Methods for Identifying Compounds That Modulate Ion Channel Activity of a Kir Channel

Abstract

Methods for identifying compounds that modulate the ion channel activity of a Kir channel are provided. Methods for identifying compounds that selectively modulate the ion channel activity of specific types of Kir channels based on the turret region of a Kir channel are also provided. Methods for identifying compounds to treat conditions associated with abnormal ion channel activity are also provided. Compounds including purified antibodies and methods of making antibodies which bind to the turret region of a Kir channel are provided. Purified polypeptides including at least a portion of the turret region of a Kir channel and nucleic acid sequences encoding these polypeptides are also provided.

1 . A method for identifying a compound that modulates ion channel activity of a Kir channel comprising:
 identifying a compound which binds the turret region of a Kir channel; and   determining if the compound modulates ion channel activity of the Kir channel.   
     
     
         2 . The method of  claim 1 , wherein the compound is an antibody. 
     
     
         3 . The method of  claim 2 , wherein the antibody is human, chimeric, or humanized. 
     
     
         4 . The method of  claim 2 , wherein the antibody is selected from the group consisting of polyclonal antibodies, monoclonal antibodies, an intact immunoglobulin molecule, an antibody fragment, a scFv, a Fab, a F(ab)2, a Fv, and a disulfide linked Fv. 
     
     
         5 . The method of  claim 1 , wherein the compound is a nucleic acid. 
     
     
         6 . The method of  claim 5 , wherein the nucleic acid is selected from the group consisting of DNA and RNA. 
     
     
         7 . The method of  claim 5 , wherein the identifying includes in vitro selection of the nucleic acid. 
     
     
         8 . The method of  claim 1 , wherein the compound is a protein/peptide. 
     
     
         9 . The method of  claim 8 , wherein the protein/peptide is attached to a protein scaffold. 
     
     
         10 . The method of  claim 8 , wherein the protein/peptide is displayed on the surface of a phage. 
     
     
         11 . The method of  claim 1 , wherein the compound is a small molecule. 
     
     
         12 . The method of  claim 1 , wherein the Kir channel is human. 
     
     
         13 . The method of  claim 1 , wherein the Kir channel is a chicken/human hybrid. 
     
     
         14 . The method of  claim 13 , wherein the chicken/human hybrid Kir channel comprises a human Kir channel turret region. 
     
     
         15 . The method of  claim 1 , wherein the identifying step comprises an ELISA and a Western blot to determine if the compound binds to a properly folded Kir channel but not to a denatured Kir channel. 
     
     
         16 . The method of  claim 1 , wherein the identifying step comprises determining if the compound binds to a Kir channel with a normal turret region but not a mutated turret region. 
     
     
         17 . The method of  claim 1  wherein the determining step comprises an electrophysiological assay. 
     
     
         18 . The method of  claim 17 , wherein the electrophysiological assay is selected from the group consisting of two-electrode voltage clamp, patch clamp, and planar lipid bilayer assays. 
     
     
         19 . The method of  claim 1 , wherein the determining step comprises a fluorescent assay. 
     
     
         20 . The method of  claim 19 , wherein the fluorescent assay utilizes a thallium specific fluorescent dye. 
     
     
         21 . A method for identifying a compound that selectively modulates ion channel activity of a specific type of Kir channel comprising:
 identifying a compound which binds the turret region of a specific type of Kir channel but does not bind to other types of Kir channels; and   determining if the compound modulates the activity of the Kir channel.   
     
     
         22 . The method of  claim 21 , wherein the identifying comprises deter pining if the compound binds the turret region of the specific type of Kir channel but does not bind the turret region of other type of Kir channels. 
     
     
         23 . A method of identifying a compound to treat a condition associated with abnormal ion channel activity by a Kir channel comprising:
 identifying a compound which binds the turret region of a Kir channel;   determining if said compound modulates ion channel activity of the Kir channel; and   administering said compound which modulates ion channel activity to a subject to determine if the compound is able to treat said condition.   
     
     
         24 . The method of  claim 23 , wherein the condition is selected from the group consisting of diabetes mellitus, hypertension, cardiac arrhythmia, and epilepsy. 
     
     
         25 .- 43 . (canceled)