Shape change is independent of tyrosine phosphorylation of p130 in human platelets

It has been previously suggested that tyrosine phosphorylation of p62, p68, and p130 might be necessary for the platelet shape change to occur. In preliminary studies we observed that high concentrations (30 mu M) of a protein kinase C inhibitor, Ro 31-8220, selectively suppressed p130 tyrosine phosphorylation induced by thrombin, the thromboxane synthetic analogue (U46619) and ADP. Therefore, we have investigated the correlation, if any, between p130 tyrosine phosphorylation and platelet shape change induced by the same agonists in the presence of Ro 31-8220. Our results demonstrated that high concentrations of this compound almost completely abolished p130 tyrosine phosphorylation, whereas they had no effect on platelet shape change, thus proving a dissociation between these two phenomena. Our data support the hypothesis that a role in platelet shape change might be played by tyrosine phosphorylation of proteins other than p130. (C) 1998 Elsevier Science Ltd.