Aquaporin-8 variant

Abstract

The invention provides a mammalian cDNA which encodes a mammalian AQP8V. It also provides for the use of the cDNA, fragments, complements, and variants thereof and of the encoded protein, portions thereof and antibodies thereto for diagnosis and treatment of pancreatic disorders, particularly type I diabetes. The invention additionally provides expression vectors and host cells for the production of the protein and a transgenic model system.

What is claimed is:  
     
         1 . An isolated polypeptide selected from the group consisting of: 
 a) a polypeptide comprising an amino acid sequence of residues M49 to R303 of SEQ ID NO: 1,    b) a polypeptide comprising a naturally occurring amino acid sequence at least 90% identical to an amino acid sequence of a), and    c) an immunogenic fragment of a polypeptide having an amino acid sequence of a).    
     
     
         2 . An isolated polypeptide of  claim 1 , comprising an amino acid sequence of residues M49 to R303 of SEQ ID NO: 1.  
     
     
         3 . An isolated polynucleotide encoding a polypeptide of  claim 2 .  
     
     
         4 . A recombinant polynucleotide comprising a promoter sequence operably linked to a polynucleotide of  claim 3 .  
     
     
         5 . A cell transformed with a recombinant polynucleotide of  claim 4 .  
     
     
         6 . A transgenic organism comprising a recombinant polynucleotide of  claim 4 .  
     
     
         7 . A method of producing a polypeptide of  claim 2 , the method comprising: 
 a) culturing a cell under conditions suitable for expression of the polypeptide, wherein said cell is transformed with a recombinant polynucleotide, and said recombinant polynucleotide comprises a promoter sequence operably linked to a polynucleotide encoding the polypeptide of  claim 2 , and    b) recovering the polypeptide so expressed.    
     
     
         8 . An isolated antibody which specifically binds to a polypeptide of  claim 1 .  
     
     
         9 . A composition comprising a polypeptide of  claim 1  and a pharmaceutically acceptable excipient.  
     
     
         10 . A composition of  claim 9 , wherein the polypeptide comprises an amino acid sequence of residues M49 to R303 of SEQ ID NO: 1.  
     
     
         11 . A method for treating a disease or condition associated with decreased expression of functional AQP8V, comprising administering to a patient in need of such treatment the composition of  claim 10 .  
     
     
         12 . A method of screening a compound for effectiveness as an agonist of a polypeptide of  claim 1 , the method comprising: 
 a) exposing a sample comprising a polypeptide of  claim 1  to a compound, and    b) detecting agonist activity in the sample.    
     
     
         13 . A composition comprising an agonist compound identified by a method of  claim 12  and a pharmaceutically acceptable excipient.  
     
     
         14 . A method for treating a disease or condition associated with decreased expression of functional AQP8V, comprising administering to a patient in need of such treatment a composition of  claim 13 .  
     
     
         15 . A method of screening a compound for effectiveness as an antagonist of a polypeptide of  claim 1 , the method comprising: 
 a) exposing a sample comprising a polypeptide of  claim 1  to a compound, and    b) detecting antagonist activity in the sample.    
     
     
         16 . A composition comprising an antagonist compound identified by a method of  claim 15  and a pharmaceutically acceptable excipient.  
     
     
         17 . A method for treating a disease or condition associated with overexpression of functional AQP8V, comprising administering to a patient in need of such treatment a composition of  claim 16 .  
     
     
         18 . A method of screening for a compound that specifically binds to the polypeptide of  claim 1 , the method comprising: 
 a) combining the polypeptide of  claim 1  with at least one test compound under suitable conditions, and    b) detecting binding of the polypeptide of  claim 1  to the test compound, thereby identifying a compound that specifically binds to the polypeptide of  claim 1 .    
     
     
         19 . A method of screening for a compound that modulates the activity of the polypeptide of  claim 1 , said method comprising: 
 a) combining the polypeptide of  claim 1  with at least one test compound under conditions permissive for the activity of the polypeptide of  claim 1 ,    b) assessing the activity of the polypeptide of  claim 1  in the presence of the test compound, and    c) comparing the activity of the polypeptide of  claim 1  in the presence of the test compound with the activity of the polypeptide of  claim 1  in the absence of the test compound, wherein a change in the activity of the polypeptide of  claim 1  in the presence of the test compound is indicative of a compound that modulates the activity of the polypeptide of  claim 1 .    
     
     
         20 . A method for detecting a condition or disease associated with the expression of AQP8V in a biological sample, the method comprising: 
 a) combining the biological sample with an antibody of  claim 8 , under conditions suitable for the antibody to bind the polypeptide and form an antibody:polypeptide complex, and    b) detecting the complex, wherein the presence of the complex correlates with the presence of the polypeptide in the biological sample.    
     
     
         21 . The antibody of  claim 8 , wherein the antibody is: 
 a) a chimeric antibody,    b) a single chain antibody,    c) a Fab fragment,    d) a F(ab′) 2  fragment, or    e) a humanized antibody.    
     
     
         22 . A composition comprising an antibody of  claim 8  and an acceptable excipient.  
     
     
         23 . A method of diagnosing a condition or disease associated with the expression of AQP8V in a subject, comprising administering to said subject an effective amount of the composition of  claim 22 .  
     
     
         24 . A composition of  claim 22 , wherein the antibody is labeled.  
     
     
         25 . A method of diagnosing a condition or disease associated with the expression of AQP8V in a subject, comprising administering to said subject an effective amount of the composition of  claim 24 .  
     
     
         26 . A method of preparing a polyclonal antibody with the specificity of the antibody of  claim 8 , the method comprising: 
 a) immunizing an animal with a polypeptide consisting of an amino acid sequence of residues M49 to R303 of SEQ ID NO: 1, or an immunogenic fragment thereof, under conditions to elicit an antibody response,    b) isolating antibodies from said animal, and    c) screening the isolated antibodies with the polypeptide, thereby identifying a polyclonal antibody which binds specifically to a polypeptide comprising an amino acid sequence of residues M49 to R303 of SEQ ID NO: 1.    
     
     
         27 . A polyclonal antibody produced by a method of  claim 26 .  
     
     
         28 . A composition comprising the polyclonal antibody of  claim 27  and a suitable carrier.  
     
     
         29 . A method of making a monoclonal antibody with the specificity of the antibody of  claim 8 , the method comprising: 
 a) immunizing an animal with a polypeptide consisting of an amino acid sequence of residues M49 to R303 of SEQ ID NO: 1, or an immunogenic fragment thereof, under conditions to elicit an antibody response,    b) isolating antibody producing cells from the animal,    c) fusing the antibody producing cells with immortalized cells to form monoclonal antibody-producing hybridoma cells,    d) culturing the hybridoma cells, and    e) isolating from the culture monoclonal antibody which binds specifically to a polypeptide comprising an amino acid sequence of residues M49 to R303 of SEQ ID NO: 1.    
     
     
         30 . A monoclonal antibody produced by a method of  claim 29 .  
     
     
         31 . A composition comprising the monoclonal antibody of  claim 30  and a suitable carrier.  
     
     
         32 . The antibody of  claim 8 , wherein the monoclonal antibody is produced by screening a Fab expression library.  
     
     
         33 . The antibody of  claim 8 , wherein the antibody is produced by screening a recombinant immunoglobulin library.  
     
     
         34 . A method of detecting a polypeptide comprising an amino acid sequence of residues M49 to R303 of SEQ ID NO: 1 in a sample, the method comprising: 
 a) incubating the antibody of  claim 8  with a sample under conditions to allow specific binding of the antibody and the polypeptide, and    b) detecting specific binding, wherein specific binding indicates the presence of a polypeptide comprising an amino acid sequence of residues M49 to R303 of SEQ ID NO: 1 in the sample.    
     
     
         35 . A method of purifying a polypeptide comprising an amino acid sequence of residues M49 to R303 of SEQ ID NO: 1 from a sample, the method comprising: 
 a) incubating the antibody of  claim 8  with a sample under conditions to allow specific binding of the antibody and the polypeptide, and    b) separating the antibody from the sample and obtaining the purified polypeptide comprising an amino acid sequence of residues M49 to R303 of SEQ ID NO: 1.    
     
     
         36 . The method of  claim 20 , wherein the sample is pancreatic tissue, and differential expression of AQP8V is measured in comparing expression of the polypeptide in the biological sample with a standard and indicates the presence of type 2 diabetes in the sample.