TRANSLOCATION OF AN SR2-CONTAINING PROTEIN-TYROSINE-PHOSPHATASE (SH-PTP1) TO THE CYTOSKELETON OF THROMBIN-ACTIVATED PLATELETS

A significant protein tyrosine phosphatase (PTP) activity was found to be associated with the cytoskeleton of thrombin-stimulated platelets. Translocation of the enzyme became maximal within 1-2 min of thrombin stimulation and was suppressed by cytochalasin D or upon inhibition o f aggregation. Immunoblotting as well as immunoprecipitation revealed that a PTP with two SH2 domains (SH-PTP1) displayed the same behaviour , translocation to the cytoskeleton showing the same time course as th at observed for pp60(c-src). We conclude that SH-PTP1 might represent a critical enzyme in the complex interplay between the various protein s regulating protein tyrosine phosphorylation in the cytoskeletal matr ix.