DNA MOLECULES ENCODING THE MELANOCORTIN 4 RECEPTOR PROTEIN FROM RHESUS MONKEY

Abstract: The present invention relates to rhesus monkey DNA molecules encoding the melanocortin-4 receptor protein, recombinant vectors comprising DNA molecules encoding rhesus MC-4R, recombinant host cells which contain a recombinant vector encoding rhesus MC-4R, the rhesus MC-4R protein encoded by the DNA molecule, and methods of identifying selective agonists and antagonists of rhesus MC-4R.

Description: TITLE OF THE INVENTION DNA MOLECULES ENCODING THE MELANOCORTIN 4 RECEPTOR PROTEIN FROM RHESUS MONKEY CROSS-REFERENCE TO RELATED APPLICATIONS The present application claims priority to U.S. Serial No. 60/107,721, filed November 9, 1998, which is hereby incorporated by reference. FIELD OF THE INVENTION The present invention relates to rhesus monkey (Macaca mulatto) DNA molecules encoding the melanocortin-4 receptor protein belonging to the rhodopsin sub-family of G-protein coupled receptors, recombinant vectors comprising DNA molecules encoding rhesus MC-4R, recombinant host cells which contain a recombinant vector encoding rhesus MC-4R, the rhesus MC-4R protein encoded by the DNA molecule, and methods of identifying selective agonists and antagonists of rhesus MC-4R. BACKGROUND OF THE INVENTION Melanocortin receptors belong to the rhodopsin sub-family of G- protein coupled receptors (GPCRs). Five different subtypes are known. These melanocortin receptors bind and are activated by peptides such as -, β, or γ- melanocyte stimulating hormones (α-, β-, γ-MSH) derived from the pro- opiomelanocortin (POMC) gene. A wide range of physiological functions are believed to be mediated by melanocortin peptides and their receptors. U.S. Patent No. 5,532,347 (issued July 2, 1996) to Cone and Mountjoy discloses human and mouse DNA molecules which encode MC-1R (also known in the art as α-MSH-R). The expressed human protein contains 317 amino acids. U.S. Patent No. 5,280,112 (issued January 18, 1994) and U.S. Patent No. 5,554,729 (issued September 10, 1996), both to Cone and Mountjoy, disclose human and mouse DNA molecules which encode MC-2R (also known in the art as ACTH-R). The human MC-2R protein contains 297 amino acids. Mountjoy, et al. (1992, Science 257: 1248-1251) describe DNA molecules and the concomitant protein for human MC-1R and human MC-2R. Chhajlani, et al. (1992, FEBS Letters 309: 417-420) also disclose a human DNA molecule comprising an open reading frame which encodes human MC1-R. Roselli-Rehfuss, et al, (1993, Proc. Natl. Acad. Sci 90: 8856-8860) disclose a cDNA clone encoding rat MC-3R cDNA. U. S. Patent No. 5,622,860 (issued April 22, 1997) and U.S. Patent No. 5,703,220 (issued December 30, 1997) to Yamada and Gantz, disclose DNA molecules which encode human MC-3R and human MC-4R, respectively (see also Gantz, et al., 1993, J. Biol. Chem. 268(11): 8246-8250). A DNA molecule encoding human MC-5R was also disclosed by Mountjoy, et al. (1994, Mol. Endocrin. 8: 1298-1308). Chhajlani, et al. (1993, Biochem. Biophys. Res. Comm., 195(2): 866- 873) disclose a DNA molecule which the authors state encodes MC-5R. This clone was initially designated MC2. Fathi, et al. (1995, Neurochemical Research 20(1):107-113) also disclose a DNA molecule thought to encode human MC-5R. There are several sequence discrepancies when compared to the DNA molecule disclosed by Chhajlani, et al., id. Griffon, et al. (1994, Biochem. Biophys. Res. Comm., 200(2): 1007- 1014) disclose DNA clones from human and rat which encode MC-5R. The human DNA sequence agrees with the human DNA sequence disclosed in Fathi et al. id. Gantz, et al. (1994, Biochem. Biophys. Res. Comm., 200(3): 11214- 11220; see also U.S. Patent No. 5,710,265, issued January 20, 1998 to Yamada and Gantz) and Labbe, et al. (1994, Biochemistry 33: 4543-4549) disclose DNA clones from mouse which encode MC-5R. Barrett, et al. (1994, J. Mol. Endocrin. 12: 203-213) disclose DNA clones from sheep which encode MC-5R. In rodents, MC-4R has been implicated as a key regulator of feeding behavior which regulates body weight through studies with peptide agonists and antagonists (Fan et al., 1997, Nature 385: 165-168) and with a MC-4R knock-out mouse (Huszar et al., 1997, Cell 88: 131-141). Compounds that bind to such receptors were previously identified by binding to human and/or rodent receptors and evaluated for their efficacy in rodents. However, the neuroendocrine process can differ between rodents and man. It is also expected that some compounds exhibit different binding affinities for different species homologues ofthe same receptor (Fong et al., 1992, J.Biol. Chem. 267:25666- 25671; Hartig et al., 1992, TIPS 13:152-159). Before compounds can be selected as a drug candidate it is first evaluated for a physiological effect in rodents and then in the rhesus primate. It is often that one compound may be effective in one animal species but not in another. Previously, it has been impossible to determine if the failure was due to an altered melanocortin pathway in different species, or due to a compounds having a lower affinity for one particular species. Past protocols required the use of a rhesus brain membrane to determine the in vitro biochemical activity of compounds, if such protocol could be successfully employed. It is desirable to correlate in vivo data with in vitro biochemical activity of compounds. It is also desirable to first select compounds that are active for the rhesus receptor in vitro. It is also desirable to identify compounds which can determine the relevance of receptor targets in rhesus and allow selection of novel drugs to treat obesity. It is further desirable to discover new drugs which effect pathophysiological processes by modulating the effects in rhesus to identify melanocortin active process in primates, followed by human clinical trials. The present invention addresses and meets these needs by disclosing an isolated nucleic acid fragment which expresses a form of rhesus MC-4R, recombinant vectors which house this nucleic acid fragment, recombinant host cells which expresses rhesus MC-4R and/or a biologically active equivalent, and pharmacological properties of this rhesus MC-4R protein. SUMMARY OF THE INVENTION The present invention relates to an isolated nucleic acid molecule (polynucleotide) which encodes a novel rhesus monkey (Macaca mulatto) melanocortin-4 receptor (rhMC-4R). The nucleic acid molecules ofthe present invention are substantially free from other nucleic acids. The present invention relates to an isolated nucleic acid molecule (polynucleotide) which encodes mRNA which expresses a novel rhesus MC-4R, this DNA molecule comprising the nucleotide sequence disclosed herein as SEQ ID NO:l. The present invention also relates to biologically active fragments or mutants of SEQ ID NO:l which encodes mRNA expressing a novel rhesus MC-4R. Any such biologically active fragment and/or mutant will encode either a protein or protein fragment which at least substantially mimics the pharmacological properties of a wild-type MC-4R protein, including but not limited to the rhesus MC-4R receptor protein as set forth in SEQ ID NO:2. Any such polynucleotide includes but is not necessarily limited to nucleotide substitutions, deletions, additions, amino-terminal truncations and carboxy-terminal truncations such that these mutations encode mRNA which express a protein or protein fragment of diagnostic, therapeutic or prophylactic use and would be useful for screening for agonists and/or antagonists for MC-4R function. A preferred aspect of this portion ofthe present invention is disclosed in Figure 1, a rhesus cDNA molecule encoding a novel MC-4R (SEQ ID NO:l). The isolated nucleic acid molecules ofthe present invention may include a deoxyribonucleic acid molecule (DNA), such as genomic DNA and complementary DNA (cDNA), which may be single (coding or noncoding strand) or double stranded, as well as synthetic DNA, such as a synthesized, single stranded polynucleotide. The isolated nucleic acid molecule ofthe present invention may also include a ribonucleic acid molecule (RNA). The present invention also relates to recombinant vectors and recombinant hosts, both prokaryotic and eukaryotic, which contain the substantially purified nucleic acid molecules disclosed throughout this specification. The present invention also relates to subcellular membrane fractions of the recombinant host cells (both prokaryotic and eukaryotic as well as both stably and transiently transformed cells) which contain the proteins encoded by the nucleic acids ofthe present invention. These subcellular membrane fractions will comprise either wild-type or mutant forms of rhesus melanocortin-4 receptor proteins at levels substantially above endogenous levels and hence will be useful in various assays to select modulators of rhesus melanocortin-4 receptor protein as described throughout this specification. The present invention also relates to a substantially purified form of the rhesus melanocortin-4 receptor protein, which comprises the amino acid sequence disclosed in Figure 2 and set forth as SEQ ID NO:2. A preferred aspect ofthe present invention is disclosed in Figure 2 and is set forth as SEQ ID NO:2, the amino acid sequence ofthe novel rhesus melanocortin-4 receptor protein. The present invention also relates to biologically active fragments and/or mutants ofthe rhesus melanocortin-4 receptor protein comprising the amino acid sequence set forth as SEQ ID NO:2, including but not necessarily limited to amino acid substitutions, deletions, additions, amino terminal truncations and carboxy-terminal truncations such that these mutations provide for proteins or protein fragments of diagnostic, therapeutic or prophylactic use and would be useful for screening for agonists and/or antagonists for MC-4R function. The present invention also relates to assays to screen or select for various modulators of MC-4R activity, methods of expressing the MC-4R protein and biological equivalents disclosed herein, recombinant host cells which comprise DNA constructs which express these receptor proteins, and compounds identified through these assays which act as agonists or antagonists of MC-4R activity. The present invention also relates to isolated nucleic acid molecules which are fusion constructions expressing fusion proteins useful in assays to identify compounds which modulate wild-type vertebrate MC-4R activity. A preferred aspect of this portion ofthe invention includes, but is not limited to, glutathione S- transferase (GST)-MC-4R fusion constructs which include, but are not limited to, either the intracellular domain of rhesus MC-4R as an in-frame fusion at the carboxy terminus ofthe GST gene, or the extracellular and transmembrane ligand binding domain of MC-4R fused to the amino terminus of GST, or the extracellular and transmembrane domain of MC-4R fused to an immuno globulin gene by methods known to one of ordinary skill in the art. Soluble recombinant GST-MC-4R fusion proteins may be expressed in various expression systems, including Spodoptera frugiperda (Sf21) insect cells (Invitrogen) using a baculovirus expression vector (pAcG2T, Pharmingen). Therefore, the present invention relates to methods of expressing the rhesus MC-4R protein and biological equivalents disclosed herein, assays employing these gene products, recombinant host cells which comprise DNA constructs which express these receptor proteins, and compounds identified through these assays which act as agonists or antagonists of MC-4R activity. The present invention also relates to polyclonal and monoclonal antibodies raised in response to either the rhesus form of MC-4R, or a biologically active fragment thereof. It is an object ofthe present invention to provide an isolated nucleic acid molecule which encodes a novel form of rhesus MC-4R, or rhesus fragments MC-4R fragments, mutants or derivatives of SEQ ID NO:2. Any such polynucleotide includes but is not necessarily limited to nucleotide substitutions, deletions, additions, amino-terminal truncations and carboxy-terminal truncations such that these mutations encode mRNA which express a protein or protein fragment of diagnostic, therapeutic or prophylactic use and would be useful for screening for agonists and/or antagonists for vertebrate MC-4R function. It is a further object ofthe present invention to provide the rhesus MC- 4R proteins or protein fragments encoded by the nucleic acid molecules referred to in the preceding paragraph. It is a further object ofthe present invention to provide recombinant vectors and recombinant host cells which comprise a nucleic acid sequence encoding rhesus MC-4R or a biological equivalent thereof. It is an object ofthe present invention to provide a substantially purified form ofthe rhesus MC-4R protein, as set forth in SEQ ID NO:2. It is an object ofthe present invention to provide for biologically active fragments and/or mutants ofthe rhesus MC-4R protein, such as set forth in SEQ ID NO:2, including but not necessarily limited to amino acid substitutions, deletions, additions, amino terminal truncations and carboxy-terminal truncations such that these mutations provide for proteins or protein fragments of diagnostic, therapeutic or prophylactic use. It is also an object ofthe present invention to provide for MC- 4R-based assays to select for modulators of this receptor protein. These assays are preferably cell based assays whereby a DNA molecule encoding MC-4R is transfected or transformed into a host cell, this recombinant host cell is allowed to grow for a time sufficient to express MC-4R prior to use in various assays described herein. It is a further object to provide for membrane preparations from host cells transfected or transformed with a DNA molecule encoding MC-4R for use in assays to select for modulators of MC-4R activity. It is also an object ofthe present invention to provide for MC-4R- based in-frame fusion constructions, methods of expressing these fusion constructs, biological equivalents disclosed herein, related assays, recombinant cells expressing these constructs, and agonistic and/or antagonistic compounds identified through the use ofthe nucleic acid encoding vertebrate MC-4R protein as well as the expressed protein. As used herein, "rh" or refers to —rhesus—. As used herein, "MC-4R" refers to —melanocortin 4 receptor—. As used herein, "GPCR" refers to — G-protein coupled receptor--. Whenever used herein, the term "mammalian host" will refer to any mammal, including a human being. BRIEF DECRIPTION OF THE FIGURES Figure 1A and Figure IB show the nucleotide sequence which encodes rhesus MC-4R, as set forth in SEQ ID NO: 1. Figure 2 shows the one-letter designation ofthe amino acid sequence of rhesus MC-4R, as also set forth in SEQ ID NO:2 as a three letter designation. DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an isolated nucleic acid molecule (polynucleotide) which encodes a novel rhesus monkey (Macaco mulatto) melanocortin-4 receptor (rhMC-4R). The nucleic acid molecules ofthe present invention are substantially free from other nucleic acids. For most cloning purposes, DNA is a preferred nucleic acid. The present invention relates to an isolated nucleic acid molecule (polynucleotide) which encodes mRNA which expresses a novel rhesus MC-4R, this DNA molecule comprising the nucleotide sequence disclosed herein as SEQ ID NO:l, shown herein as follows: GAATTCTCCT GCCAGCATGG TGAACTCCAC CCACCGTGGG ATGCACGCTT CTCTGCACCT CTGGAACCGC AGCAGCCACA GACTGCACAG CAATGCCAGT GAGTCCCTTG GAAAAGGCTA CTCTGATGGA GGGTGCTACG AGCAACTTTT TGTCTCTCCT GAGGTGTTTG TGACACTGGG TGTCATCAGC TTGTTGGAGA ATATCTTAGT GATTGTGGCA ATAGCCAAGA ACAAGAATCT GCATTCACCC ATGTACTTTT TCATCTGCAG CCTGGCTGTG GCTGATATGC TGGTGAGCGT TTCAAATGGA TCAGAAACCA TTGTCATCAC CCTATTAAAC AGTACAGATA CGGACACACA GAGTTTCACA GTGAACATTG ATAATGTTAT TGACTCAGTG ATCTGTAGCT CCTTGCTTGC ATCCATTTGC AGCCTGCTTT CAATTGCAGT GGACAGGTAC TTTACTATCT TCTATGCTCT TCAGTACCAT AACATTATGA CAGTTAAGCG GGTTGGGATC ATCATAAGTT GTATCTGGGC AGCTTGCACG GTTTCAGGCA TTTTGTTCAT CATTTACTCA GATAGTAGTG CTGTCATCAT CTGCCTCATC ACCATGTTCT TCACCATGTT GGCTCTCATG GCTTCTCTCT ATGTCCACAT GTTCCTGATG GCCAGGCTTC ACATTAAGAG GATTGCTGTC CTCCCCGGCA CTGGTGCCAT CCGCCAAGGC GCCAATATGA AGGGAGCGAT TACTTTGACC ATCCTGATTG GCGTCTTTGT TGTCTGCTGG GCCCCATTCT TCCTCCACTT AATATTCTAC ATCTCTTGTC CTCAGAATCC ATATTGTGTG TGCTTCATGT CTCACTTTAA CTTGTATCTC ATACTGATCA TGTGTAATTC AGTCATCGAT CCTCTGATTT ATGCACTCCG GAGTCAAGAA CTAAGGAAAA CCTTCAAAGA GATCATCTGT TGCTATCCCC TGGGAGGCCT ATGTGACTTG TCTAGCAGAT ATTAAATGGG GACAGAGCAC (SEQ ID NO: 1). The above-exemplified isolated DNA molecule, shown in Figure 1 and set forth as SEQ ID NO:l, contains 1030 nucleotides. This DNA molecule contains an open reading frame from nucleotide 17 to nucleotide 1012, with a "TAA" termination codon at nucleotides 1013-1015. This open reading frame encodes a rhesus MC-4R protein 332 amino acids in length, as shown in Figure 2 and as set forth in SEQ ID NO:2. The present invention also relates to biologically active fragments or mutants of SEQ LD NO:l which encodes mRNA expressing a novel rhesus MC-4R. Any such biologically active fragment and/or mutant will encode either a protein or protein fragment which at least substantially mimics the pharmacological properties of a wild-type MC-4R protein, including but not limited to the rhesus MC-4R receptor protein as set forth in SEQ ID NO:2. Any such polynucleotide includes but is not necessarily limited to nucleotide substitutions, deletions, additions, amino-terminal truncations and carboxy-terminal truncations such that these mutations encode mRNA which express a protein or protein fragment of diagnostic, therapeutic or prophylactic use and would be useful for screening for agonists and/or antagonists for MC-4R function. A preferred aspect of this portion ofthe present invention is disclosed in Figure 1, a rhesus cDNA molecule encoding a novel MC-4R (SEQ ID NO:l). The isolated nucleic acid molecules ofthe present invention may include a deoxyribonucleic acid molecule (DNA), such as genomic DNA and complementary DNA (cDNA), which may be single (coding or noncoding strand) or double stranded, as well as synthetic DNA, such as a synthesized, single stranded polynucleotide. The isolated nucleic acid molecule ofthe present invention may also include a ribonucleic acid molecule (RNA). It is known that there is a substantial amount of redundancy in the various codons which code for specific amino acids. Therefore, this invention is also directed to those DNA sequences encode RNA comprising alternative codons which code for the eventual translation ofthe identical amino acid, as shown below: A=Ala=Alanine: codons GCA, GCC, GCG, GCU C=Cys=Cysteine: codons UGC, UGU D=Asp=Aspartic acid: codons GAC, GAU E=Glu= : Glutamic acid: codons GAA, GAG F=Phe=Phenylalanine: codons UUC, UUU G=Gly=Glycine: codons GGA, GGC, GGG, GGU H=His =Histidine: codons CAC, CAU I=Ile =Isoleucine: codons AUA, AUC, AUU K=Lys=Lysine: codons AAA, AAG L=Leu=Leucine: codons UUA, UUG, CUA, CUC, CUG, CUU M=Met=Methionine: codon AUG N=Asp=Asparagine: codons AAC, AAU P=Pro=Proline: codons CCA, CCC, CCG, CCU Q=Gln=Glutamine: codons CAA, CAG R=Arg=Arginine: codons AGA, AGG, CGA, CGC, CGG, CGU S=Ser=Serine: codons AGC, AGU, UCA, UCC, UCG, UCU T=Thr=Threonine: codons ACA, ACC, ACG, ACU V=Val=Valine: codons GUA, GUC, GUG, GUU W=Trp=Tryptophan: codon UGG Y=Tyr=Tyrosine: codons UAC, UAU Therefore, the present invention discloses codon redundancy which may result in differing DNA molecules expressing an identical protein. For purposes of this specification, a sequence bearing one or more replaced codons will be defined as a degenerate variation. Also included within the scope of this invention are mutations either in the DNA sequence or the translated protein which do not substantially alter the ultimate physical properties ofthe expressed protein. For example, substitution of valine for leucine, arginine for lysine, or asparagine for glutamine may not cause a change in functionality ofthe polyp eptide. It is known that DNA sequences coding for a peptide may be altered so as to code for a peptide having properties that are different than those ofthe naturally occurring peptide. Methods of altering the DNA sequences include but are not limited to site directed mutagenesis. Examples of altered properties include but are not limited to changes in the affinity of an enzyme for a substrate or a receptor for a ligand. Included in the present invention are DNA sequences that hybridize to SEQ ID NO:l under stringent conditions. By way of example, and not limitation, a procedure using conditions of high stringency is as follows: Prehybridization of filters containing DNA is carried out for 2 hours to overnight at 65 °C in buffer composed of 6X SSC, 5X Denhardtis solution, and 100 μg/ml denatured salmon sperm DNA. Filters are hybridized for 12 to 48 hrs at 65 °C in prehybridization mixture containing 100 μg/ml denatured salmon sperm DNA and 5-20 X 10 6 cpm of 32 P-labeled probe. Washing of filters is done at 37°C for 1 hr in a solution containing 2X SSC, 0.1% SDS. This is followed by a wash in 0.1X SSC, 0.1% SDS at 50°C for 45 min. before autoradiography. Other procedures using conditions of high stringency would include either a hybridization step carried out in 5XSSC, 5X Denhardtis solution, 50% formamide at 42°C for 12 to 48 hours or a washing step carried out in 0.2X SSPE, 0.2% SDS at 65°C for 30 to 60 minutes. The present invention also relates to isolated nucleic acid molecules which are fusion constructions expressing fusion proteins useful in assays to identify compounds which modulate wild-type vertebrate MC-4R activity. A preferred aspect of this portion ofthe invention includes, but is not limited to, glutathione S- transferase (GST)-MC-4R fusion constructs which include, but are not limited to, either the intracellular domain of rhesus MC-4R as an in-frame fusion at the carboxy terminus of the GST gene or the extracellular and transmembrane ligand binding domain of MC-4R fused to an GST or immunoglobulin gene by methods known to one of ordinary skill in the art. Recombinant GST-MC-4R fusion proteins may be expressed in various expression systems, including Spodoptera frugiperda (Sf21) insect cells (Invitrogen) using a baculovirus expression vector (pAcG2T, Pharmingen). Any of a variety of procedures may be used to clone rhesus MC-4R. These methods include, but are not limited to, (1) a RACE PCR cloning technique (Frohman, et al., 1988, Proc. Natl. Acad. Sci. USA 85: 8998-9002). 5' and/or 3' RACE may be performed to generate a full-length cDNA sequence. This strategy involves using gene-specific ohgonucleotide primers for PCR amplification of rhesus MC-4R cDNA. These gene-specific primers are designed through identification of an expressed sequence tag (EST) nucleotide sequence which has been identified by searching any number of publicly available nucleic acid and protein databases; (2) direct functional expression ofthe rhesus MC-4R cDNA following the construction of a rhesus MC-4R-containing cDNA library in an appropriate expression vector system; (3) screening a rhesus MC-4R-containing cDNA library constructed in a bacteriophage or plasmid shuttle vector with a labeled degenerate ohgonucleotide probe designed from the amino acid sequence ofthe rhesus MC-4R protein; (4) screening a rhesus MC-4R-containing cDNA library constructed in a bacteriophage or plasmid shuttle vector with a partial cDNA encoding the rhesus MC-4R protein. This partial cDNA is obtained by the specific PCR amplification of rhesus MC-4R DNA fragments through the design of degenerate ohgonucleotide primers from the amino acid sequence known for other kinases which are related to the rhesus MC-4R protein; (5) screening a rhesus MC-4R-containing cDNA library constructed in a bacteriophage or plasmid shuttle vector with a partial cDNA or ohgonucleotide with homology to a mammalian MC-4R protein. This strategy may also involve using gene-specific ohgonucleotide primers for PCR amplification of rhesus MC-4R cDNA identified as an EST as described above; or (6) designing 5' and 3' gene specific oligonucleotides using SEQ ID NO: 1 as a template so that either the full-length cDNA may be generated by known RACE techniques, or a portion of the coding region may be generated by these same known RACE techniques to generate and isolate a portion ofthe coding region to use as a probe to screen one of numerous types of cDNA and or genomic libraries in order to isolate a full-length version ofthe nucleotide sequence encoding rhesus MC-4R. It is readily apparent to those skilled in the art that other types of libraries, as well as libraries constructed from other cell types-or species types, may be useful for isolating a rhesus MC-4R-encoding DNA or a rhesus MC-4R homologue. Other types of libraries include, but are not limited to, cDNA libraries derived from other rhesus cells. It is readily apparent to those skilled in the art that suitable cDNA libraries may be prepared from cells or cell lines which have MC-4R activity. The selection of cells or cell lines for use in preparing a cDNA library to isolate a cDNA encoding rhesus MC-4R may be done by first measuring cell-associated MC-4R activity using any known assay available for such a purpose. Preparation of cDNA libraries can be performed by standard techniques well known in the art. Well known cDNA library construction techniques can be found for example, in Sambrook et al., 1989, Molecular Cloning: A Laboratory Manual; Cold Spring Harbor Laboratory, Cold Spring Harbor, New York. Complementary DNA libraries may also be obtained from numerous commercial sources, including but not limited to Clontech Laboratories, Inc. and Stratagene. It is also readily apparent to those skilled in the art that DNA encoding rhesus MC-4R may also be isolated from a suitable genomic DNA library. Construction of genomic DNA libraries can be performed by standard techniques well known in the art. Well known genomic DNA library construction techniques can be found in Sambrook, et al., supra. In order to clone the rhesus MC-4R gene by one ofthe preferred methods, the amino acid sequence or DNA sequence of rhesus MC-4R or a homologous protein may be necessary. To accomplish this, the MC-4R protein or a homologous protein may be purified and partial amino acid sequence determined by automated sequenators. It is not necessary to determine the entire amino acid sequence, but the linear sequence of two regions of 6 to 8 amino acids can be determined for the PCR amplification of a partial rhesus MC-4R DNA fragment. Once suitable amino acid sequences have been identified, the DNA sequences capable of encoding them are synthesized. Because the genetic code is degenerate, more than one codon may be used to encode a particular amino acid, and therefore, the amino acid sequence can be encoded by any of a set of similar DNA oligonucleotides. Only one member ofthe set will be identical to the rhesus MC-4R sequence but others in the set will be capable of hybridizing to rhesus MC-4R DNA even in the presence of DNA oligonucleotides with mismatches. The mismatched DNA oligonucleotides may still sufficiently hybridize to the rhesus MC-4R DNA to permit identification and isolation of rhesus MC-4R encoding DNA. Alternatively, the nucleotide sequence of a region of an expressed sequence may be identified by searching one or more available genomic databases. Gene-specific primers may be used to perform PCR amplification of a cDNA of interest from either a cDNA library or a population of cDNAs. As noted above, the appropriate nucleotide sequence for use in a PCR-based method may be obtained from SEQ ID NO: 1, either for the purpose of isolating overlapping 5' and 3' RACE products for generation of a full- length sequence coding for rhesus MC-4R, or to isolate a portion ofthe nucleotide sequence coding for rhesus MC-4R for use as a probe to screen one or more cDNA- or genomic-based libraries to isolate a full-length sequence encoding rhesus MC-4R or rhesus MC-4R-like proteins. Reagents mentioned in the foregoing procedures for carrying out high stringency hybridization are well known in the art. Details ofthe composition of these reagents can be found in, e.g., Sambrook et al., 1989, Molecular Cloning: A Laboratory Manual; Cold Spring Harbor Laboratory, Cold Spring Harbor, New York. In addition to the foregoing, other conditions of high stringency which may be used are well known in the art. Melanocortin receptors belong to the rhodopsin sub-family of GPCRs. However, several features in the rhMC-4R are shared with all other receptors and are absent in most other GPCRs, including the EN motif in TM1, the lack of Cys in the loop between TM2 and TM3 or between TM4 and TM5, the MxxxxxxxY motif in TM5, and the DPxxY motif in TM7. Since all melanocortin receptors lack Cys residues in the extracellular loops that are present in other members ofthe rhodopsin sub-family, interhelical disulfide bond (e.g., between the Cys residues near the top of TM3 and TM5) may play the same function as interloop disulfide bond in most other GPCRs. The present invention also relates to a substantially purified form of the rhesus melanocortin-4 receptor protein, which comprises the amino acid sequence is disclosed in Figure 2 and set forth as SEQ ID NO:2. A preferred aspect ofthe present invention is disclosed in Figure 2 and is set forth as SEQ ID NO:2, and as herein set forth as follows: MVNSTHRGMH ASLHLWNRSS HRLHSNASES LGKGYSDGGC YEQLFVSPEV FVTLGVISLL ENILVIVAIA KNKN HSP Y FFICSLAVAD MLVSVSNGSE TIVITLLNST DTDTQSFTVN IDNVIDSVIC SS LASICS LSIAVDRYFT IFYALQYH I MTVKRVGIII SCIWAACTVS GILFIIYSDS SAVIICLITM FFTMLALMAS LYVH FL AR HIKRIAV P GTGAIRQGAN MKGAITLTIL IGVFWCWAP FFLHLIFYIS CPQNPYCVCF MSHFNLYLIL IMCNSVIDP IYALRSQE R KTFKEiiccY P GGLCDLSS RY (SEQ ID NO:2), which comprises the amino acid sequence of wild type rhesus melanocortin-4 receptor protein. The present invention also relates to biologically active fragments and or mutants ofthe rhesus melanocortin-4 receptor protein comprising the amino acid sequence set forth as SEQ ID NO:2, including but not necessarily limited to amino acid substitutions, deletions, additions, amino terminal truncations and carboxy-terminal truncations such that these mutations provide for proteins or protein fragments of diagnostic, therapeutic or prophylactic use and would be useful for screening for agonists and/or antagonists for MC-4R function. As with many receptor proteins, it is possible to modify many ofthe amino acids, particularly those which are not found in the ligand binding domain, and still retain substantially the same biological activity as the original receptor. Thus this invention includes modified rhMC-R polypeptides which have amino acid deletions, additions, or substitutions but that still retain substantially the same biological activity as rhMC-4R. It is generally accepted that single amino acid substitutions do not usually alter the biological activity of a protein (see, e.g., Molecular Biology ofthe Gene, Watson et al., 1987, Fourth Ed., The Benjamin/Cummings Publishing Co., Inc., page 226; and Cunningham & Wells, 1989, Science 244:1081-1085). Accordingly, the present invention includes isolated nucleic acid molecules and expressed MC-4R proteins wherein one amino acid substitution is generated and which this protein retains substantially the same biological activity as wild-type rhMC-R. The present invention also includes isolated nucleic acid molecules and expressed MC-4R proteins wherein two or more amino acid substitution is generated wherein this protein retains substantially the same biological activity as wild-type rhMC-4R. In particular, the present invention includes embodiments where the above-described substitutions are conservative substitutions. In particular, the present invention includes embodiments where the above-described substitutions do not occur in the ligand-binding domain of rhMC-4R. The present invention also relates to subcellular membrane fractions from the recombinant host cells (both prokaryotic and eukaryotic as well as both stably and transiently transformed cells) which contain the nucleic acids ofthe present invention. These subcellular membrane fractions will comprise either wild-type or mutant forms of rhesus melanocortin-4 receptor proteins at levels substantially above endogenous levels and hence will be useful in various assays described throughout this specification. The present invention also relates to recombinant vectors and recombinant hosts, both prokaryotic and eukaryotic, which contain the substantially purified nucleic acid molecules disclosed throughout this specification. The nucleic acid molecules ofthe present invention encoding rhMC-R, in whole or in part, can be linked with other DNA molecules, i.e., DNA molecules to which the rhMC-4R are not naturally linked, to form recombinant DNA molecules containing the receptor. The novel DNA sequences ofthe present invention can be inserted into vectors which comprise nucleic acids encoding a rhMC-R or a functional equivalent. These vectors may be comprised of DNA or RNA; for most cloning purposes DNA vectors are preferred. Typical vectors include plasmids, modified viruses, bacteriophage and cosmids, yeast artificial chromosomes and other forms of episomal or integrated DNA that can encode a rhMC-4R. It is well within the skilled artisan to determine an appropriate vector for a particular gene transfer or other use. To this end, the invention also includes vectors containing an rhMC- 4R gene, host cells containing the vectors, and methods of making substantially pure rhMC-R protein comprising the steps of introducing the rhMC-R gene into a host cell, and cultivating the host cell under appropriate conditions such that rhMC-R is produced. The rhMC-4R so produced may be harvested from the host cells in conventional ways. Therefore, the present invention also relates to methods of expressing the rhesus MC-4R protein and biological equivalents disclosed herein, assays employing these gene products, recombinant host cells which comprise DNA constructs which express these receptor proteins, and compounds identified through these assays which act as agonists or antagonists of MC-4R activity. The cloned rhesus MC-4R cDNA obtained through the methods described above may be recombinantly expressed by molecular cloning into an expression vector (such as pcDNA3.neo, pcDNA3.1, pCR2.1, pCI-neo, pBlueBacHis2 or pLITMUS28) containing a suitable promoter and other appropriate transcription regulatory elements, and transferred into prokaryotic or eukaryotic host cells to produce recombinant rhesus MC-4R. Techniques for such manipulations can be found described in Sambrook, et al., supra , are discussed at length in the Example section and are well known and easily available to the artisan of ordinary skill in the art. A variety of mammalian expression vectors may be used to express recombinant rhesus MC-4R in mammalian cells. Expression vectors are defined herein as DNA sequences that are required for the transcription of cloned DNA and the translation of their mRNAs in an appropriate host. Such vectors can be used to express eukaryotic DNA in a variety of hosts such as bacteria, blue green algae, plant cells, insect cells and animal cells. Specifically designed vectors allow the shuttling of DNA between hosts such as bacteria-yeast or bacteria-animal cells. An appropriately constructed expression vector should contain: an origin of replication for autonomous replication in host cells, selectable markers, a limited number of useful restriction enzyme sites, a potential for high copy number, and active promoters. A promoter is defined as a DNA sequence that directs RNA polymerase to bind to DNA and initiate RNA synthesis. A strong promoter is one which causes mRNAs to be initiated at high frequency. Expression vectors may include, but are not limited to, cloning vectors, modified cloning vectors, specifically designed plasmids or viruses. Commercially available mammalian expression vectors which may be suitable for recombinant rhesus MC-4R expression, include but are not limited to, pcDNA3.neo (Invitrogen), pcDNA3.1 (Invitrogen), pCI-neo (Promega), pLITMUS28, pLITMUS29, pLITMUS38 and pLITMUS39 (New England Bioloabs), pcDNAI, pcDNAIamp (Invitrogen), pcDNA3 (Invitrogen), pMClneo (Stratagene), pXTl (Stratagene), pSG5 (Stratagene), EBO-pSV2-neo (ATCC 37593) pBPV-l(8-2) (ATCC 37110), pdBPV-MMTneo(342-12) (ATCC 37224), pRSVgpt (ATCC 37199), pRSVneo (ATCC 37198), pSV2-dhfr (ATCC 37146), pUCTag (ATCC 37460), and λZD35 (ATCC 37565). Also, a variety of bacterial expression vectors may be used to express recombinant rhesus MC-4R in bacterial cells. Commercially available bacterial expression vectors which may be suitable for recombinant rhesus MC-4R expression include, but are not limited to pCR2.1 (Invitrogen), pETl la (Novagen), lambda gtl 1 (Invitrogen), and pKK223-3 (Pharmacia). In addition, a variety of fungal cell expression vectors may be used to express recombinant rhesus MC-4R in fungal cells. Commercially available fungal cell expression vectors which may be suitable for recombinant rhesus MC-4R expression include but are not limited to pYES2 (Invitrogen) and Pichia expression vector (Invitrogen). Also, a variety of insect cell expression vectors may be used to express recombinant receptor in insect cells. Commercially available insect cell expression vectors which may be suitable for recombinant expression of rhesus MC-4R include but are not limited to pBlueBacIII and pBlueBacHis2 (Invitrogen), and pAcG2T (Pharmingen). Expression of rhesus MC-4R DNA may also be performed using in vitro produced synthetic mRNA. Synthetic mRNA can be efficiently translated in various cell-free systems, including but not limited to wheat germ extracts and reticulocyte extracts, as well as efficiently translated in cell based systems, including but not limited to microinjection into frog oocytes, with microinjection into frog oocytes being preferred. To determine the rhesus MC-4R cDNA sequence(s) that yields optimal levels of rhesus MC-4R, cDNA molecules including but not limited to the following can be constructed: a cDNA fragment containing the full-length open reading frame for rhesus MC-4R as well as various constructs containing portions ofthe cDNA encoding only specific domains ofthe protein or rearranged domains ofthe protein. All constructs can be designed to contain none, all or portions ofthe 5' and/or 3' untranslated region of a rhesus MC-4R cDNA. The expression levels and activity of rhesus MC-4R can be determined following the introduction, both singly and in combination, of these constructs into appropriate host cells. Following determination ofthe rhesus MC-4R cDNA cassette yielding optimal expression in transient assays, this MC-4R cDNA construct is transferred to a variety of expression vectors (including recombinant viruses), including but not limited to those for mammalian cells, plant cells, insect cells, oocytes, bacteria, and yeast cells. Therefore, another aspect ofthe present invention includes host cells that have been engineered to contain and/or express DNA sequences encoding the rhMC-4R. Such recombinant host cells can be cultured under suitable conditions to produce rhMC-4R or a biologically equivalent form. Recombinant host cells may be prokaryotic or eukaryotic, including but not limited to, bacteria such as E. coli, fungal cells such as yeast, mammalian cells including, but not limited to, cell lines of human, bovine, porcine, monkey and rodent origin, and insect cells including but not limited to Drosophila and silkworm derived cell lines. Therefore, an expression vector containing DNA encoding a rhesus MC-4R-like protein may be used for expression of rhesus MC-4R in a recombinant host cell. Recombinant host cells may be prokaryotic or eukaryotic, including but not limited to bacteria such as E. coli, fungal cells such as yeast, mammalian cells including but not limited to cell lines of human, bovine, porcine, monkey and rodent origin, and insect cells including but not limited to Drosophila- and silkworm-derived cell lines. For instance, one insect expression system utilizes Spodoptera frugiperda (Sf21) insect cells (Invitrogen) in tandem with a baculovirus expression vector (pAcG2T, Pharmingen). Also, mammalian species which may be suitable and which are commercially available, include but are not limited to, L cells L-M(TK') (ATCC CCL 1.3), L cells L-M (ATCC CCL 1.2), Saos- 2 (ATCC HTB-85), 293 (ATCC CRL 1573), Raji (ATCC CCL 86), CV-1 (ATCC CCL 70), COS-1 (ATCC CRL 1650), COS-7 (ATCC CRL 1651), CHO-K1 (ATCC CCL 61), 3T3 (ATCC CCL 92), NIH/3T3 (ATCC CRL 1658), HeLa (ATCC CCL 2), C127I (ATCC CRL 1616), BS-C-1 (ATCC CCL 26), MRC-5 (ATCC CCL 171) and CPAΕ (ATCC CCL 209). Following expression of MC-4R in a host cell, MC-4R protein may be recovered to provide MC-4R protein in active form. Several MC-4R protein purification procedures are available and suitable for use. Recombinant MC-4R protein may be purified from cell lysates and extracts by various combinations of, or individual application of salt fractionation, ion exchange chromatography, size exclusion chromatography, hydroxylapatite adsorption chromatography and hydrophobic interaction chromatography. In addition, recombinant MC-4R protein can be separated from other cellular proteins by use of an immunoaffinity column made with monoclonal or polyclonal antibodies specific for full-length MC-4R protein, or polypeptide fragments of MC-4R protein. The assays described herein as well as protein purification schemes can be carried out with cells that have been transiently or stably transfected or transformed with an expression vector which directs expression of MC-4R. The expression vector may be introduced into host cells via any one of a number of techniques including but not limited to transformation, transfection, protoplast fusion, and electroporation. Transformation is meant to encompass a genetic change to the target cell resulting from an incorporation of DNA. Transfection is meant to include any method known in the art for introducing MC-4R into the test cells. For example, transfection includes calcium phosphate or calcium chloride mediated transfection, lipofection, infection with a retroviral construct containing MC-4R, and electroporation. The expression vector-containing cells are individually analyzed to determine whether they produce human MC-4R protein. Identification of human MC-4R expressing cells may be done by several means, including but not limited to immunological reactivity with anti-human MC-4R antibodies, labeled ligand binding and the presence of host cell-associated human MC-4R activity. The specificity of binding of compounds showing affinity for rhMC- 4R is shown by measuring the affinity ofthe compounds for recombinant cells expressing the cloned receptor or for membranes from these cells. Expression ofthe cloned receptor and screening for compounds that bind to rhMC-4R or that inhibit the binding of a known, radiolabeled ligand of rhMC-4R to these cells, or membranes prepared from these cells, provides an effective method for the rapid selection of compounds with high affinity for rhMC-4R. Such ligands need not necessarily be radiolabeled but can also be nonisotopic compounds that can be used to displace bound radiolabeled compounds or that can be used as activators in functional assays. Compounds identified by the above method are likely to be agonists or antagonists of rhMC-4R and may be peptides, proteins, or non-proteinaceous organic molecules. Accordingly, the present invention is directed to methods for screening for compounds which modulate the expression of DNA or RNA encoding a MC-4R protein as well as compounds which bind to the MC-4R receptor and which may modulate MC-4R function. Methods for identifying agonists and antagonists of other receptors are well known in the art and can be adapted to identify agonists and antagonists of MC-4R. For example, Cascieri et al. (1992, Molec. Pharmacol. 41:1096-1099) describe a method for identifying substances that inhibit agonist binding to rat neurokinin receptors and thus are potential agonists or antagonists of neurokinin receptors. The method involves transfecting COS cells with expression vectors containing rat neurokinin receptors, allowing the transfected cells to grow for a time sufficient to allow the neurokinin receptors to be expressed, harvesting the transfected cells and resuspending the cells in assay buffer containing a known radioactively labeled agonist ofthe neurokinin receptors either in the presence or the absence ofthe substance, and then measuring the binding ofthe radioactively labeled known agonist ofthe neurokinin receptor to the neurokinin receptor. If the amount of binding ofthe known agonist is less in the presence ofthe substance than in the absence ofthe substance, then the substance is a potential agonist or antagonist ofthe neurokinin receptor. Where binding ofthe substance such as an agonist or antagonist to MC-4R is measured, such binding can be measured by employing a labeled substance or agonist. The substance or agonist can be labeled in any convenient manner known to the art, e.g., radioactively, fluorescently, enzymatically. Therefore, the specificity of binding of compounds having affinity for MC-4R is shown by measuring the affinity ofthe compounds for recombinant cells expressing the cloned receptor or for membranes from these cells. Expression ofthe cloned receptor and screening for compounds that bind to MC-4R or that inhibit the binding of a known, radiolabeled ligand of MC-4R to these cells, or membranes prepared from these cells, provides an effective method for the rapid selection of compounds with high affinity for MC-4R. Such ligands need not necessarily be radiolabeled but can also be nonisotopic compounds that can be used to displace bound radiolabeled compounds or that can be used as activators in functional assays. Compounds identified by the above method are likely to be agonists or antagonists of MC-4R and may be peptides, proteins, or non-proteinaceous organic molecules. Compounds may modulate by increasing or attenuating the expression of DNA or RNA encoding MC-4R, or by acting as an agonist or antagonist ofthe MC-4R receptor protein. These compounds that modulate the expression of DNA or RNA encoding MC-4R or the biological function thereof may be detected by a variety of assays. The assay may be a simple "yes/no" assay to determine whether there is a change in expression or function. The assay may be made quantitative by comparing the expression or function of a test sample with the levels of expression or function in a standard sample. Kits containing MC-4R, antibodies to MC-4R, or modified MC- 4R may be prepared by known methods for such uses. Therefore, the present invention relates to methods of expressing rhMC-4R in recombinant systems and of identifying agonists and antagonists of rhMC-4R. When screening compounds in order to identify potential pharmaceuticals that specifically interact with a target receptor, it is necessary to ensure that the compounds identified are as specific as possible for the target receptor. To do this, it is necessary to screen the compounds against as wide an array as possible of receptors that are similar to the target receptor. Thus, in order to find compounds that are potential pharmaceuticals that interact with receptor A, it is necessary not only to ensure that the compounds interact with receptor A (the "plus target") and produce the desired pharmacological effect through receptor A, it is also necessary to determine that the compounds do not interact with receptors B, C, D, etc. (the "minus targets"). In general, as part of a screening program, it is important to have as many minus targets as possible (see Hodgson, 1992, Bio/Technology 10:973-980, @ 980). Rhesus MC-4R proteins and the DNA molecules encoding this receptor protein have the additional utility in that they can be used as "minus targets" in screens designed to identify compounds that specifically interact with other G-protein coupled receptors. Due to homology to GPCRs, the rhMC-4R of this invention is believed to function similarly to GPCRs and have similar biological activity. They are useful in understanding the biological and physiological effects in the rhesus to in identify melanocortin active process in primates, followed by human clinical trials. More notable, rhMC-4R agonists will be identified and evaluated for their effects on food intake, weight gain, and metabolic rate to identify novel-anti-obesity agents that are effective in primates. They may also be used to scan for rhesus monkey melanocortin agonists and antagonists; as in particular to test the specificity of identified ligands. To this end, the present invention relates in part to methods of identifying a substance which modulates MC-4R receptor activity, which involves: (a) combining a test substance in the presence and absence of a MC-4R receptor protein wherein said MC-4R receptor protein comprises the amino acid sequence as set forth in SEQ ID NO:2; and, (b) measuring and comparing the effect ofthe test substance in the presence and absence ofthe MC-4R receptor protein. In addition, several specific embodiments are disclosed herein to show the diverse type of screening or selection assay which the skilled artisan may utilize in tandem with an expression vector directing the expression ofthe MC-4R receptor protein. As noted above, methods for identifying agonists and antagonists of other receptors are well known in the art and can be adapted to identify agonists and antagonists of MC-4R. Therefore, these embodiments are presented as examples and not as limitations. To this end, the present invention includes assays by which MC- 4R modulators (such as agonists and antagonists) may be identified. Accordingly, the present invention includes a method for determining whether a substance is a potential agonist or antagonist of MC-4R that comprises: (a) transfecting or transforming cells with an expression vector that directs expression of MC-4R in the cells, resulting in test cells; (b) allowing the test cells to grow for a time sufficient to allow MC-4R to be expressed; (c) exposing the cells to a labeled ligand of MC-4R in the presence and in the absence ofthe substance; (d) measuring the binding ofthe labeled ligand to MC-4R; where if the amount of binding ofthe labeled ligand is less in the presence ofthe substance than in the absence ofthe substance, then the substance is a potential agonist or antagonist of MC-4R. The conditions under which step (c) ofthe method is practiced are conditions that are typically used in the art for the study of protein-ligand interactions: e.g., physiological pH; salt conditions such as those represented by such commonly used buffers as PBS or in tissue culture media; a temperature of about 4°C to about 55°C. The test cells may be harvested and resuspended in the presence ofthe substance and the labeled ligand. In a modification ofthe above-described method, step (c) is modified in that the cells are not harvested and resuspended but rather the radioactively labeled known agonist and the substance are contacted with the cells while the cells are attached to a substratum, e.g., tissue culture plates. The present invention also includes a method for determining whether a substance is capable of binding to MC-4R, i.e., whether the substance is a potential agonist or an antagonist of MC-4R, where the method comprises: (a) transfecting or transforming cells with an expression vector that directs the expression of MC-4R in the cells, resulting in test cells; (b) exposing the test cells to the substance; (c) measuring the amount of binding ofthe substance to MC-4R; (d) comparing the amount of binding ofthe substance to MC-4R in the test cells with the amount of binding ofthe substance to control cells that have not been transfected with MC-4R; wherein if the amount of binding ofthe substance is greater in the test cells as compared to the control cells, the substance is capable of binding to MC-4R. Determining whether the substance is actually an agonist or antagonist can then be accomplished by the use of functional assays such as, e.g., the assay involving the use of promiscuous G-proteins described below. The conditions under which step (b) ofthe method is practiced are conditions that are typically used in the art for the study of protein- ligand interactions: e.g., physiological pH; salt conditions such as those represented by such commonly used buffers as PBS or in tissue culture media; a temperature of about 4°C to about 55°C. The test cells are harvested and resuspended in the presence ofthe substance. Chen et al. (1995, Analytical Biochemistry 226: 349-354) describe a colorometric assay which utilizes a recombinant cell transfected with an expression vector encoding a G-protein coupled receptor with a second expression vector containing a promoter with a cAMP responsive element fused to the LacZ gene. Activity ofthe overexpressed G-protein coupled receptor is measured as the expression and OD measurement of β-Gal. Therefore, another aspect of this portion ofthe invention includes a non-radioactive method for determining whether a substance is a potential agonist or antagonist of MC-4R that comprises: (a) transfecting or transforming cells with an expression vector encoding MC-4R, resulting in test cells; (b) transfecting or transforming the test cells of step (a) with an expression vector which comprises a cAMP-inducible promoter fused to a colorometric gene such a LacZ; (c) allowing the transfected cells to grow for a time sufficient to allow MC-4R to be expressed; (d) harvesting the transfected cells and resuspending the cells in the presence of a known agonist of MC-4R and/or in both the presence and absence of the test compound; (e) measuring the binding ofthe known agonist and test compound to overexpressed MC-4R by a colorometric assay which measures expression off the cAMP-inducible promoter and comparing expression levels in the presence ofthe known agonist as well as in the presence and absence ofthe unknown substance so as to determine whether the unknown substance acts as either a potential agonist or antagonist of MC-4R. Additional methods of identifying agonists or antagonists include but are by no means limited to the following: I. (a) transfecting or transforming cells with a first expression vector which directs expression of MC-4R and a second expression vector which directs the expression of a promiscuous G-protein, resulting in test cells; (b) exposing the test cells to a substance that is a suspected agonist of MC-4R; (c) measuring the level of inositol phosphates in the cells; where an increase in the level of inositol phosphates in the cells as compared to the level of inositol phosphates in the cells in the absence ofthe suspected agonist indicates that the substance is an agonist of MC-4R. II. (a) transfecting or transforming cells with a first expression vector which directs expression of MC-4R and a second expression vector which directs the expression of a promiscuous G-protein, resulting in test cells; (b) exposing the test cells to a substance that is an agonist ofMC-4R; (c) subsequently or concurrently to step (b), exposing the test cells to a substance that is a suspected antagonist of MC-4R; (d) measuring the level of inositol phosphates in the cells; where a decrease in the level of inositol phosphates in the cells in the presence ofthe suspected antagonist as compared to the level of inositol phosphates in the cells in the absence ofthe suspected antagonist indicates that the substance is an antagonist of MC-4R. III. the method of II wherein the first and second expression vectors of step (a) are replaced with a single expression vector which expresses a chimeric MC-4R protein fused at its C-terminus to a promiscuous G-protein. The above-described methods can be modified in that, rather than exposing the test cells to the substance, membranes can be prepared from the test cells and those membranes can be exposed to the substance. Such a modification utilizing membranes rather than cells is well known in the art and is described in, e.g., Hess et al., 1992, Biochem. Biophys. Res. Comm. 184:260-268. Accordingly, another embodiment ofthe present invention includes a method for determining whether a substance binds and/or is a potential agonist or antagonist of MC-4R wherein membrane preparations from the test cells are utilized in place ofthe test cells. Such methods comprise the following and may utilized the physiological conditions as noted above: (a) transfecting or transforming cells with an expression vector that directs the expression of MC-4R in the cells, resulting in test cells; (b) preparing membranes containing MC-4R from the test cells and exposing the membranes to a ligand of MC-4R under conditions such that the ligand binds to the MC-4R in the membranes; (c) subsequently or concurrently to step (b), exposing the membranes from the test cells to a substance; (d) measuring the amount of binding ofthe ligand to the MC-4R in the membranes in the presence and the absence ofthe substance; (e) comparing the amount of binding ofthe ligand to MC-4R in the membranes in the presence and the absence ofthe substance where a decrease in the amount of binding ofthe ligand to MC-4R in the membranes in the presence ofthe substance indicates that the substance is capable of binding to MC-4R. The present invention also relates to a method for determining whether a substance is capable of binding to MC-4R comprising: (a) transfecting or transforming cells with an expression vector that directs the expression of MC-4R in the cells, resulting in test cells; (b) preparing membranes containing MC-4R from the test cells and exposing the membranes from the test cells to the substance; (c) measuring the amount of binding ofthe substance to the MC- 4R in the membranes from the test cells; (d) comparing the amount of binding ofthe substance to MC-4R in the membranes from the test cells with the amount of binding ofthe substance to membranes from control cells that have not been transfected with MC-4R, where if the amount of binding ofthe substance to MC-4R in the membranes from the test cells is greater than the amount of binding ofthe substance to the membranes from the control cells, then the substance is capable of binding to MC-4R. A preferred embodiment ofthe present invention is determining various ligand binding affinities using 125i-labeled NDP-α-MSH as the labeled ligand in the presence of varying concentration of unlabeled ligands. The activation ofthe second messenger pathway may be determined by measuring the intracellular cAMP elicited by agonist at various concentration. The present invention also relates to polyclonal and monoclonal antibodies raised in response to either the rhesus form of MC-4R, or a biologically active fragment thereof. Polyclonal or monoclonal antibodies may be raised against rhesus MC-4R or a synthetic peptide (usually from about 9 to about 25 amino acids in length) from a portion of rhesus MC-4R as disclosed in SEQ ID NO:2. Monospecific antibodies to rhesus MC-4R are purified from mammalian antisera containing antibodies reactive against rhesus MC-4R or are prepared as monoclonal antibodies reactive with rhesus MC-4R using the technique of Kohler and Milstein (1975, Nature 256: 495-497). Monospecific antibody as used herein is defined as a single antibody species or multiple antibody species with homogenous binding characteristics for rhesus MC-4R. Homogenous binding as used herein refers to the ability ofthe antibody species to bind to a specific antigen or epitope, such as those associated with rhesus MC-4R, as described above. Rhesus MC-4R-specific antibodies are raised by immunizing animals such as mice, rats, guinea pigs, rabbits, goats, horses and the like, with an appropriate concentration of rhesus MC-4R protein or a synthetic peptide generated from a portion of rhesus MC-4R with or without an immune adjuvant. Preimmune serum is collected prior to the first immunization. Each animal receives between about 0.1 μg and about 1000 μg of rhesus MC-4R protein associated with an acceptable immune adjuvant. Such acceptable adjuvants include, but are not limited to, Freund's complete, Freund's incomplete, alum-precipitate, water in oil emulsion containing Corynebacterium parvum and tRNA. The initial immunization consists of rhesus MC-4R protein or peptide fragment thereof in, preferably, Freund's complete adjuvant at multiple sites either subcutaneously (SC), intraperitoneally (IP) or both. Each animal is bled at regular intervals, preferably weekly, to determine antibody titer. The animals may or may not receive booster injections following the initial immunization. Those animals receiving booster injections are generally given an equal amount of rhesus MC-4R in Freunds incomplete adjuvant by the same route. Booster injections are given at about three week intervals until maximal titers are obtained. At about 7 days after each booster immunization or about weekly after a single immunization, the animals are bled, the serum collected, and aliquots are stored at about -20°C. Monoclonal antibodies (mAb) reactive with rhesus MC-4R are prepared by immunizing inbred mice, preferably Balb/c, with rhesus MC-4R protein. The mice are immunized by the IP or SC route with about 1 μg to about 100 μg, preferably about 10 μg, of rhesus MC-4R protein in about 0.5 ml buffer or saline incorporated in an equal volume of an acceptable adjuvant, as discussed above. Freunds complete adjuvant is preferred. The mice receive an initial immunization on day 0 and are rested for about 3 to about 30 weeks. Immunized mice are given one or more booster immunizations of about 1 to about 100 μg of rhesus MC-4R in a buffer solution such as phosphate buffered saline by the intravenous (IN) route. Lymphocytes, from antibody positive mice, preferably splenic lymphocytes, are obtained by removing spleens from immunized mice by standard procedures known in the art. Hybridoma cells are produced by mixing the splenic lymphocytes with an appropriate fusion partner, preferably myeloma cells, under conditions which will allow the formation of stable hybridomas. Fusion partners may include, but are not limited to: mouse myelomas P3/ΝSl/Ag 4-1; MPC-11; S-194 and Sp 2/0, with Sp 2/0 being prefeπed. The antibody producing cells and myeloma cells are fused in polyethylene glycol, about 1000 mol. wt, at concentrations from about 30% to about 50%. Fused hybridoma cells are selected by growth in hypoxanthine, thymidine and aminopterin supplemented Dulbecco's Modified Eagles Medium (DMEM) by procedures known in the art. Supernatant fluids are collected from growth positive wells on about days 14, 18, and 21 and are screened for antibody production by an immunoassay such as solid phase immunoradioassay (SPIRA) using rhesus MC-4R as the antigen. The culture fluids are also tested in the Ouchterlony precipitation assay to determine the isotype ofthe mAb. Hybridoma cells from antibody positive wells are cloned by a technique such as the soft agar technique of MacPherson, 1973, Soft Agar Techniques, in Tissue Culture Methods and Applications, Kruse and Paterson, Eds., Academic Press. Monoclonal antibodies are produced in vivo by injection of pristine primed Balb/c mice, approximately 0.5 ml per mouse, with about 2 x 106 to about 6 x lθ6 hybridoma cells about 4 days after priming. Ascites fluid is collected at approximately 8-12 days after cell transfer and the monoclonal antibodies are purified by techniques known in the art. In vitro production of anti-rhesus MC-4R mAb is carried out by growing the hybridoma in DMEM containing about 2% fetal calf serum to obtain sufficient quantities ofthe specific mAb. The mAb are purified by techniques known in the art. Antibody titers of ascites or hybridoma culture fluids are determined by various serological or immunological assays which include, but are not limited to, precipitation, passive agglutination, enzyme-linked immunosorbent antibody (ELISA) technique and radioimmunoassay (RIA) techniques. Similar assays are used to detect the presence of rhesus MC-4R in body fluids or tissue and cell extracts. It is readily apparent to those skilled in the art that the above described methods for producing monospecific antibodies may be utilized to produce antibodies specific for rhesus MC-4R peptide fragments, or full-length rhesus MC-4R. Rhesus MC-4R antibody affinity columns are made, for example, by adding the antibodies to Affigel-10 (Biorad), a gel support which is pre-activated with N-hydroxysuccinimide esters such that the antibodies form covalent linkages with the agarose gel bead support. The antibodies are then coupled to the gel via amide bonds with the spacer arm. The remaining activated esters are then quenched with 1M ethanolamine HC1 (pH 8). The column is washed with water followed by 0.23 M glycine HC1 (pH 2.6) to remove any non-conjugated antibody or extraneous protein. The column is then equilibrated in phosphate buffered saline (pH 7.3) and the cell culture supernatants or cell extracts containing full-length rhesus MC-4R or rhesus MC-4R protein fragments are slowly passed through the column. The column is then washed with phosphate buffered saline until the optical density (A280) falls to background, then the protein is eluted with 0.23 M glycine-HCl (pH 2.6). The purified rhesus MC-4R protein is then dialyzed against phosphate buffered saline. The specificity of binding of compounds showing affinity for rhMC- 4R is shown by measuring the affinity ofthe compounds for recombinant cells expressing the cloned receptor or for membranes from these cells. Expression ofthe cloned receptor and screening for compounds that bind to rhMC-4R or that inhibit the binding of a known, radiolabeled ligand of rhMC-4R to these cells, or membranes prepared from these cells, provides an effective method for the rapid selection of compounds with high affinity for rhMC-4R. Such ligands need not necessarily be radiolabeled but can also be nonisotopic compounds that can be used to displace bound radiolabeled compounds or that can be used as activators in functional assays. Compounds identified by the above method are likely to be agonists or antagonists of rhMC-R and may be peptides, proteins, or non-proteinaceous organic molecules. The DNA molecules, RNA molecules, recombinant protein and antibodies ofthe present invention may be used to screen and measure levels of rhesus MC-4R. The recombinant proteins, DNA molecules, RNA molecules and antibodies lend themselves to the formulation of kits suitable for the detection and typing of rhesus MC-4R. Such a kit would comprise a compartmentalized carrier suitable to hold in close confinement at least one container. The carrier would further comprise reagents such as recombinant MC-4R or anti-MC-4R antibodies suitable for detecting rhesus MC-4R. The carrier may also contain a means for detection such as labeled antigen or enzyme substrates or the like. Pharmaceutically useful compositions comprising modulators of rhesus MC-4R may be formulated according to known methods such as by the admixture of a pharmaceutically acceptable carrier. Examples of such carriers and methods of formulation may be found in Remington's Pharmaceutical Sciences. To form a pharmaceutically acceptable composition suitable for effective administration, such compositions will contain an effective amount ofthe protein, DNA, RNA, modified rhesus MC-4R, or either MC-4R agonists or antagonists including tyrosine kinase activators or inhibitors. Therapeutic or diagnostic compositions ofthe invention are administered to an individual in amounts sufficient to treat or diagnose disorders. The effective amount may vary according to a variety of factors such as the individuals condition, weight, sex and age. Other factors include the mode of administration. The pharmaceutical compositions may be provided to the individual by a variety of routes such as subcutaneous, topical, oral and intramuscular. The term "chemical derivative" describes a molecule that contains additional chemical moieties which are not normally a part ofthe base molecule. Such moieties may improve the solubility, half-life, absorption, etc. ofthe base molecule. Alternatively the moieties may attenuate undesirable side effects ofthe base molecule or decrease the toxicity ofthe base molecule. Examples of such moieties are described in a variety of texts, such as Remington's Pharmaceutical Sciences. Compounds identified according to the methods disclosed herein may be used alone at appropriate dosages. Alternatively, co-administration or sequential administration of other agents may be desirable. The present invention also has the objective of providing suitable topical, oral, systemic and parenteral pharmaceutical formulations for use in the novel methods of treatment ofthe present invention. The compositions containing compounds identified according to this invention as the active ingredient can be administered in a wide variety of therapeutic dosage forms in conventional vehicles for administration. For example, the compounds can be administered in such oral dosage forms as tablets, capsules (each including timed release and sustained release formulations), pills, powders, granules, elixirs, tinctures, solutions, suspensions, syrups and emulsions, or by injection. Likewise, they may also be administered in intravenous (both bolus and infusion), intraperitoneal, subcutaneous, topical with or without occlusion, or intramuscular form, all using forms well known to those of ordinary skill in the pharmaceutical arts. Advantageously, compounds ofthe present invention may be administered in a single daily dose, or the total daily dosage may be administered in divided doses of two, three or four times daily. Furthermore, compounds for the present invention can be administered in intranasal form via topical use of suitable intranasal vehicles, or via transdermal routes, using those forms of transdermal skin patches well known to those of ordinary skill in that art. To be administered in the form of a transdermal delivery system, the dosage administration will, of course, be continuous rather than intermittent throughout the dosage regimen. For combination treatment with more than one active agent, where the active agents are in separate dosage formulations, the active agents can be administered concurrently, or they each can be administered at separately staggered times. The dosage regimen utilizing the compounds ofthe present invention is selected in accordance with a variety of factors including type, species, age, weight, sex and medical condition ofthe patient; the severity ofthe condition to be treated; the route of administration; the renal, hepatic and cardiovascular function ofthe patient; and the particular compound thereof employed. A physician or veterinarian of ordinary skill can readily determine and prescribe the effective amount ofthe drug required to prevent, counter or aπest the progress ofthe condition. Optimal precision in achieving concentrations of drug within the range that yields efficacy without toxicity requires a regimen based on the kinetics ofthe drugs availability to target sites. This involves a consideration ofthe distribution, equilibrium, and elimination of a drug. The following examples are provided to illustrate the present invention without, however, limiting the same hereto. EXAMPLE 1 Isolation ofthe rhesus MC-4R gene A series of oligonucleotides were designed to isolate the full length MC-4R genes based on the human MC-4R gene sequence. These oligonucleotides were designed to incorporate a restriction enzyme site for cloning into the expression vector pCI-neo (Promega). The following oligos were used: rhMRC4Fl 5 ' -CCGGCTCGAGGAATTCTCCTGCCAGCATG-3 ' (SEQ ID NO: 3) rhMCR4F2 5 ' -CCGGCTCGAGCCTGCCAGCATGGTGAA-3 ' (SEQ ID N0:4) rhMCR4Rl 5 ' -CCGGTCTAGACGTGCTCTGTCCCCATTTA-3 ' (SEQ ID NO: 5) rhMCR4R2 5 • -CCGGTCTAGAGTCCCCATTTAATATCTGCTAGA-3 ' (SEQ ID NO: 6) PCR reactions were performed in a 500 μl eppendorf tube under mineral oil in 50 μl volumes using Taq Polymerase (Gibco/BRL) which included the following: lxTaq buffer (Gibco/BRL), .3 mM dGTP, .3 mM dCTP, .3 mM dATP, .3 mM dGTP, 100 ng rhesus genomic DNA (Clontech), 20 pM of each primer, and 2 mM MgC12, and 2 Units of Taq Polymerase. Reactions were set up initially lacking Taq Polymerase and performed in a Omnigene thermal cycler (Hybraid) under the following conditions: 94°C for 60 sec, 60°C for 20 sec, then held at 60°C until Taq Polymerase was added, then 72°C for 120 sec, then 35 cycles of 94°C for 20 sec, 60°C for 20 sec, and 72°C for 110 sec. The final cycle was an additional 8 min at 72°C and 10 min at 30°C. In the initial experiments, no bands were visible after running 1/10 ofthe PCR products on a 1% agarose gel. After increasing the time for the 72°C elongation step to 130 sec products were obtained ofthe predicted size (about 1.0 kb) using the four combinations of rhMCR4 primers. The products ofthe rhMRC4Fl and rhMCR4Rl primers was purified away from contaminating reaction products using a QIAquick PCR Purification kit (Qiagen), and digested with a mixture of EcoRI and Xbal restriction enzymes which were used according to the manufactures directions (Gibco/BRL). The pCI-neo vector DNA was also cleaved with EcoRI and Xbal. Both the vector and PCR products were purified on a 1% agarose gel, the approximately 1.0 kb PCR product band and the 5.5 kb vector bands were excised from the gel, and the DNA purified from the gel with a QIAquick Gel Extraction kit (Qiagen). The vector and PCR fragments were ligated in a 1 :3 ratio using T4 DNA ligase (Gibco/BRL). The resulting plasmids were transformed into DH5a cells (Library efficiency grade, Gibco/BRL), and after 1 hr of expression, plated on LB agar plates (Digene) with 100 μg/ml ampicillin (Sigma). After 24 hrs colonies were picked, grown overnight at 37°C in 1 ml cultures of Superbroth (Digene), and DNA prepared for Sequencing using the QIAwell Ultra kit (Qiagen). DNA cycle sequencing was performed on four independent PCR products using a Prism kit (Applied Biosytems), the reaction products run on an ABI 373 A DNA sequencer, and the resulting data analyzed using Sequencher (Gene Codes). Sequencing confirmed that the pVE3099 encoded a GPCR with high homology to the human MC-4R receptor. The rhMC-4R receptor gene encoded by pVE3099 is 98% identical to the human receptor gene and the rhMC-4R receptor is also 98% identical at the amino acid level to the human MC-4R receptor. EXAMPLE 2 Transient Expression of Rhesus MC-4R Four 800 ml triple flasks (Nalge Nunc) containing 125 ml of Dulbecco's modified Eagle Medium (DMEM), Gibco-BRL) supplemented with 10 % fetal bovine serum (Sigma), L-glutamine (Gibco/BRL), and Pen/Strep (Gibco/BRL) were inoculated with COS 7 cells, and incubated for 4 days. The cells in each flask were collected by pouring off the media, adding 30 ml of trypsin/EDTA (0.05%, Gibco/BRL) to each flask and letting the flasks incubate at room temp for 2 min. Then the tyrpsin solution was removed, and the flasks incubated at 37°C for 10 minutes, 30 ml of DMEM added, and the cells collected. The cells were pelleted at 1000 rpm for 8 min., washed twice with Delbecco's PBS lacking Mg ++ and Ca++ (Gibco/BRL). The cells were counted and resuspended to a density of 1.2 X 10 7 /ml of PBS lacking Mg++ and Ca ++ . DNA was introduced into the cells by electroporation; 0.85 ml of cells was mixed with 20 μg of pVE3099, the rhMCR4 expressing clone, in an ice cold 0.4 cm cuvette (BioRad). The solution was electroporated with a BioRad Gene Pulsar elctroporator set to 0.26 kV, 960 μFD. The cells from 30 electroporations were pooled into 1 liter of DMEM and dispensed 125 ml per triple flask and incubated at 37°C. Three days later the media from each flask was poured off, the cells were washed with 100 ml of Delbecco's PBS lacking Mg++ and Ca++, and 30 ml of enzyme-free dissociation buffer (Gibco/BRL) added. After incubation at room temperature for 10 min., cells were collected, centrifuged at 1000 rpm for 10 min. at 4°C, and resuspended into 15 ml of membrane buffer (10 mM Tris pH 7.4, with proteinase inhibitors). A 500 x proteinase inhibitor solution contains Leupeptin (Sigma) 2 mg/ml, Phosphoramidon (Sigma) 5 mM, Bacitracin (Sigma) 20 mg/ml, Aprotinin (Sigma) 2.5 mg/ml, and 0.05 M AEBSF (Pefabloc). Cells are disrupted with 10 strokes of a motor driven dounce, the homogenate transferred to 50 ml Falcon tubes and spun at 2200 rpm, 4°C for 10 min. The supernatant was transferred to 50 ml centrifuge tubes and spun at 18K for 20 min. in a Sorvall RC5B centrifuge. The membranes were resuspended into 0.6 ml of membrane buffer, passed 2 times through a 18 gauge needle and 5 times through a 25 guage needle, aliquoted, frozen in liquid nitrogen, and stored at -80°C until needed. EXAMPLE 3 Stable Expression of Rhesus MC-4R Chinese Hamster Ovary (CHO) cells were plated into 6 well tissue culture dishes in complete media (ISCOVEis DMEM with the following supplements: 10%) FBS , antibiotics, 2 mM glutamine, 0.1 mM sodium hypoxanthine, .016 mM thymidine (Gibco BRL)) so that 2 days post-plating they were at roughly 50% confluence. For each well, the rhesus MC-4R receptor gene (2 ug) was added to 50 μl of ISCOVE's DMEM (no supplements) and 5 μl SuperFect reagent (Qiagen) in a sterile tube, gently mixed and allowed to incubate at room temperature for 10 minutes. During the last minute of incubation, the media was removed from the cells and the monolayers were rinsed with PBS and removed. At the end ofthe 10 minute incubation, 0.35 mis of complete media was added to the DNA mixture and added dropwise to the cells. The cells were incubated with the DNA solution in a 37°C CO 2 incubator for 2-4 hrs. At the end ofthe 37°C incubation, the DNA solution was removed, cells were rinsed IX with PBS, and then fed with complete media. The next day the cells were detached with Trypsin and replated in complete media containing 1 mg/ml Geneticin (Gibco BRL). After 7-14 days Geneticin-resistant clones were identified and isolated. Clones demonstrating specific binding of I- NDP-alpha-MSH were selected. EXAMPLE 4 Pharmacological Properties of Rhesus MC-4R Competitive Binding Assays - Binding reactions (total volume = 250 μl) contained MBB (50 mM Tris pH 7.2, 2 mM CaCl 2 , 1 mM MgCl 2 ), 0.1% BSA, crude membranes prepared from cells expressing human MC3, MC4 or MC5 receptor, 200 pM [ 125 I]-NDP alpha MSH (Amersham Corp.), and increasing concentrations of unlabelled test compounds dissolved in DMSO (DMSO final concentration = 2%). Reactions were incubated for 1 hour without shaking and then filtered through 96-well filter plates (Packard corp.). Filters were washed three times with TNE buffer (50 mM Tris pH 7.4, 5 mM EDTA, 150 mM NaCl), dried and counted using Microscint-20 in a Topcount scintillation counter (Packard). Non- specific binding was determined in the presence of 2 μM unlabelled NDP alpha MSH (Peninsula laboratories). Membranes prepared from rhesus MC-4R transfected cells were evaluated alongside membranes prepared from human MC-4R, MC-4R, and MC-5R expressing cells. The data in Table 1 represents the average of 2 independent determinations. Human and rhesus MC-4R showed similar rank-order potencies for the natural ligands ACTH>alpha MSH = beta MSH >gamma MSH. The ligands alpha and gamma MSH show greater relative differences in affinity for the rhesus MC-4 receptor compared to human MC-4R. Table 1 Pharmacology of Melanocortin Peptides at the Rhesus MC-4 Receptor. IC50 in nM ieand hMC-3R hMC-4R rhMC-4R hMC-5R Alpha MSH 13 10 27 157 Beta MSH 23 12 23 166 Gamma MSH 75 761 211 2800 ACTH1-39 6 6 1.3 0.4 NDP-alpha-MSH 0.6 0.6 1.3 0.4 MTII 1.6 0.1 0.1 0.9 SHU-9119 0.3 0.1 0.2 0.1 The present invention is not to be limited in scope by the specific embodiments described herein. Indeed, various modifications ofthe invention in addition to those described herein will become apparent to those skilled in the art from the foregoing description. Such modifications are intended to fall within the scope ofthe appended claims. Various publications are cited herein, the disclosures of which are incorporated by reference in their entireties.

Claims: WHAT IS CLAIMED: 1. A purified nucleic acid molecule encoding a rhesus melanocortin 4 receptor protein which comprises the nucleotide sequence GAATTCTCCT GCCAGCATGG TGAACTCCAC CCACCGTGGG ATGCACGCTT CTCTGCACCT CTGGAACCGC AGCAGCCACA GACTGCACAG CAATGCCAGT GAGTCCCTTG GAAAAGGCTA CTCTGATGGA GGGTGCTACG AGCAACTTTT TGTCTCTCCT GAGGTGTTTG TGACACTGGG TGTCATCAGC TTGTTGGAGA ATATCTTAGT GATTGTGGCA ATAGCCAAGA ACAAGAATCT GCATTCACCC ATGTACTTTT TCATCTGCAG CCTGGCTGTG GCTGATATGC TGGTGAGCGT TTCAAATGGA TCAGAAACCA TTGTCATCAC CCTATTAAAC AGTACAGATA CGGACACACA GAGTTTCACA GTGAACATTG ATAATGTTAT TGACTCAGTG ATCTGTAGCT CCTTGCTTGC ATCCATTTGC AGCCTGCTTT CAATTGCAGT GGACAGGTAC TTTACTATCT TCTATGCTCT TCAGTACCAT AACATTATGA CAGTTAAGCG GGTTGGGATC ATCATAAGTT GTATCTGGGC AGCTTGCACG GTTTCAGGCA TTTTGTTCAT CATTTACTCA GATAGTAGTG CTGTCATCAT CTGCCTCATC ACCATGTTCT TCACCATGTT GGCTCTCATG GCTTCTCTCT ATGTCCACAT GTTCCTGATG GCCAGGCTTC ACATTAAGAG GATTGCTGTC CTCCCCGGCA CTGGTGCCAT CCGCCAAGGC GCCAATATGA AGGGAGCGAT TACTTTGACC ATCCTGATTG GCGTCTTTGT TGTCTGCTGG GCCCCATTCT TCCTCCACTT AATATTCTAC ATCTCTTGTC CTCAGAATCC ATATTGTGTG TGCTTCATGT CTCACTTTAA CTTGTATCTC ATACTGATCA TGTGTAATTC AGTCATCGAT CCTCTGATTT ATGCACTCCG GAGTCAAGAA CTAAGGAAAA CCTTCAAAGA GATCATCTGT TGCTATCCCC TGGGAGGCCT ATGTGACTTG TCTAGCAGAT ATTAAATGGG GACAGAGCAC , as set forth in SEQ ID NO:l. 2. A purified DNA molecule encoding rhesus melanocortin 4 receptor protein wherein said DNA molecule encodes a protein comprising the amino acid sequence MVNSTHRG H ASLHLWNRSS HR HSNASES LGKGYSDGGC YEQ FVSPEV FVTLGVISLL ENILVIVAIA KNKN HSPMY FFICSLAVAD MLVSVSNGSE TIVITLLNST DTDTQSFTVN IDNVIDSVIC ΞSL ASICSL LSIAVDRYFT IFYA QYHNI MTVKRVGIII SCI AACTVS GILFIIYSDS SAVIICLITM FFTMLAL AS YVHMF AR LHIKRIAVLP GTGAIRQGAN MKGAITLTIL IGVFWC AP FFLHLIFYIS CPQNPYCVCF MSHFNLYLIL IMCNSVIDPL IYALRSQELR KTF EiiccY PLGGLCDLSS RY , as set forth in a three-letter abbreviation in SEQ ID NO:2. 3. An expression vector for the expression of a rhesus MC-4R protein in a recombinant host cell wherein said expression vector comprises a DNA molecule which encodes the amino acid sequence of claim 2. 4. An expression vector of claim 3 which is a eukaryotic expression vector. 5. An expression vector of claim 3 which is a prokaryotic expression vector. 6. A host cell which expresses a recombinant rhesus MC-4R protein wherein said host cell contains the expression vector of claim 3. 7. A host cell which expresses a recombinant rhesus MC-4R protein wherein said host cell contains the expression vector of claim 4. 8. A host cell which expresses a recombinant rhesus MC-4R protein wherein said host cell contains the expression vector of claim 5. 9. A host cell of claim 6 wherein said rhesus MC-4R protein is overexpressed from said expression vector. 10. A host cell of claim 7 wherein said rhesus MC-4R protein is overexpressed from said expression vector. 11. A host cell of claim 8 wherein said rhesus MC-4R protein is overexpressed from said expression vector. 12. A subcellular membrane fraction obtained from the host cell of claim 9 which contains recombinant rhesus MC-4R protein. 13. A subcellular membrane fraction obtained from the host cell of claim 10 which contains recombinant rhesus MC-4R protein. 14. A subcellular membrane fraction obtained from the host cell of claim 11 which contains recombinant rhesus MC-4R protein. 15. A purified DNA molecule encoding a rhesus melanocortin 4 receptor protein which consists ofthe nucleotide sequence GAATTCTCCT GCCAGCATGG TGAACTCCAC CCACCGTGGG ATGCACGCTT CTCTGCACCT CTGGAACCGC AGCAGCCACA GACTGCACAG CAATGCCAGT GAGTCCCTTG GAAAAGGCTA CTCTGATGGA GGGTGCTACG AGCAACTTTT TGTCTCTCCT GAGGTGTTTG TGACACTGGG TGTCATCAGC TTGTTGGAGA ATATCTTAGT GATTGTGGCA ATAGCCAAGA ACAAGAATCT GCATTCACCC ATGTACTTTT TCATCTGCAG CCTGGCTGTG GCTGATATGC TGGTGAGCGT TTCAAATGGA TCAGAAACCA TTGTCATCAC CCTATTAAAC AGTACAGATA CGGACACACA GAGTTTCACA GTGAACATTG ATAATGTTAT TGACTCAGTG ATCTGTAGCT CCTTGCTTGC ATCCATTTGC AGCCTGCTTT CAATTGCAGT GGACAGGTAC TTTACTATCT TCTATGCTCT TCAGTACCAT AACATTATGA CAGTTAAGCG GGTTGGGATC ATCATAAGTT GTATCTGGGC AGCTTGCACG GTTTCAGGCA TTTTGTTCAT CATTTACTCA GATAGTAGTG CTGTCATCAT CTGCCTCATC ACCATGTTCT TCACCATGTT GGCTCTCATG GCTTCTCTCT ATGTCCACAT GTTCCTGATG GCCAGGCTTC ACATTAAGAG GATTGCTGTC CTCCCCGGCA CTGGTGCCAT CCGCCAAGGC GCCAATATGA AGGGAGCGAT TACTTTGACC ATCCTGATTG GCGTCTTTGT TGTCTGCTGG GCCCCATTCT TCCTCCACTT AATATTCTAC ATCTCTTGTC CTCAGAATCC ATATTGTGTG TGCTTCATGT CTCACTTTAA CTTGTATCTC ATACTGATCA TGTGTAATTC AGTCATCGAT CCTCTGATTT ATGCACTCCG GAGTCAAGAA CTAAGGAAAA CCTTCAAAGA GATCATCTGT TGCTATCCCC TGGGAGGCCT ATGTGACTTG TCTAGCAGAT ATTAAATGGG GACAGAGCAC , as set forth in SEQ ID NO: 1. 16. A purified DNA molecule which encodes a MC-4R protein which consists ofthe amino acid sequence MVNSTHRGMH ASLHLWNRSS HRLHSNASES LGKGYSDGGC YEQLFVSPEV FVTLGVISLL ENILVIVAIA KNKNLHSPMY FFICSLAVAD MLVSVSNGSE TIVITLLNST DTDTQSFTVN IDNVIDSVIC SSLLASICSL LSIAVDRYFT IFYALQYHNI MTVKRVGIII SCI AACTVS GILFIIYSDS SAVIICLITM FFTMLALMAS LYVHMFLMAR LHIKRIAVLP GTGAIRQGAN MKGAITLTIL IGVFWC AP FFLHLIFYIS CPQNPYCVCF MSHFNLYLIL IMCNSVIDPL IYALRSQELR KTFKEIICCY PLGGLCDLSS RY , as set forth in three letter abbreviation in SEQ ID NO:2. 17. The purified DNA molecule of claim 15 which consists of a nucleotide sequence from nucleotide 17 to nucleotide 1015 of SEQ ID NO:l. 18. An expression vector for the expression of a rhesus MC-4R protein in a recombinant host cell wherein said expression vector comprises a DNA molecule of claim 17. 19. An expression vector of claim 18 which is a eukaryotic expression vector. 20. An expression vector of claim 18 which is a prokaryotic expression vector. 21. A host cell which expresses a recombinant rhesus MC-4R protein wherein said host cell contains the expression vector of claim 19. 22. A host cell which expresses a recombinant rhesus MC-4R protein wherein said host cell contains the expression vector of claim 20. 23. A host cell which expresses a recombinant rhesus MC-4R protein wherein said host cell contains the expression vector of claim 21. 24. A subcellular membrane fraction obtained from the host cell of claim 22 which contains recombinant rhesus MC-4R protein. 25. A subcellular membrane fraction obtained from the host cell of claim 23 which contains recombinant rhesus MC-4R protein. 26. A process for the expression of a rhesus MC-4R protein in a recombinant host cell, comprising: (a) transfecting the expression vector of claim 3 into a suitable host cell; and, (b) culturing the host cells of step (a) under conditions which allow expression ofthe rhesus MC-4R protein from the expression vector. 27. A purified rhesus melanocortin 4 receptor protein which comprises the amino acid sequence as follows: MVNSTHRGMH ASLHLWNRSS HRLHSNASES LGKGYSDGGC YEQLFVSPEV FVTLGVISLL ENILVIVAIA KNKNLHSPMY FFICSLAVAD MLVSVSNGSE TIVITLLNST DTDTQSFTVN IDNVIDSVIC SSLLASICSL LSIAVDRYFT IFYALQYHNI MTVKRVGIII SCIWAACTVS GILFIIYSDS SAVIICLITM FFTMLALMAS LYVHMFLMAR LHIKRIAVLP GTGAIRQGAN MKGAITLTIL IGVFWCWAP FFLHLIFYIS CPQNPYCVCF MSHFNLYLIL IMCNSVIDPL IYALRSQELR KTFKEIICCY PLGGLCDLSS RY , as set forth in a three-letter abbreviation in SEQ ID NO:2. 28. A purified rhesus melanocortin 4 receptor protein which consists ofthe amino acid sequence as set forth in SEQ ID NO:2. 29. A method for determining whether a substance is capable of binding to rhMC-4R comprising: (a) providing test cells by transfecting cells with an expression vector that directs the expression of rhMC-4R in the cells; (b) exposing the test cells to the substance; (c) measuring the amount of binding ofthe substance to rhMC-4R; and, (d) comparing the amount of binding ofthe substance to rhMC-4R in the test cells with the amount of binding ofthe substance to control cells that have not been transfected with rhMC-4R. 30. A method for determining whether a substance is capable of activating rhMC-4R comprising: (a) providing test cells by transfecting cells with an expression vector that directs the expression of rhMC-4R in the cells; (b) exposing the test cells to the substance; (c) measuring the amount of accumulated intracellular cAMP; and, (d) comparing the amount of c AMP in the test cells in response to the substance with the amount of c AMP in test cells that have not been exposed to the substance. 31. A method of identifying a substance which modulates MC-4R receptor activity, comprising: (a) combining a test substance in the presence and absence of a MC-4R receptor protein wherein said MC-4R receptor protein comprises the amino acid sequence as set forth in SEQ ID NO:2; and, (b) measuring and comparing the effect ofthe test substance in the presence and absence ofthe MC-4R receptor protein. 32. A method for determining whether a substance is a potential agonist or antagonist of MC-4R comprising: (a) transfecting or transforming cells with an expression vector of claim 3 that directs expression of MC-4R in the cells, resulting in test cells; (b) allowing the test cells to grow for a time sufficient to allow MC-4R to be expressed; (c) exposing the cells to a labeled ligand ofMC-4R in the presence and in the absence ofthe substance; and, (d) measuring the binding ofthe labeled ligand to MC-4R; where if the amount of binding ofthe labeled ligand is less in the presence ofthe substance than in the absence ofthe substance, then the substance is a potential agonist or antagonist of MC-4R. 33. A method for determining whether a substance is capable of binding to MC-4R comprising: (a) transfecting or transforming cells with an expression vector of claim 3 that directs the expression of MC-4R in the cells, resulting in test cells; (b) exposing the test cells to the substance; (c) measuring the amount of binding ofthe substance to MC-4R; and, (d) comparing the amount of binding ofthe substance to MC-4R in the test cells with the amount of binding ofthe substance to control cells that have not been transfected with MC-4R; wherein if the amount of binding ofthe substance is greater in the test cells as compared to the control cells, the substance is capable of binding to MC-4R. 34. A method for determining whether a substance is capable of binding to MC-4R comprising: (a) transfecting or transforming cells with an expression vector of claim 3 that directs the expression of MC-4R in the cells, resulting in test cells; (b) preparing membranes containing MC-4R from the test cells and exposing the membranes to a ligand of MC-4R under conditions such that the ligand binds to the MC-4R in the membranes; (c) subsequently or concurrently to step (b), exposing the membranes from the test cells to a substance; (d) measuring the amount of binding ofthe ligand to the MC-4R in the membranes in the presence and the absence ofthe substance; and, (e) comparing the amount of binding ofthe ligand to MC-4R in the membranes in the presence and the absence ofthe substance where a decrease in the amount of binding ofthe ligand to MC-4R in the membranes in the presence ofthe substance indicates that the substance is capable of binding to MC-4R. 35. A method for determining whether a substance is capable of binding to MC-4R comprising: (a) transfecting or transforming cells with an expression vector of claim 3 that directs the expression of MC-4R in the cells, resulting in test cells; (b) preparing membranes containing MC-4R from the test cells and exposing the membranes from the test cells to the substance; (c) measuring the amount of binding ofthe substance to the MC- 4R in the membranes from the test cells; (d) comparing the amount of binding ofthe substance to MC-4R in the membranes from the test cells with the amount of binding ofthe substance to membranes from control cells that have not been transfected with MC-4R, where if the amount of binding ofthe substance to MC-4R in the membranes from the test cells is greater than the amount of binding ofthe substance to the membranes from the control cells, then the substance is capable of binding to MC-4R. 36. A method of identifying agonists of MC-4R comprising: (a) transfecting or transforming cells with a first expression vector of claim 3 which directs expression of MC-4R and a second expression vector which directs the expression of a promiscuous G-protein, resulting in test cells; (b) exposing the test cells to a substance that is a suspected agonist of MC-4R; and, (c) measuring the level of inositol phosphates in the cells; where an increase in the level of inositol phosphates in the cells as compared to the level of inositol phosphates in the cells in the absence ofthe suspected agonist indicates that the substance is an agonist of MC-4R. 37. A method of identifying antagonists of MC-4R comprising: (a) transfecting or transforming cells with a first expression vector of claim 3 which directs expression of MC-4R and a second expression vector which directs the expression of a promiscuous G-protein, resulting in test cells; (b) exposing the test cells to a substance that is an agonist of MC- 4R; (c) subsequently or concurrently to step (b), exposing the test cells to a substance that is a suspected antagonist of MC-4R; and, (d) measuring the level of inositol phosphates in the cells; where a decrease in the level of inositol phosphates in the cells in the presence ofthe suspected antagonist as compared to the level of inositol phosphates in the cells in the absence ofthe suspected antagonist indicates that the substance is an antagonist of MC-4R. 38. A method of identifying antagonists of MC-4R as recited in claim 37 wherein the first and second expression vectors of step (a) are replaced with a single expression vector which expresses a chimeric MC-4R protein fused at its C- terminus to a promiscuous G-protein. 39. An antibody that binds specifically to MC-4R protein wherein the MC-4R receptor protein comprises the amino acid sequence as set forth in SEQ ID NO:2.

Inventors: MACNEIL DOUGLAS J, VAN DER PLOEG LEONARDUS H T, WEINBERG DAVID H, MACNEIL, DOUGLAS, J., VAN DER PLOEG, LEONARDUS, H., T., WEINBERG, DAVID, H.
Applicants: MACNEIL DOUGLAS J, MERCK & CO INC, PLOEG LEONARDUS H T V D, WEINBERG DAVID H, MACNEIL, DOUGLAS, J., MERCK & CO., INC., VAN DER PLOEG, LEONARDUS, H., T., WEINBERG, DAVID, H.
Application year: 1999
Main classification: C07H21
IPC codes: C07K14, C07K16, C12N1, C12N5, C12N15, C12P21, C12Q1, G01N33