Mammalian galanin receptors

Abstract

The present invention provides isolated mammalian GalR3 receptors, isolated or recombinant nucleic acids and recombinant vectors encoding the same, host cells comprising the nucleic acids and vectors, and methods for making the receptors using the host cells. This invention further provides antibodies and antigen binding fragments thereof which specifically bind to the receptors and are useful for treating medical conditions caused or mediated by galanin. Also provided are screening methods for identifying specific agonists and antagonists of the mammalian GalR3 receptors.

1 . An isolated mammalian galanin receptor comprising an amino acid sequence defined by SEQ ID NO: 2 or SEQ ID NO: 4, or a conservative or allelic variant thereof. 
     
     
         2 . An antibody which specifically binds to the mammalian receptor of  claim 1 . 
     
     
         3 . The antibody of  claim 2  which is a monoclonal antibody. 
     
     
         4 . An anti-idiotypic antibody produced against the antibody of  claim 2 . 
     
     
         5 . The antibody of  claim 4  which is a monoclonal antibody. 
     
     
         6 . An isolated or recombinant nucleic acid encoding the mammalian galanin receptor of  claim 1 . 
     
     
         7 . A recombinant vector comprising the nucleic acid of  claim 6 . 
     
     
         8 . A host cell comprising the recombinant vector of  claim 7 . 
     
     
         9 . A method for making a mammalian galanin receptor comprising culturing a host cell of  claim 8  under conditions in which the nucleic acid is expressed. 
     
     
         10 . The method of  claim 9  in which the receptor is isolated from the culture. 
     
     
         11 . An isolated or recombinant nucleic acid selected from the group consisting of
 (a) a nucleic acid encoding a mammalian galanin receptor comprising an amino acid sequence defined by SEQ ID NO: 2 or SEQ ID NO: 4, or a subsequence thereof;   (b) a nucleic acid that hybridizes under moderately stringent conditions to the nucleic acid of (a) and encodes a polypeptide that (i) binds galanin and (ii) is at least 80% identical to a receptor encoded by the nucleic acid of (a); and   (c) a nucleic acid that, due to the degeneracy of the genetic code, encodes a mammalian galanin receptor encoded by a nucleic acid of (a) or (b).   
     
     
         12 . A recombinant vector comprising the nucleic acid of  claim 11 . 
     
     
         13 . A host cell comprising the recombinant vector of  claim 12 . 
     
     
         14 . A method for making a mammalian galanin receptor comprising culturing a host cell of  claim 13  under conditions in which the nucleic acid is expressed. 
     
     
         15 . The method of  claim 7  in which the receptor is isolated from the culture. 
     
     
         16 . A method for identifying a galanin receptor agonist or antagonist comprising:
 (a) contacting a polypeptide comprising an amino acid sequence set forth in SEQ ID NO: 2, SEQ ID NO: 4 or amino acids 57-424 of SEQ ID NO: 4 in the presence of a known amount of labeled galanin ligand with a sample to be tested for the presence of a galanin receptor agonist or antagonist; and   (b) measuring an amount of labeled galanin ligand specifically bound to the polypeptide;   
       whereby a galanin agonist or antagonist in the sample is identified by measuring substantially reduced binding of the labeled galanin ligand to the polypeptide, compared to that measured in the absence of such agonist or antagonist. 
     
     
         17 . The method of  claim 16  wherein the labeled galanin ligand is  125 T-galanin. 
     
     
         18 . The method of  claim 16  further comprising the following steps:
 (c) contacting a mammalian GalR1 or GalR2 receptor in the presence of a known amount of labeled galanin with a compound identified as a galanin agonist or antagonist in steps (a) and (b); and   (d) measuring the amount of labeled galanin bound to the receptor;   
       whereby a galanin agonist or antagonist specific for the GalR3 receptor is identified by measuring substantially undiminished binding of the labeled galanin to the GalR1 or GalR2, compared to that measured in the absence of such agonist or antagonist. 
     
     
         19 . The method of  claim 16  wherein the polypeptide is in a cell membrane. 
     
     
         20 . The method of  claim 16  wherein said galanin ligand is galanin, galanin peptide C7 or amino acids 2-29 of galanin. 
     
     
         21 . A method for identifying a galanin receptor antagonist comprising:
 (a) contacting a polypeptide comprising amino acids 57-424 of SEQ ID NO: 4 in the presence of a known amount of  125 I-labeled galanin with a sample to be tested for the presence of a galanin antagonist; and   (b) measuring an amount of  125 I-labeled galanin specifically bound to the polypeptide;   
       whereby a galanin antagonist in the sample is identified by measuring substantially reduced binding of the  125 I-labeled galanin to the polypeptide, compared to that measured in the absence of such antagonist.