The platelet cytoskeleton regulates the aggregation-dependent synthesis of phosphatidylinositol 3,4-bisphosphate induced by thrombin.
Pretreatment of intact platelets with cytochalasin D prevented actin polymerization and cytoskeleton reorganization induced by thrombin, but did not affect platelet aggregation. Under these conditions, synthesis of phosphatidylinositol 3,4-bisphosphate (PtdIns(3,4)P2) stimulated by thrombin was strongly inhibited, while production of phosphatidic acid was unaffected. The inhibitory effect of cytochalasin D was not observed when platelet aggregation was prevented by the RGDS peptide. We also found that cytochalasin D did not affect PtdIns(3,4)P2 synthesis induced by concanavalin A (ConA), which is known to occur through an aggregation-independent mechanism. Moreover, thrombin, but not ConA, induced the translocation of phosphatidylinositol 3-kinase to the cytoskeleton. This process was equally inhibited by both the RGDS peptide and cytochalasin D. These results demonstrate that the cytoskeleton represents a functional link between thrombin-induced aggregation and synthesis of PtdIns(3,4)P2.
Torti
M
M
Department of Biochemistry, University of Pavia, Italy.
Bertoni
A
A
Sinigaglia
F
F
Balduini
C
C
Payrastre
B
B
Plantavid
M
M
Chap
H
H
Mauco
G
G
D001792:Blood Platelets / Q000187:drug effects* / Q000502:physiology; D015638:Cytochalasin D / Q000494:pharmacology; D003599:Cytoskeleton / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D066298:In Vitro Techniques; D018129:Phosphatidylinositol Phosphates / Q000138:chemical synthesis*; D010974:Platelet Aggregation; D013917:Thrombin / Q000494:pharmacology*
D018129:Phosphatidylinositol Phosphates; C060980:phosphatidylinositol 3,4-diphosphate; D015638:Cytochalasin D; D013917:Thrombin