Abundance of PDCD4 in myotubes is regulated by the proteasome. L6 myotubes were incubated in differentiation (Ctl) or starvation medium as described in Figure 1. They were then harvested (Stv) or refed in the differentiation medium supplemented with DMSO (−) or 10 μM MG132 (+) for 1 or 3 h. (A) Total PDCD4 and γ tubulin were analyzed by immunoblotting. (B) PDCD4 signals were quantified and expressed relative to γ-tubulin. Means ± SE; n = 4–6; bars with different letters differ (P < 0.05).