| First Author | Cipolla L | Year | 2013 |
| Journal | J Thromb Haemost | Volume | 11 |
| Issue | 2 | Pages | 345-56 |
| PubMed ID | 23216754 | Mgi Jnum | J:195447 |
| Mgi Id | MGI:5484487 | Doi | 10.1111/jth.12099 |
| Citation | Cipolla L, et al. (2013) The proline-rich tyrosine kinase Pyk2 regulates platelet integrin alphaIIbbeta3 outside-in signaling. J Thromb Haemost 11(2):345-56 |
| abstractText | 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 alpha2beta1. OBJECTIVE: In this study we have investigated the involvement of Pyk2 in integrin alphaIIbbeta3 outside-in signaling in human and murine platelets. METHODS: We analyzed the stimulation of intracellular signaling pathways in platelets from Pyk2 knockout mice adherent to immobilized fibrinogen. RESULTS: Pyk2 was rapidly phosphorylated and activated in human and murine platelets adherent to fibrinogen through integrin alphaIIbbeta3. Activation of Pyk2 was Src-dependent, but did not require phospholipase Cgamma2 activity. Platelets from Pyk2 knockout mice showed a defective ability to adhere and spread on fibrinogen, in association with a dramatic reduction of phosphatidylinositol 3-kinase (PI3K) activation and Akt phosphorylation. Pharmacological and genetic analysis demonstrated that integrin alphaIIbbeta3 engagement selectively stimulated the beta-isoform of PI3K (PI3Kbeta), and that, as for Pyk2, PI3Kbeta activation required Src family kinases activity, but not phospholipase Cgamma2. In fibrinogen-adherent platelets, both Pyk2 and PI3Kbeta were necessary for stimulation of the small GTPase Rap1b, a regulator of cell adhesion and spreading. Integrin alphaIIbbeta3 engagement triggered the association of the PI3Kbeta regulatory subunit p85 with the adaptor protein c-Cbl, which was mediated by the p85 SH3 domain, and was independent of c-Cbl tyrosine phosphorylation. However, p85-associated c-Cbl was tyrosine phosphorylated by activated Pyk2 in fibrinogen adherent platelets. CONCLUSIONS: These results identify a novel pathway of integrin alphaIIbbeta3 outside-in signaling and recognize the tyrosine kinase Pyk2 as a major regulator of platelet adhesion and spreading on fibrinogen. |
