title: Protein tyrosine phosphorylation in human platelets induced by interaction between glycoprotein Ib and von Willebrand factor.
abstract: The interaction between von Willebrand factor (vWF) and glycoprotein Ib (GPIb) induced by ristocetin or botrocetin resulted in associated platelet aggregation, protein tyrosine phosphorylation (PTP) of a 64 kDa protein, as detected by a monoclonal antibody against phosphotyrosine (PY-20), and intracellular Ca2+ elevation that is largely dependent upon Ca2+ influx in human platelets. It is of interest that 75-80, 97 and 125 kDa proteins which are strongly tyrosine-phosphorylated in platelet activation induced by thrombin and other agonists were not detected. Neither vWF nor a coaggregating agent (ristocetin or botrocetin) alone induced aggregation, [Ca2+]i elevation or the 64 kDa PTP. NMC-4, an antibody which inhibits both ristocetin- or botrocetin-induced vWF binding to GPIb, abolished the appearance of the 64 kDa PTP as well as other responses, suggesting that it is specifically induced by the GPIb-vWF interaction. Aspirin, or ONO-3708, a competitive inhibitor of thromboxane A2, did not modify the 64 kDa PTP, while [Ca2+]i elevation was moderately suppressed. Depletion of extracellular Ca2+ or RGD peptides suppressed neither the 64 kDa PTP nor aggregation. H-7, a protein kinase C inhibitor, did not inhibit the 64 kDa PTP, while staurosporine, a potent protein kinase inhibitor, inhibited the 64 kDa PTP and Ca2+ influx, but not aggregation, in a dose-dependent manner. It is suggested that the 64 kDa PTP is associated with platelet aggregation induced by the interaction between GPIb and vWF.
authors.affiliation: Department of Clinical and Laboratory Medicine, Yamanashi Medical University, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Ozaki
authors.forename: K
authors.initials: K
authors.lastname: Satoh
authors.forename: Y
authors.initials: Y
authors.lastname: Yatomi
authors.forename: S
authors.initials: S
authors.lastname: Miura
authors.forename: Y
authors.initials: Y
authors.lastname: Fujimura
authors.forename: S
authors.initials: S
authors.lastname: Kume
mesh_terms: D000470:Alkaloids / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000097:blood; D003435:Crotalid Venoms / Q000494:pharmacology; D011464:Epoprostenol / Q000494:pharmacology; D006801:Humans; D010750:Phosphoproteins / Q000097:blood*; D010766:Phosphorylation; D019000:Phosphotyrosine; D010974:Platelet Aggregation / Q000187:drug effects; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism*; D012310:Ristocetin / Q000494:pharmacology; D019311:Staurosporine; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000097:blood; D014841:von Willebrand Factor / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D000470:Alkaloids; D003435:Crotalid Venoms; D010750:Phosphoproteins; D010980:Platelet Membrane Glycoproteins; D014841:von Willebrand Factor; D012310:Ristocetin; D019000:Phosphotyrosine; D014443:Tyrosine; C030961:botrocetin; D011464:Epoprostenol; D019311:Staurosporine; D002118:Calcium