Specific role for p85/p110β in GTP-binding-protein-mediated activation of Akt

We prepared CHO (Chinese hamster ovary) cells expressing both IR (insulin receptor) and A, R (A, adenosine receptor). Treatment of the cells with insulin or PIA [N(6)-(2-phenylisopropyl)adenosine], a specific A, R agonist increased Akt activity in the cells in a PI3K- (phosphoinositide 3-kinase) dependent manner. Transfection of p110 into the cells augmented the action of PIA with little effect on insulin. Introduction of a pH1 vector producing shRNA (short hairpin RNA) that targets p110 beta abolished PIA-induced Akt activation. By contrast, an shRNA probe targeting p110 alpha did not impair the effects of PIA. The effect of PIA in p110 alpha-deficient cells was attenuated effectively by both Delta p85 and beta ARK-CT (beta-adrenergic receptor kinase-C-terminal peptide). A Delta p85-derived protein possessing point mutations in its two SH2 domains did not impair PIA action. These results suggest that. tyrosine-phosphorylated proteins and G beta gamma (beta gamma subunits of GTP-binding protein) are necessary for the specific function of p110 beta in intact cells. The p110 beta-middle (middle part of p110 beta) may play an important role in signal reception from GPCRs (GTP-binding-protein-coupled receptor), because transfection of the middle part impaired PIA sensitivity.