FIG. 4.

Membrane targeting of PKB is required for S6K1 activation. (A and C) Wild-type HA-PKBα, HA-PKBα-T308D/S473D, and m/p-HA-PKBα-S473A were cotransfected into human 293 cells with an Myc-S6K1 reporter construct. Panel A shows the activity of the indicated PKB constructs as well as that of m/p-HA-PKBα-T308D/S473D. S6K1 activity is presented as in Fig. 2 (C, upper panel). Expression levels of Myc-S6K1 and the different HA-tagged PKB constructs are shown in the lower panels (A and C). (B) Myc–GSK-3β was cotransfected with the empty vector, m/p-HA-PKBα-S473A, or m/p-HA-PKBα. GSK-3 activity is presented as a percentage of PP2A-induced activity. (D) Wild-type HA-PKBα and HA-PKBα-S473A were expressed together with S6K1. S6 kinase activity is shown in the upper panel (Fig. 2), and expression levels are shown in the middle and lower panels, as indicated. Error bars indicate standard deviations.