Yuan Jiaming, Yao Chenjuan, Tang Jing, Liu Yingqi, Huang Chunyan, Yu Shali, Wei Haiyan, Han Yu, Chen Gang
Department of Occupational Medicine and Environmental Toxicology, College of Public Health, Nantong University, Nantong, Jiangsu, 226019, China.
Department of Molecular Oral Physiology, Institute of Health Biosciences, University of Tokushima Graduate School, Tokushima-Shi, Tokushima, 770-8504, Japan.
Toxicology. 2021 Oct;462:152962. doi: 10.1016/j.tox.2021.152962. Epub 2021 Sep 21.
Inorganic arsenic is widely present in the environment. Exposure to moderate to high concentrations of arsenic from drinking water or air can cause various cancers and multisystem dysfunction. Glucose-regulated protein 78 (GRP78) is an endoplasmic reticulum (ER) stress sensor of unfolded protein response (UPR) under stress conditions and it enhances cell survival. The aim of this study is to investigate molecular mechanisms of arsenic-induced GRP78 expression in BEAS-2B cells model. We found that GRP78 protein expression was enhanced, while the level of GRP78 mRNA expression did not change under arsenic trioxide (AsO)-induced ER stress condition in BEAS-2B cells. Cycloheximide, a protein synthesis inhibitor, completely inhibited AsO-induced GRP78 protein expression. GRP78 mRNA expression was inhibited by actinomycin-D (Act-D). However, GRP78 protein expression was upregulated in the presence of Act-D under AsO-induced ER stress condition. These data indicated that the upregulation of GRP78 protein under AsO-induced UPR condition was possibly due to the increased biosynthesis of GRP78 protein. Moreover, both inositol-requiring enzyme 1α (IRE1α) RNase and kinase inhibitor KIRA6 and IRE1α kinase inhibitor APY29 completely inhibited AsO-induced GRP78 protein expression and phosphorylation of JNK, ERK and p38 MAPK. Activation of apoptotic signaling kinase 1 (ASK1) is a downstream effector of IRE1α kinase. ASK1 inhibitor selonsertib and p38 MAPK inhibitor SB203580 partially inhibited AsO-induced GRP78 protein expression, respectively. Our results suggested that AsO enhanced GRP78 protein expression in BEAS-2B cells via IRE1α kinase/ASK1/p38 MAPK signaling pathway. To our knowledge, this is the first report on illuminating the related mechanisms of increased GRP78 protein expression in AsO-induced ER stress condition through a novel IRE1α pathway.
无机砷广泛存在于环境中。通过饮用水或空气接触中等至高浓度的砷会导致各种癌症和多系统功能障碍。葡萄糖调节蛋白78（GRP78）是应激条件下未折叠蛋白反应（UPR）的内质网（ER）应激传感器，可增强细胞存活能力。本研究的目的是探讨在BEAS-2B细胞模型中砷诱导GRP78表达的分子机制。我们发现，在三氧化二砷（AsO）诱导的BEAS-2B细胞内质网应激条件下，GRP78蛋白表达增强，而GRP78 mRNA表达水平未发生变化。蛋白质合成抑制剂环己酰亚胺完全抑制了AsO诱导的GRP78蛋白表达。放线菌素D（Act-D）抑制了GRP78 mRNA表达。然而，在AsO诱导的内质网应激条件下，存在Act-D时GRP78蛋白表达上调。这些数据表明，在AsO诱导的UPR条件下GRP78蛋白的上调可能是由于GRP78蛋白生物合成增加所致。此外，肌醇需求酶1α（IRE1α）核糖核酸酶和激酶抑制剂KIRA6以及IRE1α激酶抑制剂APY29完全抑制了AsO诱导的GRP78蛋白表达以及JNK、ERK和p38丝裂原活化蛋白激酶（MAPK）的磷酸化。凋亡信号激酶1（ASK1）的激活是IRE1α激酶的下游效应器。ASK1抑制剂塞洛西布和p38 MAPK抑制剂SB203580分别部分抑制了AsO诱导的GRP78蛋白表达。我们的结果表明，AsO通过IRE1α激酶/ASK1/p38 MAPK信号通路增强了BEAS-2B细胞中GRP78蛋白的表达。据我们所知，这是首次通过一条新的IRE1α途径阐明AsO诱导的内质网应激条件下GRP78蛋白表达增加相关机制的报告。
