Role and regulation of phosphatidylinositol 3-kinase ß in platelet integrin α2ß1 signaling
MetadataShow full item record
Integrin α2β1–mediated adhesion of human platelets to monomeric type I collagen or to the GFOGER peptide caused a time-dependent activation of PI3K and Akt phosphorylation. This process was abrogated by pharmacologic inhibition of PI3Kβ, but not of PI3Kγ or PI3Kα. Moreover, Akt phosphorylation was undetectable in murine platelets expressing a kinase-dead mutant of PI3Kβ (PI3KβKD), but occurred normally in PI3KγKD platelets. Integrin α2β1 failed to stimulate PI3Kβ in platelets from phospholipase Cγ2 (PLCγ2)–knockout mice, and we found that intracellular Ca2+ linked PLCγ2 to PI3Kβ activation. Integrin α2β1 also caused a time-dependent stimulation of the focal kinase Pyk2 downstream of PLCγ2 and intracellular Ca2+. Whereas activation of Pyk2 occurred normally in PI3KβKD platelets, stimulation of PI3Kβ was strongly reduced in Pyk2-knockout mice. Neither Pyk2 nor PI3Kβ was required for α2β1–mediated adhesion and spreading. However, activation of Rap1b and inside-out stimulation of integrin αIIbβ3 were reduced after inhibition of PI3Kβ and were significantly impaired in Pyk2-deficient platelets. Finally, both PI3Kβ and Pyk2 significantly contributed to thrombus formation under flow. These results demonstrate that Pyk2 regulates PI3Kβ downstream of integrin α2β1, and document a novel role for Pyk2 and PI3Kβ in integrin α2β1 promoted inside-out activation of integrin αIIbβ3 and thrombus formation.
Showing items related by title, author, creator and subject.
Cipolla, L.; Consonni, A.; Guidetti, G.; Canobbio, I.; Okigaki, M.; Falasca, Marco; Ciraolo, E.; Hirsch, E.; Balduini, C.; Torti, M. (2013)Background: The proline-rich tyrosine kinase Pyk2 is a focal adhesion kinase expressed in blood platelets, and is activated downstream of G-protein coupled receptors as well as integrin a2ß1. Objective: In this study we ...
Activation of phosphatidylinositol 3-kinase ß by the platelet collagen receptors integrin a2ß1 and GPVI: The role of Pyk2 and c-CblManganaro, D.; Consonni, A.; Guidetti, G.; Canobbio, I.; Visconte, C.; Kim, S.; Okigaki, M.; Falasca, Marco; Hirsch, E.; Kunapuli, S.; Torti, M. (2015)Phosphatidylinositol 3-kinaseβ (PI3Kβ) plays a predominant role in integrin outside-in signaling and in platelet activation by GPVI engagement. We have shown that the tyrosine kinase Pyk2 mediates PI3Kβ activation downstream ...
Role of Focal Adhesion Tyrosine Kinases in GPVI-Dependent Platelet Activation and Reactive Oxygen Species FormationCarrim, N.; Walsh, T.; Consonni, A.; Torti, M.; Berndt, Michael; Metharom, Pat (2014)BackgroundWe have previously shown the presence of a TRAF4/p47phox/Hic5/Pyk2 complex associated with the platelet collagen receptor, GPVI, consistent with a potential role of this complex in GPVI-dependent ROS formation. ...