WO2007141322A1

WO2007141322A1 - G protein coupled receptor 39 (gpr39)

Info

Publication number: WO2007141322A1
Application number: PCT/EP2007/055636
Authority: WO
Inventors: Benoit Christian Jean-Claude Moreaux; Diederik Willem Elisabeth Moechars; Luc August Laurentius Ver Donck
Original assignee: Janssen Pharmaceutica N.V.
Priority date: 2006-06-08
Filing date: 2007-06-08
Publication date: 2007-12-13
Also published as: MX2008015670A; CA2652398A1; CN101467047A; EP2030024A1; JP2009539362A

Abstract

The present invention relates to the functional characterization of the G protein coupled receptor GPR39 and to compounds, which modify or regulate GPR39 protein activity. In particular the present invention relates to methods of screening for agonists or antagonists of GPR39 in order to identify compounds capable of modulating carbohydrate metabolism and to the therapeutic uses of these compounds. In particular to the use of GPR39 in methods to identify compounds that are capable to enhance glucose control in a subject and which are effective for preventing and/or treating pathologies related with an impaired carbohydrate metabolism, in particular in the prevention and/or treatment of diabetes including associated complications thereof, or of the metabolic syndrome including associated complications thereof. Including Type 1 (insulin-dependent or IDDM), Type 2 (non- insulin- dependent diabetes mellitus), maturity-onset diabetes of the young (MODY) and gestational diabetes.

Description

G PROTEIN-COUPLED RECEPTOR 39 (GPR39 )

Field of the Invention

The present invention relates to the functional characterization of the G protein coupled receptor GPR39 and to compounds, which modify or regulate GPR39 protein activity. In particular the present invention relates to methods for enhancing glucose control in a subject in need of such control which comprises administering to the subject a composition comprising a therapeutically effective amount of a compound capable of modulating or regulating GPR39 protein activity. In another embodiment the present invention relates to the involvement of GPR39 signalling in glucose regulation and thus in glycaemia observed in diabetes and in metabolic syndrome including obesity, diabetes, cardiovascular diseases, atherosclerosis, atherogenic dyslipidemia, hypertension, hypertriglyceridemia and adipose tissue disorders.

Background to the Invention

GTP-binding proteins (G proteins) act as intermediaries between binding of ligands such as hormones and other chemical mediators to G protein coupled receptors (GPCRs) and activation of intracellular effectors. Upon binding of a ligand to a GPCR, the cytoplasmic domains of the receptor undergo conformational changes, which enable interaction of the receptor with a G protein, which in turn enables activation of intracellular intermediaries such as adenylate cyclase, phospholipase C or ion channels. Such a system allows amplification of the original signal as many second messengers can be produced in response to the binding of a single ligand at the GPCR. Through this mechanism, cells are able to sense and respond to alterations in their external environment. G protein coupled receptors form a superfamily of integral plasma membrane proteins, each receptor sharing the common feature of seven hydrophobic transmembrane domains, each of which is 20 -30 amino acids long and which are linked by hydrophilic amino acid sequences of varied length. The amino terminus of the receptor is extracellular with the carboxy terminus found in the cytoplasm of the cell.

GPCRs are found in a wide range of tissues and cell types and are involved in many different physiological processes. They are activated by a broad range of ligands, for example, hormones such as luteinizing hormone, follicle stimulating hormone, chorionic gonadotrophin, thyrotropin, adrenocorticotrophin, glucagon and vasopressin or neurotransmitters such as 5-HT, acetylcholine (muscarinic AchR) , histamine, prostaglandins, calcitonin, leukotrienes and Ca²⁺. The broad distribution and wide variety of roles of GPCRs indicate that GPCRs may play important roles in a variety of pathological conditions. Indeed, GPCRs have "been found to be involved in diseases related to bronchoconstriction, hypertension, inflammation, hormonal disturbance, diabetes, apoptosis, nociception, facilitation of neurotransmission and tremor disorders.

Within the G-protein-coupled receptor ' superfamily, the putative GPCRs for which the natural ligands are unknown are called "orphan receptors". G protein-coupled receptor have been proven to be valuable drug targets, since they are the target of about 50% of the marketed drugs.

Therefore many orphan GPCR are being evaluated to identify new potential targets.

GPR39 was identified based upon is sequence similarity with the growth hormone secretagogue receptor (GHS-R) and the neurotensin receptors 1 and 2 (NT-Rl and NT-R2) (McKee et SLI., 1997) . The predicted 453-amino acid GRP39 protein contains the 7 transmembrane domains characteristic of GPCRs. By sequence comparison with other GPCRs,' McKee et al. (1997) found that the protein sequence of GPR39 is

27%, 29% and 32% identical to that of GSHR, MTLRl (motilin receptor) and neurotensin receptor-1, respectively. Northern blot analysis revealed that GPR39 has a wide tissue distribution. A single hybridizing mRNA transcript of 1.8-2 kb, was detected in most brain regions tested. However, in addition to this species, an alternate transcript, 3-kb in length, was observed in several peripheral tissues such as stomach and small intestine. In tissues such as pancreas, thyroid and colon, this 3-kb species was the only transcript detected (McKee et al . ,

1997). By fluorescence in situ hybridization, McKee et al . (1997) mapped the GPR39 gene to 2q21-q22. An acidic residue in TM3 is conserved in GPR39. It is known that this residue is essential for the binding and activation of the GHS-R by structurally dissimilar GHSs.

Based on these tissue distribution studies GPR39 has been hypothesized to be involved in cardiovascular disease states (WO2001/081634 & WO2004/004279) , cancers and in particular brain cancers such as glioblastoma (WO2001/036685 & WO01042288) , inflammation and neurological disease states (US 2003/ 232769 & WO2004/004279) and in gastrointestinal and liver diseases (WO2004/004279) . Only recently obestatin, the putative ligand for GPR39 has been identified (Zhang J. V. et al . , 2005) . It was found that obestatin suppress food intake and reduces the gastrointestinal functions including gastric emptying and jejunal motility. Based on these anorexigenic actions GPR39 has been postulated as a novel anti-obesity target. Nonetheless, in none of the cited references a functional role for GPR39 in energy homeostasis and in particular in carbohydrate metabolism has been provided.

Diabetes is caused by occurrence of abnormal metabolism of glucose, protein and lipids due to an insufficiency of the actions of insulin. Typical signs of diabetes include an abnormal increase in the serum glucose levels, insulin insufficiency and an excretion of glucose in the urine.

Several clinical subclasses are recognized, including: Type 1 Cinsulin-dependent or IDDM) , Type 2 (non-insulin- dependent diabetes mellitus) , maturity-onset diabetes of the young (MODY) and gestational diabetes. They differ in etiology, pathology, genetics, age of onset, and treatment .

Type 1 diabetes, the more severe form of diabetes accounts for 5 to 10 percent of diabetes and occurs most often in children and young adults. In this form of diabetes the body does not produce any insulin and without regular injections of insulin the sufferer lapses into a coma and dies. Individuals suffering from Type 1 diabetes are totally insulin dependent.

Type 2 diabetes, the more prevalent type of diabetes, is usually characterized by gradual onset and occurs mainly in people over 40. Type 2 diabetes is a metabolic disorder resulting from the body's inability to make enough insulin or to properly use insulin to meet the body's needs, especially when the person is overweight. It is the most common form of the disease and accounts for 90 to 95 percent cases of diabetes. Initially the combination of dietary measures, weight reduction and oral medication can keep the condition under control for a period of time, but most people with Type 2 diabetes ultimately require insulin injections.

Diabetes may be controlled with insulin and in some cases through careful diet, but there is a need for a safe and effective treatment for diabetes with minimal side effects and without the invasive procedure of insulin injection.

Impaired carbohydrate metabolism, and in particular diabetes or metabolic syndrome, is also associated with several complications, including (poly) neuropathy (peripheral, autonomic, proximal, focal), nephropathy, renal disease, kidney failure, bladder dysfunction, retinopathy, large- and small vessel vascular complications, stroke,, myocardial infarction, large vessel occlusive disease, coronary (ischemic) artery disease, cerebral vascular disease, heart failure, peripheral arterial disease, hypertension, sexual dysfunction, gastroparesis. Said complications will also benefit from a treatment of the impaired carbohydrate metabolism according to the present invention.

Summary of the Invention As noted above, the present invention concerns identification of novel functions of the GPR39 receptor. As shown in the examples hereinafter, GPR39 mutations in mammals affect blood glucose concentrations and designate GPR39 as a key element in the regulation of carbohydrate metabolism. This discovery provides an avenue for new therapeutic approaches in the treatment of diabetes including associated complications thereof, or of the metabolic syndrome including associated complications thereof through modulation of GPR39 activity. This discovery provides an avenue for new therapeutic approaches in the treatment of diabetes including associated complications thereof, or of the metabolic syndrome including associated complications thereof through modulation of GPR39 activity. This discovery also provides for new screening methods for identifying compounds useful for the prevention or the treatment of diabetes including associated complications thereof, or of the metabolic syndrome including associated complications thereof .

Therefore, a first aspect of the invention provides for the use of all or part of GPR39 protein in a method for identifying compounds that enhance glucose control in a subject and which are effective for preventing and/or treating pathologies related with an impaired carbohydrate metabolism, in particular in the prevention and/or treatment of diabetes including associated complications thereof, or of the metabolic syndrome including associated complications thereof. Alternatively, the invention provides for the use of cells expressing all or part of the GPR39 protein in such method. In a specific embodiment GPR39 is an isolated protein having an amino acid sequence selected from the group consisting of SEQ ID No: 2, SEQ ID NO : 4 , a splice variant of the proteins having the aforementioned SEQ ID's, and an amino acid sequence having at least 80% and preferably at least 90%, 95%, 96%, 97%, or 98% sequence identity to the amino acid sequence of SEQ ID NO: 2 or SEQ ID N0:4.

Parts of the GPR39 protein, as used hereinbefore, are meant to include fragments of the polypeptide of SEQ ID NO: 2 or SEQ ID NO : 4 , said fragments being of at least 10, for example at least 20, 30 40, 50, 75, 100 or 150 or more amino acids in size. Such fragments may be derived from the N-terminal region of SEQ ID NO: 2 or SEQ ID NO : 4 respectively. Fragments including the ¹N-terminal region may be used to reconstitute the extracellular portion of the receptor to provide receptor binding sites. Preferably, fragments will retain the ability to bind an agent known to bind to GPR39, including the natural ligand as well as agonists and/or antagonists of the receptor as defined hereinafter, in particular retaining the capability to bind the putative ligand of GPR39, i.e. to bind obestatin.

The present invention also provides the use of an isolated nucleic acid sequence encoding all or part of the polypeptide of SEQ ID NO: 2 or SEQ ID NO : 4 in a method for identifying compounds that enhance glucose control in a subject and which are effective for preventing and/or treating pathologies related with an impaired carbohydrate metabolism, in particular in the prevention and/or treatment of diabetes including associated complications thereof, or of the metabolic syndrome including associated complications thereof. The nucleic acid sequences as used in the methods of the present invention are meant to include the isolated nucleic acid sequences consisting of SEQ ID N0:l or SEQ ID NO : 3 , and nucleic acid sequences having at least 80% and preferably at least 90%, 95%, 96%, 97% or 98% sequence identity to the nucleic acid sequence of SEQ ID N0:l or SEQ ID NO : 3.

Nucleic acids of the invention further include nucleic acids which comprise a sequence having at least 80% and preferably at least 90%, 95%, 96%, 97% or 98% sequence identity to the nucleic acid sequences of SEQ ID NO: 1, or SEQ ID NO: 3 or their complements. Preferably, these sequences will hybridise to the corresponding nucleic acid under conditions controlled to minimise non-specific binding. Preferably stringent to moderately stringent hybridisation conditions are preferred. Suitable conditions include, e.g. for detection of sequences that are about 80-90% identical, hybridization overnight at 42 ⁰C in 0.25M Na₂HPO₄, pH 7.2, 6.5% SDS, 10% dextran sulfate and a final wash at 55 ⁰C in 0. IX SSC, 0.1% SDS. For detection of sequences that are greater than about 90% identical, suitable conditions include hybridization overnight at 65 ⁰C in 0.25M Na₂HPO₄, pH 7.2, 6.5% SDS, 10% dextran sulfate and a final wash at 60 ⁰C in 0. IX SSC, 0.1% SDS.

It will be appreciated that such nucleic acids do not necessarily encode "full length" polypeptides, and will thus include nucleic acids which represent, for example, mutant forms of the GPR39 gene in which the coding sequence has been prematurely terminated by either a substitution resulting in a stop codon or a frameshift mutation. These are also nucleic acids of the invention.

The invention also provides the use of nucleic acids that are fragments of the nucleic acids encoding a polypeptide of the invention. In one aspect, the invention provides nucleic acids primers which consist essentially of from 15 to 50, for example from 15 to 35, 18 to 35, 15 to 24, 18 to 30, 18 to 21 or 21 to 24 nucleotides of a sequence encoding a polypeptide of the invention or its complement.

Nucleic acids and polypeptides of the invention may be used therapeutically to treat disease. In particular, they may be used to treat diseases, the pathology of which is associated with action at GPR39 receptors, particularly those associated with preventing and/or treating pathologies related with an impaired carbohydrate metabolism, in particular in the prevention and/or treatment of diabetes including associated complications thereof , or of the metabolic syndrome including associated complications thereof.

In a further aspect, there are provided vectors comprising the sequences of said nucleic acids, particularly expression vectors comprising a promoter operably linked to the nucleic acid sequences of the invention. The vectors may be carried by a host cell, and expressed within said cell. Following said expression, said cells can be used in the methods according to the invention.

As mentioned hereinbefore, it is an object of the invention to provide assay methods for the identification of compounds (hereinafter also referred to as agents) , which bind to or modulate the activity of polypeptides of the invention. In particular it is envisaged that such compounds are an organic or inorganic assembly of atoms of any size, and includes small molecules (less than about 2500 Daltons) or larger molecules such as peptides, polypeptides, whole proteins and polynucleotides, wherein said compounds may be used in methods of treatment as described above.

As the present inventors are the first to identify GPR39 as a receptor as a key element in the regulation of carbohydrate metabolism, the present invention opens up the possibility of using GPR39 itself and/or compounds agonising or antagonising this receptor in therapeutic applications. Therefore the invention further extends to a method of treatment of a human or animal body, said method comprising the use of a GPR39 agonist or antagonist. As used herein an "agonist" refers to an agent that binds to GPR39 and activates it, i.e. producing a pharmacological response, and includes positive allosteric modulators which bind to a site different from the agonist binding site on the receptor and which enhance the receptor responsiveness to the natural agonist of the receptor. An "antagonist" as used herein refers to agents that attenuate the effects of an agonist for GPR39. Antagonism can be competitive and reversible (i.e. it binds to a region of the receptor in common with the agonist and can be replaced with a sufficient large amount of agonist) or it can be non-competitive and/or irreversible (i.e. the antagonist binds covalently to the binding site and no amount of agonist can overcome the inhibition) . Other types of antagonism are non-competitive antagonism wherein the agent binds to an allosteric site of the receptor or inverse agonism wherein for a constitutive receptor, as reported for GPR39 (Hoist et al . , 2004), the agent binds to the agonist binding site and attenuates the constitutive activity of the receptor.

In particular, the present invention provides a method of treating disease conditions related with an impaired carbohydrate metabolism, in particular in the prevention and/or treatment of diabetes including associated complications thereof, or of the metabolic syndrome including associated complications thereof. Said method comprising in those conditions wherein a decrease in basal glucose levels is required, administering to the human or animal a therapeutically active dosage of a GPR39 receptor agonist. The use of a GPR39 agonist is of particular use in the treatment of the metabolic syndrome including associated complications thereof , in particular comprising the use of a GPR39 agonist identifiable using a method of the present invention. Alternatively, in the treatment of diabetes including associated complications thereof, said method comprises administering to the human or animal a therapeutically active dosage of a GPR39 receptor antagonist, in particular comprising the use of a GPR39 antagonist identifiable using a method of the present invention.

These and other aspects of the invention are described herein in more detail.

Description of sequences.

SEQ ID N0:l is the nucleotide sequence for mice GPR39. SEQ ID NO: 2 is the amino acid sequence for mice GPR39.

SEQ ID NO: 3 is the nucleotide sequence for human GPR39.

SEQ ID NO : 4 is the amino acid sequence for human GPR39.

SEQ ID No : 5 is human obestatin

SEQ ID No : 6 is monkey obestatin SEQ ID No: 7 is mouse obestatin

SEQ ID No: 8 is rat obestatin

SEQ ID No: 9 is gerbil obestatin

SEQ ID No: 10 is pig obestatin

SEQ ID No: 11 is cat obestatin SEQ ID No: 12 is dog obestatin

SEQ ID No: 13 is goat obestatin

SEQ ID No: 14 is sheep obestatin

SEQ ID No: 15 is Cattle obestatin

SEQ ID No: 16 is the consensus sequence for obestatin

Brief Description of the Drawings

Figure 1 GPR39-LacZ expression in pancreas. In the GPR39^~A derived pancreas, expression was detected in the islets of

Langerhans (encircled) as evidenced from the blue staining (Fig IA. , 4Ox) . No staining was present in WT pancreas

(Fig IB. , 4Ox)

Figure 2 Comparison of the body weight of GPRSg^'''^" and WT mice followed in both male and female animals from the age of 8 - 12 up to 16 - 20 weeks. Data are expressed in mean ± SD .

Figure 3 Comparison of the baseline blood glucose concentration in both fed (A) and fasted (B) conditions of GPRS-T^ and WT mice followed in both male and female animals.

Figure 4 Comparison of the glucose tolerance test of fasted GPRB.T''^" and WT mice followed in both male and female animals. Blood glucose concentration was determined at 15, 30, 45, 60, 90 and 120 min. post glucose administration and expressed as percentage change from the baseline values. Data are expressed in mean ± SD.

Figure 5 Comparison of the body composition of GPRB.T¹''^" and WT mice followed in both male and female mice. Fat and lean masses are expressed in percentage of body weight. Data are expressed in mean ± SD.

Figure 6A is an alignment of the human (NP 001499) , mouse (AAH85285) , rat (XP 222578), dog (partial) (XP 853332) and cattle (partial) (XP 589836) GPR39 protein sequences. The alignment shows the human GPR39 protein sequence at the top, other species in decreasing order of sequence similarity to human. The name of each sequence reflects the sequence accession number in the NCBI nr database, the gene symbol, and the species name.

The dog and cattle sequences in the alignment differ from the original public domain sequence: the C-terminal amino acids lacking similarity to other GPR39 sequences were removed. The argument is that deleted amino acids were from lower quality sequencing results.

The human sequence is used as reference and amino acids are coloured grey. Amino acids of other sequences are coloured if similar to the human sequence. Figure 6B provides a matrix that shows identity, similarity and gaps between every sequence. There are more gaps between dog, cattle sequence and all other sequences, because former sequences are partial. For the overlapping fragments the degree of identity is given by the sum of the %identity with the %gaps . For example, for dog with human the degree of identity for the overlapping fragment is 86%.

Detailed Description of the Invention

Nucleic acid

Nucleic acid as used in the methods of the present invention includes DNA (including both genomic and cDNA) and RNA. Where nucleic acid according to the invention includes RNA, reference to the sequences shown in the accompanying listings should be construed as reference to the RNA equivalent, with U substituted for T.

Nucleic acid of the invention may be single or double stranded. Single stranded nucleic acids of the invention include anti-sense nucleic acids. Thus it will be understood that reference to SEQ ID NO : 1 or sequences comprising SEQ ID NO : 1 or fragments thereof include complementary sequences unless the context is clearly to the contrary. The same applies to SEQ ID NO: 3.

Generally, nucleic acid according to the present invention is provided as an isolate, in isolated and/or purified form, or free or substantially free of material with which it is naturally associated, such as free or substantially free of nucleic acid flanking the gene in the human genome, except possibly one or more regulatory sequence (s) for expression. Nucleic acid may be wholly or partially synthetic and may include genomic DNA, cDNA or RNA. In other words "isolated" indicates that a naturally occurring sequence has been removed from its normal cellular context. Thus, the sequence may be in a cell- free solution or placed in a different cellular environment or nucleic acid context. Therefore, the nucleic acids claimed herein can be present as heterologous material in whole cells or in cell lysates or in a partially, substantially or wholy purified form.

The invention also provides nucleic acids that are fragments of the nucleic acids encoding a polypeptide of the invention. In one aspect, the invention provides nucleic acids primers which consist essentially of from 15 to 50, for example from 15 to 35, 18 to 35, 15 to 24, 18 to 30, 18 to 21 or 21 to 24 nucleotides of a sequence encoding a polypeptide of the invention or its complement.

The term Aconsist essentially of≡ refers to nucleic acids which do not include any additional 5 ' or 3 ' nucleic acid sequences. In a further aspect of the invention, nucleic acids of the invention which consist essentially of from 15 to 30 nucleotides as defined above may however be linked at the 3' but preferably 5' end to short (e.g from 4 to 15, such as from 4 to 10 nucleotides) additional sequences to which they are not naturally linked. Such additional sequences are preferably linkers which comprise a restriction enzyme recognition site to facilitate cloning when the nucleic acid of the invention is used for example as a PCR primer.

Primers of the invention are desirably capable of selectively hybridising to nucleic acids encoding the polypeptides of the invention. By Aselective=, it is meant selective with respect to sequences encoding other purine receptors and in particular with respect to receptors other than adenine receptors. The ability of the sequence to hybridise selectively may be determined by experiment or calculated.

For example, one way to calculate Tm of a primer is by reference to the formula for calculating the Tm of primers to a homologous target sequence. This formula is Tm(⁰C) = 2(A+T) + 4 (G+C) - 5. This will provide the Tm under conditions of 3xSSC and 0.1% SDS (where SSC is 0.15M NaCl, 0.015M sodium citrate, pH 7) . This formula is generally suitable for primers of up to about 50 nucleotides in length. In the present invention, this formula may be used as an algorithm to calculate a nominal Tm of a primer for a specified sequence derived from a sequence encoding a polypeptide of the invention. The Tm may be compared to a calculated Tm for GPCR sequences of humans and rats, based upon the maximum number of matches to any part of these other sequences.

Suitable conditions for a primer to hybridise to a target sequence may also be measured experimentally. Suitable experimental conditions comprise hybridising a candidate primer to both nucleic acid encoding a polypeptide of the invention and nucleic acid encoding other G-protein coupled receptors on a solid support under low stringency hybridising conditions (e.g. 6xSSC at 55°C) , washing at reduced SSC and/or higher temperature, for example at 0.2xSSC at 45°C, and increasing the hybridisation temperature incrementally to determine hybridisation conditions which allow the primer to hybridise to nucleic acid encoding a polypeptide of the invention but not other GPCR encoding nucleic acids. Nucleic acids of the invention, particularly primers, may- carry a revealing label. Suitable labels include radioisotopes such as ³²P or ³⁵S, fluorescent labels, enzyme labels, or other protein labels such as biotin. Such labels may be added to polynucleotides or primers of the invention and may be detected using by techniques known per se .

Primers of the present invention may be comprised of synthetic nucleic acids, such as those with modified backbone structures intended to improve stability of the nucleic acid in a cell. A number of different types of modification to oligonucleotides are known in the art. These include methylphosphonate and phosphorothioate backbones, addition of acridine or polylysine chains at the 3' and/or 5¹ ends of the molecule. For the purposes of the present invention, it is to be understood that the polynucleotides described herein may be modified by any method available in the art. Such modifications may be carried out in order to enhance the in vivo activity or lifespan of polynucleotides of the invention.

Also included within the scope of the invention are antisense sequences based on the nucleic acid sequences described herein, preferably in the form of oligonucleotides, particularly stabilized oligonucleotides, or ribozymes.

Antisense oligonucleotides may be designed to hybridise to the complementary sequence of nucleic acid, pre-mRNA or mature mRNA, interfering with the production of polypeptide encoded by a given target DNA sequence, so that its expression is reduced or prevented altogether. Ribozymes will be designed to cleave mRNA encoded by an GPR39 GPCR encoding nucleic acid sequence of the invention, desirably at a target sequence specific to the GPR39 GPCR, i.e one which is not common to other GPCR sequences. The construction of antisense sequences and their use is described in Peyman and Ulman, Chemical Reviews, 90:543-584, (1990), Crooke, Ann. Rev.

Pharmacol. Toxicol., 32:329-376, (1992), and Zamecnik and Stephenson, P. N.A. S, 75:280-284, (1974). The construction of ribozymes and their use is described in for instance Gibson and Shillitoe, Molecular Biotechnology 7(2): 125- 137, (1997) .

In one embodiment, RNA of the invention can be used for induction of RNA interference (RNAi) , using double stranded (dsRNA) (Fire et al . , Nature 391: 806-811. 1998) or short-interfering RNA (siRNA) sequences (Yu et al . ,

Proc Natl Acad Sci USA. 99:6047-52. 2002). "RNAi" is the process by which dsRNA induces homology-dependent degradation of complimentary mRNA. In one embodiment, a nucleic acid molecule of the invention is hybridized by complementary base pairing with a "sense" ribonucleic acid of the invention to form the double stranded RNA. The dsRNA antisense and sense nucleic acid molecules are provided that correspond to at least about 20, 25, 50, 100, 250 or 500 nucleotides or an GPR39 coding strand, or to only a portion thereof. In an alternative embodiment, the siRNAs are 30 nucleotides or less in length, and more preferably 21- to 23 -nucleotides , with characteristic 2- to 3-nucleotide 3 ' -overhanging ends, which are generated by ribonuclease III cleavage from longer dsRNAs . See e.g. Tuschl T. (Nat Biotechnol . 20:446-48. 2002).

Intracellular transcription of small RNA molecules can be achieved by cloning the siRNA templates into RNA polymerase III (Pol III) transcription units, which normally encode the small nuclear RNA (snRNA) U6 or the human RNAse P RNA Hl . Two approaches can be used to express siRNAs: in one embodiment, sense and antisense strands constituting the siRNA duplex are transcribed by individual promoters (Lee, et al . Nat. Biotechnol . 20, 500-505. 2002); in an alternative embodiment, siRNAs are expressed as stem-loop hairpin RNA structures that give rise to siRNAs after intracellular processing (Brummelkamp et al . Science 296:550-553. 2002) (herein incorporated by reference) .

The dsRNA/siRNA is most commonly administered by annealing sense and antisense RNA strands in vitro before delivery to the organism. In an alternate embodiment, RNAi may be carried out by administering sense and antisense nucleic acids of the invention in the same solution without annealing prior to administration, and may even be performed by administering the nucleic acids in separate vehicles within a very close timeframe. Nucleic acid molecules encoding fragments, homologs, derivatives and analogs of a GPR39 or antisense nucleic acids complementary to a GPR39 nucleic acid sequence are additionally provided.

Antisense, siRNAs and ribozyme sequences of the invention may be introduced into mammalian cells lines in culture to study the function of GPR39 GPCR, for example by causing down-regulation of this gene and observing phenotypic effects, or the expression or location of proteins described herein which associate with GPR39 GPCR. In cells where aberrant expression of GPR39 GPCR occurs, such antisense, siRNA and ribozyme sequences may be used to down-regulate the expression of the gene.

The cDNA sequence of the GPCR of the invention may be cloned using standard PCR (polymerase chain reaction) cloning techniques. This involves making a pair of primers to 5 ' and 3 ' ends on opposite strands of SEQ ID N0:l, bringing the primers into contact with mRNA or cDNA obtained from a mammalian cortical cell, performing a polymerase chain reaction under conditions which bring about amplification of the desired region, isolating the amplified fragment (e.g. by purifying the reaction mixture on an agarose gel) and recovering the amplified DNA. The primers may be designed to contain suitable restriction enzyme recognition sites so that the amplified DNA can be cloned into a suitable cloning vector. The same applies to SEQ ID NO: 3.

Polynucleotides which are not 100% homologous to the sequence of SEQ ID N0:l or SEQ ID NO: 3 but which encode either SEQ ID NO: 2 or SEQ ID NO : 4 or other polypeptides of the invention can be obtained in a number of ways.

For example, site directed mutagenesis of the sequence of SEQ ID NO: 1 or SEQ ID NO : 3 may be performed. This is useful where for example silent codon changes are required to sequences to optimise codon preferences for a particular host cell in which the polynucleotide sequences are being expressed. Other sequence changes may be desired in order to introduce restriction enzyme recognition sites, or to alter the property or function of the polypeptides encoded by the polynucleotides. Further changes may be desirable to represent particular coding changes which are required to provide, for example, conservative substitutions.

Nucleic acids of the invention may comprise additional sequences at the 5' or 3 ' end. For example, synthetic or natural 5 ' leader sequences may be attached to the nucleic acid encoding polypeptides of the invention. The additional sequences may also include 5 ' or 3 ' untranslated regions required for the transcription of nucleic acid of the invention in particular host cells.

In addition, other animal, particularly mammalian (e.g. humans or rabbits) , more particularly primate including human, homologues of GPR39 may be obtained and used in the methods of the present invention. Such sequences may be obtained by making or obtaining cDNA libraries made from dividing cells or tissues or genomic DNA libraries from other animal species, and probing such libraries with probes comprising all or part of SEQ ID N0:l or of SEQ ID NO: 3 under conditions of medium to high stringency (for example 0.03M sodium chloride and 0.03M sodium citrate at from about 50^NC to about 60^NC) .

The present invention further extends to an isolated DNA sequence comprising sequences encoding a polypeptide of the invention but in which the encoding sequences are divided up into two or more (preferably no more than five, e.g. four or three) exons . Such exon sequences may be natural and obtained from genomic clones, or synthetic. Exon sequences may be used in the construction of mini- gene sequences which comprise nucleic acid encoding polypeptides of the invention which sequences are interrupted by one or more exon sequences.

Mini -genes may also be constructed using heterologous exons, derived from any eukaryotic source.

Polypeptides .

Isolated polypeptides used in the methods of the present invention will be those as defined above in isolated form, free or substantially free of material with which it is naturally associated such as other polypeptides with which it is found in the cell. The polypeptides may of course be formulated with diluents or adjuvants and still for practical purposes be isolated - for example the polypeptides will normally be mixed with gelatin or other carriers if used to coat microtitre plates for use in immunoassays. The polypeptides may be glycosylated, either naturally or by systems of heterologous eukaryotic cells, or they may be (for example if produced by expression in a prokaryotic cell) unglycosylated.

Polypeptides may be phosphorylated and/or acetylated.

A polypeptide of the invention may also be in a substantially purified form, in which case it will generally comprise the polypeptide in a preparation in which more than 90%, e.g. 95%, 98% or 99% of the polypeptide in the preparation is a polypeptide of the invention.

Polypeptides of the invention may be modified for example by the addition of histidine residues to assist their purification or by the addition of a signal sequence to promote their secretion from a cell.

As is shown in the alignment in Figure 6, the mammalian GPR39 proteins have an overall sequence identity of at least 80% with either the human or mouse sequence. For said reason, polypeptides having at least 80%, for example 90%, 95%,, 96%, 97% or 98% sequence identity to SEQ ID NO : 2 or SEQ ID NO: 4 are also provided by the present invention. Said polypeptides include polypeptides which are amino acid sequence, variants, alleles, derivatives or mutants of SEQ ID NO: 2 or SEQ ID NO: 4 respectively. For example such a polypeptide may have an amino acid sequence which differs from that given in SEQ ID NO: 2 or SEQ ID NO : 4 by one or more of addition, substitution, deletion and insertion of one or more {such as from 1 to 20, for example 2, 3, 4, or 5 to 10) amino acids.

The percentage identity of polypeptide sequences can be calculated using commercially available algorithms which compare a reference sequence ( e.g. SEQ ID NO : 2 or SEQ ID NO: 4 of the present invention) with a query sequence. Further details of assessing identity are described below.

Where a query sequence is determined to have an identity to that of SEQ ID NO: 2 or SEQ ID NO : 4 of at least 80% and preferably at least 90%, 95%, 96%, 97% or 98% said sequence being that of a polypeptide retaining GPR39 receptor activity, such a sequence forms part of the present invention.

A polypeptide according to the present invention may be isolated and/or purified (e.g. using an antibody) for instance after production by expression from encoding nucleic acid. The isolated and/or purified polypeptide may be used in formulation of a composition, which may include at least one additional component, for example a pharmaceutical composition including a pharmaceutically acceptable excipient, vehicle or carrier.

A polypeptide according to the present invention may be used as an immunogen or otherwise in obtaining specific antibodies. Antibodies are useful in purification and other manipulation of polypeptides, diagnostic screening and therapeutic contexts.

A polypeptide according to the present invention may be used in screening for molecules which bind to it or modulate its activity or function. Such molecules may be useful in a therapeutic (possibly including prophylactic) context .

A polypeptide or labelled polypeptide of the invention or fragment thereof may also be fixed to a solid phase, for example the surface of an immunoassay well or dipstick.

Such labelled and/or immobilized polypeptides may be packaged into kits in a suitable container along with suitable reagents, controls, instructions and the like.

Such polypeptides and kits may be used in methods of detection of antibodies to such polypeptides present in a sample or active portions or fragments thereof by immunoassay.

Immunoassay methods are well known in the art and will generally comprise:

(a) providing a polypeptide comprising an epitope bindable by an antibody against said protein;

(b) incubating a biological sample with said polypeptide under conditions which allow for the formation of an antibody-antigen complex; and

(c) determining whether antibody-antigen complex comprising said polypeptide is formed.

Sequence Identity

The percentage identity of nucleic acid and polypeptide sequences can be calculated using commercially available algorithms which compare a reference sequence with a query sequence. The following programs (provided by the National Center for Biotechnology Information) may be used to determine homologies/identities : BLAST, gapped BLAST, BLASTN and PSI-BLAST, which may be used with default parameters . The algorithm GAP (Genetics Computer Group, Madison, WI) uses the Needleman and Wunsch algorithm to align two complete sequences that maximizes the number of matches and minimizes the number of gaps. Generally, the default parameters are used, with a gap creation penalty = 12 and gap extension penalty = 4.

Another method for determining the best overall match between a nucleic acid sequence or a portion thereof, and a query sequence is the use of the FASTDB computer program based on the algorithm of Brutlag et al (Comp. App . Biosci., 6; 237-245 (1990)). The program provides a global sequence alignment . The result of said global sequence alignment is in percent identity. Suitable parameters used in a FASTDB search of a DNA sequence to calculate percent identity are: Matrix=Unitary, k-tuple=4, Mismatch penalty=l, Joining Penalty=30, Randomization Group Length=0, Cutoff Score=l, Gap Penalty=5, Gap Size Penalty=0.05_y and Window Size=500 or query sequence length in nucleotide bases, whichever is shorter. Suitable parameters to calculate percent identity and similarity of an amino acid alignment are: Matrix=PAM 150, k-tuple=2, Mismatch Penalty=l, Joining Penalty=20, Randomization Group Length=0, Cutoff Score=l, Gap Penalty=5, Gap Size

Penalty=0.05, and Window Size=500 or query sequence length in nucleotide bases, whichever is shorter.

Vectors Isolated nucleic acid sequences of the present invention may be incorporated into vectors, particularly expression vectors. The vector may be used to replicate the nucleic ^< acid in a compatible host cell. Thus in a further embodiment, the invention provides a method of making polynucleotides of the invention by introducing an isolated polynucleotide of the invention into a replicable vector, introducing the vector into a compatible host cell, and growing the host cell under conditions which bring about replication of the vector. The vector may be recovered from the host cell. Suitable host cells are described below in connection with expression vectors.

Preferably, an isolated polynucleotide of the invention in a vector is operably linked to a control sequence which is capable of providing for the expression of the coding sequence by the host cell, i.e. the vector is an expression vector.

The term "operably linked" refers to a juxtaposition wherein the components described are in a relationship permitting them to function in their intended manner. A control sequence "operably linked" to a coding sequence is ligated in such a way that expression of the coding sequence is achieved under condition compatible with the control sequences.

Suitable vectors can be chosen or constructed, containing appropriate regulatory sequences, including promoter sequences, terminator fragments, polyadenylation sequences, enhancer sequences, marker genes and other sequences as appropriate. Vectors may be plasmids, viral e.g. phage, phagemid or baculoviral, cosmids, YACs, BACs, or PACs as appropriate. Vectors include gene therapy vectors, for example vectors based on adenovirus, adeno- associated virus, retrovirus (such as HIV or MLV) or alpha virus vectors.

The vectors may be provided with an origin of replication, optionally a promoter for the expression of the said polynucleotide and optionally a regulator of the promoter. The vectors may contain one or more selectable marker genes, for example an ampicillin resistance gene in the case of a bacterial plasmid or a neomycin resistance gene for a mammalian vector. Vectors may be used in vitro, for example for the production of RNA or used to transfect or transform a host cell. The vector may also be adapted to be used in vivo, for example in methods of gene therapy. Systems for cloning and expression of a polypeptide in a variety of different host cells are well known. Suitable host cells include bacteria, eukaryotic cells such as mammalian and yeast, and baculovirus systems. Mammalian cell lines available in the art for expression of a heterologous polypeptide include Chinese hamster ovary cells, HeLa cells, baby hamster kidney cells, COS cells and many others .

Promoters and other expression regulation signals may be selected to be compatible with the host cell for which the expression vector is designed. For example, yeast promoters include S. cerevisiae GAL4 and ADH promoters, S. pombe nmtl and adh promoter. Mammalian promoters include the metallothionein promoter which can be induced in response to heavy metals such as cadmium. Viral promoters such as the SV40 large T antigen promoter or adenovirus promoters may also be used. All these promoters are readily available in the art.

The vectors may include other sequences such as promoters or enhancers to drive the expression of the inserted nucleic acid sequences so that the polypeptide is produced as a fusion and/or nucleic acid encoding secretion signals so that the polypeptide produced in the host cell is secreted from the cell.

Vectors for production of polypeptides of the invention of for use in gene therapy include vectors which carry a mini-gene sequence of the invention. It is accordingly an object of the present invention to provide a method for treating abnormal conditions related to an under- expression of GPR39 GPCR and its activity, said method comprising the use of a polynucleotide encoding a GPR39 GPCR. In particular in a method to treat impaired carbohydrate metabolism, such as diabetes including associated complications thereof. In gene therapy an isolated polynucleotide of the invention is used to effect the endogenous production of GPR39 GPCR by the relevant cells in the subject. For example, a polynucleotide encoding a GPR39 GPCR may be engineered for expression in a replication defective retroviral vector as provided above. The retroviral expression construct may then be isolated and introduced into a packaging cell transduced with a retroviral plasmid vector containing RNA encoding a polypeptide of the present invention such that the packaging cell now produces infectious viral particles containing the gene of interest. These producer cells may be administered to a subject for engineering cells in vivo and expression of the polypeptide in vivo. For review of gene therapy, see Chapter 20, Gene Therapy and other Molecular Genetic-based Therapeutic Approaches, in Human Molecular Genetics, T. Strachan and A. P. Read, BIOS Scientific Publishers Ltd. (1996) .

For further details see, for example, Molecular Cloning: a Laboratory Manual: 2nd edition, Sambrook et al . , 1989, Cold Spring Harbor Laboratory Press . Many known techniques and protocols for manipulation of nucleic acid, for example in preparation of nucleic acid constructs, mutagenesis, sequencing, introduction of DNA into cells and gene expression, and analysis of proteins, are described in detail in Current Protocols in Molecular Biology, Ausubel et al . eds . , John Wiley & Sons, 1992.

Vectors may be transformed into a suitable host cell as described above to provide for expression of a polypeptide of the invention. Thus, in a further aspect the invention provides a process for preparing polypeptides according to the invention which comprises cultivating a host cell transformed or transfected with an expression vector as described above under conditions to provide for expression by the vector of a coding sequence encoding the polypeptides, and recovering the expressed polypeptides. Polypeptides may also be expressed in vitro systems, such as reticulocyte lysate .

A further embodiment of the invention provides host cells transformed or transfected with the vectors for the replication and expression of polynucleotides of the invention. The cells will be chosen to be compatible with the said vector and may for example be bacterial, yeast, insect or mammalian. The host cells may be cultured under conditions for expression of the gene, so that the encoded polypeptide is produced. If the polypeptide is expressed coupled to an appropriate signal leader peptide it may be secreted from the cell into the culture medium. Following production by expression, a polypeptide may be isolated and/or purified from the host cell and/or culture medium, as the case may be, and subsequently used as desired, e.g. in the formulation of a composition which may include one or more additional components, such as a pharmaceutical composition which includes one or more pharmaceutically acceptable excipients, vehicles or carriers

Polynucleotides according to the invention may also be inserted into the vectors described above in an antisense orientation in order to provide for the production of antisense RMA or ribozymes.

Assays

It is an object of the present invention to provide an assay for identifying compounds that enhance glucose control in a subject and which are effective for preventing and/or treating pathologies related with an impaired carbohydrate metabolism, in particular in the prevention and/or treatment of diabetes including associated complications thereof, or of the metabolic syndrome including associated complications thereof, which assay comprises: providing all or part of a GPR39 receptor protein according to the invention, contacting said protein with a putative binding compound; and determining whether said compound is able to interact with said protein. As it is known for GPCRs that they may interact with G proteins, as well as with other accessory proteins, the assays as provided herein may comprise in addition to all or part of the GPR39 receptor protein, G proteins or other accessory proteins.

GPCR's are known to interact with G proteins, as well as with other accessory proteins including arrestins, receptor activity modifying proteins (RAMPs) , PDZ domain containing proteins and others. Interaction of a GPCR with such accessory protein may result in the determination of various important biological properties of a receptor such as transport to or from the membrane, definition of its pharmacology, determination of its glycosylation state or transmission of signal through mechanisms that function independent of G protein coupling (Laburthe et al 2002) . As an example, association of calcitonin receptor- like receptor with RAMPl, a specific single transmembrane protein, leads to expression of the calcitonin receptor- like receptor able to bind calcitonin gene-reated peptide, whereas association with RAMP2 or RAMP3 leads to expression as an adrenomedullin binding receptor (Latchie et al 1998) . A similar interaction of RAMPs has been documented for the VPACl-^*, glucagon-, PTHl- and PHT2- receptors (Christopoulos et al 2001, 2003), suggesting a more generalised role for accessory proteins in modulating G protein-coupled receptor signaling.

In one embodiment of the assay, the receptor or subunits of the receptor may be employed in a binding assay. Binding assays may be competitive or non-competitive. Such an assay can accommodate the rapid screening of a large number of compounds to determine which compounds, if any, are capable of binding to the polypeptides. Subsequently, more detailed assays can be carried out with those compounds found to bind, to further determine whether such compounds act as agonists or antagonists of the polypeptides of the invention.

It is accordingly an object of the present invention to provide for a ^'method for identifying a compound that enhances glucose regulation in a subject and which are effective for preventing and/or treating pathologies related with an impaired carbohydrate metabolism, in particular in the prevention and/or treatment of diabetes including associated complications thereof, or of the metabolic syndrome including associated complications thereof, which method comprises:

(i) contacting host cells expressing all or part of the GPR39 receptor protein according to the invention, with said compound under conditions suitable for binding, and (ii) detecting binding of the compound to said receptor protein. In a further embodiment this invention provides a method for identifying a compound that enhances glucose regulation in a subject and which are effective for preventing and/or treating pathologies related with an impaired carbohydrate metabolism, in particular in the prevention and/or treatment of diabetes including associated complications thereof, or of the metabolic syndrome including associated complications thereof, which method comprises: (i) contacting membrane preparations from host cells expressing all or part of the GPR39 receptor protein according to the invention, with said compound under conditions suitable for binding, and (ii) detecting binding of the compound to said receptor protein.

In a still further embodiment the present invention provides a method for identifying a compound that enhances glucose regulation in a subject and which are effective

^■for preventing and/or treating pathologies related with an impaired carbohydrate metabolism, in particular in the prevention and/or treatment of diabetes including associated complications thereof, or of the metabolic syndrome including associated complications thereof, which method involves a competitive binding assay wherein:

(i) host cells expressing all or part of the GPR39 receptor protein according to the invention are contacted with a compound known to bind to the GPR39 receptor protein both in the presence and absence of the compound to be tested, and (i-i) the effect of said compound on the binding of the compound known to bind to the GPR39 receptor protein is being assessed. A decrease in the binding of the compound known to bind to the GPR39 receptor protein in the presence of the compound to be tested is an indication that said compound binds to the GPR39 receptor protein. Obestatin, the natural ligand for the GPR39 receptor protein has recently been identified (Zhang, J. V. et al . , 2004 Science Vol.310;996- 999) as another peptide derived from the same prohormone as ghrelin. In a particular embodiment the compound known to bind to the receptor consists of obestatin, more in particular selected from one of the obestatin sequences selected from SEQ ID No's 5 to 16, more in particular SEQ ID No.5 or SEQ ID No .7. Alternatively the obestatin as used herein refers to a peptide having at least 60%, 70%, 80%, 90%, 95%, 98% or 99% sequence identity to the amino acid sequence of SEQ ID NO : 5 or SEQ ID NO : 7.

In an alternative embodiment, the aforementioned competitive binding assay is performed on membrane preparations of host cells expressing all or part of the GPR39 receptor protein according to the invention.

Methods for preparing said host cells and for preparing membrane preparations from such cells are described hereinafter.

In a specific embodiment the GPR39 receptor protein in the aforementioned binding assays is an isolated protein having an amino acid sequence selected from the group consisting of SEQ ID No: 2, SEQ ID NO:4, a splice variant of the proteins having the aforementioned SEQ ID's, and an amino acid sequence having at least 80% and preferably at least 90%, 95%, 96%, 97%, 98% or 99% sequence identity to the amino acid sequence of SEQ ID NO : 2 or SEQ ID NO:4.

Parts of the GPR39 protein, as used hereinbefore, are meant to include fragments of the polypeptide of SEQ ID NO: 2 or SEQ ID NO: 4, said fragments being of at least 10, for example at least 20, 30 40, 50, 75, 100 or 150 or more amino acids in size. Such fragments may be derived from the N-terminal region of SEQ ID NO : 2 or SEQ ID NO : 4 respectively. Fragments including the N-terminal region may be used to reconstitute the extracellular portion of the receptor to provide receptor binding sites. Preferably, fragments will retain the ability to bind the compound known to bind to the GPR39 receptor protein. More in particular, fragments will retain the ability to bind obestatin as defined hereinbefore.

Membrane preparations

Cell membranes expressing the receptor protein of this invention are useful for certain types of assays including but not restricted to ligand binding assays, GTP-γ-S binding assays and others.- The specifics of preparing such cell membranes may in some cases be determined by the nature of the ensuing assay but typically involve harvesting whole cells and disrupting the cell, for example by sonication in ice cold buffer (e.g. 20 τtιM Tris HCl, .1 mM EDTA, pH 7.4 at 4°C) . The resulting crude cell lysate is subsequently cleared of cell debris by low speed centrifugation, for example at 200xg for 5 min at 4⁰C. Further clearance and membrane enrichment is finally done using a high speed centrifugation step, such as for example 40,000xg for 20 min at 4⁰C, and the resulting membrane pellet is washed by suspending in ice cold buffer and repeating the high speed centrifugation step. The final washed membrane pellet is resuspended in assay buffer. Protein concentrations are determined by the method of Bradford (1976) using bovine serum albumin as a standard. The membranes may be used immediately or frozen for later use. Radiolabeled ligand binding assays

Cells expressing the receptor of this invention may be used to screen for ligands for said receptor. The same assays may be used to identify agonists or antagonists of the receptor that may be employed for a variety of therapeutic purposes.

Radioligand binding assays are performed by diluting membranes prepared from cells expressing the receptor in an appropriate buffer, such as for example 50 mM Tris buffer (pH = 7.4 at 0⁰C) containing 2.1% bovine serum albumin (Sigma), aprotinin (0.005 mg/ml , Boehringer Mannheim) and bestatin (01. mM, Sigma) as protease inhibitors. The final protein concentration in the assay is typically within 12-40 μg/ml .

Membranes are then incubated with radiolabeled ligand either in the presence or absence of competing ligands on ice for 60 min in a total volume of 250 μl 96 well microtiter plates. The bound ligand is then separated from free ligands by filtration through GF/B filters presoaked in 0.5% polyethyleneimine (PEI), using a Tomtec (Wallac) vacuum filtration device. After addition of Ready Safe (Beckman) scintillation fluid, bound radioactivity is quantitated using a Trilux (Wallac) scintillation counter (approximately 40% counting efficiency of bound counts) . Alternatively, it may be preferable to collect bound ligand and then separate ligand from receptor using procedures well known in the art. Data is fit to non- linear curves using curve-fitting software such as GraphPad prism.

In this manner, agonist or antagonist compounds that bind to the receptor may be identified as they inhibit the binding of the radiolabeled ligand to the membrane protein of cells expressing the said receptor. Non- specific binding is defined as the amount of radioactivity remaining after incubation of membrane protein in the presence of 100 nM of the unlabeled peptide corresponding to the radioligand used.^' In equilibrium saturation binding assays membrane preparations or intact cells transfected with the receptor are incubated in the presence of increasing concentrations of the labeled compound to determine the binding affinity of the labeled ligand. The binding affinities of unlabeled compounds may be determined in equilibrium competition binding assays, using a fixed concentration of labeled compound in the presence of varying concentrations of the displacing ligands.

In a particular embodiment the aforementioned radioligand binding assay is performed using radiolabeled obestatin as defined hereinbefore. Labeling of obestatin and receptor binding has been described in Zhang, J.V. et al . (2004 Science VoI .310 ; 996-999) . Briefly;

Iodination of obestatin was performed using the Iodogen (Pierce, Upland, IN) procedure. Mixtures of the peptide (20 μg) and 1 mCi [¹²⁵I] jjal were transferred to precoated Iodogen vials and incubated for 4 min. The 1251-labeled peptide was applied to a Sep-Pak C18 cartridge (Waters) before elution with 60% acetonitrile/0.1%TFA. For radioligand binding assays, rat jejunum or other tissues were washed with buffer A (20 mM Hepes, 5 mM EDTA, 1 mM dithiothreitol (DTT) , 10 μM amidinophenylmethanesulfonyl fluoride, 5 mg/L leupeptin, 100 mM KCl, pH 7.5), cut into small pieces, and homogenized using a motorized homogenizer. The homogenates were centrifuged at 1,000 g for 5 min. and the supernatant was centrifuged at 300,000 g for 1 hour at 2⁰C. The pellets (crude membrane fractions) were resuspended with buffer A without KCl, quickly frozen under liquid nitrogen, and stored at -80⁰C until use. Tissue homogenates were incubated in 100 μl of phosphate buffered saline containing 0.1% bovine serum albumin for 18 hours at room temperature with varying concentrations of ¹²⁵I-obestatin in the presence or absence of unlabeled obestatin at 1, 000-fold excess. After incubation, the tubes were centrifuged for 10 min. at 10,000 g, and pellets were washed twice in ice-cold PBS before quantitation of radioactivity with a γ- spectrophotometer . Specific binding was calculated by subtracting nonspecific binding from total binding. For displacement curves, a fixed concentration of ¹²⁵I- obestatin was incubated with or without increasing concentrations of obestatin or other peptides.

In addition to the aforementioned binding assays, it is also an object of the present invention to provide functional assays for identifying compounds that enhance glucose control in a subject, characterized in that said compounds modulate the activity of the GPR39 receptor proteins according to the invention. Such an assay comprises the steps of;

(i) contacting all or parts of the GPR39 receptor protein with the compound to be tested, and

(ii) measuring the activity of the GPR39 receptor protein, wherein the change of GPR39 activity in the presence of the test compound is an indication of the compounds capability to modulate carbohydrate metabolism.

Given the observed involvement of GPR39 in carbohydrate metabolism, in all of the disclosed embodiments to identify compounds that bind to and/or modulate GPR39 activity, said assays can be used to identify compounds that may affect glucose homeostasis in a subject, including humans and warm-blooded animals.

A compound that modulates the activity of a polypeptide of the invention refers to a compound that alters the activity of the polypeptide so that it behaves differently in the presence of the compound than in the absence of the compound. Compounds affecting modulation include agonists and antagonists. An agonist encompasses a compound which activates GPR39 GPCR function. Alternatively, an antagonist includes a compound that interferes with GPR39 GPCR function. Typically, the effect of an antagonist is observed as a blocking of agonist-induced receptor activation, however in the case of GPR39, which has recently been described as a constitutive active receptor, the compounds that interferes with GPR39 GPCR function also include inverse agonists, i.e. agent which binds to the same receptor binding-site as an agonist for that receptor but exerts the opposite pharmacological effect. Antagonists include competitive as well as non-competitive antagonists. A competitive antagonist (or competitive blocker) interacts with or near the site specific for agonist binding. A non-competitive antagonist or blocker inactivates the function of the receptor by interacting with a site other than the agonist interaction site.

It is thus an object of the present invention to provide a method for identifying compounds capable to enhance glucose control in a subject, said method comprising;

(i) contacting host cells expressing all or part of the GPR39 receptor protein with the compound to be tested under conditions permitting the activation of said receptor protein, and (ii) detecting any increase in GPR39 receptor activity, thereby identifying the test compound as a compound capable to enhance glucose control in a subject.

In a further embodiment the present invention provides a method for identifying compounds capable to decrease GPR39 activity, said method comprising;

(i) contacting host cells expressing all or part of the GPR39 receptor protein with the compound to be tested under conditions permitting the activation of said receptor protein, and (ii) detecting any decrease in GPR39 receptor activity, thereby identifying the test compound as a compound capable to normalise glucose tolerance in a human or animal, i.e identifying the test compound as useful in the treatment of diabetes including associated complications thereof .

Again, as for the binding assays mentioned hereinbefore, the aforementioned activity assays can also be used to identify compounds that would modulate carbohydrate metabolism. Based on the observed phenotype in the glucose tolerance test, it is to be expected that compounds that increase GPR39 activity would result in a lowering of blood glucose tolerance and compounds that decrease GPR39 activity would result in an increase in blood glucose tolerance. In a particular embodiment the present invention provides a method for identifying compounds capable to decrease blood glucose tolerance said method comprising; (i) contacting host cells expressing all or part of the GPR39 receptor protein with the compound to be tested under conditions permitting the activation of said receptor protein, and (ii) detecting any increase in GPR39 receptor activity, thereby identifying the test compound as a compound capable to decrease blood glucose tolerance.

The effect of the compounds on GPR39 activity may be an increase or decrease of an intracellular second messenger formation that is mediated by GPR39 such as intracellular calcium, cAMP or a reporter gene product. GPR39 belongs to the class of proteins known as G-protein coupled receptors (GPCRs) . GPCRs transmit signals across cell membranes upon the binding of the ligand. The ligand- bound GPCR activates intracellular signalling events mediated by heterotrimeric G proteins, such as activation of the adenylate cyclase pathway or activation of the phospholipase C-β pathway. Assays to assess the activation of the aforementioned intracellular signalling events are generally known in the art and include amongst others cell based assays for signal transduction comprising chimeric ligand-inducible transcription factors, binding assays for G-protein-coupled receptors using fluorescence intensity distribution analysis, cell- signaling assays using cyclic nucleotides coupled to luminophores or measurement of responses from G protein coupled receptors using a multiple response element or cAMP response element-directed reporter assay. Description of several such assays follows.

The present invention also provides a bioassay for identifying compounds which modulate the regulatory regions of the GPR39 GPCR gene. Such an assay is conducted utilising rat or human cells capable of expressing a polypeptide of the invention (preferably of SEQ ID NO: 2 or SEQ ID NO: 4) . The cells are contacted with at least one compound wherein the ability of said compound to modulate the regulatory region is known. Thereafter, the cells are monitored for expression of the nucleic acid of the invention. Alternatively, the promoter may be linked to a reporter gene. Suitable reporter genes that may be employed include, for example, the chloramphenicol acetyltransferase gene, the luciferase gene, and the like.

As understood by these of skill in the art, bioassay methods for identifying compounds that modulate the activity of receptors such as polypeptides of the invention generally require comparison to a control. One type of control is a cell or culture that is treated substantially the same as the test cell or test culture exposed to the compound, with the distinction that the control cell or culture is not exposed to^' the compound. Another type of control cell or culture that can be employed is a cell or culture that is identical to transfected cells, the exception that the control cell or culture does not express functional GPR39 GPCR. Accordingly, the response of the transfected cell can be compared with that of the control cell or culture to the same compound under the same reaction conditions.

Particularly preferred types of assays include binding assays and functional assays which may be performed as follows :

Binding assays

Over-expression of nucleic acid encoding polypeptides of the invention in cell lines (including mammalian HEK 293 cells, CHO cells and Sf9 insect cells) may be used to produce membrane preparations bearing said polypeptides (referred to in this section as GPR39 GPCR for convenience) for ligand binding studies. These membrane preparations can be used in conventional filter-binding assays {eg. Using Brandel filter assay equipment) or in high throughput Scintillation Proximity type binding assays (SPA and Cytostar-T flashplate technology; Amersham Pharmacia Biotech) to detect binding of radio-labelled ligand and displacement of such radio-ligands by competitors for the binding site. Radioactivity can be measured with Packard Topcount, or similar instrumentation, capable of making rapid measurements from 96-, 384-, 1536- microtitre well formats. SPA/Cytostar-T technology is particularly amenable to high throughput screening and therefore this technology is suitable to use as a screen for compounds able to displace standard ligands .

Another approach to study binding of ligands to GPR39 GPCR protein in an environment approximating the native situation makes use of a surface plasmon resonance effect exploited by the Biacore instrument (Malmqvist M., Biochem Soc Trans. 1999 Feb; 27 (2) :335-40) . GPR39 GPCR in membrane preparations or whole cells could be attached to the biosensor chip of a Biacore and binding of ligands examined in the presence and absence of compounds to identify competitors of the binding site.

Functional assays Since GPR39 GPCR acts via Gi or Go (inhibitory G protein), which usually interacts with GIRK (inward rectifying potassium channels) , potassium ion flux should result on activation of these receptors. This flux of ions may be measured in real time using a variety of techniques to determine the agonistic or antagonistic effects of particular compounds. Therefore, recombinant GPR39 GPCR receptors expressed in cell lines or, for example, Xenopus oocytes can be characterised using whole cell and single channel electrophysiology to determine the mechanism of action of compounds of interest. Electrophysiological screening, for compounds active at GPR39 GPCR, may be performed using conventional electrophysiological techniques and when they become available, novel high throughput methods currently under development.

Fluorescence - Calcium and sodium fluxes are measurable using several ion-sensitive fluorescent dyes, including fluo-3, fluo-4, fluo~5N, fura red, Sodium Green, SBFI and other similar probes from suppliers including Molecular Probes. Calcium and sodium influx as a result of GPR39 GPCR can thus be characterised in real time, using fluorometric and fluorescence imaging techniques, including fluorescence microscopy with or without laser confocal methods combined with image analysis algorithms.

Another approach is a high throughput screening assay for compounds active as either agonists or modulators which affect calcium transients. This assay is based around an instrument called a FLuorescence Imaging Plate Reader ( (FLIPR^®) , Molecular Devices Corporation) . In its most common configuration, it excites and measures fluorescence emitted by fluorescein-based dyes. It uses an argon-ion laser to produce high power excitation at 488 nm of a fluorophore, a system of optics to rapidly scan the over the bottom of a 96-/384-well plate and a sensitive, cooled CCD camera to capture the emitted fluorescence. It also contains a 96-/384-well pipetting head allowing the instrument to deliver solutions of test agents into the wells of a 96-/384-well plate. The FLIPR assay is designed to measure fluorescence signals from populations of cells before, during and after addition of compounds, in real time, from all 96-/3S4-wells simultaneously. The FLIPR assay may be used to screen for and characterise compounds functionally active at recombinant GPR39 GPCR, eg rat or human GPR39 GPCR, expressed in cell lines. As described below, calcium transients in cells transfected with GPR39 GPCR were measured using the FLIPR assay in order to measure activation of the receptors by various substrates in order to determine the natural ligand of the receptor.

Cyclic AMP (cAMP) assay - The receptor-mediated stimulation or inhibition of cyclic AMP (cAMP) formation may be assayed in cells expressing the receptor. An exemplary protocol for a cAMP assay is provided hereinafter .

In this protocol COS- 7 cells are transiently transfected with the receptor gene using the DEAE-dextran method and plated in 96-well places. 48 hours after transfection, cells are washed twice with Dulbecco's phosphate buffered saline (FES) supplemented with 10 mM HEPES, 10 mM glucose and 5 mM theophylline and are incubated in the same buffer for 20 min at 37⁰C, in 5% CO₂- Test compounds are added and cells are incubated for an additional 10 min at 37⁰C. The medium is then aspirated and the reaction stopped by the addition of 100 mM HCl. The plates are stored at - 20⁰C for 2-5 days For cAMP measurement, plates are thawed and the cAMP contend in each well is measured by cAMP Scintillation Proximity Assay (Amersham Pharmacia Biotech) . Radioactivity is quantified using microbeta Trilux counter (Wallac) .

Microphysiometric assay - Because cellular metabolism is intricately involved in a broad range of cellular events (including receptor activation of multiple messenger pathways) , the use of microphysiometric measurements of cell metabolism can in provide a generic assay of cellular activity arising from the activation of any orphan receptor regardless of the specifics of the receptor's signaling pathway. General guidelines for transient receptor expression, cell preparation and microphysiometric recording are described elsewhere (Salon, J. A. and Cwicki, J. A., 1996). Typically cells expressing receptors are harvested and seeded at 3 x 10⁵ cells per microphysiometer capsule in complete media 24 hours prior to an experiment. The media is replaced with serum free media 16 hours prior to recording to minimize non-specific metabolic stimulation by assorted and ill-defined serum factors. On the day of the experiment the cell capsules are transferred to the microphysiometer and allowed to equilibrate in recording media (low buffer RPMI 1640, no bicarbonate, no serum (Molecular Devices Corporation, Sunnyvale, CA) containing 0.1-1% fatty acid free BSA), during which a baseline measurement of basal metabolic activity is established.

A standard recording protocol specifies a 100 μl/min flow rate, with a 2 min total pump cycle which includes a 30 sec flow interruption during which the acidification rare measurement is taken. Ligand challenges involve a 1 min 20 sec exposure to the sample just prior to the first post challenge rate measurement being taken, followed by two additional pump cycles for a total of 5 min 20 sec sample exposure. Typically, drugs in a primary screen are presented to the cells at 10 μM final concentration.

Follow up experiments to examine dose-dependency of active compounds are then done by sequentially challenging the cells with a drug concentration range that exceeds the amount needed to generate responses ranging from threshold to maximal levels. Ligand samples are then washed out and the acidification rates reported are expressed as a percentage increase of the peak response over the baseline rate observed just prior to challenge.

Compounds found to modulate the activity of the polypeptides of the present invention have a number of therapeutic uses, based on the finding that GPR39 is involved in the regulation of .carbohydrate metabolism. In specific, this includes diseases related to increased blood glucose levels such as for example, diabetes (including associated complications thereof) , including Type 1 (insulin-dependent or IDDM) , Type 2 (non-insulin- dependent diabetes mellitus) , maturity-onset diabetes of the young (MODY) and gestational diabetes. In summary GPR39 GPCR and related receptors can be used as a valuable tool for drug development in a variety of therapeutic areas.

Binding agents

Thus the invention further provides novel binding agents, including modulatory agents obtained by an assay according to the present invention, and compositions comprising such agents. Agents which bind to the receptor and which may have agonist or antagonist activity may be used in methods of treating diseases as characterized hereinbefore, whose pathology is characterised by action via the GPR39 GPCR receptor, and such use forms a further aspect of the invention.

The agents may be administered an effective amount of an agent of the invention. Since many of the above-mentioned conditions are chronic and often incurable, it will be understood that "treatment" is intended to include achieving a reduction in the symptoms for a period of time such as a few hours, days or weeks, and to include slowing the progression of the course of the disease. Such agents may be formulated into compositions comprising an agent together with a pharmaceutically acceptable carrier or diluent. The agent may in the form of a physiologically functional derivative, such as an ester or a salt, such as an acid addition salt or basic metal salt, or an N or S oxide. Compositions may be formulated for any suitable route and means of administration. Pharmaceutically acceptable carriers or diluents include those used in formulations suitable for oral, rectal, nasal, inhalable, topical (including buccal and sublingual) , vaginal or parenteral (including subcutaneous, intramuscular, intravenous, intradermal, intrathecal and epidural) administration. The choice of carrier or diluent will of course depend on the proposed route of administration, which, may depend on the agent and its therapeutic purpose. The formulations may conveniently be presented in unit dosage form and may be prepared by any of the methods well known in the art of pharmacy. Such methods include the^' step of bringing into association the active ingredient with the carrier which constitutes one or more accessory ingredients. In general the formulations are prepared by uniformly and intimately bringing into association the active ingredient with liquid carriers or finely divided solid carriers or both, and then, if necessary, shaping the product.

For solid compositions, conventional non-toxic solid carriers include, for example, pharmaceutical grades of mannitol, lactose, cellulose, cellulose derivatives, starch, magnesium stearate, sodium saccharin, talcum, glucose, sucrose, magnesium carbonate, and the like may be used. The active compound as defined above may be formulated as suppositories using, for example, polyalkylene glycols, acetylated triglycerides and the like, as the carrier. Liquid pharmaceutically administrable compositions can, for example, be prepared by dissolving, dispersing, etc, an active compound as defined above and optional pharmaceutical adjuvants in a carrier, such as, for example, water, saline aqueous dextrose, glycerol, ethanol, and the like, to thereby form a solution or suspension. If desired, the pharmaceutical composition to be administered may also contain minor amounts of non-toxic auxiliary substances such as wetting or emulsifying agents, pH buffering agents and the like, for example, sodium acetate, sorbitan monolaurate, triethanolamine sodium acetate, sorbitan monolaurate, triethanolamine oleate, etc. Actual methods of preparing such dosage forms are known, or will be apparent, to those skilled in this art; for example, see Remington=s Pharmaceutical Sciences, Mack Publishing Company, Easton, Pennsylvania, 15th Edition, 1975.

The composition or formulation to be administered will, in any event, contain a quantity of the active compound (s) in an amount effective to alleviate the symptoms of the subject being treated.

Dosage forms or compositions containing active ingredient in the range of 0.25 to 95% with the balance made up from non-toxic carrier may be prepared.

For oral administration, a pharmaceutically acceptable non-toxic composition is formed by the incorporation of any of the normally employed excipients, such as, for example, pharmaceutical grades of mannitol, lactose, cellulose, cellulose derivatives, sodium crosscarmellose, starch, magnesium stearate, sodium saccharin, talcum, glucose, sucrose, magnesium, carbonate, and the like. Such compositions take the form of solutions, suspensions, tablets, pills, capsules, powders, sustained release formulations and the like. Such compositions may contain l%-95% active ingredient, more preferably 2-50%, most preferably 5-8%.

Parenteral administration is generally characterized by injection, either subcutaneously, intramuscularly or intravenously. Injectables can be prepared in conventional forms, either as liquid solutions or suspensions, solid forms suitable for solution or suspension in liquid prior to injection, or as emulsions.

Suitable excipients are, for example, water, saline, dextrose, glycerol, ethanol or the like. In addition, if desired, the pharmaceutical compositions to be administered may also contain minor amounts of non-toxic auxiliary substances such as wetting or emulsifying agents, pH buffering agents and the like, such as for example, sodium acetate, sorbitan monolaurate, triethanolamine oleate, triethanolamine sodium acetate, etc .

The percentage of active compound contained in such parental compositions is highly dependent on the specific nature thereof, as well as the activity of the compound and the needs of the subject. However, percentages of active ingredient of 0.1% to 10% in solution are employable, and will be higher if the composition is a solid which will be subsequently diluted to the above percentages. Preferably, the composition will comprise 0.2-2% of the active agent in solution.

It is accordingly an object of the present invention to provide a pharmaceutical composition for the treatment of impaired carbohydrate metabolism in a subject such as for example, diabetes (including associated complications thereof) , including Type 1 (insulin-dependent or IDDM) , Type 2 (non-insulin-dependent diabetes mellitus) , maturity-onset diabetes of the young (MODY) and gestational diabetes, said composition comprising a GPR39 receptor antagonist.

Diagnostic product

The present inventions also provides for a diagnostic product comprising an isolated nucleic acid sequence selected from the group consisting of;

(i) a nucleic acid sequence encoding all or part of the polypeptides of SEQ ID NO : 2 or SEQ ID No:4,

(ii) a nucleic acid sequence consisting of SEQ ID

N0:l or SEQ ID NO : 3 , or (iii) a nucleic acid sequence having at least 80% sequence identity, and preferably at least 90%, 95%, 96%,

97% or 98% sequence identity, to the nucleic acid sequence of SEQ ID N0:l or SEQ ID NO : 3.

By using the DNA, antisense DNA, siRNA of the present invention as probes, a gene abnormality of the DNA or mRNA encoding the GPR39 receptor or parts thereof in mammals including humans, can be detected and therefore these nucleic acid sequences are useful gene diagnostic agents for damage of the DNA or mRNA encoding the GPR39 receptor or parts thereof, mutations thereof, underexpression thereof or overexpression thereof.

The above described gene diagnosis can be performed by, for example, publicly known Northern hybridization assay or PCR-SSCP assay.

When an underexpression of the GPR39 receptor is detected, it can be diagnosed that the subject suffers from a disease associated with dysfunction of the GPR39 receptor, such as for example metabolic syndrome including associated complications thereof.

When an overexpression of the GPR39 receptor is detected, it can be diagnosed that the subject suffers from a disease associated with overexpression of the GPR39 receptor, such as for example diabetes including associated complications thereof.

The present invention also provide for a diagnostic product comprising all or part of the GPR39 receptor protein. Said protein can for example be detected in a suitable sample, for example a blood sample, in order to diagnose under- or overexpression of the GPR39 receptor.

This invention will be better understood by reference to the Experimental Details that follow, but those skilled in the art will readily appreciate that these are only illustrative of the invention as described more fully in the claims that follow thereafter. Additionally, throughout this application, various publications are cited. The disclosure of these publications is .hereby incorporated by reference into this application to describe more fully the state of the art to which this invention pertains .

EXAMPLES

The following examples illustrate the invention. Other embodiments will occur to the person skilled in the art in light of these examples.

Materials and Methods GPR39 knock-out mouse

GPRC39 knock-out mice were obtained from Lexicon Genetics Inc. Disruption of the open reading frame of GPR39 was performed by replacing the coding region of the first coding exon of the GPR39 gene with an IRES LacZ/MCl-Neo reporter gene/selection cassette. Animals were maintained in an SPF facility that meets all Belgian and European requirements for animal care. Mice were group-housed in a climate-controlled animal colony with a 12h dark-light cycle (light on 7:00 EST) with free access to food and water, unless indicated differently. Adequate measures were taken to minimize pain or discomfort. All experiments were carried out in accordance with the European Communities Council Directives (86/609/EEC) and were approved by the local ethical committee.

Histological analysis of GPR39 expression in pancreas

Pancreas was dissected from WT and GPR39^~/~ mice and whole- mount LacZ staining was performed. Briefly, tissue was dissected into PBS solution on ice, fixed for 2 h at 4°C in 0.5% glutaraldehyde in PBS. Next tissue was rinsed 3 times in PBS with gentle shaking. Staining was performed overnight at 30⁰C in a staining buffer supplemented with lmg/ml X-gal, 5mM potassium ferricyanide and 5mM potassium ferrocyanide . After staining, tissue was rinsed in PBS wash buffer, dehydrated in alcohol, cleared in xylol embedded in paraffin and sectioned at 5μm. Histological examination was performed on lOμm tissue sections with and without Harris H&E counterstaining.

Comparison of body weight in WT and GPR39^-/~ mice

Animals were housed individually in cages at 22 ± 1°C with a 12h-12h light-dark cycle. Animals were fed ad libitum with a standard diet (22% proteins, 4.3% fat and 4% cellulose from U.A. R. , France) . Body weight was followed in these animals starting at the age of 8-12 up to 16-20 weeks .

Glucose tolerance test in WT and GPR39^-/~ mice GPR39^~/~ and WT mice (male and female) were fasted overnight (starting at 5.30 p.m.) and then injected subcutaneousIy with 2 g/kg glucose (saline solution at a final concentration of 200 mg/ral) . Blood samples were taken by tail venesection. Firstly baseline was taken before weighing animals, then glucose was administered. Blood glucose concentration was determined at 15, 30, 45, 60, 90 and 120 min post glucose administration by means of One Touch Ultra (Lifescan Inc., USA) .

Comparison of body composition of WT and GPR39 mice Body fat and body muscle were measured in conscious

GPR39^'/" and wild type mice between 9.00 and 11.00a.m. by quantitative nuclear magnetic resonance (NMR) (Minispec mqlO NMR analyser, Bruker, Germany) . This is a method developed specially for non-invasive rapid determination of body composition in conscious mice. Lean body, body fat and fluid were quantified by NMR. The animals were weighed prior to NMR measurement .

RESULTS

Histological analysis of GPR39 expression in pancreas

■ In the GPR39^~;'^~ mice at hand the coding region of the first coding exon is replaced by the LacZ reporter gene, therefore we examined LacZ expression as an indicator of the endogenous GPR39 expression pattern in pancreas. In the pancreas, expression was detected throughout the islets of Langerhans, the endocrine portion of the pancreas in GPR39^'/~ (Fig IA) but not in WT mice (Fig IB)

Comparison of body weight in WT and GPR39^~/~ mice

Body weight was followed in these animals starting at the age of 8-12 up to 16-20 weeks. Male GPR39^'/" mice gained more weight than the corresponding male wild type mice

(Fig 2) . No difference was observed in these female mice in this age range.

Glucose tolerance test in WT and GPR39^~^^~ mice

After a fasting period of 16h, blood glucose was not significantly changed in GPR39^~/~ mice (male + female) in comparison with WT mice (male + female) (aged 12 - 16 weeks) . In fed condition also no difference in blood glucose was observed between both genotypes (Fig.3) .

After glucose administration, blood glucose was significantly less increased in male GPR39^"/" mice compared to male WT mice (aged 12-16 weeks) (P<0.05). In female mice no difference was observed between both genotypes (aged 12-16 weeks) . (Fig 4) .

Comparison of body composition of WT and GPRSS^'^^' mice

Body composition was measured in mice at the age of 13-17 and 16-20 weeks. In 13-16 weeks-old mice no difference was observed in body composition between both genotypes fed with standard diet. Three weeks later, in the same animals, body fat in male GPRSi-T''^" mice appeared increased compared to male wild type mice (15.76+5.30% vs. 11.97+2.60%) while body lean mass appeared decreased in male GPR39^"7" compared to wild type mice (41.22+3.41% vs. 43.45±1.78%) (Fig.5) . Discussion

Based on earlier findings that the GPR39 receptor is highly expressed in pancreas tissue, together with results from the phenotypic analysis of GPR39^"/" mice that show increased cholesterol levels in both sexes of the GPR39 knock-out mice compared to the wild type littermates (unpublished data) , a possible role for the GPR39 receptor in the control of glycemia should be investigated. Confirmation of the involvement of GPR39 in the control of glycemia would validate this receptor as a good target to treat diabetic diseases including complications thereof, and all diseases related to the metabolic syndrome. For these reasons the aim of our work was firstly to localize the GPR39 receptor in pancreas tissue using the lacZ expression technique, secondly to test the GPR 39^~^^~ mice versus WT littermate mice in glucose tolerance test. In function of these results, determination of insulin concentration will be performed before and after the glucose administration in glucose tolerance test to confirm the possible role played by GPR39 in the glycemia control. In parallel of all these studies, the body composition was also determined using a NMR device. Here also in function of the preliminary results, it's possible that metabolism of the GPR 39^'/- mice in comparison of WT littermate mice will be investigated in a standard metabolism cage set-up.

Ref erences :

Bradford, M. M., A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. Anal. Biochem. 1976; 72:248-254.

Hoist, B., Holliday, N.D. , Bach, A., Elling CE. , Coc, H. M. and Schwartz, T. W., Common structural basis for constitutive activity of the Ghrelin receptor family. J. Biol. Chem. 2004, 279 (51) : 53806-53817.

Date Y, Nakazato M, Murakami N, Koj ima M, Kangawa K, Matsukura S. Ghrelin acts in the central nervous system to stimulate gastric acid secretion. Biochem Biophys Res Commun. 2001 Jan 26; 280 (3) : 904-7.

Ghoos Y, Maes B, Geypens B, Mys G, Hiele M, Rutgeerts P and Vantrappen G. Measurement of gastric emptying rate of solids by means of a carbon labeled octanoic acid breath test. Gastroenterol. 1993; 104: 1640-7.

Inui A, Asakawa A, Bowers CY, Mantovani G, Laviano A, Meguid MM, Fuj imiya M. Ghrelin, appetite, and gastric motility: the emerging role of the stomach as an endocrine organ. FASEB J. 2004 Mar; 18 (3 ) :439-56.

Maes B, Ghoos Y, Geypens B, Mys G, Hiele M, Rutgeerts P and Vantrappen G. The combined ¹³C-glycine/¹⁴C-octanoic acid breath test : a double carbon labeled breath test to monitor gastric emptying rate of liquids and solids. J. Nucl. Med. 1994; 35: 824-31.

McKee K K, Tan C P, Palyha 0 C, Liu J, Feighner S D, Hreniuk D L, Smith R G, Howard A D and Van der Ploeg L H T. Cloning and characterization of two human G protein- coupled receptor genes (GPR38 and GPR39) related to the growth hormone secretagogue and neurotensin receptors . Genomics 46: 426-434, 1997.

Trudei L, Tomasetto C, Rio M C, Bouin M, Plourde V, Eberling P and Poitras P (2002) Ghrelin/motilin-related peptide is a potent prokinetic to reverse gastric postoperative ileus in rat. Am. J. Physiol. 282, G948-G952.

Peeters TL. Central and peripheral mechanisms by which ghrelin regulates gut motility. J Physiol Pharmacol. 2003 Dec; 54 Suppl 4:95-103.

Salon J.A. and Owicki J.A. Real-time measurement of receptor activity: Application of microphysiometric techniques to receptor biology. Meth. Neurosci. 1996; 25:201-224.

Zhang J. V. , Ren P-G., Avsian-Kretchmer 0. , Luo, C-W., Rauch R., Klein C, Hsueh A. J. W. (2004) Obestatin, a peptide encoded by the ghrelin gene, opposes ghrelin' s effects on food intake. Science VoI .310 ; 996-999.

Laburthe M. Couvineau A. Marie J C. VPAC receptors for VIP and PACAP. Receptors & Channels. 8:137-153, 2002.

McLatchie LM. Fraser NJ. Main MJ. Wise A. Brown J. Thompson N. Solari R. Lee MG. Foord SM. RAMPs regulate the transport and ligand specificity of the calcitonin- receptor-like receptor. Nature. 393:333-339, 1998.

Christopoulos A. Christopoulos G. Morfis M. Laburthe M. Couvineau A. Sexton PM. Receptor activity modifying proteins (RAMPS) interact with the VPACl receptor: evidence for differential ramp modulation of multiple signaling pathways. Proceedings Society for Neuroscience, 2001. abstract 5508 (http://sfn.scholarone.com/itin2001/).

Christopoulos A. Christopoulos G. Morfis M. Udawela M.

Laburthe M. Couvineau A. Kuwasako K. Tilakaratne N. Sexton PM. Novel receptor partners and function of receptor activity-modifying proteins. Journal of Biological Chemistry. 278:3293-3297, 2003.

Claims

-63-CLAIMS

1. A method to identify compounds that enhance glucose control in a subject and which are effective for preventing and/or treating pathologies related with an impaired carbohydrate metabolism, in particular in the prevention and/or treatment of diabetes including associated complications thereof, or of the metabolic syndrome including associated complications thereof, said method comprising the use of all or part of the GPR39 receptor protein.

2. A method according to claim 1 wherein the GPR39 receptor protein is being selected from the group consisting of SEQ ID No:2, SEQ ID No: 4, a splice variant of the proteins having the aforementioned SEQ ID'S, and an amino acid sequence having at least 80% and preferably at least 90%, 95%, 96% or 98% sequence identity to the amino acid sequence of SEQ ID No : 2 or SEQ ID No:4.

3. A method according to claim 1 or 2 wherein a part of the GPR39 receptor protein consist of a fragment of at least 10 amino acids of the polypeptide of SEQ ID No : 2 or SEQ ID No:4.

4. A method for identifying a compound that enhances glucose regulation in a subject and which are effective for preventing and/or treating pathologies related with an impaired carbohydrate metabolism, in particular in the prevention and/or treatment of diabetes including associated complications thereof, or of the metabolic syndrome including associated complications thereof, which method comprises: -64-

(i) contacting host cells expressing all or part of the GPR39 receptor protein according to the invention, with said compound under conditions suitable for binding, and

(ii) detecting binding of the compound to said receptor protein

5. A method for identifying a compound that enhances glucose regulation in a subject and which are effective for preventing and/or treating pathologies related with an impaired carbohydrate metabolism, in particular in the prevention and/or treatment of diabetes including associated complications thereof, or of the metabolic syndrome including associated complications thereof, which method comprises:

(i) contacting membrane preparations from host cells expressing all or part of the GPR39 receptor protein according to the invention, with said compound under conditions suitable for binding, and

(ii) detecting binding of the compound to said receptor protein.

6. A method according to claims 4 or 5 wherein the binding of the compound to the GPR39 receptor protein is being detected by means of a label directly or indirectly associated with the compound to be tested or in an assay involving competition with a labelled competitor.

7. A method according to claim 6 wherein the¹ labelled competitor is labelled obestatin.

8. A method according to any one of claims 4 to 7 wherein in step (i) , the compounds are contacted with host

.65- cells expressing all or part of the GPR39 protein as defined in claims 2 and 3.

9. A method to identify compounds that modulate carbohydrate metabolism, said method comprising the steps

Of;

10. A method according to claim 9 wherein in step i) , the compounds are contacted with host cells expressing all or part of the GPR39 protein as defined in claims 2 and 3.

11. A method according to claims 9 or 10 wherein the activity of the GPR39 receptor protein is being measured as the modulation of an intracellular messenger.

12. The method according to claim 11, wherein the intracellular second messenger is cAMP, calcium or a reporter gene product .

13. Use of an isolated nucleic acid sequence selected from the group consisting of;

Ci) a nucleic acid sequence encoding all or part of the polypeptides of SEQ ID NO: 2 or SEQ ID No : 4 ,

(ii) a nucleic acid sequence consisting of SEQ ID N0:l or SEQ ID NO : 3 , or

(iii)a nucleic acid sequence having at least 80% sequence identity to the nucleic acid sequence -66- of SEQ ID N0:l or SEQ ID NO : 3 , in a method according to any one of claims 1 to 12.

14. Use of a vector comprising a nucleic acid sequence as defined in claim 13, in a method according to any one of claims 1, 4, 5, 8, 9 or 10.

15. Use of a host cell comprising a nucleic acid sequence as defined in claim 13 or a vector as defined in claim 14, in a method according to any one of claims 1, 4, 5, 8, 9 or 10.

16. A pharmaceutical composition for the treatment of impaired glucose control in a human or animal comprising a GPR39 receptor agonist or antagonist.

17. Use of a GPR39 agonist or antagonist in the manufacture of a medicament for the treatment of a disease condition related to an impaired carbohydrate metabolism, in particular diabetes (including associated complications thereof) , including Type 1 (insulin-dependent or IDDM) , Type 2 (non-insulin-dependent diabetes mellitus) , maturity-onset diabetes of the young (MODY) and gestational diabetes.

18. A diagnostic product comprising an. isolated nucleic acid sequence selected from the group consisting of;

(i) a nucleic acid sequence encoding all or part of the polypeptides of SEQ ID NO: 2 or SEQ ID No:4,

(ii) a nucleic acid sequence consisting of SEQ ID N0:l or SEQ ID NO : 3 , or

(iii) a nucleic acid sequence having at least 80% sequence identity to the nucleic acid sequence of SEQ ID NO : 1 or SEQ ID NO : 3. -67-

19. A diagnostic product according to claim 18 wherein in step (i) , the part of the polypeptide is as defined in claim 3.

20. A diagnostic product comprising all or part of the GPR39 receptor protein.

21. A diagnostic product according to claim 20 wherein the GPR39 receptor protein is as defined in claim 2 and the part of the GPR39 receptor protein is as defined in claim 3.