Ligand for G-protein coupled receptor GPR43 and uses thereof

Abstract

The present invention is related to the G-protein coupled orphan receptor GPR 43 and the identification of short chain fatty acids as natural ligands of the receptor. The invention further relates to assays for the identification of agents that modulate GPR 43 ligand binding and signalling activity, as well as compositions consisting essentially of an isolated GPR 43 polypeptide and an isolated short chain fatty acid. The invention also relates to diagnostic methods and kits that take advantage of the novel interaction of GPR 43 with short chain fatty acids.

1 . A method of detecting the presence of a disease characterized by the dysregulation of GPR43, comprising:
 a) contacting a GPR43 polypeptide present in the membrane of a PMN cell with a short chain fatty acid;   b) measuring the binding of said GPR43 polypeptide to said short chain fatty acid; and   c) comparing the binding detected in step (b) with a standard, wherein a difference in binding relative to said standard is indicative of the presence of a disease characterized by the dysregulation of GPR43.   
     
     
         2 . A method of detecting the presence of a disease characterized by the dysregulation of GPR43, comprising:
 a) contacting a GPR43 polypeptide present in the membrane of a PMN cell with a short chain fatty acid;   b) measuring a signalling activity of said GPR43 polypeptide; and   c) comparing the signalling activity detected in step (b) with a standard, wherein a difference in binding relative to said standard is indicative of the presence of a disease characterized by the dysregulation of GPR43.   
     
     
         3 . A method of diagnosing a disease or disorder characterized by dysregulation of GPR43 signalling, said method comprising:
 a) contacting a tissue sample comprising a GPR43 polypeptide with a short chain fatty acid   b) detecting binding of said short chain fatty acid to said GPR43; and   c) comparing the binding detected in step (b) with a standard, wherein a difference in binding relative to said standard is indicative of the presence of a disease characterized by the dysregulation of GPR43.   
     
     
         4 . A method of diagnosing a disease or disorder characterized by dysregulation of GPR43 signaling, said method comprising:
 a) contacting a tissue sample comprising a GPR43 polypeptide with a short chain fatty acid   b) detecting a signaling activity of said GPR43 polypeptide in said tissue sample; and   c) comparing the signaling activity detected in step (b) with a standard, wherein a difference in said signaling activity relative to said standard is indicative of the presence of a disease characterized by the dysregulation of GPR43.   
     
     
         5 . The method of  claim 1  or  3 , wherein said measuring is performed using a method selected from the group consisting of label displacement, surface plasmon resonance, fluorescence resonance energy transfer, fluorescence quenching, and fluorescence polarization. 
     
     
         6 . The method of  claim 2  or  4 , wherein said step of measuring a signalling activity of said GPR43 polypeptide comprises detecting a change in the level of a second messenger. 
     
     
         7 . The method of  claim 2  or  4 , wherein the step of measuring a signalling activity comprises measurement of guanine nucleotide binding or exchange, adenylate cyclase activity, cAMP, Protein Kinase C activity, phosphatidylinosotol breakdown, diacylglycerol, inositol triphosphate, intracellular calcium, arachinoid acid, MAP kinase activity, tyrosine kinase activity, or reporter gene expression. 
     
     
         8 . The method of  claim 6 , wherein said measuring a signaling activity comprises using an aequorin-based assay.