Identification of a unique co-operative phosphoinositide 3-kinase signaling mechanism regulating integrin aIIb?3 adhesive function in platelets

Simone Marianne Schoenwaelder, Akiko Ono, Sharelle Anne Sturgeon, Siew Mei Chan, Pierre Mangin, Mhairi Jane Maxwell, Shannon Turnbull, Megha Mulchandani, Karen Elizabeth Anderson, Gilles Kauffenstein, Gordon W Rewcastle, Jackie Kendall, Christian Gachet, Hatem Hassan Salem, Shaun Jackson

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Abstract

Phosphoinositide (PI) 3-kinases play an important role in regulating the adhesive function of a variety of cell types through affinity modulation of integrins. Two type I PI 3-kinase isoforms (p110 beta and p110 gamma) have been implicated in G(i)-dependent integrin alpha(IIb)beta(3) regulation in platelets, however, the mechanisms by which they coordinate their signaling function remains unknown. By employing isoform-selective PI 3-kinase inhibitors and knock-out mouse models we have identified a unique mechanism of PI 3-kinase signaling co-operativity in platelets. We demonstrate that p110 beta is primarily responsible for G(i)-dependent phosphatidylinositol 3,4-bisphosphate (PI(3,4)P(2)) production in ADP-stimulated platelets and is linked to the activation of Rap1b and AKT. In contrast, defective integrin alpha(IIb)beta(3) activation in p110 gamma(-/-) platelets was not associated with alterations in the levels of PI(3,4)P(2) or active Rap1b/AKT. Analysis of the effects of active site pharmacological inhibitors confirmed that p110 gamma principally regulated integrin alpha(IIb)beta(3) activation through a non-catalytic signaling mechanism. Inhibition of the kinase function of PI 3-kinases, combined with deletion of p110 gamma, led to a major reduction in integrin alpha(IIb)beta(3) activation, resulting in a profound defect in platelet aggregation, hemostatic plug formation, and arterial thrombosis. These studies demonstrate a kinase-independent signaling function for p110 gamma in platelets. Moreover, they demonstrate that the combined catalytic and non-catalytic signaling function of p110 beta and p110 gamma is critical for P2Y(12)/G(i)-dependent integrin alpha(IIb)beta(3) regulation. These findings have potentially important implications for the rationale design of novel antiplatelet therapies targeting PI 3-kinase signaling pathways.
Original languageEnglish
Pages (from-to)28648 - 28658
Number of pages11
JournalJournal of Biological Chemistry
Volume282
Issue number39
Publication statusPublished - 2007

Cite this

Schoenwaelder, S. M., Ono, A., Sturgeon, S. A., Chan, S. M., Mangin, P., Maxwell, M. J., Turnbull, S., Mulchandani, M., Anderson, K. E., Kauffenstein, G., Rewcastle, G. W., Kendall, J., Gachet, C., Salem, H. H., & Jackson, S. (2007). Identification of a unique co-operative phosphoinositide 3-kinase signaling mechanism regulating integrin aIIb?3 adhesive function in platelets. Journal of Biological Chemistry, 282(39), 28648 - 28658.