Department of Biosciences, University of Oslo, Postboks 1066 Blindern, 0316 Oslo, Norway; Institute for Cancer Genetics and Informatics, Oslo University Hospital, 0310 Oslo, Norway.
Department of Biosciences, University of Oslo, Postboks 1066 Blindern, 0316 Oslo, Norway.
Metabolism. 2019 Apr;93:75-85. doi: 10.1016/j.metabol.2019.01.014. Epub 2019 Jan 30.
Chronic ER stress and dysfunction is a hallmark of obesity and a critical contributor to metaflammation, abnormal hormone action and altered substrate metabolism in metabolic tissues, such as liver and adipocytes. Lack of STAMP2 in lean mice induces inflammation and insulin resistance on a regular diet, and it is dysregulated in the adipose tissue of obese mice and humans. We hypothesized that the regulation of STAMP2 is disrupted by ER stress.
3T3-L1 and MEF adipocytes were treated with ER stress inducers thapsigargin and tunicamycin, and inflammation inducer TNFα. The treatments effect on STAMP2 expression and enzymatic function was assessed. In addition, 3T3-L1 adipocytes and HEK cells were utilized for Stamp2 promoter activity investigation performed with luciferase and ChIP assays.
ER stress significantly reduced both STAMP2 mRNA and protein expression in cultured adipocytes whereas TNFα had the opposite effect. Concomitant with loss of STAMP2 expression during ER stress, intracellular localization of STAMP2 was altered and total iron reductase activity was reduced. Stamp2 promoter analysis by reporter assays and chromatin immunoprecipitation, showed that induction of ER stress disrupts C/EBPα-mediated STAMP2 expression.
These data suggest a clear link between ER stress and quantitative and functional STAMP2-deficiency.
慢性内质网应激和功能障碍是肥胖的标志，也是代谢组织（如肝脏和脂肪细胞）中代谢炎症、异常激素作用和代谢底物改变的关键因素。瘦鼠中 STAMP2 的缺失会在正常饮食下引起炎症和胰岛素抵抗，而肥胖鼠和人类脂肪组织中 STAMP2 则失调。我们假设内质网应激会破坏 STAMP2 的调节。
用内质网应激诱导剂他普西醇和衣霉素以及炎症诱导剂 TNFα 处理 3T3-L1 和 MEF 脂肪细胞，评估 STAMP2 表达和酶功能的变化。此外，用荧光素酶和 ChIP 测定法研究 3T3-L1 脂肪细胞和 HEK 细胞中的 Stamp2 启动子活性。
内质网应激显著降低了培养脂肪细胞中 STAMP2 的 mRNA 和蛋白表达，而 TNFα 则有相反的作用。在 ER 应激过程中 STAMP2 表达丧失的同时，STAMP2 的细胞内定位发生改变，总铁还原酶活性降低。通过报告基因分析和染色质免疫沉淀分析，发现内质网应激诱导破坏了 C/EBPα 介导的 STAMP2 表达。
这些数据表明内质网应激与定量和功能性 STAMP2 缺乏之间存在明确的联系。
