Read Danielle E, Gupta Ananya, Cawley Karen, Fontana Laura, Agostinis Patrizia, Samali Afshin, Gupta Sanjeev
Discipline of Pathology, Cancer Progression and Treatment Research Group, Lambe Institute for Translational Research, School of Medicine, National University of Ireland-Galway, H91 TK33 Galway, Ireland.
Discipline of Physiology, School of Medicine, National University of Ireland-Galway, H91 TK33 Galway, Ireland.
Life (Basel). 2021 Jan 6;11(1):30. doi: 10.3390/life11010030.
An important event in the unfolded protein response (UPR) is activation of the endoplasmic reticulum (ER) kinase PERK. The PERK signalling branch initially mediates a prosurvival response, which progresses to a proapoptotic response upon prolonged ER stress. However, the molecular mechanisms of PERK-mediated cell death are not well understood. Here we show that expression of the primary miR-17-92 transcript and mature miRNAs belonging to the miR-17-92 cluster are decreased during UPR. We found that miR-17-92 promoter reporter activity was reduced during UPR in a PERK-dependent manner. Furthermore, we show that activity of the miR-17-92 promoter is repressed by ectopic expression of ATF4 and NRF2. Promoter deletion analysis mapped the region responding to UPR-mediated repression to a site in the proximal region of the miR-17-92 promoter. Hypericin-mediated photo-oxidative ER damage reduced the expression of miRNAs belonging to the miR-17-92 cluster in wild-type but not in PERK-deficient cells. Importantly, ER stress-induced apoptosis was inhibited upon miR-17-92 overexpression in SH-SY5Y and H9c2 cells. Our results reveal a novel function for ATF4 and NRF2, where repression of the miR-17-92 cluster plays an important role in ER stress-mediated apoptosis. Mechanistic details are provided for the potentiation of cell death via sustained PERK signalling mediated repression of the miR-17-92 cluster.
未折叠蛋白反应（UPR）中的一个重要事件是内质网（ER）激酶PERK的激活。PERK信号分支最初介导一种促生存反应，在长时间内质网应激时会转变为促凋亡反应。然而，PERK介导的细胞死亡的分子机制尚不清楚。在这里，我们表明在UPR过程中，初级miR-17-92转录本和属于miR-17-92簇的成熟miRNA的表达会降低。我们发现，在UPR过程中，miR-17-92启动子报告基因活性以PERK依赖的方式降低。此外，我们表明，ATF4和NRF2的异位表达会抑制miR-17-92启动子的活性。启动子缺失分析将响应UPR介导的抑制的区域定位到miR-17-92启动子近端区域的一个位点。金丝桃素介导的光氧化内质网损伤降低了野生型细胞中属于miR-17-92簇的miRNA的表达，但在PERK缺陷型细胞中则没有。重要的是，在SH-SY5Y和H9c2细胞中，miR-17-92过表达可抑制内质网应激诱导的细胞凋亡。我们的结果揭示了ATF4和NRF2的一种新功能，即miR-17-92簇的抑制在ER应激介导的细胞凋亡中起重要作用。通过持续的PERK信号介导的miR-17-92簇的抑制来增强细胞死亡的机制细节也已给出。
