DSP-3 dual-specificity phosphatase

Abstract

Compositions and methods are provided for the treatment of conditions associated with cell proliferation, cell differentiation and cell survival. In particular, the dual-specificity phosphatase DSP-3, and polypeptide variants thereof that stimulate dephosphorylation of DSP-3 substrates, are provided. The polypeptides may be used, for example, to identify antibodies and other agents that inhibit DSP-3 activity. The polypeptides and agents may be used to modulate cell proliferation, differentiation and survival.

1 - 46 . (canceled)  
     
     
         47 . A method for screening a molecule for the ability to interact with a DSP-3 polypeptide comprising the amino acid sequence set forth in SEQ ID NO:2, comprising the steps of: 
 (a) contacting a candidate molecule with a DSP-3 substrate trapping mutant polypeptide under conditions and for a time sufficient to permit the candidate molecule and polypeptide to interact, wherein the DSP-3 substrate trapping mutant polypeptide comprises an amino acid sequence that differs from the amino acid sequence set forth in SEQ ID NO:2 by a substitution at position 57 or position 88 of SEQ ID NO:2; and    (b) detecting the presence or absence of binding of the candidate molecule to the polypeptide, and therefrom determining whether the candidate molecule interacts with the DSP-3 polypeptide.    
     
     
         48 . The method according to  claim 47 , wherein the step of detecting comprises an affinity purification step.  
     
     
         49 . The method according to  claim 47 , wherein the step of detecting comprises a yeast two hybrid screen or a screen of a phage display library.  
     
     
         50 - 98 . (canceled)  
     
     
         99 . The method according to  claim 47  wherein the DSP-3 substrate trapping mutant polypeptide comprises an amino acid substitution at position  57  of SEQ ID NO:2.  
     
     
         100 . The method according to  claim 99  wherein the amino acid substitution at position 57 comprises an alanine residue.  
     
     
         101 . The method according to  claim 47  wherein the DSP-3 substrate trapping mutant polypeptide comprises an amino acid substitution at position 88 of SEQ ID NO:2.  
     
     
         102 . The method according to  claim 101  wherein the amino acid substitution at position 88 comprises a serine residue.  
     
     
         103 . The method according to  claim 47  wherein the DSP-3 substrate trapping mutant polypeptide comprises an amino acid substitution at position 57 of SEQ ID NO:2 and an amino acid substitution at position 88 of SEQ ID NO:2.  
     
     
         104 . The method according to  claim 103  wherein the amino acid substitution at position 57 comprises an alanine residue and the amino acid substitution at position 88 comprises a serine residue.  
     
     
         105 . An isolated polynucleotide encoding a DSP-3 substrate trapping mutant polypeptide, wherein the DSP-3 substrate trapping mutant polypeptide comprises an amino acid sequence that differs from the amino acid sequence set forth in SEQ ID NO:2 by a substitution at position 57 or position 88 of SEQ ID NO:2.  
     
     
         106 . The polynucleotide according to  claim 105  wherein the DSP-3 substrate trapping mutant polypeptide comprises an amino acid substitution at position 57 of SEQ ID NO:2.  
     
     
         107 . The polynucleotide according to  claim 106  wherein the amino acid substitution at position 57 comprises an alanine residue.  
     
     
         108 . The polynucleotide according to  claim 105  wherein the DSP-3 substrate trapping mutant polypeptide comprises an amino acid substitution at position 88 of SEQ ID NO:2.  
     
     
         109 . The polynucleotide according to  claim 108  wherein the amino acid substitution at position 88 comprises a serine residue.  
     
     
         110 . The polynucleotide according to  claim 105  wherein the DSP-3 substrate trapping mutant polypeptide comprises an amino acid substitution at position 57 of SEQ ID NO:2 and an amino acid substitution at position 88 of SEQ ID NO:2.  
     
     
         111 . The polynucleotide according to  claim 110  wherein the amino acid substitution at position 57 comprises an alanine residue and the amino acid substitution at position 88 comprises a serine residue.  
     
     
         112 . An expression vector comprising the polynucleotide according to  claim 105 .  
     
     
         113 . A host cell transfected or transformed with the expression vector according to  claim 112 .  
     
     
         114 . A method of producing a DSP-3 substrate trapping mutant polypeptide encoded by the polynucleotide according to  claim 105 , said method comprising: (a) culturing the host cell according to  claim 113  under conditions that permit expression of the DSP-3 substrate trapping mutant polypeptide; and (b) isolating the DSP-3 substrate trapping mutant polypeptide from the host cell culture.