Altered Lipid Droplet Trafficking: Role in Alcoholic Fatty Liver Disease

改变脂滴运输：在酒精性脂肪肝病中的作用

• 批准号: 8462022
• 负责人: Carol A. Casey
• 金额: $ 1.9万
• 依托单位: UNIVERSITY OF NEBRASKA MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-08-10 至 2016-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8462022
• 关键词: Actins; Acute; Address; Affect; Alcohol abuse; Alcoholic Fatty Liver; Alcoholic Liver Diseases; Alcoholic beverage heavy drinker; Alcohols; Area; Attenuated; Biological; Capsid Proteins; Caveolae; Caveolins; Cell physiology; Cellular Membrane; Cellular biology; Chronic; Cirrhosis; Cytoskeleton; Data; Dynamin; Dynamin 2; Enzymes; Ethanol; Event; Family; Family member; Fatty Acids; Fatty Liver; Fatty acid glycerol esters; Fibrosis; Funding; Goals; Grant; Guanosine Triphosphate Phosphohydrolases; Health; Hepatic; Hepatocyte; Imaging technology; Impairment; Injury; Investigation; Knockout Mice; Laboratories; Lead; Lipids; Lipolysis; Liver; Liver diseases; Lysosomes; Mediating; Membrane; Membrane Protein Traffic; Metabolic; Metabolism; Molecular; National Institute on Alcohol Abuse and Alcoholism; Organelles; Pathway interactions; Principal Investigator; Process; Proteins; Recruitment Activity; Request for Applications; Research; Role; Severities; Signal Transduction; Staging; Steatohepatitis; Surface; System; Testing; Therapeutic; Therapeutic Intervention; alcohol exposure; base; in vivo; innovation; insight; lipid metabolism; new technology; novel; prevent; problem drinker; response; scaffold; src-Family Kinases; trafficking

DESCRIPTION (provided by applicant): This proposal is in response to the Request for Applications (RFA) from NIAAA entitled "Alcohol-Induced Metabolic and Hepatic Injury (AIMHI)". The goal of this multiple-PI application is to examine how ethanol exposure can lead to impaired membrane trafficking events in the liver hepatocyte that results in increased fat accumulation due to altered dynamics of large fat storage organelles termed lipid droplets (LDs). During alcoholic fatty liver disease (AFLD), almost all heavy drinkers develop fatty liver, which is marked by the aberrant and significant accumulation of intrahepatocellular fatty acids in the form of LDs. The cellular processes contributing to this marked increase in the number and size of these organelles is considered a prime target for therapeutic intervention to block further progression as it is an initial stage of the injury, and thus reversible. It appears that the cyclical formation, accumulation and subsequent metabolism of LDs are dependent on an intricate trafficking process in the hepatocyte that share marked similarities with the endocytic and secretory trafficking pathways. We have found that central to LD dynamics in hepatocytes are several GTPases (dynamins and rabs in particular) that can act as molecular switches to regulate membrane traffic. In preliminary data obtained by Drs. Casey and McNiven in a recently funded "Challenge Grant" it was shown that disruption of these GTPases (by ethanol or by experimental manipulation) could dramatically increase accumulation of LDs in the liver cell. These findings support our central hypothesis that ethanol exposure leads to an impairment of the membrane trafficking machinery in the hepatocyte that attenuates LD disassembly resulting in hepatic steatosis. The two principal investigators involved in this proposed project have complementary strengths; one is an expert in alcoholic-induced liver damage (Casey), and the other in hepatocyte membrane-cytoskeleton dynamics (McNiven). We will utilize a variety of state-of-the art membrane trafficking and imaging technologies that are novel to this area of research in our investigations of how LD formation and utilization is affected by ethanol in hepatocytes. Novel and innovative biological concepts pursued in this proposal include: one, ETOH disrupts vesiculation of LDs normally used to aid in lipolysis, two, the hepatocyte endocytic machinery is utilized in this LD vesiculation process and compromised by ETOH exposure, three, ubiquitinylation of LD proteins is markedly attenuated by ETOH and aids in targeting of the LDs to the lysosome for subsequent degradation. Successful completion of these studies will provide new technologies and insights as to how ethanol affects LD dynamics in the liver, and provide information which could lead to therapeutic strategies aimed at reducing the severity of steatosis and blocking the further progression to steatohepatitis, fibrosis and cirrhosis.

描述（由申请人提供）：本提案是对 NIAAA 题为“酒精诱发的代谢和肝损伤 (AIMHI)”的申请请求 (RFA) 的回应。这种多重 PI 应用的目标是检查乙醇暴露如何导致肝脏肝细胞中的膜运输事件受损，从而由于称为脂滴 (LD) 的大型脂肪储存细胞器的动力学改变而导致脂肪积累增加。在酒精性脂肪肝 (AFLD) 期间，几乎所有酗酒者都会患上脂肪肝，其特点是肝细胞内脂肪酸以 LD 的形式异常且显着积累。导致这些细胞器的数量和大小显着增加的细胞过程被认为是阻止进一步进展的治疗干预的主要目标，因为它是损伤的初始阶段，因此是可逆的。 LD 的周期性形成、积累和随后的代谢似乎依赖于肝细胞中复杂的运输过程，该过程与内吞和分泌运输途径具有明显的相似性。我们发现，肝细胞中 LD 动力学的核心是几种 GTP 酶（特别是动力蛋白和 rab），它们可以充当调节膜运输的分子开关。在博士获得的初步数据中。 Casey 和 McNiven 在最近资助的“挑战资助”中表明，破坏这些 GTP 酶（通过乙醇或通过实验操作）可以显着增加肝细胞中 LD 的积累。这些发现支持我们的中心假设，即乙醇暴露会导致肝细胞中的膜运输机制受损，从而减弱 LD 分解，从而导致肝脂肪变性。参与本项目的两位主要研究者具有互补优势；一位是酒精性肝损伤方面的专家（凯西），另一位是肝细胞膜-细胞骨架动力学方面的专家（麦克尼文）。我们将利用该研究领域新颖的各种最先进的膜运输和成像技术来研究肝细胞中乙醇如何影响 LD 的形成和利用。该提案中追求的新颖和创新的生物学概念包括：一，ETOH 破坏通常用于帮助脂肪分解的 LD 的囊泡，二，在该 LD 囊泡形成过程中利用肝细胞内吞机制，并因 ETOH 暴露而受到损害，三，LD 蛋白的泛素化被 ETOH 显着减弱，并有助于将 LD 靶向 溶酶体进行后续降解。这些研究的成功完成将为乙醇如何影响肝脏中的LD动态提供新技术和见解，并提供可能导致旨在降低脂肪变性严重程度并阻止进一步进展为脂肪性肝炎、纤维化和肝硬化的治疗策略的信息。