Agonist-induced changes of platelet tubulin phosphorylation.

Changes in the phosphorylation of platelet tubulin were analyzed as a function of platelet activation. Non-activated platelets incubated with [32P]-phosphate showed multiple peaks of radioactivity when solubilized platelet proteins were analyzed by SDS-polyacrylamide gradient gel electrophoresis. Both tubulin monomers were found to be phosphorylated. Agonistic stimulation (thrombin or 1,2-diacylglycerol) resulted in a lowering of the phosphate incorporation into alpha- and beta-tubulin. Such changes we believe are important in the modulation of the reversible polymerization-depolymerization of platelet tubulin that occurs in the course of the agonistic stimulation of platelets.