MTMR4 and Atrophy: We found that levels of both MTMR4 and FGFR1 proteins decreased in the denervated gastrocnemius muscle of control mice coincident to the increase in Nedd4-1 (Figures 7A and 7B), but there was no attenuation of that decrease for either protein in the denervated gastrocnemius of Nedd4-1 SMS-KO mice, suggesting that neither MTMR4 nor FGFR1 are substrates involved in Nedd4-1's mediation of denervation induced muscle atrophy.