FIGURE 7.

Proposed model for AT2R-mediated regulation of satellite cell differentiation. Initial cue(s) directing differentiation lead to rapid up-regulation of AT2R expression. During satellite cell differentiation, ERK1/2 phosphorylation is suppressed at the initial stage of differentiation, followed by an increase in the later stage (dotted line). AT2R inhibits ERK1/2 signaling at all stages of differentiation, resulting in activation of myogenic gene expression (myogenin and desmin) and myoblast differentiation. ERK1/2 inhibition increases AT2R expression, suggesting a positive feedback regulation. It is of note that it has been suggested that ERK1/2 positively regulates myotube formation in the later stage of differentiation, independently from the regulation of differentiation markers (data not shown; see “Discussion”).