17-DMAG이 마우스 골격근에서 autophagy flux에 미치는 영향

Abstract

The purpose of this study was to determine if heat shock proteins are involved in autophagy in skeletal muscle. We used the autophagy flux strategy, which is an LC3 II/p62 turnover assay conducted with and without an autophagy inhibitor, to determine whether 17-DMAG (an Hsp90 inhibitor/Hsp72 activator) stimulates autophagy in skeletal muscle. We treated C2C12 cells with 17-DMAG (500 nM) for 24 hr with and without the autophagy inhibitor (Bafilomycin A1, 200 ng/ml), and we injected C57BL/6 mice i.p. with 17-DMAG (10 mg/kg) daily for 7 days with and without colchicine as an autophagy inhibitor (0.4 mg/kg/day, administered on the last 2 days). C2C12 myotubes and tibialis anterior muscles were harvested for analysis of mTOR-dependent autophagy signaling pathway proteins and autophagic marker proteins (p62 and LC3 II) by Western blot analysis. The blots showed that 17-DMAG upregulated hsp72 and decreased Akt protein levels and S6 phosphorylation in C2C12 cells. However, an in vitro autophagic flux assay demonstrated that 17-DMAG did not increase LC3 II and p62 protein concentrations to a greater extent than Bafilomycin A1 treatment alone. Similarly, 17DMAG increased Hsp72 protein levels and decreased the expression of Akt and the phosphorylation of S6 in mouse skeletal muscle. However, unlike the response seen in C2C12 myotubes, the p62 protein levels were significantly decreased in 17-DMAG-treated mouse skeletal muscle (~50%; p<0.05). The LC3 II protein levels in 17-DMAG-treated mice were increased ~2-fold more when degradation was inhibited by colchicine (p<0.01). This suggests that 17-DMAG stimulates basal autophagy in skeletal muscle but is not found in C2C12 myotubes.