Receptor ligands and methods of modulating receptors

Abstract

The invention provides natural ligands of various receptors and methods of identifying modulators of various receptors using the ligands. Methods of using the modulators to treat diseases or disorder associated with dysfunction of the receptor are also provided.

1 . A method of identifying a modulator of a TGR18 polypeptide that has G-protein coupled receptor activity and (A) comprises at least 70% amino acid sequence identity to SEQ ID NO:16 (B) consists of at least 50 contiguous amino acids of SEQ ID NO:16, or (C) comprises the amino acid sequence of SEQ ID NO:16; wherein the method comprises: 
 contacting the polypeptide with: a candidate modulator compound and succinic acid; and    determining the level of activity of the polypeptide in comparison to the level of activity of the polypeptide in the absence of succinic acid.    
     
     
         2 . The method of  claim 1 , wherein the step of determining the level of activity comprises a competitive assay.  
     
     
         3 . The method of  claim 1 , wherein the compound is contacted with the polypeptide before the succinic acid is contacted with the polypeptide.  
     
     
         4 . The method of  claim 1 , wherein the step of determining the level of activity comprises a binding assay.  
     
     
         5 . The method of  claim 1 , wherein the TGR18 polypeptide is recombinant.  
     
     
         6 . A method of treating a patient with a TGR18-associated disorder, the method comprising administering a therapeutically effective amount of a compound identified using the method of  claim 1 .  
     
     
         7 . The method of  claim 6 , wherein the TGR18-associated disorder is a renal disease.  
     
     
         8 . A method of identifying a modulator of a TGR164 polypeptide that has G-protein coupled receptor activity and (A) comprises at least 70% amino acid sequence identity to SEQ ID NO:18 (B) consists of at least 50 contiguous amino acids of SEQ ID NO:18, or (C) comprises the amino acid sequence of SEQ ID NO:18; wherein the method comprises: 
 contacting the polypeptide with: a candidate modulator compound and α-keto-glutaric acid; and    determining the level of activity of the polypeptide in comparison to the level of activity of the polypeptide in the absence of α-keto-glutaric acid.    
     
     
         9 . The method of  claim 8 , wherein the step of determining the level of activity comprises a competitive assay.  
     
     
         10 . The method of  claim 8 , wherein the compound is contacted with the polypeptide before the α-keto-glutaric acid is contacted with the polypeptide.  
     
     
         11 . The method of  claim 8 , wherein the step of determining the level of activity comprises a binding assay.  
     
     
         12 . The method of  claim 8 , wherein the TGR164 polypeptide is recombinant.  
     
     
         13 . A method of treating a patient with a TGR164-associated disorder, the method comprising administering a therapeutically effective amount of a compound identified using the method of  claim 8 .  
     
     
         14 . The method of  claim 13 , wherein the TGR164-associated disorder is a renal disease.