The Orphan Nuclear Receptor NR4A1 Protects Pancreatic β-Cells from Endoplasmic Reticulum (ER) Stress-mediated Apoptosis.
The Orphan Nuclear Receptor NR4A1 Protects Pancreatic β-Cells from Endoplasmic Reticulum (ER) Stress-mediated Apoptosis.
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孤儿核受体 NR4A1 保护胰腺 β 细胞免受内质网 (ER) 应激介导的细胞凋亡
DOI：
10.1074/jbc.m115.654863
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发表时间：
2015-08-21
期刊：
影响因子：
--
通讯作者：
Wang X
中科院分区：
文献类型：
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作者：
Yu C;Cui S;Zong C;Gao W;Xu T;Gao P;Chen J;Qin D;Guan Q;Liu Y;Fu Y;Li X;Wang X
背景：NR 4A 1是否在内质网应激诱导的β细胞凋亡中发挥作用尚不清楚。结果如下：在ER应激诱导剂处理后，β细胞或胰岛中NR 4A 1表达与Survivin表达呈正相关，与CHOP表达和凋亡率呈负相关。结论：NR 4A 1可能通过上调Survivin和下调CHOP的表达，保护β细胞免受内质网应激诱导的凋亡。意义：我们的发现为预防糖尿病提供了线索。NR 4A 1在细胞凋亡中的作用是有争议的。胰腺β细胞通常在不利条件下面临内质网（ER）应激，如高游离脂肪酸（FFA）浓度和持续高血糖症。严重的内质网应激导致β细胞凋亡。本研究的目的是分析NR 4A 1在内质网应激介导的β细胞凋亡中的作用及其相关机制。我们证实，在用ER应激诱导剂毒胡萝卜素（TG）或棕榈酸（PA）处理后，MIN 6细胞和小鼠胰岛中NR 4A 1的mRNA和蛋白水平迅速增加。MIN 6细胞中NR 4A 1过表达可抵抗TG或PA诱导的细胞丢失，如MTT（3-（4，5-二甲基噻唑-2-基）-2，5-二苯基四唑溴化物）测定所评估的，TUNEL测定表明NR 4A 1过表达也可保护ER应激诱导的细胞凋亡。这一结论通过利用siRNA敲低MIN 6细胞中NR 4A 1表达或利用NR 4A 1敲除小鼠的实验进一步证实。MIN 6细胞中NR 4A 1过表达可降低TG或PA诱导的C/EBP同源蛋白（CHOP）表达和Caspase 3激活。NR 4A 1在MIN 6细胞或小鼠胰岛中的过表达导致Survivin上调。在Survivin启动子（−1872 bp至−1866 bp）中鉴定了一个关键调控元件，具有推定的NR 4A 1结合位点; ChIP分析表明NR 4A 1与Survivin启动子物理缔合。综上所述，NR 4A 1通过上调Survivin表达和下调CHOP表达保护胰腺β细胞免受内质网应激介导的凋亡，我们称之为“正、负调控”。
Background: It is not known whether NR4A1 plays a role in ER stress-induced β-cell apoptosis. Results: NR4A1 expression in β-cells or islets correlated positively with Survivin expression and negatively with CHOP expression and apoptosis rate upon treatment with ER stress inducers. Conclusion: NR4A1 protects β-cells from ER stress-induced apoptosis by up-regulating Survivin and down-regulating CHOP expression. Significance: Our findings provide clues to prevent diabetes. The role of NR4A1 in apoptosis is controversial. Pancreatic β-cells often face endoplasmic reticulum (ER) stress under adverse conditions such as high free fatty acid (FFA) concentrations and sustained hyperglycemia. Severe ER stress results in β-cell apoptosis. The aim of this study was to analyze the role of NR4A1 in ER stress-mediated β-cell apoptosis and to characterize the related mechanisms. We confirmed that upon treatment with the ER stress inducers thapsigargin (TG) or palmitic acid (PA), the mRNA and protein levels of NR4A1 rapidly increased in both MIN6 cells and mouse islets. NR4A1 overexpression in MIN6 cells conferred resistance to cell loss induced by TG or PA, as assessed by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, and TUNEL assays indicated that NR4A1 overexpression also protected against ER stress-induced apoptosis. This conclusion was further confirmed by experiments exploiting siRNA to knockdown NR4A1 expression in MIN6 cells or exploiting NR4A1 knock-out mice. NR4A1 overexpression in MIN6 cells reduced C/EBP homologous protein (CHOP) expression and Caspase3 activation induced by TG or PA. NR4A1 overexpression in MIN6 cells or mouse islets resulted in Survivin up-regulation. A critical regulatory element was identified in Survivin promoter (−1872 bp to −1866 bp) with a putative NR4A1 binding site; ChIP assays demonstrated that NR4A1 physically associates with the Survivin promoter. In conclusion, NR4A1 protects pancreatic β-cells against ER stress-mediated apoptosis by up-regulating Survivin expression and down-regulating CHOP expression, which we termed as “positive and negative regulation.”