Department of Pathology and Laboratory Medicine, University of British Columbia - The Heart + Lung Institute - St. Paul's Hospital, Vancouver, Canada.
Cell Microbiol. 2012 Jan;14(1):133-46. doi: 10.1111/j.1462-5822.2011.01708.x. Epub 2011 Nov 10.
The IRG protein Irgm3 preserves cell survival during coxsackievirus B3 (CVB3) infection. However, the molecular mechanisms are not clear. Here, we examined the effect of Irgm3 expression on ER stress triggered by pharmacological agents or CVB3 infection. In Tet-On/Irgm3 HeLa cells, Irgm3 expression suppressed either chemical- or CVB3-induced upregulation of glucose-regulated protein 78. Further, Irgm3 strongly inhibited the activation of both the PERK and ATF6 pathways of ER stress responses, which further led to the diminished phosphorylation of eIF2α, reduced cleavage/activation of transcription factor SREBP1 and attenuated induction of proapoptotic genes CHOP and GADD34. These data were further supported by experiments using Irgm3 knockout mouse embryonic fibroblasts, in which the ER stress induced by CVB3 was not relieved due to the lack of Irgm3 expression. In addition, the tunicamycin-triggered ER stress promoted the subsequent CVB3 infection. The effect of Irgm3 on ER stress and CVB3 infection was diminished by the PI3K inhibitor, LY294002, while inhibitors of ERK, JNK and p38 had no effect. These data were further corroborated by transfection of cells with a dominant negative Akt. Taken together, these data suggest that Irgm3 relieves the ER stress response via a PI3K/Akt dependent mechanism, which contributes to host defence against CVB3 infection.
IRG 蛋白 Irgm3 在柯萨奇病毒 B3（CVB3）感染期间保持细胞存活。然而，其分子机制尚不清楚。在这里，我们研究了 Irgm3 表达对药理学试剂或 CVB3 感染引发的 ER 应激的影响。在 Tet-On/Irgm3 HeLa 细胞中，Irgm3 表达抑制了化学诱导或 CVB3 诱导的葡萄糖调节蛋白 78 的上调。此外，Irgm3 强烈抑制 ER 应激反应中 PERK 和 ATF6 途径的激活，这进一步导致 eIF2α 的磷酸化减少，转录因子 SREBP1 的切割/激活减少，以及促凋亡基因 CHOP 和 GADD34 的诱导减弱。这些数据进一步得到了 Irgm3 敲除小鼠胚胎成纤维细胞实验的支持，由于缺乏 Irgm3 表达，CVB3 引起的 ER 应激在这些细胞中未得到缓解。此外，衣霉素引发的 ER 应激促进了随后的 CVB3 感染。PI3K 抑制剂 LY294002 减弱了 Irgm3 对 ER 应激和 CVB3 感染的作用，而 ERK、JNK 和 p38 的抑制剂则没有作用。这些数据进一步通过转染细胞中的显性失活 Akt 得到证实。总之，这些数据表明，Irgm3 通过一种依赖于 PI3K/Akt 的机制缓解 ER 应激反应，这有助于宿主抵抗 CVB3 感染。
