Figure 8.

Constitutive activation of p38 accelerates myogenic differentiation in DMEM in a NF-κB-dependent manner. (A) p38-induced muscle-specific gene expression is reduced by inhibition of NF-κB activity. C2C12 cells were transfected with an empty vector or with the MKK6(E) plasmid, with or without IκBα(S32/36A) coexpression, and maintained in DMEM for 24 h, in the absence or presence of SB203580. Myogenin mRNA expression was analyzed by RT-PCR as an index of myogenic differentiation. GAPDH and luciferase expression were analyzed as controls for RT-PCR and transfection efficiency, respectively. (B) p38-induced muscle-specific promoter activity is reduced by inhibition of NF-κB activity. C2C12 myoblast were transiently transfected with MCK-Luc, together with expression plasmids for MKK6(E), IκBα(S32/36A) or an empty vector, and cultured in DMEM, in the presence or absence of SB203580. Luciferase activities are expressed relative to the activity of MCK-Luc, which was given a value of 1. pRSV-lacZ plasmid was used as a transfection control, and the corresponding β-galactosidase activities were used to normalize the luciferase values. Error bars represent the SE of the mean value.