Cellular and molecular mechanisms of fatty liver disease

脂肪肝疾病的细胞和分子机制

基本信息

批准号：
9317353
负责人：
Liqing Yu
金额：
$ 34.09万
依托单位：
GEORGIA STATE UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2016
资助国家：
美国
起止时间：
2016-07-18 至 2020-06-30
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/9317353
关键词：
Adipose tissue Animal Model Animals Autophagocytosis Binding Capsid Proteins Cells Cirrhosis Comparative Study Data Defect Diet Digestion Disease Progression Ensure Failure Fatty Liver Fatty acid glycerol esters Fibrosis Genes Health Hepatic Hepatocyte Hsc70 protein Human Hydrolysis Ichthyoses In Vitro Inflammation Insulin Resistance Knock-out Knockout Mice Lipase Lipids Lipolysis Liver Liver Fibrosis Liver diseases Lysosomes Mediating Modeling Molecular Molecular Chaperones Mus Mutation Organelles Outcome Pathogenesis Pathway interactions Patients Phenotype Positioning Attribute Process Proteins Proteomics Public Health Reporting Research Research Personnel Rodent Role Signal Pathway Signal Transduction Skin Testing Triglycerides Work base cell type comparative energy balance experience experimental study human disease inhibition of autophagy innovation lipid metabolism liver injury model development mouse model mutant non-alcoholic fatty liver nonalcoholic steatohepatitis novel perilipin protein protein interaction

项目摘要

Project Summary Cytosolic accumulation of triglyceride (TG)-rich lipid droplets (LDs) is a hallmark of nonalcoholic fatty liver disease (NAFLD). Many LD-associated proteins are implicated in the pathogenesis of human and rodent NAFLD, including CGI-58 (Comparative Gene Identification-58). Mutations in human CGI-58 gene cause ichthyosis (thickened dry scaly skin) and TG-rich LD accumulation in most cell types. Patients display NAFLD ranging from simple steatosis to nonalcoholic steatohepatitis (NASH), fibrosis and cirrhosis. CGI-58 was shown to promote TG hydrolysis in vitro by activating Adipose Triglyceride Lipase (ATGL), but ATGL mutations in humans cause no ichthyosis. While liver-specific CGI-58 knockout (LivKO) mice develop severe hepatic steatosis, NASH and fibrosis even on a regular chow diet, liver-specific ATGL KO mice display only mild hepatic steatosis without NASH and fibrosis. These phenotypic differences between ATGL and CGI-58 mutations provide us a unique opportunity to exploit molecular mechanisms of NAFLD progression. Two major pathways are implicated in intracellular LD breakdown: 1) Cytosolic/Neutral Lipolysis mainly mediated by ATGL, and 2) Lysosomal/Acidic Lipolysis mediated by a lipid-specific macroautophagy (lipophagy). Lipophagy brings cytosolic LDs to lysosomes for degradation by acidic lipases, but its molecular details are unknown. Our preliminary data suggest that hepatic autophagy-related proteins are reduced, the major upstream autophagy inhibitory signaling pathway (mTORC1) is activated, and there is a defect in association between LDs and acidic organelles in CGI-58-deficient liver and/or hepatocytes. It was recently shown that perilipin 2, a major LD coat protein known to interact with CGI-58, also binds the heat shock cognate protein of 70 kDa (hsc70) for degradation via chaperone-mediated autophagy (CMA), and inhibition of CMA reduces both Neutral and Acidic Lipolysis, leading to severe hepatic steatosis and liver damage. Based on these observations and our preliminary data, we hypothesize that CGI-58 may coordinate with hsc70 to stimulate LD uncoating by promoting perilipin 2 degradation via CMA, thereby activating both ATGL lipolysis and lipophagy. Lipophagy failure may in turn inhibit autophagy by altering cellular energy balance. This hypothesis may explain why ATGL and CGI-58 mutations cause overlapping yet distinct phenotypes. We will test this central hypothesis by comparing liver-specific CGI-58 and ATGL KO mice to determine whether liver CGI-58 and ATGL differentially, regulates lipophagy and autophagy. We will then perform detailed protein-protein interaction studies to examine whether CGI-58 and hsc70 coordinate CMA-mediated LD uncoating (degradation of perilipin 2). Finally we will determine if mTORC1 inhibition and autophagy induction protect against NAFLD progression in CGI-58 LivKO mice. Given that CGI-58 resides at the critical crossroad of cellular fat breakdown, this project holds promise of revealing general mechanisms for progression of NAFLD, a major public health problem.

项目摘要甘油三酸酯（TG）的胞质积累 - 富含脂质的脂质液滴（LDS）是非酒精脂肪肝的标志疾病（NAFLD）。许多与LD相关的蛋白有关人类和啮齿动物的发病机理 NAFLD，包括CGI-58（比较基因鉴定-58）。人CGI-58基因的突变引起在大多数细胞类型中，鱼质病（干燥干燥的鳞状皮肤增厚）和富含TG的LD积累。患者显示NAFLD 从简单的脂肪变性到非酒精性脂肪性肝炎（NASH），纤维化和肝硬化。 CGI-58是通过激活脂肪甘油三酸酯脂肪酶（ATGL），可以在体外促进TG水解，但ATGL突变在人类中，没有引起鱼鳞病。而肝脏特异性CGI-58敲除（Livko）小鼠出现严重的肝脂肪变性，纳什和纤维化即使在常规的食物饮食中，肝脏特异性ATGL KO小鼠仅显示温和肝脏脂肪变性，无氮和纤维化。 ATGL和CGI-58之间的这些表型差异突变为我们提供了开发NAFLD进展的分子机制的独特机会。两个主要途径与细胞内LD分解有关：1）胞质/中性脂肪分解主要由ATGL介导 2）由脂质特异性大量噬菌体（脂肪）介导的溶酶体/酸性脂解。寄生虫带来胞质LDS溶酶体酸性脂肪酶降解，但其分子细节尚不清楚。我们的初步数据表明肝自噬相关蛋白减少了，这是主要上游自噬抑制信号通路（MTORC1）被激活，LDS和 CGI-58缺陷肝脏和/或肝细胞中的酸性细胞器。最近证明，Perilipin 2（主要LD）已知与CGI-58相互作用的外套蛋白也结合了70 kDa（HSC70）的热休克同源蛋白通过伴侣介导的自噬（CMA）降解，CMA的抑制作用可降低中性和酸性脂解，导致严重的肝脂肪变性和肝损伤。基于这些观察和我们的初步数据，我们假设CGI-58可以与HSC70进行协调以刺激LD不涂层通过CMA促进Perilipin 2降解，从而激活ATGL脂肪分解和脂肪摄氏。脂肪失败可能会通过改变细胞能量平衡来抑制自噬。这个假设可以解释为什么 ATGL和CGI-58突变会导致重叠但不同的表型。我们将通过比较肝脏特异性CGI-58和ATGL KO小鼠，以确定肝CGI-58和ATGL是否差异化，调节寄生虫和自噬。然后，我们将进行详细的蛋白质 - 蛋白质相互作用研究检查CGI-58和HSC70是否协调CMA介导的LD脱涂层（Perilipin 2的降解）。最后，我们将确定MTORC1抑制和自噬诱导是否可以防止NAFLD进展 CGI-58 Livko小鼠。鉴于CGI-58驻留在细胞脂肪崩溃的关键十字路口中，该项目有望揭示NAFLD发展的一般机制，NAFLD是一个主要的公共卫生问题。