Figure 5

MST1 phosphorylates FOXO3a at Ser207 during muscle atrophy. A. Representative western blotting of MST1/2 and FOXO3a in atrophic TA muscles. B. Phosphorylation of FOXO3a at serine 207 by MST1 kinase was increased (by 29.5% ± 7.40%) in WT TA muscles but not in MST1 deficient muscles at denervation Day 3. FOXO3a Ser207 phosphorylation was decreased both in WT and MST1 KO muscles at Day 7 after denervation. C. Total FOXO3a protein level was continuously increased at Day 3 and Day 7 after denervation in WT TA muscles. D and E. Both the expression levels of MST1 and MST2 kinases were increased in atrophic muscles. MST2 protein levels were similarly increased in wild type and MST1 deficient muscles and WT muscles after denervation. At Dday 7 after denervation, comparing with the contralateral, the protein levels of MST2 kinase were increased 2.91 ± 0.15 and 2.92 ± 0.10 folds in the atrophic TA muscles obtained from WT and MST1 KO mice, respectively. * P < 0.05 by two-tailed Student's test.