The Fzd7 receptor complex contains PI3K and the G protein Gαs (a) Coimmunoprecipitation analyses demonstrated that Fzd7YFP binds the p85 subunit of PI3K in myotubes but not in myoblasts. (b) Blocking of PI3K activity with the specific inhibitor LY294002 abrogated the hypertrophy induced by Wnt7a. Fibre diameter was measured 5 days after induction of differentiation in C2C12 control cells as well as in C2C12 cells expressing Wnt7a-HA (n=4), *** p<0.001. (c) IP-Western coimmunoprecipitation analysis demonstrated that Fzd7 binds G protein Gαs. (d). Suramin, a specific inhibitor of the G protein Gαs23 completely blocked Wnt7a induced hypertrophy, n=3, *** p<0.001. (e) Suramin inhibits Wnt7a induced phosphorylation of Akt and S6. (f) Knockdown of GNAS1 abrogates Wnt7a induced hypertrophy in C2C12 cells, n=3, *** p<0.001. Error bars represent SEM. See S6 for uncropped images of blots.