Le Hien Thi, Kim Yonghwan, Kim Mi-Jeong, Hyun Seung Hwa, Kim Hyeeun, Chung Su Wol, Joe Yeonsoo, Chung Hun Taeg, Shin Dong-Myung, Back Sung Hoon
School of Biological Sciences, University of Ulsan, Ulsan 44610, Korea.
Department of Cell and Genetic Engineering, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505, Korea.
Mol Cells. 2025 May;48(5):100210. doi: 10.1016/j.mocell.2025.100210. Epub 2025 Mar 13.
eIF2α Phosphorylation helps maintain cellular homeostasis and overcome endoplasmic reticulum (ER) stress through transcriptional and translational reprogramming. This study aims to elucidate the transcriptional regulation of glutathione (GSH) and nicotinamide adenine dinucleotide phosphate hydrogen (NADPH) homeostasis through eIF2α phosphorylation and its impact on cell death during ER stress. eIF2α phosphorylation-deficient (A/A) cells exhibited decreased expression of multiple genes involved in GSH synthesis and NADPH production, leading to an exacerbated depletion of both cellular and mitochondrial GSH, as well as mitochondrial NADPH, during ER stress. Impaired GSH homeostasis resulted from deficient expression of ATF4 and/or its dependent factor, Nrf2, which are key transcription factors in the antioxidant response during ER stress. In contrast, the exacerbation of NADPH depletion may primarily be attributed to the dysregulated expression of mitochondrial serine-driven 1-carbon metabolism pathway genes, which are regulated by an unidentified eIF2α phosphorylation-dependent mechanism during ER stress. Moreover, the eIF2α phosphorylation-ATF4 axis was responsible for upregulation of ferroptosis-inhibiting genes and downregulation of ferroptosis-activating genes upon ER stress. Therefore, ER stress strongly induced ferroptosis of A/A cells, which was significantly inhibited by treatments with cell-permeable GSH and the ferroptosis inhibitor ferrostatin-1. ATF4 overexpression suppressed impairment of GSH homeostasis in A/A cells during ER stress by promoting expression of downstream target genes. Consequently, ATF4 overexpression mitigated ferroptosis as well as apoptosis of A/A cells during ER stress. Our findings underscore the importance of eIF2α phosphorylation in maintaining GSH/NADPH homeostasis and inhibiting ferroptosis through ATF4 and unidentified eIF2α phosphorylation-dependent target(s)-mediated transcriptional reprogramming during ER stress.
真核生物翻译起始因子2α（eIF2α）磷酸化通过转录和翻译重编程有助于维持细胞内稳态并克服内质网（ER）应激。本研究旨在阐明通过eIF2α磷酸化对谷胱甘肽（GSH）和烟酰胺腺嘌呤二核苷酸磷酸（NADPH）内稳态的转录调控及其在ER应激期间对细胞死亡的影响。eIF2α磷酸化缺陷（A/A）细胞表现出参与GSH合成和NADPH产生的多个基因表达降低，导致在ER应激期间细胞内和线粒体GSH以及线粒体NADPH的消耗加剧。GSH内稳态受损是由于ATF4和/或其依赖因子Nrf2表达不足所致，它们是ER应激期间抗氧化反应中的关键转录因子。相比之下，NADPH消耗加剧可能主要归因于线粒体丝氨酸驱动的一碳代谢途径基因表达失调，这些基因在ER应激期间由一种未知的eIF2α磷酸化依赖机制调控。此外，eIF2α磷酸化-ATF4轴负责在ER应激时上调铁死亡抑制基因并下调铁死亡激活基因。因此，ER应激强烈诱导A/A细胞发生铁死亡，而细胞可渗透的GSH和铁死亡抑制剂铁抑素-1处理可显著抑制这种铁死亡。ATF4过表达通过促进下游靶基因表达抑制了ER应激期间A/A细胞中GSH内稳态的损伤。因此，ATF4过表达减轻了ER应激期间A/A细胞的铁死亡以及凋亡。我们的研究结果强调了eIF2α磷酸化在ER应激期间通过ATF4和未知的eIF2α磷酸化依赖靶点介导的转录重编程来维持GSH/NADPH内稳态和抑制铁死亡的重要性。
