in the brain.
- any NGPCR fusion protein or NGPCR conjugated protein whose presence can be detected can be administered.
- NGPCR fusion or conjugated proteins labeled with a radio-opaque or other appropriate compound can be administered and visualized in vivo, as discussed, above for labeled antibodies.
- NGPCR fusion proteins as AP-NGPCR on NGPCR-Ap fusion proteins can be utilized for in vi tro diagnostic procedures.
- immunoassays or fusion protein detection assays, as described above, can be utilized on biopsy and autopsy samples in vi tro to permit assessment of the expression pattern of the NGPCR.
- Such assays are not confined to the use of antibodies that define a NGPCR ECD, but can include the use of antibodies directed to epitopes of any of the domains of a NGPCR, e.g., the ECD, the TM and/or CD.
- the use of each or all of these labeled antibodies will yield useful information regarding translation and intracellular transport of the NGPCR to the cell surface, and can identify defects in processing.
- the tissue or cell type to be analyzed will generally include those which are known, or suspected, to express the NGPCR gene.
- the protein isolation methods employed herein may, for example, be such as those described in Harlow and Lane (Harlow, E. and Lane, D., 1988, "Antibodies: A
- the isolated cells can be derived from cell culture or from a patient.
- the analysis of cells taken from culture may be a necessary step in the assessment of cells that could be used as part of a cell -based gene therapy technique or, alternatively, to test the effect of compounds on the expression of a NGPCR gene.
- antibodies, or fragments of antibodies, such as those described, above, in Section 5.3, useful in the present invention may be used to quantitatively or qualitatively detect the presence of NGPCR gene products or conserved variants or peptide fragments thereof. This can be accomplished, for example, by immunofluorescence techniques employing a fluorescently labeled antibody (see below, this Section) coupled with light microscopic, flow cytometric, or fluorimetric detection. Such techniques are especially preferred if such NGPCR gene products are expressed on the cell surface.
- the antibodies (or fragments thereof) or NGPCR fusion or conjugated proteins useful in the present invention may, additionally, be employed histologically, as in immunofluorescence, immunoelectron microscopy or non-immuno assays, for in si tu detection of NGPCR gene products or conserved variants or peptide fragments thereof, or for NGPCR binding (in the case of labeled NGPCR ligand fusion protein) .
- si tu detection may be accomplished by removing a histological specimen from a patient, and applying thereto a labeled antibody or fusion protein of the present invention.
- the antibody (or fragment) or fusion protein is preferably applied by overlaying the labeled antibody (or fragment) onto a biological sample.
- Immunoassays and non-immunoassays for NGPCR gene products or conserved variants or peptide fragments thereof will typically comprise incubating a sample, such as a biological fluid, a tissue extract, freshly harvested cells, or lysates of cells which have been incubated in cell culture, in the presence of a detectably labeled antibody capable of identifying NGPCR gene products or conserved variants or peptide fragments thereof, and detecting the bound antibody by any of a number of techniques well-known in the art.
- the biological sample may be brought in contact with and immobilized onto a solid phase support or carrier such as nitrocellulose, or other solid support which is capable of immobilizing cells, cell particles or soluble proteins.
- a solid phase support or carrier such as nitrocellulose, or other solid support which is capable of immobilizing cells, cell particles or soluble proteins.
- the support may then be washed with suitable buffers followed by treatment with the detectably labeled NGPCR antibody or NGPCR ligand fusion protein.
- the solid phase support may then be washed with the buffer a second time to remove unbound antibody or fusion protein.
- the amount of bound label on solid support may then be detected by conventional means.
- solid phase support or carrier is intended any support capable of binding an antigen or an antibody.
- Supports or carriers include glass, polystyrene, polypropylene, polyethylene, dextran, nylon, amylases, natural and modified celluloses, polyacrylamides, gabbros, and magnetite.
- the nature of the carrier can be either soluble to some extent or insoluble for the purposes of the present invention.
- the support material may have virtually any possible structural configuration so long as the coupled molecule is capable of binding to an antigen or antibody.
- the support configuration may be spherical, as in a bead, or cylindrical, as in the inside surface of a test tube, or the external surface of a rod. Alternatively, the surface may be flat such as a sheet, test strip, etc.
- Preferred supports include polystyrene beads. Those skilled in the art will know many other suitable carriers for binding antibody or antigen, or will be able to ascertain the same by use of routine experimentation.
- binding activity of a given lot of NGPCR antibody or NGPCR ligand fusion protein may be determined according to well known methods. Those skilled in the art will be able to determine operative and optimal assay conditions for each determination by employing routine experimentation.
- NGPCR antibody With respect to antibodies, one of the ways in which the NGPCR antibody can be detectably labeled is by linking the same to an enzyme and use in an enzyme immunoassay (EIA)
- the enzyme that is bound to the antibody will react with an appropriate substrate, preferably a chromogenic substrate, in such a manner as to produce a chemical moiety which can be detected, for example, by spectrophotometric, fluorimetric or by visual means.
- Enzymes which can be used to detectably label the antibody include, but are not limited to, malate dehydrogenase, staphylococcal nuclease, delta-5-steroid isomerase, yeast alcohol dehydrogenase, alpha- glycerophosphate, dehydrogenase, triose phosphate isomerase, horseradish peroxidase, alkaline phosphatase, asparaginase, glucose oxidase, beta-galactosidase, ribonuclease, urease, catalase, glucose-6-phosphate dehydrogenase, glucoamylase and acetylcholinesterase .
- the detection can be accomplished by colorimetric methods which employ a chromogenic substrate for the enzyme. Detection may also be accomplished by visual comparison of the extent of enzymatic reaction of a substrate in comparison with similarly prepared standards.
- Detection may also be accomplished using any of a variety of other immunoassays.
- a radioimmunoassay RIA
- the radioactive isotope can be detected by such means as the use of a gamma counter or a scintillation counter or by autoradiography .
- fluorescent labeling compounds fluorescein isothiocyanate, rhodamine, phycoerythrin, phycocyanin, allophycocyanin, o-phthaldehyde and fluorescamine .
- the antibody can also be detectably labeled using fluorescence emitting metals such as 152 Eu, or others of the lanthanide series. These metals can be attached to the antibody using such metal chelating groups as diethylenetriaminepentacetic acid (DTPA) or ethylenediaminetetraacetic acid (EDTA) .
- DTPA diethylenetriaminepentacetic acid
- EDTA ethylenediaminetetraacetic acid
- the antibody also can be detectably labeled by coupling it to a chemiluminescent compound. The presence of the chemiluminescent-tagged antibody is then determined by detecting the presence of luminescence that arises during the course of a chemical reaction. Examples of particularly useful chemiluminescent labeling compounds are luminol, isoluminol, theromatic acridinium ester, imidazole, acridinium salt and oxalate ester.
- Bioluminescence is a type of chemiluminescence found in biological systems in, which a catalytic protein increases the efficiency of the chemiluminescent reaction. The presence of a bioluminescent protein is determined by detecting the presence of luminescence. Important bioluminescent compounds for purposes of labeling are luciferin, luciferase and aequorin.
- the following assays are designed to identify compounds that interact with (e.g., bind to) NGPCRs (including, but not limited to an ECD or CD of a NGPCR) , compounds that interact with ( e . g. , bind to) intracellular proteins that interact with
- NGPCR including but not limited to the TM and CD of NGPCR
- compounds that interfere with the interaction of NGPCR with transmembrane or intracellular proteins involved in NGPCR- mediated signal transduction and to compounds which modulate the activity of NGPCR gene (i.e., modulate the level of NGPCR gene expression) or modulate the level of NGPCR.
- Assays may additionally be utilized which identify compounds which bind to NGPCR gene regulatory sequences (e.g., promoter sequences) and which may modulate NGPCR gene expression. See e.g.,
- the compounds that can be screened in accordance with the invention include but are not limited to peptides, antibodies and fragments thereof, and other organic compounds (e.g., peptidomimetics) that bind to an ECD of a NGPCR and either mimic the activity triggered by the natural ligand (i.e., agonists) or inhibit the activity triggered by the natural ligand (i.e., antagonists); as well as peptides, antibodies or fragments thereof, and other organic compounds that mimic the
- Such compounds may include, but are not limited to, peptides such as, for example, soluble peptides, including but not limited to members of random peptide libraries; (see, e.g., Lam, K.S. et al . , 1991, Nature 354:82-84; Houghten, R. et al . , 1991, Nature 354:84-86), and combinatorial chemistry- derived molecular library made of D- and/or L- configuration amino acids, phosphopeptides (including, but not limited to members of random or partially degenerate, directed phosphopeptide libraries; see, e.g., Songyang, Z. et al . ,
- antibodies including, but not limited to, polyclonal, monoclonal, humanized, anti-idiotypic, chimeric or single chain antibodies, and FAb, F(ab') 2 and FAb expression library fragments, and epitope-binding fragments thereof), and small organic or inorganic molecules.
- Other compounds which can be screened in accordance with the invention include but are not limited to small organic molecules that are able to cross the blood-brain barrier, gain entry into an appropriate cell (e.g., in the choroid plexus, the hypothalamus, etc.) and affect the expression of a NGPCR gene or some other gene involved in the NGPCR signal transduction pathway (e.g., by interacting with the regulatory region or transcription factors involved in gene expression) ; or such compounds that affect the activity of the NGPCR (e.g., by inhibiting or enhancing the enzymatic activity of a CD) or the activity of some other intracellular factor involved in the NGPCR signal transduction pathway.
- small organic molecules that are able to cross the blood-brain barrier, gain entry into an appropriate cell (e.g., in the choroid plexus, the hypothalamus, etc.) and affect the expression of a NGPCR gene or some other gene involved in the NGPCR signal transduction pathway (e.g., by interacting with the regulatory region
- Computer modeling and searching technologies permit identification of compounds, or the improvement of already identified compounds, that can modulate NGPCR expression or activity. Having identified such a compound or composition, the active sites or regions are identified. Such active sites might typically be ligand binding sites.
- the active site can be identified using methods known in the art including, for example, from the amino acid sequences of peptides, from the nucleotide sequences of nucleic acids, or from study of complexes of the relevant compound or composition with its natural ligand. In the latter case, chemical or X-ray crystallographic methods can be used to find the active site by finding where on the factor the complexed ligand is found.
- the three dimensional geometric structure of the active site is determined. This can be done by known methods, including X-ray crystallography, which can determine a complete molecular structure. On the other hand, solid or liquid phase NMR can be used to determine certain intramolecular distances. Any other experimental method of structure determination can be used to obtain partial or complete geometric structures.
- the geometric structures may be measured with a complexed ligand, natural or artificial, which may increase the accuracy of the active site structure determined.
- the methods of computer based numerical modeling can be used to complete the structure or improve its accuracy.
- Any recognized modeling method may be used, including parameterized models specific to particular biopolymers such as proteins or nucleic acids, molecular dynamics models based on computing molecular motions, statistical mechanics models based on thermal ensembles, or combined models.
- standard molecular force fields representing the forces between constituent atoms and groups, are necessary, and can be selected from force fields known in physical chemistry.
- the incomplete or less accurate experimental structures can serve as constraints on the complete and more accurate structures computed by these modeling methods.
- candidate modulating compounds can be identified by searching databases containing compounds along with information on their molecular structure. Such a search seeks compounds having structures that match the determined active site structure and that interact with the groups defining the active site. Such a search can be manual, but is preferably computer assisted. These compounds found from this search are potential NGPCR modulating compounds.
- these methods can be used to identify improved modulating compounds from an already known modulating compound or ligand.
- the composition of the known compound can be modified and the structural effects of modification can be determined using the experimental and computer modeling methods described above applied to the new composition.
- the altered structure is then compared to the active site structure of the compound to determine if an improved fit or interaction results. In this manner systematic variations in composition, such as by varying side groups, can be quickly evaluated to obtain modified modulating compounds or ligands of improved specificity or activity.
- CHARMm performs the energy minimization and molecular dynamics functions.
- QUANTA performs the construction, graphic modeling and analysis of molecular structure. QUANTA allows interactive construction, modification, visualization, and analysis of the behavior of molecules with each other.
- a number of articles review computer modeling of drugs interactive with specific proteins, such as Rotivinen, et al . ,
- Cell-based systems can also be used to identify compounds that bind NGPCRs as well as assess the altered activity associated with such binding in living cells.
- One tool of particular interest for such assays is green fluorescent protein which is described, inter alia, in U.S. Patent No.
- Cells that may be used in such cellular assays include, but are not limited to, leukocytes, or cell lines derived from leukocytes, lymphocytes, stem cells, including embryonic stem cells, and the like.
- expression host cells e.g., B95 cells, COS cells, CHO cells, OMK cells, fibroblasts, Sf9 cells
- B95 cells, COS cells, CHO cells, OMK cells, fibroblasts, Sf9 cells genetically engineered to express a functional NGPCR of interest and to respond to activation by the test, or natural, ligand, as measured by a chemical or phenotypic change, or induction of another host cell gene, can be used as an end point in the assay.
- Compounds identified via assays such as those described herein may be useful, for example, in elaborating certain biological functions of a NGPCR gene product. Such compounds can be administered to a patient at therapeutically effective doses to treat any of a variety of physiological or mental disorders.
- a therapeutically effective dose refers to that amount of the compound sufficient to result in any amelioration, impediment, prevention, or alteration of any biological or overt symptom.
- Toxicity and therapeutic efficacy of such compounds can be determined by standard pharmaceutical procedures in cell cultures or experimental animals, e.g., for determining the
- LD 50 the dose lethal to 50% of the population
- ED 50 the dose therapeutically effective in 50% of the population
- the dose ratio between toxic and therapeutic effects is the therapeutic index and it can be expressed as the ratio LD 50 /ED 50 .
- Compounds which exhibit large therapeutic indices are preferred. While compounds that exhibit toxic side effects may be used, typically care should be taken to design a delivery system that targets such compounds to the site of affected tissue in order to minimize potential damage to uninfected cells and, thereby, reduce side effects.
- the data obtained from the cell culture assays and animal studies can be used in formulating a range of dosage for use in humans.
- the dosage of such compounds lies preferably within a range of circulating concentrations that include the ED 50 with little or no toxicity.
- the dosage may vary within this range depending upon the dosage form employed and the route of administration utilized.
- the therapeutically effective dose can be estimated initially from cell culture assays.
- a dose may be formulated in animal models to achieve a circulating plasma concentration range that includes the IC 50 ( i . e . , the concentration of the test compound which achieves a half-maximal inhibition of symptoms) as determined in cell culture.
- IC 50 i . e .
- levels in plasma may be measured, for example, by high performance liquid chromatography.
- compositions for use in accordance with the present invention may be formulated in conventional manner using one or more physiologically acceptable carriers or excipients.
- the compounds and their physiologically acceptable salts and solvates may be formulated for administration by inhalation or insufflation (either through the mouth or the nose) or oral, buccal, parenteral, intracranial , intrathecal, or rectal administration.
- the pharmaceutical compositions may take the form of, for example, tablets or capsules prepared by conventional means with pharmaceutically acceptable excipients such as binding agents (e.g., pregelatinised maize starch, polyvinylpyrrolidone or hydroxypropyl methylcellulose) ; fillers (e.g., lactose, microcrystalline cellulose or calcium hydrogen phosphate) ; lubricants (e.g., magnesium stearate, talc or silica); disintegrants (e.g., potato starch or sodium starch glycolate) ; or wetting agents (e.g., sodium lauryl sulphate) .
- binding agents e.g., pregelatinised maize starch, polyvinylpyrrolidone or hydroxypropyl methylcellulose
- fillers e.g., lactose, microcrystalline cellulose or calcium hydrogen phosphate
- lubricants e.g., magnesium stearate, talc or silica
- disintegrants
- Liquid preparations for oral administration may take the form of, for example, solutions, syrups or suspensions, or they may be presented as a dry product for constitution with water or other suitable vehicle before use.
- Such liquid preparations may be prepared by conventional means with pharmaceutically acceptable additives such as suspending agents (e.g., sorbitol syrup, cellulose derivatives or hydrogenated edible fats) ; emulsifying agents (e.g., lecithin or acacia); non-aqueous vehicles (e.g., almond oil, oily esters, ethyl alcohol or fractionated vegetable oils); and preservatives (e.g., methyl or propyl-p-hydroxybenzoates or sorbic acid) .
- the preparations may also contain buffer salts, flavoring, coloring and sweetening agents as appropriate.
- compositions for oral administration may be suitably formulated to give controlled release of the active compound.
- compositions for buccal administration may take the form of tablets or lozenges formulated in conventional manner.
- the compounds for use according to the present invention are conveniently delivered in the form of an aerosol spray presentation from pressurized packs or a nebulizer, with the use of a suitable propellant, e.g., dichlorodifluoromethane, trichlorofluoromethane, dichlorotetrafluoroethane, carbon dioxide or other suitable gas.
- a suitable propellant e.g., dichlorodifluoromethane, trichlorofluoromethane, dichlorotetrafluoroethane, carbon dioxide or other suitable gas.
- the dosage unit may be determined by providing a valve to deliver a metered amount.
- Capsules and cartridges of e.g. gelatin for use in an inhaler or insufflator may be formulated containing a powder mix of the compound and a suitable powder base such as lactose or starch.
- the compounds may be formulated for parenteral administration by injection, e.g., by bolus injection or continuous infusion.
- Formulations for injection may be presented in unit dosage form, e.g., in ampoules or in multi- dose containers, with an added preservative.
- the compositions may take such forms as suspensions, solutions or emulsions in oily or aqueous vehicles, and may contain formulatory agents such as suspending, stabilizing and/or dispersing agents.
- the active ingredient may be in powder form for constitution with a suitable vehicle, e.g., sterile pyrogen- free water, before use.
- the compounds may also be formulated in rectal compositions such as suppositories or retention enemas, e.g., containing conventional suppository bases such as cocoa butter or other glycerides .
- the compounds may also be formulated as a depot preparation. Such long acting formulations may be administered by implantation (for example subcutaneously or intramuscularly) or by intramuscular injection.
- the compounds may be formulated with suitable polymeric or hydrophobic materials (for example as an emulsion in an acceptable oil) or ion exchange resins, or as sparingly soluble derivatives, for example, as a sparingly soluble salt.
- compositions may, if desired, be presented in a pack or dispenser device which may contain one or more unit dosage forms containing the active ingredient.
- the pack may for example comprise metal or plastic foil, such as a blister pack.
- the pack or dispenser device may be accompanied by instructions for administration.
- Compounds identified may be useful, for example, in modulating the activity of wild type and/or mutant NGPCR gene products; may be useful in elaborating certain biological functions of the NGPCR; may be utilized in screens for identifying compounds that disrupt normal NGPCR interactions; or may in themselves disrupt such interactions.
- the principle of the assays used to identify compounds that bind to the NGPCR involves preparing a reaction mixture of the NGPCR and the test compound under conditions and for a time sufficient to allow the two components to interact and bind, thus forming a complex which can be removed and/or detected in the reaction mixture.
- the NGPCR species used can vary depending upon the goal of the screening assay.
- a peptide corresponding to a ECD or a fusion protein containing one or more NGPCR ECD fused to a protein or polypeptide that affords advantages in the assay system e. g. , labeling, isolation of the resulting complex, etc.
- peptides corresponding to the NGPCR CD and fusion proteins containing the NGPCR CD can be used.
- the screening assays can be conducted in a variety of ways.
- one method to conduct such an assay would involve anchoring the NGPCR protein, polypeptide, peptide or fusion protein or the test substance onto a solid phase and detecting NGPCR/test compound complexes anchored on the solid phase at the end of the reaction.
- the NGPCR reactant may be anchored onto a solid surface, and the test compound, which is not anchored, may be labeled, either directly or indirectly.
- microtiter plates may conveniently be utilized as the solid phase.
- the anchored component may be immobilized by non-covalent or covalent attachments. Non- covalent attachment may be accomplished by simply coating the solid surface with a solution of the protein and drying.
- an immobilized antibody preferably a monoclonal antibody, specific for the protein to be immobilized may be used to anchor the protein to the solid surface.
- the surfaces may be prepared in advance and stored.
- the nonimmobilized component is added to the coated surface containing the anchored component. After the reaction is complete, unreacted components are removed (e.g., by washing) under conditions such that any complexes formed will remain immobilized on the solid surface.
- the detection of complexes anchored on the solid surface can be accomplished in a number of ways. Where the previously nonimmobilized component is pre-labeled, the detection of label immobilized on the surface indicates that complexes were formed.
- an indirect label can be used to detect complexes anchored on the surface; e.g., using a labeled antibody specific for the previously nonimmobilized component (the antibody, in turn, may be directly labeled or indirectly labeled with a labeled anti-Ig antibody) .
- a reaction can be conducted in a liquid phase, the reaction products separated from unreacted components, and complexes detected; e.g., using an immobilized antibody specific for a NGPCR protein, polypeptide, peptide or fusion protein or the test compound to anchor any complexes formed in solution, and a labeled antibody specific for the other component of the possible complex to detect anchored complexes .
- cell-based assays can be used to identify compounds that interact with NGPCR.
- cell lines that express NGPCR or cell lines (e.g., COS cells, CHO cells, fibroblasts, etc.) that have been genetically engineered to express NGPCR (e.g., by transfection or transduction of NGPCR DNA) can be used.
- Interaction of the test compound with, for example, a ECD of a NGPCR expressed by the host cell can be determined by comparison or competition with native ligand.
- ASSAYS FOR INTRACELLULAR PROTEINS THAT INTERACT WITH NGPCRs Any method suitable for detecting protein-protein interactions may be employed for identifying transmembrane proteins or intracellular proteins that interact with a NGPCR.
- traditional methods which may be employed are co-immunoprecipitation, crosslinking and co-purification through gradients or chromatographic columns of cell lysates or proteins obtained from cell lysates and a NGPCR to identify proteins in the lysate that interact with the NGPCR.
- the NGPCR component used can be a full length NGPCR, a soluble derivative lacking the membrane-anchoring region (e.g., a truncated NGPCR in which a TM is deleted resulting in a truncated molecule containing a ECD fused to a CD) , a peptide corresponding to a CD or a fusion protein containing a CD of a NGPCR.
- a truncated NGPCR in which a TM is deleted resulting in a truncated molecule containing a ECD fused to a CD e.g., a truncated NGPCR in which a TM is deleted resulting in a truncated molecule containing a ECD fused to a CD
- a peptide corresponding to a CD or a fusion protein containing a CD of a NGPCR e.g., a truncated NGPCR in which a TM is
- amino acid sequence of an intracellular protein which interacts with a NGPCR can be ascertained using techniques well known to those of skill in the art, such as via the Edman degradation technique. (See, e.g., Creighton,
- amino acid sequence obtained may be used as a guide for the generation of oligonucleotide mixtures that can be used to screen for gene sequences encoding such intracellular proteins. Screening can be accomplished, for example, by standard hybridization or PCR techniques. Techniques for the generation of oligonucleotide mixtures and the screening are well-known. (See, e.g.,
- methods may be employed which result in the simultaneous identification of genes which encode the transmembrane or intracellular proteins interacting with NGPCR.
- These methods include, for example, probing expression, libraries, in a manner similar to the well known technique of antibody probing of ⁇ gtll libraries, using labeled NGPCR protein, or an NGPCR polypeptide, peptide or fusion protein, e.g., an NGPCR polypeptide or NGPCR domain fused to a marker (e.g., an enzyme, fluor, luminescent protein, or dye) , or an Ig-Fc domain.
- a marker e.g., an enzyme, fluor, luminescent protein, or dye
- plasmids are constructed that encode two hybrid proteins : one plasmid has nucleotides encoding the DNA-binding domain of a transcription activator protein fused to a NGPCR nucleotide sequence encoding NGPCR, an NGPCR polypeptide, peptide, or fusion protein, and the other plasmid has nucleotides encoding the transcription activator protein's activation domain fused to a cDNA encoding an unknown protein which has been recombined into this plasmid as part of a cDNA library.
- the DNA-binding domain fusion plasmid and the cDNA library are transformed into a strain of the yeast Saccharomyces cerevisiae that contains a reporter gene (e . g. , HBS or lacZ) whose regulatory region contains the transcription activator's binding site.
- a reporter gene e . g. , HBS or lacZ
- the two-hybrid system or related methodology may be used to screen activation domain libraries for proteins that interact with the "bait" gene product.
- a NGPCR may be used as the bait gene product .
- Total genomic or cDNA sequences are fused to the DNA encoding an activation domain.
- DNA-binding domain are cotransformed into a yeast reporter strain, and the resulting transformants are screened for those that express the reporter gene.
- a bait NGPCR gene sequence such as the open reading frame of a NGPCR (or a domain of a NGPCR) can be cloned into a vector such that it is translationally fused to the DNA encoding the DNA-binding domain of the GAL4 protein. These colonies are purified and the library plasmids responsible for reporter gene expression are isolated. DNA sequencing is then used to identify the proteins encoded by the library plasmids.
- a cDNA library of the cell line from which proteins that interact with bait NGPCR gene product are to be detected can be made using methods routinely practiced in the art. According to a particular system described herein, for example, the cDNA fragments can be inserted into a vector such that they are translationally fused to the transcriptional activation domain of GAL4.
- This library can be co-transformed along with the bait NGPCR gene-GAL4 fusion plasmid into a yeast strain which contains a lacZ gene driven by a promoter which contains GAL4 activation sequence.
- a cDNA encoded protein, fused to GAL4 transcriptional activation domain, that interacts with bait NGPCR gene product will reconstitute an active GAL4 protein and thereby drive expression of the HIS3 gene.
- Colonies which express HIS3 can be detected by their growth on petri dishes containing semi-solid agar based media lacking histidine. The cDNA can then be purified from these strains, and used to produce and isolate the bait NGPCR gene- interacting protein using techniques routinely practiced in the art .
- binding partners The macromolecules that interact with the NGPCR are referred to, for purposes of this discussion, as "binding partners.” These binding partners are likely to be involved in the NGPCR signal transduction pathway. Therefore, it is desirable to identify compounds that interfere with or disrupt the interaction of such binding partners which may be useful in regulating the activity of a NGPCR and controlling disorders associated with NGPCR activity. For example, given their expression pattern, the described NGPCRs are contemplated to be particularly useful in methods for identifying compounds useful in the therapeutic treatment of obesity, inflammation, immune disorders, diabetes, heart and coronary disease, metabolic disorders, and cancer.
- the basic principle of the assay systems used to identify compounds that interfere with the interaction between a NGPCR and its binding partner or partners involves preparing a reaction mixture containing NGPCR protein, polypeptide, peptide or fusion protein as described in Sections 5.5.1 and 5.5.2 above, and the binding partner under conditions and for a time sufficient to allow the two to interact and bind, thus forming a complex.
- the reaction mixture is prepared in the presence and absence of the test compound.
- the test compound may be initially included in the reaction mixture, or may be added at a time subsequent to the addition of the NGPCR moiety and its binding partner. Control reaction mixtures are incubated without the test compound or with a placebo.
- any complexes between the NGPCR moiety and the binding partner is then detected.
- the formation of a complex in the control reaction, but not in the reaction mixture containing the test compound, indicates that the compound interferes with the interaction of the NGPCR and the interactive binding partner.
- complex formation within reaction mixtures containing the test compound and normal NGPCR protein may also be compared to complex formation within reaction mixtures containing the test compound and a mutant NGPCR. This comparison may be important in those cases wherein it is desirable to identify compounds that specifically disrupt interactions of mutant, or mutated, NGPCRs but not normal NGPCRs .
- the assay for compounds that interfere with the interaction of a NGPCR and its binding partners can be conducted in a heterogeneous or homogeneous format.
- Heterogeneous assays involve anchoring either the NGPCR moiety product or the binding partner onto a solid phase and detecting complexes anchored on the solid phase at the end of the reaction.
- homogeneous assays the entire reaction is carried out in a liquid phase. In either approach, the order of addition of reactants can be varied to obtain different information about the compounds being tested.
- test compounds that interfere with the interaction by competition can be identified by conducting the reaction m the presence of the test substance; i.e., by adding the test substance to the reaction mixture prior to, or simultaneously with, a NGPCR moiety and interactive binding partner.
- test compounds that disrupt preformed complexes e.g. compounds with higher binding constants that displace one of the components from the complex, can be tested by adding the test compound to the reaction mixture after complexes have been formed.
- Various formats, according to certain embodiments are described briefly below.
- a NGPCR moiety or an interactive binding partner is anchored onto a solid surface, while the non-anchored species is labeled, either directly or indirectly.
- the anchored species may be immobilized by non-covalent or covalent attachments. Non- covalent attachment may be accomplished simply by coating the solid surface with a solution of the NGPCR gene product or binding partner and drying. Alternatively, an immobilized antibody specific for the species to be anchored may be used to anchor the species to the solid surface. The surfaces may be prepared in advance and stored.
- the partner of the immobilized species is exposed to the coated surface with or without the test compound. After the reaction is complete, unreacted components are removed (e.g., by washing) and any complexes formed will remain immobilized on the solid surface.
- the detection of complexes anchored on the solid surface can be accomplished in a number of ways. Where the non- immobilized species is pre-labeled, the detection of label immobilized on the surface indicates that complexes were formed.
- an indirect label can be used to detect complexes anchored on the surface; e.g., using a labeled antibody specific for the initially non-immobilized species (the antibody, in turn, may be directly labeled or indirectly labeled with a labeled anti- Ig antibody) .
- the antibody in turn, may be directly labeled or indirectly labeled with a labeled anti- Ig antibody
- test compounds which inhibit complex formation or which disrupt preformed complexes can be detected.
- the reaction can be conducted in a liquid phase in the presence or absence of the test compound, the reaction products separated from unreacted components, and complexes detected; e.g., using an immobilized antibody specific for one of the binding components to anchor any complexes formed in solution, and a labeled antibody specific for the other partner to detect anchored complexes.
- test compounds which inhibit complex or which disrupt preformed complexes can be identified.
- a homogeneous assay in which a preformed complex of a NGPCR moiety and an interactive binding partner is prepared in which either the NGPCR or its binding partner is labeled, but the signal generated by the label is quenched due to formation of the complex (see, e.g., U.S. Patent No. 4,109,496 by
- a NGPCR fusion can be prepared for immobilization.
- a NGPCR or a peptide fragment e.g., corresponding to a CD, can be fused to a glutathione-S-transferase (GST) gene using a fusion vector, such as pGEX-5X-l, in such a manner that its binding activity is maintained in the resulting fusion protein.
- GST glutathione-S-transferase
- the interactive binding partner can be purified and used to raise a monoclonal antibody, using methods routinely practiced in the art and described above, in Section 5.3.
- This antibody can be labeled with the radioactive isotope 125 I , for example, by methods routinely practiced in the art.
- the GST-NGPCR fusion protein can be anchored to glutathione-agarose beads.
- the interactive binding partner can then be added in the presence or absence of the test compound in a manner that allows interaction and binding to occur.
- unbound material can be washed away, and the labeled monoclonal antibody can be added to the system and allowed to bind to the complexed components.
- the interaction between a NGPCR gene product and the interactive binding partner can be detected by measuring the amount of radioactivity that remains associated with the glutathione-agarose beads. A successful inhibition of the interaction by the test compound will result in a decrease in measured radioactivity.
- the GST-NGPCR fusion protein and the interactive binding partner can be mixed together in liquid in the absence of the solid glutathione-agarose beads.
- the test compound can be added either during or after the species are allowed to interact. This mixture can then be added to the glutathione-agarose beads and unbound material is washed away. Again the extent of inhibition of the NGPCR/binding partner interaction can be detected by adding the labeled antibody and measuring the radioactivity associated with the beads.
- these same techniques can be employed using peptide fragments that correspond to the binding domains of a NGPCR and/or the interactive or binding partner (in cases where the binding partner is a protein) , in place of one or both of the full length proteins.
- Any number of methods routinely practiced in the art can be used to identify and isolate the binding sites. These methods include, but are not limited to, mutagenesis of the gene encoding one of the proteins and screening for disruption of binding in a co-immunoprecipitation assay.
- Compensatory mutations in the gene encoding the second species in the complex can then be selected. Sequence analysis of the genes encoding the respective proteins will reveal the mutations that correspond to the region of the protein involved in interactive binding.
- one protein can be anchored to a solid surface using methods described above, and allowed to interact with and bind to its labeled binding partner, which has been treated with a proteolytic enzyme, such as trypsin. After washing, a relatively short, labeled peptide comprising the binding domain may remain associated with the solid material, which can be isolated and identified by amino acid sequencing.
- short gene segments can be engineered to express peptide fragments of the protein, which can then be tested for binding activity and purified or synthesized.
- a NGPCR gene product can be anchored to a solid material as described, above, by making a GST-NGPCR fusion protein and allowing it to bind to glutathione agarose beads.
- the interactive binding partner can be labeled with a radioactive isotope, such as 35 S, and cleaved with a proteolytic enzyme such as trypsin.
- Cleavage products can then be added to the anchored GST-NGPCR fusion protein and allowed to bind. After washing away unbound peptides, labeled bound material, representing the intracellular binding partner binding domain, can be eluted, purified, and analyzed for amino acid sequence by well-known methods. Peptides so identified can be produced synthetically or fused to appropriate facilitative proteins using recombinant DNA technology.
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