Fig. 4.

ERK1/2/mTOR/p70S6K pathway contributes to lactate-induced autophagy activation in differentiated C2C12 myotubes. a1–a3 Effects of U0126 (2.5 µM), Rapamycin (10 nM), or BI-D1870 (10 µM) on protein levels of ERK1/2/mTOR/p70S6K signaling pathway components in C2C12 cells maintained in the vehicle or lactate 10 mM for 8 h. Erk1/2 inhibition by U0126 deterred lactate effects on values of P-mTOR and p-p70S6K expression which restored them to their control values (dashed line). mTOR inhibition by SB203580 decreased p-p70S6K levels, p70S6K inhibition had no effect on P-ERK 1/2 and P-mTOR levels. a4 Autophagy-related gene expression and a5, 6 autophagic flux in C2C12 cells maintained in vehicle or lactate (6, 10, and 20 mM, 8 h) in the absence or presence of U0126, Rapamycin, or BI-D1870. For all protein measurements, fold changes in protein levels were normalized for β-actin and relative to their expression in basal condition (vehicle). ^* Significant difference with basal values (P < 0.01), ⁺ Significant difference with lactate + U0126 group (P < 0.01), ^{^} Significant difference with lactate + Rapamycin group (P < 0.01). N = 6 per group