Fig. 9.

Attenuation of neuregulin-induced expression of endogenous ε-mRNA by dominant-negative JNK1. C2C12 myoblasts were transfected with pCMV, pCMV–JNK1(WT), or pCMV–JNK1(ALF). All DNA constructs contained the G418-resistant gene neo. The FLAG epitope was tagged between the codons 1 and 2 of JNK. G418-resistant clones were isolated and characterized for JNK1 expression and AChR gene expression in response to NRG.A, Western blot analysis showing expression of wild-type and mutant JNK1 in the parental and stable cell lines JNK1(WT)#2 and JNK1(ALF)#1. Forty micrograms of proteins extracted from the indicated myotubes were resolved on a 10% SDS-PAGE gel, transferred, and blotted with anti-FLAG antibodies. Similar levels of JNK1 expression were observed in other stable cell lines described in B.B, Northern blot analysis. Twenty micrograms of total RNA were used. The loading was uniform as evidenced by an equal amount of GAPDH mRNA. C, Histograms showing mean ± SD of three different samples. The mRNA level of the parental cell line in the absence of neuregulin was considered to be 100%. **p < 0.01 in comparison with the neuregulin-mediated increase in parental, pCMV, or JNK1(WT)#2 cells.