| First Author | Manganaro D | Year | 2015 |
| Journal | Biochim Biophys Acta | Volume | 1853 |
| Issue | 8 | Pages | 1879-88 |
| PubMed ID | 25960397 | Mgi Jnum | J:230524 |
| Mgi Id | MGI:5762747 | Doi | 10.1016/j.bbamcr.2015.05.004 |
| Citation | Manganaro D, et al. (2015) Activation of phosphatidylinositol 3-kinase beta by the platelet collagen receptors integrin alpha2beta1 and GPVI: The role of Pyk2 and c-Cbl. Biochim Biophys Acta 1853(8):1879-88 |
| abstractText | Phosphatidylinositol 3-kinasebeta (PI3Kbeta) 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 PI3Kbeta activation downstream of integrin alphaIIbbeta3, and promotes the phosphorylation of the PI3K-associated adaptor protein c-Cbl. In this study, we compared the functional correlation between Pyk2 and PI3Kbeta upon recruitment of the two main platelet collagen receptors, integrin alpha2beta1 and GPVI. PI3Kbeta-mediated phosphorylation of Akt was inhibited in Pyk2-deficient platelets adherent to monomeric collagen through integrin alpha2beta1, but occurred normally upon GPVI ligation. Integrin alpha2beta1 engagement led to Pyk2-independent association of c-Cbl with PI3K. However, c-Cbl was not phosphorylated in adherent platelets, and phosphorylation of Akt occurred normally in c-Cbl-deficient platelets, indicating that the c-Cbl is dispensable for Pyk2-mediated PI3Kbeta activation. Stimulation of platelets with CRP, a selective GPVI ligand, induced c-Cbl phosphorylation in the absence of Pyk2, but failed to promote its association with PI3K. Pyk2 activation was completely abrogated in PI3KbetaKD, but not in PI3KgammaKD platelets, and was strongly inhibited by Src kinases and phospholipase C inhibitors, and by BAPTA-AM. The absence of PI3Kbeta activity also hampered GPVI-induced tyrosine-phosphorylation and activation of PLCgamma2, preventing intracellular Ca2+ increase and phosphorylation of pleckstrin. Moreover, GPVI-induced intracellular Ca2+ increase and pleckstrin phosphorylation were also strongly inhibited in human platelets treated with the PI3Kbeta inhibitor TGX-221. These results outline important differences in the regulation of PI3Kbeta by GPVI and integrin alpha2beta1 and suggest that inhibition of Pyk2 may target PI3Kbeta activation in a selective context of platelet stimulation. |
