Isolation of a cDNA encoding a novel protein tyrosine phosphatase which localizes to focal adhesions and uses therefor

Abstract

DNA which encodes a protein homologous to the protein tyrosine phosphatases (PTPases) which catalyze the dephosphorylation of proteins in which tyrosyl residues have been phosphorylated through the action of a protein kinase. The protein, which appears as if it will localize to focal adhesions, is also the subject of the present invention. In particular, it relates to CDNA encoding a protein, referred to as PTPH1. Overexpression of PTPH1 may be a powerful approach to countering the effects of oncogenic protein tyrosine kinases, such as those of transforming viruses, and interfering with or reversing cell transformation. This would provide a means of preventing or reversing abnormally high levels of phosphotyrosine associated with any diseases or condition, such as preventing or reversing malignancy associated with the activity of a protein tyrosine kinase. In the present method, DNA or RNA encoding PTPH1 or a functional equivalent of PTPH1 is administered to an individual in an appropriate gene transfer vehicle which can infect mammalian cells and, once inside the mammalian cells, express and make available PTPH1 or its functional equivalent in sufficient quantities to overcome or counteract the protein tyrosine kinase activity. As a result, phosphorylation of tyrosine residues at abnormal levels is prevented or reversed, resulting in turn in prevention or reversal of malignancy of cells.

1 . Isolated RNA encoding a protein tyrosine phosphatase, which protein tyrosine phosphatase comprises an amino acid sequence as shown in FIGS.  1 A- 1 B.  
     
     
         2 . A retroviral vector comprising the RNA of  claim 1 .  
     
     
         3 . A method of treating or preventing a condition in which abnormally high levels of phosphotyrosine occur in a mammalian cell, comprising introducing into the mammalian cell an agent which comprises DNA or RNA encoding encoding all or a portion of a protein tyrosine phosphatase polypeptide, under conditions sufficient to express the protein tyrosine phosphatase polypeptide, which polypeptide comprises all or a portion of an amino acid sequence as shown in FIGS.  1 A- 1 B wherein the polypeptide can catalyze dephosphorylation of tyrosyl residues that are phosphorylated through action of a protein tyrosine kinase.  
     
     
         4 . A method of reversing a malignant phenotype of a mammalian cell which is associated with tyrosyl phosphorylation catalyzed by a protein tyrosine kinase, comprising introducing into the mammalian cell an agent which comprises DNA or RNA encoding all or a portion of a protein tyrosine phosphatase polypeptide, under conditions sufficient to express the protein tyrosine phosphatase polypeptide, which polypeptide comprises all or a portion of an amino acid sequence as shown in FIGS.  1 A- 1 B wherein the polypeptide can catalyze dephosphorylation of tyrosyl residues that are phosphorylated through action of the protein tyrosine kinase.  
     
     
         5 . The method of either  claim 3  or  claim 4  wherein the agent comprises a recombinant retrovirus or a recombinant vaccinia virus.  
     
     
         6 . The method of either  claim 3  or  claim 4  wherein at least one tyrosyl residue that is dephosphorylated by the protein tyrosine phosphatase polypeptide can be aberrantly phosphorylated by pp60 v-src .