Mechanism of ER protein misfolding-induced mitochondrial dysfunction

项目摘要 非酒精性脂肪性肝病（NAFLD）的患病率在西方世界几乎为30%， 预计将在未来十年上升。NAFLD的特征是内质网中的蛋白质错误折叠， 内质网（ER）激活未折叠蛋白反应（UPR）。长期的内质网应激条件进一步导致 氧化应激，蛋白质聚集，细胞器损伤，细胞生物能量崩溃，并最终 细胞死亡最近的研究表明，ER中的蛋白质错误折叠有助于肝细胞衰竭 与NAFLD、非酒精性脂肪性肝炎（NASH）和肝细胞癌（HCC）相关。 通过对肝细胞功能的详细描述，我们的初步结果使我们提出ER 蛋白质错误折叠导致线粒体功能障碍，导致进一步的蛋白质错误折叠，最终导致 肝细胞衰竭虽然以前的研究表明，蛋白质错误折叠在内质网的肝细胞， 与代谢综合征和NAFLD有关，从来没有仔细描述过如何 ER蛋白错误折叠导致灾难性的细胞事件，导致氧化损伤、纤维化和细胞凋亡。 死亡我们已经证明，ER中凝血因子VIII（FVIII）的错误折叠破坏了ER的复合物1， 电子传递链令人惊讶的是，我们证明了用一种靶向肿瘤的治疗方法， 抗氧化剂纠正缺陷的线粒体功能，并改善细胞中ER中的FVIII折叠 文化这一前所未有的发现表明，ER蛋白错误折叠 和线粒体生物能量学缺陷在拟议的研究中，我们将使用两个不同的模型， 在肝细胞中体内诱导ER应激;（i）高果糖饮食的过量营养，或（ii）FVIII的表达 阐明ER蛋白错误折叠如何破坏线粒体生物能量学和动力学。目前， 正在进行的临床研究使用病毒将FVIII递送至血友病A患者的肝细胞。 此外，我们将应用代谢组学和RNA-Seq的无偏见技术，使用新的遗传学方法， 小鼠模型，以阐明蛋白质错误折叠如何导致Ca 2+从ER泄漏并进入 线粒体基质以破坏线粒体生物能量学和/或动力学。有证据表明， 蛋白质错误折叠和线粒体功能缺陷存在于所有退行性疾病中。此外，本发明还提供了一种方法， 广泛的研究结果表明，ER中的蛋白质错误折叠与许多人的肝功能衰竭有关， 常见的急性疾病，包括病毒感染，乙醇中毒，对乙酰氨基酚中毒和缺血 再灌注损伤我们对未知领域的基本探索无疑会产生 ER蛋白错误折叠对线粒体电子传递影响的新假说 链这些研究将为ER和线粒体功能是如何相互作用的提供基本的机制见解。 它调节并导致NAFLD和其他蛋白质错误折叠疾病的新疗法。

PROJECT SUMMARY The prevalence of non-alcoholic fatty liver disease (NAFLD) is almost 30% in the western world and is expected to rise in the next decade. NAFLD is characterized by protein misfolding in the endoplasmic reticulum (ER) activating the unfolded protein response (UPR). Prolonged ER stress conditions further lead to oxidative stress, protein aggregation, organelle damage, cellular bioenergetic collapse, and eventually cell death. Recent studies indicate that protein misfolding in the ER contributes to hepatocyte failure associated with NAFLD, non-alcoholic steatohepatitis (NASH) and hepatocellular carcinoma (HCC). Through detailed characterization of hepatocyte function, our preliminary results lead us to propose that ER protein misfolding causes mitochondrial dysfunction that leads to further protein misfolding culminating in hepatocyte failure. Although previous studies demonstrated that protein misfolding in the ER of hepatocytes is associated with metabolic syndrome and NAFLD, there has never been a careful characterization of how ER protein misfolding causes catastrophic cellular events leading to oxidative damage, fibrosis and cell death. We have shown that misfolding of coagulation factor VIII (FVIII) in the ER disrupts complex 1 of the electron transport chain. Amazingly, we demonstrated that treatment with a mitochondrial-targeted antioxidant corrects he defective mitochondrial function and also improves FVIII folding in the ER in cell culture. This unprecedented finding indicates an unappreciated association between ER protein misfolding and defective mitochondrial bioenergetics. In the proposed studies, we will use two separate models to induce ER stress in vivo in hepatocytes; (i) excess nutrition of a high fructose diet, or (ii) expression of FVIII to elucidate how ER protein misfolding disrupts mitochondrial bioenergetics and dynamics. Presently, ongoing clinical studies are using viral delivery of FVIII to hepatocytes in hemophilia A patients. Furthermore, we will apply non-biased technologies of metabolomics and RNA-Seq using novel genetic murine models to elucidate how protein misfolding causes Ca2+ leak from the ER and entry into the mitochondrial matrix to disrupt mitochondrial bioenergetics and/or dynamics. Evidence supports that ER protein misfolding and defective mitochondrial function exist in all degenerative diseases. In addition, extensive findings demonstrate that protein misfolding in the ER is associated with liver failure in a number of common acute conditions including viral infection, ethanol toxicity, acetaminophen toxicity and ischemia reperfusion injury. Our fundamental novel exploration into unchartered territory will undoubtedly generate new hypotheses concerning the impact of ER protein misfolding on the mitochondrial electron transport chain. The studies will provide fundamental mechanistic insight into how ER and mitochondrial functions are reciprocally regulated and lead to novel therapies for NAFLD and other diseases of protein misfolding.