FIG. 5.

Rac1-mediated activation of Akt/PKB requires functional PI 3-kinase, but PI 3-kinase-mediated activation of Akt/PKB does not require functional Rac1. (A) Cells were transfected with Akt/PKB together with either the empty vector or the construct encoding constitutively active Rac1 (L61Rac), in the presence or in the absence of LY294002 inhibitor, in triplicate. Eighteen hours later, samples were harvested and assayed for kinase activity. Kinase activity was calculated as fold induction of basal activity (bottom) and presented as the mean ± standard deviation of triplicate samples of one representative experiment out of four. (B) Cells were transfected with Akt/PKB together with either the empty vector or the construct encoding active PI 3-kinase (rCD2p110), in the presence or in the absence of N17Rac, in triplicate. Eighteen hours later, samples were harvested and assayed for kinase activity, which is presented as the mean fold induction ± standard deviation of triplicate samples (bottom). (C) Conditions were the same as those in panel B except that rCD2p110 was replaced by p110K227E to simulate Akt/PKB activity.