Novel mechanisms of UPR sensing and nonalcoholic fatty liver disease

UPR传感和非酒精性脂肪肝的新机制

• 批准号: 9026108
• 负责人: Zihai Li
• 金额: $ 33.64万
• 依托单位: MEDICAL UNIVERSITY OF SOUTH CAROLINA
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-12-10 至 2020-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9026108
• 关键词: Address; Adopted; Apoptotic; Awards and Prizes; Binding; Biochemical; Biogenesis; Biology; Calcium; Cell Death; Cells; Cessation of life; Characteristics; Data; Dimerization; Disease; Dissociation; Endoplasmic Reticulum; Ensure; Epidemic; Eukaryotic Cell; Fatty Liver; Hepatology; High Fat Diet; Homeostasis; Homo; Incidence; Knock-out; Knockout Mice; Lead; Light; Link; Lipoproteins; Liver; Liver diseases; Low Density Lipoprotein Receptor; Medicine; Membrane; Mitochondria; Modeling; Molecular; Molecular Chaperones; Morus; Mus; Obesity; Pathogenesis; Pathway interactions; Physiology; Proteins; Public Health; Published Comment; Quality Control; Research; Research Personnel; Role; Signal Transduction; Stress; System; Time; Transactivation; Update; Work; endoplasmic reticulum stress; lipid biosynthesis; lipid metabolism; liver function; non-alcoholic fatty liver; novel; overexpression; pandemic disease; programs; protein misfolding; public health relevance; response; sensor; structural biology; success

 DESCRIPTION (provided by applicant): This project addresses the mechanism of unfolded protein response (UPR) and non-alcoholic fatty liver disease (NAFLD). Upon accumulation of unfolded or misfolded proteins in the lumen of the endoplasmic reticulum (ER), eukaryotic cells adopt a conserved and fundamentally important UPR pathway to turn on the expression of major ER chaperones and proteins involved in ER-associated degradation to alleviate stress. This critical protein quality control mechanism is transmitted by three ER trans-membrane UPR sensors including IRE1, PERK and ATF6. The significance of UPR research is far-reaching in medicine; it is highlighted and supported by the 2014 Albert Lasker Prize awarded to Drs. Kazutoshi Mori and Peter Walter. The mechanism whereby UPR sensors are triggered however remains a subject of intense debate, which is important to resolve given the ubiquitous implication of UPR in physiology and diseases. Present models include direct binding of ER sensors by misfolded proteins and dissociation of Grp78 from the luminal domains of ER sensors. Neither of the models sufficiently explains the exquisite sensitivity and high efficiency of the system which allows cells to react and adapt to stress in real time. We have produced an exciting body of evidence implicating CNPY2, a previously unknown ER protein in UPR, in activating all three UPR sensors in response to ER stress. CNPY2 is highly expressed in the liver in the steady state and can be further induced by UPR via direct transactivation by CHOP. Knockout (KO) of cnpy2 from mice silences UPR pathways, blocks CHOP expression, and protects cells from UPR-induced cell death. Remarkably, the KO mice are rendered highly protective against high fat diet (HFD)-induced ER stress and non-alcoholic fatty liver disease (NAFLD). In turn, CNPY2 overexpression increases the UPR and apoptotic signals in cells upon ER stress induction. Thus, a novel model of UPR sensing that involves CNPY2 is emerging. We hypothesize that CNPY2 is a critical positive initiator for general UPR in the liver, and that it i required for ER stress-induced NAFLD. We propose two specific aims to address our hypothesis. Aim 1 will determine the molecular mechanism of CNPY2- regulated UPR initiation, using biochemical, biophysical and structural approaches. Aim 2 will be focused on untangling the mechanisms of CNPY2 in regulating hepatosteatosis by systemically studying the roles of CNPY2 in: 1) lipogenesis and lipid metabolism; 2) regulating lipoprotein secretion and the biogenesis of LDL receptor; 3) controlling calcium homeostasis related to mitochondria-ER cross-talk. Collectively, this proposal shall have a significant impact in understanding the mechanism of UPR sensing, and the pathogenesis of NAFLD.

 描述（由申请人提供）：该项目研究了未折叠蛋白反应（UPR）和非酒精性脂肪肝疾病（NAFLD）的机制。当未折叠或错误折叠的蛋白质在内质网 (ER) 腔中积累时，真核细胞采用保守且极其重要的 UPR 途径来开启主要 ER 伴侣和参与 ER 相关降解的蛋白质的表达，以缓解应激。这种关键的蛋白质质量控​​制机制由三个 ER 跨膜 UPR 传感器（包括 IRE1、PERK 和 ATF6）传输。 UPR研究在医学上的意义是深远的； 2014 年授予 Drs. Albert Lasker 奖强调并支持了这一点。森一俊和彼得·沃尔特。然而，UPR 传感器的触发机制仍然是一个激烈争论的话题，考虑到 UPR 在生理学和疾病中的普遍意义，解决这一问题非常重要。目前的模型包括错误折叠蛋白直接结合 ER 传感器以及 Grp78 从 ER 传感器的腔域解离。这两个模型都不足以解释该系统的精确灵敏度和高效率，该系统使细胞能够实时反应并适应压力。我们已经提供了大量令人兴奋的证据，表明 CNPY2（UPR 中一种以前未知的 ER 蛋白）在激活所有三个 UPR 传感器以响应 ER 应激中。 CNPY2 在稳态下在肝脏中高表达，并且可以通过 CHOP 的直接反式激活进一步被 UPR 诱导。敲除 (KO) 小鼠的 cnpy2 可沉默 UPR 通路、阻断 CHOP 表达并保护细胞免遭 UPR 诱导的细胞死亡。值得注意的是，KO 小鼠对高脂肪饮食 (HFD) 诱导的内质网应激和非酒精性脂肪肝 (NAFLD) 具有高度保护作用。反过来，CNPY2 过表达会增加细胞内 ER 应激诱导时的 UPR 和凋亡信号。因此，一种涉及 CNPY2 的 UPR 传感新模型正在出现。我们假设 CNPY2 是肝脏中一般 UPR 的关键正向引发剂，并且是 ER 应激诱导的 NAFLD 所必需的。我们提出两个具体目标来解决我们的假设。目标 1 将使用生物化学、生物物理和结构方法确定 CNPY2 调节 UPR 启动的分子机制。目标2将重点通过系统研究CNPY2在以下方面的作用来阐明CNPY2调节肝脂肪变性的机制：1）脂肪生成和脂质代谢； 2）调节脂蛋白分泌和LDL受体的生物发生； 3）控制与线粒体-内质网串扰相关的钙稳态。总的来说，该提案将对理解 UPR 传感机制和 NAFLD 的发病机制产生重大影响。