Purwana Indri, Liu Jun J, Portha Bernard, Buteau Jean
Alberta Diabetes Institute, University of Alberta, Li Ka Shing Centre, Edmonton, AB, T6G 2E1, Canada.
Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, Canada.
Diabetologia. 2017 Aug;60(8):1432-1441. doi: 10.1007/s00125-017-4310-7. Epub 2017 May 25.
AIMS/HYPOTHESIS: Heat shock factor protein 1 (HSF1) is a transcription factor that regulates the expression of key molecular chaperones, thereby orchestrating the cellular response to stress. This system was recently implicated in the control of insulin sensitivity and is therefore being scrutinised as a novel therapeutic avenue for type 2 diabetes. However, the regulation and biological actions of HSF1 in beta cells remain elusive. Herein, we sought to investigate the regulation of HSF1 in pancreatic beta cells and to study its potential role in cell survival.
We exposed human islets and beta cell lines to glucolipotoxicity and thapsigargin. HSF1 activity was evaluated by gel shift assay. HSF1 acetylation and interaction with the protein acetylase cAMP response element binding protein (CBP) were investigated by western blot. We measured the expression of HSF1 and its canonical targets in islets from Goto-Kakizaki (GK) rat models of diabetes and delineated the effects of HSF1 acetylation using mutants mimicking constitutive acetylation and deacetylation of the protein.
Glucolipotoxicity promoted HSF1 acetylation and interaction with CBP. Glucolipotoxicity-induced HSF1 acetylation inhibited HSF1 DNA binding activity and decreased the expression of its target genes. Restoration of HSF1 activity in beta cells prevented glucolipotoxicity-induced endoplasmic reticulum stress and apoptosis. However, overexpression of a mutant protein (K80Q) mimicking constitutive acetylation of HSF1 failed to confer protection against glucolipotoxicity. Finally, we showed that expression of HSF1 and its target genes were altered in islets from diabetic GK rats, suggesting that this pathway could participate in the pathophysiology of diabetes and constitutes a potential site for therapeutic intervention.
CONCLUSIONS/INTERPRETATION: Our results unravel a new mechanism by which HSF1 inhibition is required for glucolipotoxicity-induced beta cell apoptosis. Restoring HSF1 activity may represent a novel strategy for the maintenance of a functional beta cell mass. Our study supports the therapeutic potential of HSF1/heat shock protein-targeting agents in diabetes treatment.
目的/假设：热休克因子蛋白1（HSF1）是一种转录因子，可调节关键分子伴侣的表达，从而协调细胞对应激的反应。该系统最近被认为与胰岛素敏感性的控制有关，因此正作为2型糖尿病的一种新治疗途径而受到审视。然而，HSF1在β细胞中的调节和生物学作用仍不清楚。在此，我们试图研究胰腺β细胞中HSF1的调节，并探讨其在细胞存活中的潜在作用。
我们将人胰岛和β细胞系暴露于糖脂毒性和毒胡萝卜素中。通过凝胶迁移试验评估HSF1活性。通过蛋白质印迹法研究HSF1的乙酰化及其与蛋白质乙酰化酶环磷酸腺苷反应元件结合蛋白（CBP）的相互作用。我们测量了糖尿病Goto-Kakizaki（GK）大鼠模型胰岛中HSF1及其典型靶标的表达，并使用模拟该蛋白组成型乙酰化和去乙酰化的突变体来描述HSF1乙酰化的作用。
糖脂毒性促进HSF1乙酰化及其与CBP的相互作用。糖脂毒性诱导的HSF1乙酰化抑制了HSF1的DNA结合活性，并降低了其靶基因的表达。恢复β细胞中的HSF1活性可预防糖脂毒性诱导的内质网应激和细胞凋亡。然而，模拟HSF1组成型乙酰化的突变蛋白（K80Q）的过表达未能赋予对糖脂毒性的保护作用。最后，我们表明糖尿病GK大鼠胰岛中HSF1及其靶基因的表达发生了改变，这表明该途径可能参与糖尿病的病理生理学过程，并构成治疗干预的潜在靶点。
结论/解读：我们的结果揭示了一种新机制，即糖脂毒性诱导的β细胞凋亡需要抑制HSF1。恢复HSF1活性可能是维持功能性β细胞群的一种新策略。我们的研究支持HSF1/热休克蛋白靶向药物在糖尿病治疗中的治疗潜力。
