Differential requirements for calcium and Src family kinases in platelet GPIIb/IIIa activation and thromboxane generation downstream of different G-protein pathways.
G(12/13) or G(q) signaling pathways activate platelet GPIIb/IIIa when combined with G(i) signaling. We tested whether combined G(i) and G(z) pathways also cause GPIIb/IIIa activation and compared the signaling requirements of these events. Platelet aggregation occurred by combined stimulation of G(i) and G(z) pathways in human platelets and in P2Y1-deficient and G alpha(q)-deficient mouse platelets, confirming that the combination of G(i) and G(z) signaling causes platelet aggregation. When G(i) stimulation was combined with G(z) stimulation, there was a small mobilization of intracellular calcium. Chelation of intracellular calcium decreased the extent of this platelet aggregation, whereas it abolished the G(q) plus G(i)-mediated platelet aggregation. Costimulation of G(i) plus G(z) pathways also caused thromboxane generation that was dependent on outside-in signaling and was inhibited by PP2, a Src family tyrosine kinase inhibitor. Src family tyrosine kinase inhibitors also inhibited platelet aggregation and decreased the PAC-1 binding caused by costimulation of G(i) and G(z) signaling pathways in aspirin-treated platelets. However, Src family kinase inhibitors did not affect G(q) plus G(i)-mediated platelet aggregation. We conclude that the combination of G(i) plus G(z) pathways have different requirements than G(q) plus G(i) pathways for calcium and Src family kinases in GPIIb/IIIa activation and thromboxane production.
Dorsam
Robert T
RT
Department of Pharmacology, and The Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, PA 19140, USA.
Kim
Soochong
S
Murugappan
Swaminathan
S
Rachoor
Swathi
S
Shankar
Haripriya
H
Jin
Jianguo
J
Kunapuli
Satya P
SP
D000818:Animals; D001241:Aspirin / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010974:Platelet Aggregation / Q000187:drug effects / Q000502:physiology; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013268:Stimulation, Chemical; D013931:Thromboxanes / Q000378:metabolism*; D019061:src-Family Kinases / Q000378:metabolism*
D010975:Platelet Aggregation Inhibitors; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D013931:Thromboxanes; D019869:Phosphatidylinositol 3-Kinases; D019061:src-Family Kinases; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D001241:Aspirin; D002118:Calcium