ASSOCIATION OF THE PROTEIN-TYROSINE-PHOSPHATASE PTP1C WITH THE PROTEIN-TYROSINE KINASE C-SRC IN HUMAN PLATELETS

Protein tyrosine phosphatase 1C (PTP1C), highly expressed in hematopoi etic cells, is a soluble protein tyrosine phosphatase containing two S rc homology 2 (SH2) domains at the N-terminus and two putative sites o f tyrosine phosphorylation at the C-terminus. This paper reports that PTP1C and c-Src could be coimmunoprecipitated during thrombin-induced platelet activation. Moreover, association between the two signalling proteins occurred only after PTP1C had been tyrosine phosphorylated. I n in vitro experiments, PTP1C bound to the SH2 domain of c-Src, sugges ting that association between tyrosine phosphorylated PTP1C and c-Src was mediated by the SH2 domain of c-Src. Finally, in resting platelets , PTP1C was mainly found in the Nonidet P-40 soluble fraction whereas following thrombin-induced activation, around 17% of PTP1C was associa ted with the insoluble fraction.