Department of Pediatrics, School of Medicine and Public Health, University of Wisconsin, Madison, WI 53792, USA.
J Immunol. 2012 Nov 1;189(9):4630-9. doi: 10.4049/jimmunol.1102737. Epub 2012 Oct 1.
IFN regulatory factor 3 (IRF3) regulates early type I IFNs and other genes involved in innate immunity. We have previously shown that cells undergoing an endoplasmic reticulum (ER) stress response called the unfolded protein response produce synergistically augmented IFN-β when stimulated with pattern recognition receptor agonists such as LPS. Concomitant ER stress and LPS stimulation resulted in greater recruitment of the IRF3 transcription factor to ifnb1 gene regulatory elements. In this study, we used murine cells to demonstrate that both oxygen-glucose deprivation and pharmacologic unfolded protein response inducers trigger phosphorylation and nuclear translocation of IRF3, even in the absence of exogenous LPS. Different ER stressors used distinct mechanisms to activate IRF3: IRF3 phosphorylation due to calcium-mobilizing ER stress (thapsigargin treatment, oxygen-glucose deprivation) critically depended upon stimulator of IFN gene, an ER-resident nucleic acid-responsive molecule. However, calcium mobilization alone by ionomycin was insufficient for IRF3 phosphorylation. In contrast, other forms of ER stress (e.g., tunicamycin treatment) promote IRF3 phosphorylation independently of stimulator of IFN gene and TANK-binding kinase 1. Rather, IRF3 activation by tunicamycin and 2-deoxyglucose was inhibited by 4-(2-aminoethyl)-benzenesulfonyl fluoride hydrochloride, a serine protease inhibitor that blocks activating transcription factor 6 processing. Interfering with ER stress-induced IRF3 activation abrogated IFN-β synergy. Together, these data suggest ER stress primes cells to respond to innate immune stimuli by activating the IRF3 transcription factor. Our results also suggest certain types of ER stress accomplish IRF3 phosphorylation by co-opting existing innate immune pathogen response pathways. These data have implications for diseases involving ER stress and type I IFN.
IFN 调节因子 3（IRF3）调节早期 I 型 IFN 和其他参与固有免疫的基因。我们之前已经表明，经历内质网（ER）应激反应（称为未折叠蛋白反应）的细胞在用模式识别受体激动剂（如 LPS）刺激时会产生协同增强的 IFN-β。同时的 ER 应激和 LPS 刺激导致 IRF3 转录因子更大量地募集到 ifnb1 基因调控元件。在这项研究中，我们使用鼠细胞证明，氧葡萄糖剥夺和药理学未折叠蛋白反应诱导物都可触发 IRF3 的磷酸化和核转位，即使在没有外源性 LPS 的情况下也是如此。不同的 ER 应激源使用不同的机制来激活 IRF3：由于钙动员 ER 应激（他普西庚处理、氧葡萄糖剥夺）引起的 IRF3 磷酸化严重依赖于 IFN 基因刺激物，这是一种内质网驻留的核酸反应分子。然而，离子霉素引起的钙动员本身不足以引起 IRF3 磷酸化。相比之下，其他形式的 ER 应激（例如，衣霉素处理）独立于 IFN 基因刺激物和 TANK 结合激酶 1 促进 IRF3 磷酸化。相反，衣霉素和 2-脱氧葡萄糖对 IRF3 的激活被 4-(2-氨乙基）-苯磺酰氟盐酸盐抑制，这是一种丝氨酸蛋白酶抑制剂，可阻断激活转录因子 6 的加工。干扰 ER 应激诱导的 IRF3 激活会破坏 IFN-β 的协同作用。总的来说，这些数据表明 ER 应激通过激活 IRF3 转录因子使细胞对先天免疫刺激物做出反应。我们的结果还表明，某些类型的 ER 应激通过利用现有的先天免疫病原体反应途径来完成 IRF3 磷酸化。这些数据对于涉及 ER 应激和 I 型 IFN 的疾病具有重要意义。
