摘要
Yes-associated protein (YAP) is a transcriptional coactivator in the Hippo pathway that regulates cell proliferation, differentiation, and apoptosis. The MEK5/ERK5 MAPK cascade is essential for the early step of myogenesis. In this study, we generated C2C12 stable cell lines that expressed YAP (C2C12-YAP cells) and found that ERK5 and MEK5 were activated in C2C12-YAP cells compared with control C2C12 (C2C12-vector) cells.C2C12- YAP stable cells also differentiated into myotubes better than C2C12-vector cells, and expressed elevated levels of myogenin, a transcription factor that regulates myogenesis, as well as elevated levels of myosin heavy chain, a skeletalmusclemarker. Western blot analysis revealedthatSrc andc-Abl (Abelsonmurine leukemia viral oncogene homolog 1) activationwere enhancedinC2C12-YAPcells.Conversely, treatment of inhibitors of c-Abl,Src, orMEK5 inhibited activation of MEK5 and ERK5 and myogenesis of C2C12 myoblasts. Specific interactions between YAP and proteins in the ERK5 pathway, such asMEK kinase 3 (MEKK3) and ERK5, were illustrated by coimmunoprecipitation experiments. MEKK3 contains the PPGY motif (aa 178-181), which may interact with YAP. Site-directed mutagenesis experiments revealed that expression of MEKK3 Y181F mutant inhibited MEK5/ERK5 activation and myogenic differentiation. These results suggest that YAP promotes muscle differentiation by activatingtheAbl/Src/MEKK3/MEK5/ERK5kinase cascade.