FIG. 2.

LY294002 inhibits the phosphorylation of rpS6 as well as the translational activation of TOP mRNAs upon growth or mitogenic stimulation. (a) PC12 cells were serum starved for 72 h and then either treated with 50 ng of NGF per ml (+NGF) or serum refed (+Serum) for 30 min without (−) or with (+) 50 μM LY294002. Subsequently, cells were harvested and subjected to polysomal analysis, as described in the legend to Fig. 1. (b and c) PC12 cells were serum starved for 72 h (0 min) and then either treated with 50 ng of NGF per ml (b) or serum refed (c) without (−) or with (+) 50 μM LY294002 for the indicated times. The cytoplasmic proteins were subjected to Western blot analysis with the indicated antibodies. α and β represent hypophosphorylated and hyperphosphorylated forms of rpS6, respectively.