Fig. 5.

PIF pocket ligands block S6K1 activation, but have only a weak effect on AKT activation in cells. (A) Effect of increasing doses of RS1 or control compounds on the phosphorylation of S6. Cell lysates were immunoblotted with antibodies for phospho-S6 S235/6 and α-tubulin. (B) Effect of increasing doses of RS1 or control compounds on the phosphorylation of AKT. The experiment was the same as that depicted in A, except that antibodies against phospho-AKT T308 and α-tubulin were used. The level of phosphorylation was quantified from the infrared signal and normalized to the α-tubulin signal. Error bars are ± SD (n = 2). The following drugs were used: GSK, a selective ATP-competitive inhibitor of PDK1; PS210, a dicarboxylate PIF pocket ligand that does not enter cells; and PS423, a diester prodrug of PS210.