Role of PI3K and PKB in the modulation of mTORC2 and mTORC1 by albumin. LLC-PK1 cells were preincubated with mTOR inhibitors (1 μm WYE-345 or 0.1 μm rapamycin) for 30 min before concomitant incubation with albumin for 30 min. Modulation by mTOR inhibitors of the effect of physiologic albumin (alb) concentrations on mTORC1 activity by S6K phosphorylation at Thr-389 (A), mTOR phosphorylation at Ser-2481 (B), and PKB phosphorylation at Ser-473 (C). Shown is the effect on albumin-mediated modulation of mTORC1 activity (D) and on mTOR phosphorylation at Ser-2448 (E) of the PI3K inhibitors wortmannin (wort; 0.05 μm) and LY294002 (LY; 25 μm). F, effect of 10 μm PKB inhibitor (PKBi) on mTOR phosphorylation at Ser-2448. The results are shown as means ± S.E. (n = 4). *, p < 0.05 versus control; #, p < 0.05 versus 0.01 mg/ml albumin.