Molecular Cloning of a Novel Cytoplasmic Protein Tyrosine Phosphatase PTPϵ

Abstract

We have isolated a cDNA of a novel cytoplasmic variant of the protein tyrosine phosphatase ϵ (PTPϵ) from rat spleen cDNA library. Its deduced amino acid sequence of 642 residues was 94.6% identical to C-terminal 642 residues of human PTPϵ (HPTPϵ). However, N-terminal 12 amino acid residues of the rat PTPϵ had no homology to HPTPϵ. The unique N-terminal sequence of the rat PTPϵ was shorter and much more hydrophilic than the transmembrane domain of HPTPϵ. These results strongly suggest that the rat PTPϵ, designated here as PTPϵC, is a novel cytoplasmic PTP with two tandem catalytic domains. We also isolated by RT-PCR a rat transmembrane PTPϵ cDNA, designated as PTPϵM, which has the extracellular and transmembrane domains in addition to the common sequence to the PTPϵC. These results suggested that the PTPϵC and PTPϵM are generated from a single gene and may be involved in multiple functions in signal transduction.