Effects of actin modification reagents on protein phosphorylation of activated platelets

Abstract

We studied the effects of cytochalasin B and phalloidin on platelet secretion and protein phosphorylation induced by ionophore A23187.
(1) Preincubation of platelets with cytochalasin B or phalloidin suppressed the ATP release induced by A23187 in a dose dependent manner.
(2) In the absence of these reagents, exposure of ³²P-labelled platelets to A23187 resulted in increased phosphorylation of the 20, 000-dalton protein (P20) and the 47, 000-dalton protein (P47).
(3) Treatment of ³²P-labelled platelets with cytochalasin B or phalloidin suppressed the increased phosphorylation of both P20 and P47 caused by A23187.
In conclusion, it was considered that intact network configuration of actin filaments would support full phosphorylation of P20 and P47 during platelet activation.