Inhibition of PP2A with okadaic acid confers resistance to rapamycin inhibition of IGF-1-induced phosphorylation of Erk1/2 and cell motility.

<p>(A) Serum-starved Rh1 cells were pretreated treated with or without OA (100 nM) for 1 h, and then treated with or without rapamycin (Rapa, 100 ng/ml) for 2 h, followed by stimulation with or without IGF-1 (10 ng/ml) for 15 min. Cell lysates were analyzed by Western blotting using indicated antibodies. β-tubulin served as loading control. (B) Motility of Rh1 cells was determined by the wound healing assay, as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0010578#s2" target="_blank"><i>Materials and Methods</i></a>. Following wounding, serum-starved Rh1 cells were pretreated treated with or without OA (100 nM) for 1 h, and then treated with or without rapamycin (Rapa, 100 ng/ml) for 2 h, followed by stimulation with or without IGF-1 (10 ng/ml) for 22 h. Cells migrated over the denuded area were observed and photographed with an Olympus inverted phase-contrast microscope equipped with Quick Imaging system. The number of cells migrating per millimeter of scratch was counted. Results are means ± SE of 3–4 independent experiments. ^a<i>P</i><0.05, difference <i>vs.</i> control group; ^b<i>P</i><0.05, difference <i>vs.</i> IGF-1 group.