Figure 3
Local expression of SOD1G93A induces muscle atrophy via the negative modulation of the Akt pathway. (A-C) Immunoblot analysis (n = 5) of total Akt and the phosphorylated form of Akt, mammalian target of rapamycin (mTOR) and p70S6K proteins in muscles of 4-month-old control (WT) and MLC/SOD1G93A mice. (A) Akt phosphorylation (pAkt) was significantly reduced in MLC/SOD1G93A muscle, with a slight change in total Akt levels compared to WT muscle. Right: Densitometric analysis of the ratio between total Akt and the phosphorylated form of Akt. (B and C) The phosphorylation levels of the downstream Akt intermediates, (B) mTOR and (C) p70S6K, resulted in significant downmodulation in the muscle of MLC/SOD1G93A mice. Right: Densitometric analysis of five separate immunoblot experiments showing the ratio between total and phosphorylated forms of (B) mTOR and (C) p70S6K expression. (D and E) Representative Western blot analysis of (D) forkhead box O1 (FoxO1) (n = 5) and (E) FoxO3 (n = 3) expression in muscles of both WT and MLC/SOD1G93A transgenic mice. Right: Densitometric analysis for FoxO1 and FoxO3 expression. Immunoblotting for α-tubulin served as a control for protein loading. *P < 0.05. Mean values ± SEM for pAkt/Akt: WT = 1.48 ± 0.14 and MLC/SOD1G93A = 0.66 ± 0.12. Mean values ± SEM for pmTOR/mTOR: WT = 5.21 ± 0.88 and MLC/SOD1G93A = 2.65 ± 0.73. Mean values ± SEM for p-p70/p70: WT = 1.21 ± 0.12 and MLC/SOD1G93A = 0.64 ± 0.08. Mean values ± SEM for FoxO1: WT = 0.35 ± 0.01 and MLC/SOD1G93A = 0.35 ± 0.15. Mean values ± SEM for FoxO3: WT = 0.37 ± 0.19 and MLC/SOD1G93A = 1 ± 0.47.