ABSTRACT
The high altitude/hypoxic environment induced skeletal muscle atrophy is considered to be the interaction of multi-system and multi-organ, but the direct mechanism of hypoxia on muscle cells in this process is not clear. This study intended to investigate the effects of hypoxia exposure on proteins in ubiquitin and autophagy pathways, and explored the possible mechanism of hypoxia induced change of myotube diameter. The expression of myosin, hypoxia inducible factor-1 α (HIF-1α), forkhead box protein O1 (FoxO1), and ubiquitin protease pathway (MuRF1 and Atrogin1) and autophagy lysosomal pathway (p62, Beclin1, LC3) related proteins were detected by Western blot; The integrated optical density (IOD) of Myosin and LC3 was detected by IF. The results showed that the diameters of myotube at 6 h and 12 h were significantly reduced, and the expression of myosin was significantly reduced at 6 h after hypoxia exposure (P<0. 05); the protein levels of HIF-1α and FoxO1 were significantly increased at 6 h (P<0. 05); The expression of MuRF1 in each time points of hypoxia was significantly higher than 0 h (P<0. 05), but no difference of Atrogin1 expression was detected; Compared with 0 h, the expression of p62 was reduced significantly in response to hypoxia. The protein expression of Beclin1 and the IOD of LC3 was increased significantly at 6 h, and the LC3Ⅱ/Ⅰ ratio was significantly higher at 6 h, but significantly lower at 12 h and 24 h (P<0. 05).The results above indicated that the reduction of the myotube diameter of L6 skeletal muscle cells was induced by hypoxia exposure (1% O
ABSTRACT
OBJECTIVE: To explore the effects of human A30P mutant α-synuclein (α-syn) on autophagy lysosome pathway and ubiquitin proteasome system. METHODS: Constructing stable cell lines expressing human A30P mutant α-syn in PC12 cells, and detecting the levels of autophagy related proteins LC3-II and p62 as well as ubiquitinated proteins. Furthermore, the influence of A30P mutant α-syn on cell viability upon normal and stress conditions was conducted by MTT assay. RESULTS: Expressing A30P mutant α-syn could significantly reduce autophagy related protein LC3-II level and increase level of autophagy substrate p62, as well as promote aggregation of ubiquitinated proteins. Otherwise, expressing A30P mutant α-syn did not reduce cell viability under normal conditions. However, cell viability was significantly reduced under treatment with neurotoxin rotenone or serum free condition in A30P mutant α-syn groups compared with empty vector group. CONCLUSION: Over expression of human A30P mutant α-syn could impair the protein degradation system and increase the sensitivity of cells to toxic insults.