Apoptosis and Cell Survival Research Lab, Department of Biosciences, School of Biosciences and Technology, VIT University, Vellore, Tamil Nadu, India.
PLoS One. 2018 Apr 9;13(4):e0194310. doi: 10.1371/journal.pone.0194310. eCollection 2018.
The endoplasmic reticulum (ER) not only performs its basic function of regulating calcium homeostasis, lipid biosynthesis, folding, modifying and transporting proteins but also plays a decisive role in regulating multiple cellular processes ranging from cell growth and differentiation to apoptosis and autophagy. Disturbances in ER homeostasis initiate the unfolded protein response (UPR) implicated in the pathogenesis of many human diseases. Drugging the UPR components for therapeutic interventions has received considerable attention. The purpose of this study is to identify genes that are previously unsuspected to be regulated under ER stress. Because ER stress-inducible gene expression is majorly regulated under ERSE elements, we screened human genome by adopting an in silico approach using ERSE elements (I, II, III) as probes and identified 337 candidate genes. Having knowledge of the importance of E3 ubiquitin ligase in the ERAD machinery; we validated our preliminary search by focusing on one of the hits i.e. ASB7 gene that encodes E3 ubiquitin ligase. In HeLa cells, we found that pharmacological induction of ER stress led to an increase in the expression of ASB7 with simultaneous activation of UPR pathways. Although knockdown of ASB7 expression leads to significant reduction in GRP78 and CHOP mRNA levels, it did not protect cells from ER stress-induced cell death. Also, an up-regulation in the expression of pro-inflammatory genes like TNF-α and IL-1β in ASB7 knockdown cells was observed under ER stress. Collectively, our findings suggest that ASB7 is regulated under ER stress and this study also identifies several other genes that could apparently be regulated under ER stress.
内质网 (ER) 不仅执行其调节钙稳态、脂质生物合成、折叠、修饰和蛋白质转运的基本功能，而且在调节从细胞生长和分化到细胞凋亡和自噬的多种细胞过程中也起着决定性作用。内质网稳态的紊乱会引发未折叠蛋白反应 (UPR)，这与许多人类疾病的发病机制有关。针对 UPR 成分进行药物干预受到了广泛关注。本研究旨在鉴定以前未被认为受内质网应激调节的基因。由于内质网应激诱导的基因表达主要受 ERSE 元件调控，我们采用 ERSE 元件 (I、II、III) 作为探针的计算方法筛选人类基因组，鉴定出 337 个候选基因。鉴于 E3 泛素连接酶在 ERAD 机制中的重要性；我们通过关注其中一个命中即编码 E3 泛素连接酶的 ASB7 基因，验证了我们的初步搜索。在 HeLa 细胞中，我们发现内质网应激的药理学诱导导致 ASB7 的表达增加，同时激活 UPR 途径。尽管 ASB7 表达的敲低导致 GRP78 和 CHOP mRNA 水平显著降低，但它不能保护细胞免受 ER 应激诱导的细胞死亡。此外，在 ASB7 敲低细胞中，在 ER 应激下观察到促炎基因如 TNF-α 和 IL-1β 的表达上调。总之，我们的研究结果表明，ASB7 受内质网应激调节，本研究还鉴定出其他一些显然受内质网应激调节的基因。
