FIG. 5.

Constitutive activation of the p38 pathway confers partial protection of myotubes against atrophy. Lysates were prepared from wild-type C2C12 cells and constitutively active MKK3 (CA MKK3)-expressing myoblasts that were grown for 4 days in differentiation media. (a) Total proteins were separated by SDS-PAGE and then analyzed by Western-blotting using an anti-phospho-p38 antibody. (b) Myoblasts from these 2 cell lines were allowed to grow in differentiation media for 4 days and harvested at the different time points. Lysates were probed with antimyogenin, anti-phospho-Akt, and total Akt antibodies. (c) Wild-type C2C12 (WT) cells and constitutively active MKK3 (CA MKK3)-expressing myoblasts were grown for 4 days in differentiation media and then starved in HBSS for 12 h. Cells were observed by transmitted-light microscopy (upper panel). Myotube diameters were determined as described in Materials and Methods. Results are expressed as the mean ± SEM and summarized on a histogram (lower panel). * indicates a significant difference (P < 0.001).