Figure 3.

SGK-1 inhibits activation of Atrogin1 and MuRF1 via FoxO and Smad2/3 signaling pathways. (A) Representative Western blot indicates levels of signaling proteins in TA muscles of WT and SGK-1-KO mice after 4 weeks. (n=5 per group). (B) C2C12 cells were transfected with either an siRNA against SGK-1 or dominant negative FoxO1/FoxO3a plasmids; they then were treated with the cytokine cocktail. Atrogin1 and MuRF1 mRNAs were analyzed by RT-PCR. (C) Western blots analysis of Smad2/3 expression and phosphorylation in muscles of control and CKD in WT and SGK-1-KO mice (n=5). (D) C2C12 cells were transfected with control or SGK-1 siRNA, or (E) they were infected with control or AdSGK-1 adenovirus; the TGF-β1 addition (2 ng/ml at 30 minutes) induced pSmad2/3. (F) C2C12 cells were treated as indicated, and Atrogin1 and MuRF1 were determined by RT-PCR. CTL, control; DN, dominant negative; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; siRNA, short interfering RNA. *P<0.05 versus control; ^#P<0.05 versus control siRNA; ^‡P<0.05 versus SGK-1 siRNA only (n=3 repeats).