Rapamycin activates PP2A in an mTOR-dependent manner.

<p>Serum-starved Rh30 cells were exposed to rapamycin (Rapa, 100 ng/ml) for the indicated time (A), or pretreated with or without rapamycin (Rapa, 100 ng/ml) or okadaic acid (OA, 100 nM) for 2 h, and then stimulated with or without IGF-1 (10 ng/ml) for 1 h (B), or the indicated serum-starved Rh30 cells were exposed to rapamycin (Rapa, 100 ng/ml) for 2 h (C, D). PP2A in cell lysates was immunoprecipitated with antibodies to PP2A catalytic subunit (PP2Ac) plus protein A/G agarose beads, followed by <i>in vitro</i> phosphatase assay using Ser/Thr Phosphatase Assay Kit 1 (Millipore). Data represent mean ± SE from 3–4 independent experiments. ^a<i>P</i><0.05 <i>vs.</i> controls, ^b<i>P</i><0.05 <i>vs.</i> Rapa group.