National Engineering Laboratory for Druggable Gene and Protein Screening, Northeast Normal University, 2555 Jingyue Street, Changchun 130117, China; Laboratory of Chemical Biology and State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022, China.
Key Laboratory of Structure-based Drug Design & Discovery, Ministry of Education, Shenyang Pharmaceutical University, Shenyang 110016, China.
Eur J Pharmacol. 2018 Oct 5;836:75-82. doi: 10.1016/j.ejphar.2018.08.001. Epub 2018 Aug 7.
Endoplasmic reticulum (ER) stress, together with unfolded protein response (UPR), can remove unfolded proteins and promote survival. However, severe and prolonged ER stress leads to cell death, tissue injury, and many serious diseases. Therefore, it is essential to identify drugs that can attenuate ER stress for ER-related disease treatment. A great deal of research shows that selenoprotein S (SelS) is a sensitive and ideal marker of ER stress. Here, we used a firefly luciferase reporter driven by SelS gene promoter to screen natural compounds that can attenuate ER stress. Then we identified compound 20(S)-25-methoxyl-dammarane-3β,12β,20-triol (25-OCH-PPD) could inhibit the promoter activity of SelS, further results showed that 25-OCH-PPD effectively inhibited tunicamycin (TM) induced up-regulation of SelS expression in both mRNA and protein levels. Moreover, 25-OCH-PPD significantly inhibited glucose-regulated protein 78 (GRP78; the major ER stress marker) expression in TM-induced ER stress in HepG2 and HEK293T cells, suggesting that 25-OCH-PPD could attenuate ER stress in these cells. Mechanism studies showed that 25-OCH-PPD significantly activated ERK/MAPK signaling pathway, and the inhibition of ERK/MAPK by U0126 dramatically abolished the inhibitory effect of 25-OCH-PPD on ER stress, suggesting that 25-OCH-PPD attenuated ER stress at least partially through activation of ERK/MAPK signaling pathway. Taken together, our studies indicate that 25-OCH-PPD is a novel small molecular compound reducing ER stress, and a potential drug for treating diseases associated with ER stress.
内质网（ER）应激与未折叠蛋白反应（UPR）一起，可以清除未折叠的蛋白质并促进存活。然而，严重和持久的 ER 应激会导致细胞死亡、组织损伤和许多严重疾病。因此，鉴定可以减轻 ER 相关疾病治疗中 ER 应激的药物是至关重要的。大量研究表明，硒蛋白 S（SelS）是 ER 应激的敏感和理想标志物。在这里，我们使用 SelS 基因启动子驱动的萤火虫荧光素酶报告基因来筛选可以减轻 ER 应激的天然化合物。然后，我们鉴定出化合物 20(S)-25-甲氧基-达玛烷-3β,12β,20-三醇（25-OCH-PPD）可以抑制 SelS 基因启动子的活性，进一步的结果表明，25-OCH-PPD 有效抑制了衣霉素（TM）诱导的 SelS 表达在 mRNA 和蛋白水平上的上调。此外，25-OCH-PPD 显著抑制了 TM 诱导的 HepG2 和 HEK293T 细胞中葡萄糖调节蛋白 78（GRP78；主要的 ER 应激标志物）的表达，表明 25-OCH-PPD 可以减轻这些细胞的 ER 应激。机制研究表明，25-OCH-PPD 显著激活了 ERK/MAPK 信号通路，而 U0126 抑制 ERK/MAPK 则显著消除了 25-OCH-PPD 对 ER 应激的抑制作用，表明 25-OCH-PPD 至少部分通过激活 ERK/MAPK 信号通路来减轻 ER 应激。总之，我们的研究表明，25-OCH-PPD 是一种新型的减轻 ER 应激的小分子化合物，是治疗与 ER 应激相关疾病的潜在药物。
