Shenzhen Key Laboratory of Marine Biotechnology and Ecology, Department of Marine Biology, Shenzhen University, Shenzhen 518060, China; Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China.
College of Life Sciences and Oceanography, Shenzhen Key Laboratory of Microbial Genetic Engineering, Shenzhen University, Shenzhen 518060, China.
Neurotoxicology. 2018 Sep;68:25-37. doi: 10.1016/j.neuro.2018.07.004. Epub 2018 Jul 10.
Severity or duration of endoplasmic reticulum (ER) stress leads to two different cellular events: cell survival and apoptosis. Drug-induced ER stress or neurotoxicity has been observed as one of the main side effects. However, how ER stress affects cellular signaling cascades leading to neuronal damage is still not well understood. In this study, the toxicological mechanisms of two typical ER stress inducers, tunicamycin (Tm) and dithiothreitol (DTT), were investigated by cell viability, unfolded protein response, apoptosis and proteomic responses in mouse neuro-2a cells. A large portion of differentially expressed proteins (DEPs) that participate in protein synthesis and folding were identified in the Tm treated group, indicating adaptive cellular responses like the unfolded protein response were activated, which was not the case in the DTT treated group. Interestingly, KEGG pathway analysis and validation experiments revealed that proteins involved in proteasomal degradation were down-regulated by both inducers, while proteins involved in ubiquitination were up-regulated by Tm and down-regulated by DTT. A protein responsible for delivering ubiquitinated proteins to the proteasome, the UV excision repair protein RAD23 homolog A (HR23 A), was discovered as a DEP altered by both Tm and DTT. This protein was down-regulated in the Tm treated group and up-regulated in the DTT treated group, which explained the differences we observed in the ubquintination and proteasomal degradation pathways. Autophagy was activated in the Tm treated group, suggesting that it may serve as a compensatory effect to proteasomal degradation. Our work provides new insights into the neurotoxicity generated by various ER stress inducers and the underlying mechanisms.
内质网 (ER) 应激的严重程度或持续时间会导致两种不同的细胞事件：细胞存活和细胞凋亡。已观察到药物诱导的 ER 应激或神经毒性是主要副作用之一。然而，内质网应激如何影响导致神经元损伤的细胞信号级联仍不清楚。在这项研究中，通过细胞活力、未折叠蛋白反应、凋亡和蛋白质组学反应，研究了两种典型内质网应激诱导剂——衣霉素 (Tm) 和二硫苏糖醇 (DTT) 在鼠神经-2a 细胞中的毒理学机制。在 Tm 处理组中鉴定出大量参与蛋白质合成和折叠的差异表达蛋白 (DEP)，表明激活了适应性细胞反应，如未折叠蛋白反应，但在 DTT 处理组中并非如此。有趣的是，KEGG 通路分析和验证实验表明，两种诱导剂均下调参与蛋白酶体降解的蛋白质，而 Tm 上调参与泛素化的蛋白质，下调 DTT 上调的蛋白质。一种负责将泛素化蛋白递送到蛋白酶体的蛋白质，即紫外线切除修复蛋白 RAD23 同源物 A (HR23A)，被发现是 Tm 和 DTT 改变的 DEP。该蛋白在 Tm 处理组中下调，在 DTT 处理组中上调，这解释了我们在泛素化和蛋白酶体降解途径中观察到的差异。自噬在 Tm 处理组中被激活，表明它可能作为蛋白酶体降解的补偿作用。我们的工作为各种内质网应激诱导剂产生的神经毒性及其潜在机制提供了新的见解。
