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: 8203794
• 负责人: Carol A. Casey
• 金额: $ 45.33万
• 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/8203794
• 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. PUBLIC HEALTH RELEVANCE: The goal of this proposal is to examine how alcohol exposure can lead to impaired membrane trafficking events in the liver which would eventually result in increased fat due to altered dynamics of the large fat storage organelles, lipid droplets (LDs). We hypothesize that ethanol exposure leads to hepatic steatosis as a result of attenuated LD vesiculation and subsequent trafficking to lysosomes. This leads to altered LD disassembly which then contributes to hepatic steatosis. Successful completion of these studies will provide novel insights as to how ethanol affects LD dynamics in the liver cells, and provide information which could lead to therapeutic strategies that might reduce the severity of steatosis and block the further progression to steatohepatitis, fibrosis and cirrhosis.

描述（由申请人提供）：本提案是对NIAAA题为“酒精诱导的代谢和肝损伤（AIMHI）"的申请请求（RFA）的回应。这种多重PI应用的目的是研究乙醇暴露如何导致肝细胞中膜运输事件受损，导致脂肪蓄积增加，这是由于称为脂滴（LD）的大型脂肪储存细胞器的动力学改变。在酒精性脂肪肝病（AFLD）期间，几乎所有重度饮酒者都会发生脂肪肝，其特征是肝细胞内脂肪酸以LD形式异常和显著积累。有助于这些细胞器的数量和大小显著增加的细胞过程被认为是治疗干预的主要目标，以阻止进一步进展，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与内吞和分泌运输途径具有显著相似性的复杂运输过程。我们已经发现，在肝细胞中LD动力学的核心是几种GTP酶（特别是动力蛋白和rabs），它们可以作为分子开关来调节膜交通。在凯西和麦克尼文博士在最近资助的“挑战基金”中获得的初步数据中，显示这些GTP酶的破坏（通过乙醇或通过实验操作）可以显著增加肝细胞中LD的积累。这些发现支持我们的中心假设，即乙醇暴露导致肝细胞膜运输机制受损，从而减弱LD分解，导致肝脂肪变性。参与该项目的两名主要研究人员优势互补;一位是酒精性肝损伤专家（凯西），另一位是肝细胞膜-细胞骨架动力学专家（麦克尼文）。我们将利用各种最先进的膜运输和成像技术，这是新的研究领域，在我们的研究如何LD的形成和利用是由乙醇在肝细胞的影响。在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解的LD的囊泡形成，二，肝细胞内吞机制在该LD囊泡形成过程中被利用，并且被ETOH暴露所损害，三，LD蛋白的泛素化被ETOH显著减弱，并且有助于将LD靶向溶酶体以进行后续降解。这些研究的成功完成将为乙醇如何影响肝脏中的LD动力学提供新的技术和见解，并提供可能导致旨在降低脂肪变性严重程度和阻止脂肪性肝炎，纤维化和肝硬化进一步发展的治疗策略的信息。 公共卫生关系：该提案的目的是研究酒精暴露如何导致肝脏中膜运输事件受损，最终导致脂肪增加，这是由于大型脂肪储存细胞器，脂滴（LD）的动力学改变。我们推测，乙醇暴露导致肝脏脂肪变性的结果衰减LD囊泡和随后的运输到溶酶体。这导致改变的LD分解，然后导致肝脂肪变性。这些研究的成功完成将为乙醇如何影响肝细胞中的LD动力学提供新的见解，并提供可能导致治疗策略的信息，这些治疗策略可能会降低脂肪变性的严重程度，并阻止脂肪性肝炎，纤维化和肝硬化的进一步发展。