Functional implications of tyrosine protein phosphorylation in platelets. Simultaneous studies with different agonists and inhibitors

C. Bachelot, E. Cano, F. Grelac, S. Saleun, Brian Druker, S. Levy-Toledano, S. Fischer, F. Rendu

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Abstract

During activation of platelets by agonists, a number of proteins become phosphorylated at tyrosine residues. Using immunoblotting with a monoclonal anti-phosphotyrosine antibody, we have compared the different phosphotyrosine-protein (PTP) profiles of platelets stimulated with thrombin, collagen, ADP, arachidonic acid, phorbol myristate acetate and P256, an anti-glycoprotein-Ilb IIIa (GPIIb IIIa) monoclonal antibody (mAb). Only a few PTPs were observed in resting platelets, of molecular masses 130, 64, 56-60 and 36 kDa. After stimulation by different agonists these proteins were more intensely phosphorylated and additional PTPs appeared with molecular masses of 170, 150, 140, 120, 105/97 (doublet), 85, 80, 75 and 45 kDa. The kinetics of phosphorylation differed from one agonist to another, but no significant differences in the overall patterns were detected, except in presence of ADP and P256-F(ab')2, which induced only the additional tyrosine phosphorylation of the 64 kDa protein and to a lesser extent that of a 75 kDa protein. The use of various agonists and the inhibitors (staurosporine, ajoene and RGDS) permitted a better characterization of the relationship between the different steps of activation and phosphorylation on tyrosine residues. The studies suggest the following conclusions: (i) stimulation of tyrosine phosphorylation occurs after activation of protein kinase C; (ii) there is a relationship between ligand binding to GPIIb IIIa and the tyrosine phosphorylation of the 64 kDa protein. and (iii) there is a close relationship between PTP formation and the intensity of platelet activation and aggregation.

Original languageEnglish (US)
Pages (from-to)923-928
Number of pages6
JournalBiochemical Journal
Volume284
Issue number3
Publication statusPublished - 1992
Externally publishedYes

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ASJC Scopus subject areas

  • Biochemistry

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Bachelot, C., Cano, E., Grelac, F., Saleun, S., Druker, B., Levy-Toledano, S., ... Rendu, F. (1992). Functional implications of tyrosine protein phosphorylation in platelets. Simultaneous studies with different agonists and inhibitors. Biochemical Journal, 284(3), 923-928.