Fig. 7.

IGF-I activates the mammalian target of rapamycin (mTOR) pathway leading to fibronectin expression. A: mTOR substrates S6 kinase (S6K) and eukaryotic initiation factor binding protein 4E-BP1 are phosphorylated within 5 min in response to treatment with 250 ng/ml IGF-I. 30 μg of RIPA lysates were separated by SDS-PAGE and probed in rat, mouse, and human proximal tubular epithelial cells, as described in materials and methods. B: IGF-I-induced fibronectin expression is inhibited by a selective inhibitor of mTOR [25 nM rapamycin (Rapa)] in rat PTCs. Histogram represents the intensity of the fibronectin expression to GAPDH quantified by densitometry. Values are means ± SE (n = 3); **P < 0.01.