Kuang Xiu-Li, Liu Yimei, Chang Yuhua, Zhou Jing, Zhang He, Li Yiping, Qu Jia, Wu Shengzhou
School of Optometry and Ophthalmology and the Eye Hospital, Wenzhou Medical University, 270 Xueyuan Road, Wenzhou, Zhejiang 325003, PR China; Cultivation Base and Key Laboratory of Vision Science, Ministry of Health and Zhejiang Provincial Key Laboratory of Ophthalmology and Optometry, Wenzhou Medical University, 270 Xueyuan Road, Wenzhou, Zhejiang 325003, PR China.
Laboratory of Molecular Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, PR China.
Cell Calcium. 2016 Apr;59(4):172-80. doi: 10.1016/j.ceca.2016.01.007. Epub 2016 Mar 3.
Dysfunction of the ubiquitin-proteasome system (UPS) and calcium homeostasis has been implicated in the neurodegeneration of Alzheimer's and Parkinson's diseases. The cytosolic calcium concentration is maintained by store-operated calcium entry (SOCE), which is repressed by Alzheimer's disease-associated mutants, such as mutant presenilins. We hypothesized that inhibition of UPS impacts SOCE. This study showed that pretreatment with sub-lethal levels of proteasome inhibitors, including MG-132 and clasto-lactacystin-β-lactone (LA), reduced SOCE after depletion of endoplasmic reticulum calcium in rat neurons. With the same treatment, MG-132 and LA reduced the protein levels of stromal interaction molecule 1and 2 (STIM1/2), but not the levels of Orai1 and canonical transient receptor potential channel 1 (TRPC1). STIM1 or STIM2 protein was mobilized to lysosome by MG-132/LA treatment as observed under an immunofluorescence confocal laser microscope. In the neurons, MG-132 and LA degraded p62/SQSTM1, promoted autophagy, converted LC3I to LC3II, and promoted co-localization of LC3 and lysosomes. Rapamycin, which enhances autophagy, reduced STIM1/2 protein levels, whereas bafilomycin, which inhibits autophagy, increased their protein levels. The protein levels of STIM1/2 and the amplitude of SOCE were decreased in SH-SY5Y with decreased protein level of proteasome subunit beta type-5 induced by shRNA. We conclude that sub-lethal levels of proteasome inhibition reduce SOCE and promote autophagy-mediated degradation of STIM1/2. UPS inhibition, a common finding in neurodegenerative diseases, interferes with calcium homeostasis via repression of SOCE.
泛素 - 蛋白酶体系统（UPS）功能障碍和钙稳态失衡与阿尔茨海默病和帕金森病的神经退行性变有关。胞质钙浓度由储存 - 操作性钙内流（SOCE）维持，而SOCE会受到阿尔茨海默病相关突变体（如早老素突变体）的抑制。我们推测UPS的抑制会影响SOCE。本研究表明，用亚致死水平的蛋白酶体抑制剂（包括MG - 132和克拉托乳胞素 - β - 内酯（LA））预处理大鼠神经元后，在内质网钙耗尽后可降低SOCE。同样的处理方式下，MG - 132和LA降低了基质相互作用分子1和2（STIM1/2）的蛋白水平，但不影响Orai1和典型瞬时受体电位通道1（TRPC1）的水平。如免疫荧光共聚焦激光显微镜下观察到的，MG - 132/LA处理可使STIM1或STIM2蛋白转运至溶酶体。在神经元中，MG - 132和LA降解p62/SQSTM1，促进自噬，将LC3I转化为LC3II，并促进LC3与溶酶体的共定位。增强自噬的雷帕霉素降低了STIM1/2蛋白水平，而抑制自噬的巴佛洛霉素则增加了它们的蛋白水平。在通过shRNA诱导蛋白酶体亚基β5型蛋白水平降低的SH - SY5Y细胞中，STIM1/2蛋白水平和SOCE幅度均下降。我们得出结论，亚致死水平的蛋白酶体抑制可降低SOCE并促进自噬介导的STIM1/2降解。UPS抑制是神经退行性疾病中的常见现象，它通过抑制SOCE干扰钙稳态。
