A study on the mechanism of PI3K/AKT pathway activation by v-Crk oncogene

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v-Crk, an oncogene product of avian sarcoma virus CT10, transforms chicken embryo fibroblasts (CEF) efficiently. We have recently reported that phosphatidylinositide 3-kinase(PI3K)/AKT pathway is constitutively activated and play a critical role in the oncogenic transformation of CEF by v-Crk. In this study, we investigated how v-Crk activates PI3K/AKT pathway and revealed the involvement of focal adhesion kinase (FAK) and H-Ras in this process. v-Crk induces phosphorylation of Tyr 397 residue in FAK through the activation of src-family tyrosine kinase(s), in which SH2 domain of v-Crk is responsible, and promotes the binding of N-terminal SH2 domain of PI3K p85 regulatory subunit to this site. v-Crk fails to activate PI3K/AKT pathway in FAK null cells. In addition, we found that v-Crk stimulates the interaction of H-Ras with Ras binding domain in PI3K p110 catalytic subunit, and that the expression of H-Ras or its guanine nucleotide exchange factor mSOS, which binds to SH3 domain of v-Crk, enhances the v-Crk-induced activation of AKT, while a doninant negative mutant of H-Ras almost completely suppresses this activation. Our data demonstrated that v-Crk activates PI3K/AKT pathway by promoting both the interaction of p85 with tyrosine phosphorylated FAK and the interaction of p110 with H-Ras.