v-Crk activates the phosphoinositide 3-kinase/AKT pathway in transformation

v-Crk induces cellular tyrosine phosphorylation and transformation of chick en embryo fibroblasts (CEF). We studied the molecular mechanism of the v-Cr k-induced transformation. Experiments with Src homology (SH)2 and SH3 domai n mutants revealed that the induction of tyrosine phosphorylation of cellul ar proteins requires only the SH2 domain, but both the SHZ and SH3 domains are required for complete transformation. Analysis of three well defined si gnaling pathways, the mitogen-activated protein kinase (MAPK) pathway, the Jun N-terminal kinase (JNK) pathway, and the phosphoinositide 3-kinase (PI3 K)/AKT pathway, demonstrated that only the PI3K/AKT pathway is constitutive ly activated in v-Crk-transformed CEF, Both the SH2 and SH3 domains are req uired for this activation of the PI3K/AKT pathway in CEF. We also found tha t the colony formation of CEF is strongly induced by a constitutively activ e PI3K mutant, and that a PI3K inhibitor, LY294002, suppresses the v-Crk-in duced transformation. These results strongly suggest that constitutive acti vation of the PI3K/AKT pathway plays an essential role in v-Crk-induced tra nsformation of CEF.