Human neuropeptide receptor

Human neuropeptide receptor polypeptides and DNA (RNA) encoding such polypeptides and a procedure for producing such polypeptides by recombinant techniques is disclosed. Also disclosed are methods for utilizing such polypeptides for identifying antagonists and agonists to such polypeptides and methods of using the agonists and antagonists therapeutically to treat conditions related to the underexpression and overexpression of the neuropeptide receptor polypeptides, respectively. Also disclosed are diagnostic methods for detecting a mutation in the neuropeptide receptor nucleic acid sequences and an altered level of the soluble form of the receptors.

This invention relates to newly identified polynucleotides, polypeptides encoded by such polynucleotides, the use of such polynucleotides and polypeptides, as well as the production of such polynucleotides and polypeptides. The polypeptides of the present invention are human 7-transmembrane G-protein coupled receptors. More particularly, the polypeptides of the present invention are neuropeptide receptor polypeptides, sometimes hereinafter referred to as neuropeptide receptor polypeptides. The invention also relates to inhibiting the action of such polypeptides.

Obesity is the commonest nutritional disorder in Western societies. More than three in ten adult Americans weigh at least 20% in excess of their ideal body weight (Burroa, M., The New York Times, Jul. 17, 1994). Increased body weight is an important public health problem because it is associated with Type II diabetes, hypertension, hyperlipidemia and certain cancers (Grundy, S. M., and Barnett, J. P., Disease-a-Month, 36:645-696 (1990)).

Five single-gene mutations in the mouse obesity gene (ob) which result in an obese phenotype have been described (Friedman, J. M. & Leibel, R. L., Cell, 66:217-220 (1990)). The cloning and sequencing of the mouse ob gene and its human homologue have been reported (Zhang, Y., et al., Nature, 372:425-431 (1994)). The ob gene encodes a 4.5-kb adipose tissue mRNA with a highly conserved 167-amino-acid open reading frame. The predicted amino-acid sequence is 84% identical between human and mouse and has features of a secreted protein. The ob gene product may function as part of a signalling pathway from adipose tissue that acts to regulate the size of the body fat depot (id. 425).

Of the brain regions implicated in the regulation of feeding behavior, the ventromedial nucleus of the hypothalamus (VMH) is considered to be the most important satiety center in the central nervous system (CNS). The energy balance in mammals is therefore postulated to be controlled by a feedback loop in which the amount of stored energy is sensed by the hypothalamus, which adjusts food intake and energy expenditure to maintain a constant body weight (Ombeck, J. R., Yale J. Biol. Med., 20:545-552 (1948) and Kennedy, G. C., Proc. R. Soc. 148:578-592 (1953)). In the lipostasis theory, the size of the body fat depot is regulated by the CNS, with a product of body fat metabolism affecting energy balance by interacting with the hypothalamus (Kennedy, G. C., Proc. R. Soc. 148:578-592 (1953)).

The inability to identify the putative signal from fat has hindered the validation of the lipostasis theory. The possibility that at least one component of the signalling system circulates in the bloodstream was first suggested by Hervey (Dietrich, W., et al., Genetics, 131:423-447 (1992)), who showed that the transfer of blood from an animal with a VMH lesion across a vascular graft to an untreated animal (a parabiosis experiment) resulted in a reduction of food intake in the intact animal. It is now significant that there is evidence that the ob gene product is secreted, suggesting that ob may encode this circulating factor.

The ob signal may act directly or indirectly on the CNS to inhibit food intake and/or regulate energy expenditure as part of a homeostatic mechanism to maintain constancy of the adipose mass (Zhang, Y., et al., Nature, 372:425-431, 431 (1994)). The ob gene apparently encodes a protein secreted by fat, and mutations apparently prevent translation or expression of the gene (Rink, T., Nature, 372:406-407 (1994)).

Parabiosis experiments suggest that the ob receptor is encoded by the mouse db (diabetes) gene (Coleman, D. L., Diabetologia, 14:141-148 (1978)). Mice having a mutation in the db gene are also obese, with the defect possibly being a receptor defect. (Id. at 406).

Neuropeptide Y is similar to the ob gene product in that it mediates the feeding response. Neuropeptide Y acts on at least four types of neuropeptide Y receptors called Y 1 , Y 2 , Y 3 and an atypical Y 1 receptor, which mediates the feeding response stimulated by neuropeptide Y.

Neuropeptide Y has a wide range of biological functions. Neuropeptide Y is found to be widely distributed in the central nervous system (CNS) and the peripheral nervous system (PNS). In the PNS, neuropeptide Y is found in the noradrenergic sympathetic innervation of blood vessels and other smooth muscle tissues and in neurons within the enteric nervous system. Neuropeptide Y immunoreactive fibers also occur in the non-vascular smooth muscle, surrounding exocrine glands and surface epithelia. Neuropeptide Y also occurs in subpopulations of neurons and is generally co-localized with other neurotransmitters, particular noradrenaline.

In the CNS, neuropeptide Y is contained in GABAergic interneurons in higher centers and in predominantly catecholaminergic cells that project further caudally. For example, neuropeptide Y is contained in interneurons in the cortex, hippocampus, amygdala, basal forebrain and striatum, whereas in the brain stem, neuropeptide Y is contained in noradrenergic neurons of the A 1 and A 2 groups in the medulla, and the locus coeruleus (LC). In the hypothalamus, neuropeptide Y is found predominantly in the arcuate nucleus and lateral hypothalamus.

Within the peripheral nervous system, neuropeptide Y is present in postganglionic sympathetic nerves, and is co-localized as stated above with other neurotransmitters, including catecholamines. When used pharmacologically, neuropeptide Y has been shown to have a potent vasoconstrictor activity as well as dramatically potentiating the vasoconstriction caused by many other pressor agents. Particularly high concentrations of neuropeptide Y are found in the sympathetic nerves supplying the coronary, cerebral and renal vasculature and when infused into these vascular beds, neuropeptide Y causes prolonged vasoconstriction that is not reversed by adrenergic blocking agents. These observations have lead to the proposal that neuropeptide Y is the candidate transmitter for pathological vasospasm, a major cause of morbidity and mortality when involving the coronary and cerebral vessels.

Neuropeptide Y also appears to be involved in interaction with the renin angiotensin system. Neuropeptide Y containing sympathetic nerve terminals are found on the juxta-glomerular apparatus of the renal cortex and neuropeptide Y influences renin release. These data, together with the demonstration of all durations in neuropeptide Y concentrations in hypertensive animal models and the pressor response to infusion of the peptide, have resulted in implications of this peptide in hypertension.

Within the central nervous system neuropeptide Y is located predominantly within interneurons where it appears to have a regulatory role. It therefore has widespread and diverse effects including effects on memory and a possible role in Alzheimer's disease. Neuropeptide Y is the most potent known substance to cause an increase in feeding and may play a role in the genetic basis of Type II Diabetes Mellitus. Neuropeptide Y may also play a role as a regulatory agent and pituitary function as well as potential neuromodulatory function in stress responses and in reproductive function.

In accordance with one aspect of the present invention, there are provided novel mature receptor polypeptides as well as biologically active and diagnostically or therapeutically useful fragments, analogs and derivatives thereof. The receptor polypeptides of the present invention are of human origin.

In accordance with another aspect of the present invention, there are provided isolated nucleic acid molecules encoding the receptor polypeptides of the present invention, including mRNAs, DNAs, cDNAs, genomic DNA as well as antisense analogs thereof and biologically active and diagnostically or therapeutically useful fragments thereof.

In accordance with a further aspect of the present invention, there are provided processes for producing such receptor polypeptides by recombinant techniques comprising culturing recombinant prokaryotic and/or eukaryotic host cells, containing nucleic acid sequences encoding the receptor polypeptides of the present invention, under conditions promoting expression of said polypeptides and subsequent recovery of said polypeptides.

In accordance with yet a further aspect of the present invention, there are provided antibodies against such receptor polypeptides.

In accordance with another aspect of the present invention there are provided methods of screening for compounds which bind to and activate or inhibit activation of the receptor polypeptides of the present invention.

In accordance with still another embodiment of the present invention there are provided processes of administering compounds to a host which bind to and activate the receptor polypeptide of the present invention which are useful in the prevention and/or treatment of obesity, hyperlipidemia, certain cancers, to stimulate neuronal growth, to regulate neurotransmission, to enhance activity levels and utilization of ingested foods.

In accordance with another aspect of the present invention there is provided a method of administering the receptor polypeptides of the present invention via gene therapy to treat conditions related to underexpression of the polypeptides or underexpression of a ligand to the receptor polypeptide.

In accordance with still another embodiment of the present invention there are provided processes of administering compounds to a host which bind to and inhibit activation of the receptor polypeptides of the present invention which are useful in the prevention and/or treatment of Alzheimer's disease, Type II Diabetes Mellitus, epilepsy, stress, anxiety, hypertension, cardiovascular disease, psychotic conditions and obesity caused by neuropeptide Y.

In accordance with yet another aspect of the present invention, there are provided nucleic acid probes comprising nucleic acid molecules of sufficient length to specifically hybridize to the polynucleotide sequences of the present invention.

In accordance with still another aspect of the present invention, there are provided diagnostic assays for detecting diseases related to mutations in the nucleic acid sequences encoding such polypeptides and for detecting an altered level of the soluble form of the receptor polypeptides.

In accordance with yet a further aspect of the present invention, there are provided processes for utilizing such receptor polypeptides, or polynucleotides encoding such polypeptides, for in vitro purposes related to scientific research, synthesis of DNA and manufacture of DNA vectors.

These and other aspects of the present invention should be apparent to those skilled in the art from the teachings herein.

Bacterial Expression and Purification of the Neuropeptide Receptor

The DNA sequence encoding for neuropeptide receptor, ATCC 97128 is initially amplified using PCR oligonucleotide primers corresponding to the 5 and 3 end sequences of the processed neuropeptide receptor gene (minus the signal peptide sequence) and the vector sequences 3 to the gene. Additional nucleotides corresponding to neuropeptide receptor nucleotide sequence are added to the 5 and 3 sequences respectively. The 5 oligonucleotide primer has the sequence 5 CACTAAAGCTTAATGGAGCCCTCAGCCACC 3 (SEQ ID NO:7) contains a Hind III restriction enzyme site followed by 18 nucleotides of neuropeptide receptor coding sequence starting from the presumed terminal amino acid of the processed protein codon. The 3 sequence 5 ACAAGTCCTTGTCCTTCTAGAGGGC 3 (SEQ ID NO:8) and contains an Xba1 site. The restriction enzyme sites correspond to the restriction enzyme sites on the bacterial expression vector pQE-9 (Qiagen, Inc. Chatsworth, Calif.). pQE-9 encodes antibiotic resistance (Amp r ), a bacterial origin of replication (ori), an IPTG-regulatable promoter operator (P/O), a ribosome binding site (RBS), a 6-His tag and restriction enzyme sites. pQE-9 is then digested with Hind III and Xba1. The amplified sequences are ligated into pQE-9 and are inserted in frame with the sequence encoding for the histidine tag and the RBS. The ligation mixture is then used to transform E. coli strain M15/rep 4 (Qiagen, Inc.) by the procedure described in Sambrook, J. et al., Molecular Cloning: A Laboratory Manual, Cold Spring Laboratory Press, (1989). M15/rep4 contains multiple copies of the plasmid pREP4, which expresses the lacI repressor and also confers kanamycin resistance (Kan r ). Transformants are identified by their ability to grow on LB plates and ampicillin/kanamycin resistant colonies are selected. Plasmid DNA is isolated and confirmed by restriction analysis. Clones containing the desired constructs are grown overnight (O/N) in liquid culture in LB media supplemented with both Amp (100 ug/ml) and Kan (25 ug/ml). The O/N culture is used to inoculate a large culture at a ratio of 1:100 to 1:250. The cells are grown to an optical density 600 (O.D. 600 ) of between 0.4 and 0.6. IPTG ( Isopropyl-B-D-thiogalacto pyranoside ) is then added to a final concentration of 1 mM. IPTG induces by inactivating the lacI repressor, clearing the P/O leading to increased gene expression. Cells are grown an extra 3 to 4 hours. Cells are then harvested by centrifugation. The cell pellet is solubilized in the chaotropic agent 6 Molar Guanidine HCl. After clarification, solubilized neuropeptide receptor is purified from this solution by chromatography on a Nickel-Chelate column under conditions that allow for tight binding by proteins containing the 6-His tag (Hochuli, E. et al., J. Chromatography 411:177-184 (1984). The protein is eluted from the column in 6 molar guanidine HCl pH 5.0 and for the purpose of renaturation adjusted to 3 molar guanidine HCl, 100 mM sodium phosphate, 10 mmolar glutathione (reduced) and 2 mmolar glutathione (oxidized). After incubation in this solution for 12 hours the protein is dialyzed to 10 mmolar sodium phosphate.

Expression of Recombinant Neuropeptide Receptor in COS Cells

The expression of plasmid, neuropeptide receptor HA is derived from a vector pcDNA3/Amp (Invitrogen) containing: 1) SV40 origin of replication, 2) ampicillin resistance gene, 3) E. coli replication origin, 4) CMV promoter followed by a polylinker region, a SV40 intron and polyadenylation site. A DNA fragment encoding the entire neuropeptide receptor precursor and a HA tag fused in frame to its 3 end is cloned into the polylinker region of the vector, therefore, the recombinant protein expression is directed under the CMV promoter. The HA tag corresponds to an epitope derived from the influenza hemagglutinin protein as previously described (I. Wilson, H. Niman, R. Heighten, A Cherenson, M. Connolly, and R. Lerner, 1984, Cell 37, 767). The infusion of HA tag to the target protein allows easy detection of the recombinant protein with an antibody that recognizes the HA epitope.

The plasmid construction strategy is described as follows:

The DNA sequence encoding for neuropeptide receptor, ATCC 97128, is constructed by PCR using two primers: the 5 primer 5 CCTAGGATGCCCCTCTGCTGCAGCGG 3 (SEQ ID NO:9) contains a BamHI site; the 3 sequence 5 ACAAGTCCTTGTCCTTCTAGAGGGC 3 (SEQ ID NO:10) contains complementary sequences to an XbaI site, translation stop codon, and the last 17 nucleotides of the neuropeptide receptor coding sequence (not including the stop codon). Therefore, the PCR product contains a BamHI site, coding sequence, a translation termination stop codon and an XbaI site. The PCR amplified DNA fragment and the vector, pcDNA3/Amp, are digested with BamHI and XbaI restriction enzymes and ligated. The ligation mixture is transformed into E. coli strain SURE (Stratagene Cloning Systems, La Jolla, Calif.) the transformed culture is plated on ampicillin media plates and resistant colonies are selected. Plasmid DNA is isolated from transformants and examined by restriction analysis for the presence of the correct fragment. For expression of the recombinant neuropeptide receptor, COS cells are transfected with the expression vector by DEAE-DEXTRAN method (J. Sambrook, E. Fritsch, T. Maniatis, Molecular Cloning: A Laboratory Manual, Cold Spring Laboratory Press, (1989)). The expression of the neuropeptide receptor HA protein is detected by radio-labelling and immunoprecipitation method (E. Harlow, D. Lane, Antibodies: A Laboratory Manual, Cold Spring Harbor Laboratory Press, (1988)). Cells are labelled for 8 hours with 35 S-cysteine two days post transfection. Culture media are then collected and cells are lysed with detergent (RIPA buffer (150 mM NaCl, 1% NP-40, 0.1% SDS, 1% NP-40, 0.5% DOC, 50 mM Tris, pH 7.5). (Wilson, I. et al., Id. 37:767 (1984)). Both cell lysate and culture media are precipitated with a HA specific monoclonal antibody. Proteins precipitated are analyzed on 150 SDS-PAGE gels.

Cloning and Expression of Neuropentide Receptor Using the Baculovirus Expression System

The DNA sequence encoding the full length neuropeptide receptor protein, ATCC 97128, is amplified using PCR oligonucleotide primers corresponding to the 5 and 3 sequences of the gene:

The 5 primer has the sequence 5 CGGGATCCGCCATC ATG GAGCCCTCAGCCACC 3 (SEQ ID NO:11) and contains a BamHI restriction enzyme site (in bold) followed by 6 nucleotides resembling an efficient signal for the initiation of translation in eukaryotic cells (J. Mol. Biol. 1987, 196, 947-950, Kozak, M.). The initiation codon for translation ATG is underlined).

The 3 primer has the sequence 5 ACAAGTCCTTGTCCTTCTAGAGGGC 3 (SEQ ID NO:12) and contains the cleavage site for the restriction endonuclease XbaI and 5 nucleotides complementary to the 3 non-translated sequence of the neuropeptide receptor gene. The amplified sequences are isolated from a 1% agarose gel using a commercially available kit ( Geneclean, BIO 101 Inc., La Jolla, Calif.). The fragment is then digested with the endonucleases BamHI and XbaI and then purified as described in Example 1. This fragment is designated F2.

The vector pA2 (modification of pVL941 vector, discussed below) is used for the expression of the neuropeptide receptor protein using the baculovirus expression system (for review see: Summers, M. D. and Smith, G. E. 1987, A manual of methods for baculovirus vectors and insect cell culture procedures, Texas Agricultural Experimental Station Bulletin NO:1, 3 and 5555). This expression vector contains the strong polyhedrin promoter of the Autographa californica nuclear polyhidrosis virus (AcMNPV) followed by the recognition sites for the restriction endonucleases BamHI and XbaI. The polyadenylation site of the simian virus (SV)40 is used for efficient polyadenylation. For an easy selection of recombinant viruses the beta-galactosidase gene from E.coli is inserted in the same orientation as the polyhedrin promoter followed by the polyadenylation signal of the polyhedrin gene. The polyhedrin sequences are flanked at both sides by viral sequences for the cell-mediated homologous recombination of co-transfected wild-type viral DNA. Many other baculovirus vectors could be used in place of pRG1 such as pAc373, pVL941 and pAcIM1 (Luckow, V. A. and Summers, M. D., Virology, 170:31-39).

The plasmid is digested with the restriction enzymes BamHI and XbaI and then dephosphorylated using calf intestinal phosphatase by procedures known in the art. The DNA is then isolated from a 16 agarose gel as described in Example 1. This vector DNA is designated V2.

Fragment F2 and the dephosphorylated plasmid V2 are ligated with T4 DNA ligase. DH 5 u are then transformed and bacteria identified that contained the plasmid (pBac neuropeptide receptor) with the neuropeptide receptor gene using the enzymes BamHI and XbaI. The sequence of the cloned fragment is confirmed by DNA sequencing. 5 g of the plasmid pBac neuropeptide receptor are co-transfected with 1.0 g of a commercially available linearized baculovirus ( BaculoGold baculovirus DNA , Pharmingen, San Diego, Calif.) using the lipofection method (Felgner et al. Proc. Natl. Acad. Sci. USA, 84:7413-7417 (1987)). 1 g of BaculoGold virus DNA and 5 g of the plasmid pBac neuropeptide receptor are mixed in a sterile well of a microtiter plate containing 50 l of serum free Grace's medium (Life Technologies Inc., Gaithersburg, Md.). Afterwards 10 l Lipofectin plus 90 l Grace's medium are added, mixed and incubated for 15 minutes at room temperature. Then the transfection mixture is added drop wise to the Sf9 insect cells (ATCC CRL 1711) seeded in a 35 mm tissue culture plate with 1 ml Grace' medium without serum. The plate is rocked back and forth to mix the newly added solution. The plate is then incubated for 5 hours at 27 C. After 5 hours the transfection solution is removed from the plate and 1 ml of Grace's insect medium supplemented with 10% fetal calf serum is added. The plate is put back into an incubator and cultivation continued at 27 C. for four days.

After four days the supernatant is collected and a plaque assay performed similar as described by Summers and Smith (supra). As a modification an agarose gel with Blue Gal (Life Technologies Inc., Gaithersburg) is used which allows an easy isolation of blue stained plaques. (A detailed description of a plaque assay can also be found in the user's guide for insect cell culture and baculovirology distributed by Life Technologies Inc., Gaithersburg, page 9-10).

Four days after the serial dilution the virus is added to the cells and blue stained plaques are picked with the tip of an Eppendorf pipette. The agar containing the recombinant viruses is then resuspended in an Eppendorf tube containing 200 l of Grace's medium. The agar is removed by a brief centrifugation and the supernatant containing the recombinant baculoviruses is used to infect Sf9 cells seeded in 35 mm dishes. Four days later the supernatants of these culture dishes are harvested and then stored at 4 C.

Sf9 cells are grown in Grace's medium supplemented with 10% heat-inactivated FBS. The cells are infected with the recombinant baculovirus V-neuropeptide receptor at a multiplicity of infection (MOI) of 2. Six hours later the medium is removed and replaced with SF900 II medium minus methionine and cysteine (Life Technologies Inc., Gaithersburg). 42 hours later 5 Ci of 35 S-methionine and 5 Ci 35S cysteine (Amersham) are added. The cells are further incubated for 16 hours before they are harvested by centrifugation and the labelled proteins visualized by SDS-PAGE and autoradiography.

Expression Via Gene Therapy

Fibroblasts are obtained from a subject by skin biopsy. The resulting tissue is placed in tissue-culture medium and separated into small pieces. Small chunks of the tissue are placed on a wet surface of a tissue culture flask, approximately ten pieces are placed in each flask. The flask is turned upside down, closed tight and left at room temperature over night. After 24 hours at room temperature, the flask is inverted and the chunks of tissue remain fixed to the bottom of the flask and fresh media (e.g., Ham's F12 media, with 10% FBS, penicillin and streptomycin, is added. This is then incubated at 37 C. for approximately one week. At this time, fresh media is added and subsequently changed every several days. After an additional two weeks in culture, a monolayer of fibroblasts emerge. The monolayer is trypsinized and scaled into larger flasks. pMV-7 (Kirschmeier, P. T. et al, DNA, 7:219-25 (1988) flanked by the long terminal repeats of the Moloney murine sarcoma virus, is digested with EcoRI and HindIII and subsequently treated with calf intestinal phosphatase. The linear vector is fractionated on agarose gel and purified, using glass beads.

The cDNA encoding a polypeptide of the present invention is amplified using PCR primers which correspond to the 5 and 3 end sequences respectively. The 5 primer contains an EcoRI site and the 3 primer contains a HindIII site. Equal quantities of the Moloney murine sarcoma virus linear backbone and the EcoRI and HindIII fragment are added together, in the presence of T4 DNA ligase. The resulting mixture is maintained under conditions appropriate for ligation of the two fragments. The ligation mixture is used to transform bacteria HB101, which are then plated onto agar-containing kanamycin for the purpose of confirming that the vector had the gene of interest properly inserted.

The amphotropic pA317 or GP am12 packaging cells are grown in tissue culture to confluent density in Dulbecco's Modified Eagles Medium (DMEM) with 10% calf serum (CS), penicillin and streptomycin. The MSV vector containing the gene is then added to the media and the packaging cells are transduced with the vector. The packaging cells now produce infectious viral particles containing the gene (the packaging cells are now referred to as producer cells).

Fresh media is added to the transduced producer cells, and subsequently, the media is harvested from a 10 cm plate of confluent producer cells. The spent media, containing the infectious viral particles, is filtered through a millipore filter to remove detached producer cells and this media is then used to infect fibroblast cells. Media is removed from a sub-confluent plate of fibroblasts and quickly replaced with the media from the producer cells. This media is removed and replaced with fresh media. If the titer of virus is high, then virtually all fibroblasts will be infected and no selection is required. If the titer is very low, then it is necessary to use a retroviral vector that has a selectable marker, such as neo or his.

The engineered fibroblasts are then injected into the host, either alone or after having been grown to confluence on cytodex 3 microcarrier beads. The fibroblasts now produce the protein product.

Numerous modifications and variations of the present invention are possible in light of the above teachings and, therefore, within the scope of the appended claims, the invention may be practiced otherwise than as particularly described.