Identification of protein-tyrosine phosphatases prevalent in adipocytes by molecular cloning.

Protein-tyrosine phosphatases (PTPases) are among the fastest growing family of enzymes that are closely linked to signal transduction pathways involving reversible tyrosine phosphorylation. In order to identify PTPase homologs expressed in adipocytes that might regulate the action of insulin or growth factors in this tissue, we screened a rat adipocyte cDNA library at reduced stringency with a panel of candidate PTPase probes. After subcloning and sequence analysis of the positive plaques, this approach enabled us to identify the expression of LRP/RPTP-alpha, PTPase 1B, SH-PTP2/Syp, and LAR in adipocytes at an abundance of 16, 7, 6 and 3 per million, respectively. Furthermore, a sequence variant of SH-PTP2/Syp was identified that may have significance in the tissue-specific activity of this enzyme. These data provide insight into PTPase homologs that may have a physiological role in the regulation of phosphotyrosyl turnover in hormone signalling pathways in adipocytes.