Gu Yong, Lee Waisin, Shen Jiangang
School of Chinese Medicine, the University of Hong Kong, Hong Kong SAR, P. R. China.
1] School of Chinese Medicine, the University of Hong Kong, Hong Kong SAR, P. R. China [2] Research Center of Heart, Brain, Hormone &Healthy Aging, The University of Hong Kong, Hong Kong SAR, P. R. China.
Sci Rep. 2014 Sep 3;4:6268. doi: 10.1038/srep06268.
Site-2 protease (S2P) is a membrane-embedded protease that site-specifically cleaves intramembrane transcription factors, a necessary step for their maturation. S2P is well known to regulate cholesterol biosynthesis and endoplasmic reticulum stress in mammalian cells. In this study, we hypothesized that S2P could be responsible for the regulation of cellular oxidative injury under oxidative stress. Wild type Chinese hamster ovary (WT CHO) cells and their mutant M19 cells with defective S2P gene were exposed to different oxidative stress conditions. Results showed that oxidative stress significantly up-regulated S2P expression in WT CHO cells. Notably, M19 cells had remarkably higher level of superoxide and elevated rates of cell death than WT CHO cells. The vulnerability to oxidative stress was reversed by the transfection of S2P gene but not rescued by exogenous supplement of cholesterol, oleate, and mevalonate, indicating that lack of S2P gene leads cells to be more vulnerable to oxidative stress. Furthermore, compared with WT CHO cells, M19 cells had higher nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity and lower paraoxonase-2 expression. Taken together, these results suggest that S2P can be a protease responding to oxidative stress and has the function of regulating cellular oxidative injury.
2号位点蛋白酶（S2P）是一种膜嵌入蛋白酶，可对膜内转录因子进行位点特异性切割，这是其成熟的必要步骤。众所周知，S2P在哺乳动物细胞中调节胆固醇生物合成和内质网应激。在本研究中，我们假设S2P可能在氧化应激下负责调节细胞氧化损伤。将野生型中国仓鼠卵巢（WT CHO）细胞及其S2P基因缺陷的突变体M19细胞暴露于不同的氧化应激条件下。结果表明，氧化应激显著上调了WT CHO细胞中S2P的表达。值得注意的是，M19细胞中的超氧化物水平显著高于WT CHO细胞，细胞死亡率也更高。转染S2P基因可逆转对氧化应激的易感性，但补充外源性胆固醇、油酸和甲羟戊酸并不能挽救这种情况，这表明缺乏S2P基因会使细胞更容易受到氧化应激的影响。此外，与WT CHO细胞相比，M19细胞具有更高的烟酰胺腺嘌呤二核苷酸磷酸（NADPH）氧化酶活性和更低的对氧磷酶-2表达。综上所述，这些结果表明S2P可能是一种对氧化应激作出反应的蛋白酶，具有调节细胞氧化损伤的功能。
