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: 9921268
• 负责人: Carol A. Casey
• 金额: $ 56.39万
• 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 2021-09-24
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9921268
• 关键词: ABL1 gene; Acute; Address; Adipocytes; Affect; Agonist; Alcohol abuse; Alcoholic Fatty Liver; Alcoholic Liver Diseases; Alcoholic beverage heavy drinker; Alcoholic steatohepatitis; Alcohols; Attenuated; Autophagocytosis; Autophagosome; Award; Biological; Capsid Proteins; Catabolic Process; Catabolism; Caveolins; Cell physiology; Cells; Cellular biology; Chronic; Cirrhosis; Cyclic AMP; Cytoskeleton; Data; Defect; Dynamin; Ethanol; Ethanol Metabolism; Event; Excision; Fatty Liver; Fatty acid glycerol esters; Fibrosis; Forskolin; Foundations; Funding; G-Protein-Coupled Receptors; GTP-Binding Protein alpha Subunits, Gs; Goals; Guanosine Triphosphate Phosphohydrolases; Health; Hepatocyte; Imaging technology; Impairment; Individual; Injury; Investigation; Isoproterenol; Lead; Lipids; Lipolysis; Liver; Liver diseases; Lysosomes; Measurable; Membrane; Membrane Protein Traffic; Molecular; National Institute on Alcohol Abuse and Alcoholism; Nutrient; Organelles; Outcome; Pathway interactions; Phosphotransferases; Principal Investigator; Process; Property; Proteins; Research; Role; SRC gene; Sampling; Severities; Signal Transduction; Solid; Steatohepatitis; Stress; Surface; Therapeutic; Triglycerides; Ubiquitination; alcohol exposure; attenuation; base; innovation; insight; lipid metabolism; liver injury; medical specialties; novel; nutrient deprivation; perilipin; prevent; problem drinker; response; trafficking

ABSTRACT This proposal is a competitive renewal of a multiple-PI R01 funded through NIAAA. The goal of the application is to examine how ethanol exposure contributes to fat accumulation in the liver due to altered dynamic properties of the fat storage organelle, the lipid droplet (LD). Specifically we will examine how alcohol exposure compromises both the lipolytic and lipophagic machineries in hepatocytes via disrupting signaling cascades and membrane trafficking effectors, ultimately leading to a fatty liver. During alcoholic liver disease, almost all heavy drinkers develop fatty liver, which is marked by the aberrant and significant accumulation of intrahepatocellular triglycerides in the form of LDs. Understanding the cellular processes contributing to this fat accumulation will provide important information for preventing further progression of injury, as it is known that alcoholic fatty liver is the initial, but entirely reversible stage of liver injury. Our research in the previously- funded R01 examined how LD dynamics in hepatocytes are regulated by several GTPases (dynamins and Rabs in particular) that can act as molecular switches to regulate membrane traffic. We showed that ethanol- induced disruption of these GTPases dramatically increases accumulation of LDs in the liver cell. Preliminary data in support of this continuation application show that the lipolytic machinery of hepatocytes, is activated by agonists of cAMP kinase (isoproterenol, forskolin) but this response is markedly inhibited by ethanol exposure. Additionally, we show that the hepatocyte utilizes sequential mechanisms to catabolize LDs that entail lipolysis followed by lipophagy. Further, it appears that activation of non-receptor tyrosine kinases that reside on the LD-autophagosome (AP) surface function to drive lipophagy, and that alcohol impairs this process. Finally, in addition to engulfment of LDs by APs, removal or “sampling” of lipids away from LDs seems to occur by a transient, measurable interaction that is sensitive to ethanol exposure. These recent, novel findings provide an excellent foundation for this proposal, and support our central hypothesis that ethanol exposure compromises both the lipolytic and lipophagic machineries in the hepatocyte by disrupting signaling cascades and membrane trafficking events, leading to hepatic steatosis. The two principal investigators directing this project have complementary strengths: Dr. Casey is a biochemist whose expertise is in alcoholic-induced liver damage. Dr. McNiven is a cell biologist whose specialty is membrane-cytoskeleton dynamics. This unique collaborative effort has proven very beneficial to the field of alcoholic liver disease and will continue to result in outcomes otherwise unattainable by individual efforts. The proposed investigation will utilize state-of-the-art membrane trafficking and imaging technologies to quantify specific molecular events that contribute to alcohol- induced fatty liver. Successful completion of these studies will provide novel insights as to how ethanol affects LD dynamics in liver cells, and important information for therapeutic strategies aimed at reducing or eliminating the severity of steatosis and blocking its further progression to alcoholic steatohepatitis, fibrosis and cirrhosis.

抽象的 该提案是对通过 NIAAA 资助的多 PI R01 的竞争性更新。申请的目标 是为了检查乙醇暴露如何因动态改变而导致肝脏脂肪积累 脂肪储存细胞器脂滴（LD）的特性。具体来说，我们将研究酒精如何 暴露通过破坏信号传导损害肝细胞中的脂肪分解和脂肪吞噬机制 级联和膜运输效应器，最终导致脂肪肝。在酒精性肝病期间， 几乎所有酗酒者都会患上脂肪肝，其特点是体内异常且大量的酒精蓄积。 LD 形式的肝细胞内甘油三酯。了解形成这种脂肪的细胞过程 积累将为防止损伤进一步进展提供重要信息，因为众所周知 酒精性脂肪肝是肝损伤的初始但完全可逆的阶段。我们之前的研究—— 资助的 R01 研究了肝细胞中的 LD 动态如何受几种 GTPases（动力和 尤其是 Rabs）可以充当分子开关来调节膜流量。我们证明乙醇- 这些 GTP 酶的诱导破坏会显着增加肝细胞中 LD 的积累。初步的 支持该继续申请的数据表明，肝细胞的脂肪分解机制被激活 cAMP 激酶激动剂（异丙肾上腺素、毛喉素），但乙醇暴露会显着抑制这种反应。 此外，我们还发现肝细胞利用顺序机制来分解代谢导致脂肪分解的 LD 其次是脂肪吞噬。此外，似乎驻留在非受体酪氨酸激酶的激活 LD-自噬体 (AP) 表面具有驱动脂肪吞噬的功能，而酒精会损害这一过程。最后，在 除了 AP 吞噬 LD 之外，从 LD 中去除或“取样”脂质似乎还通过 对乙醇暴露敏感的瞬时、可测量的相互作用。这些最近的新颖发现提供了一个 该提案的良好基础，并支持我们的中心假设，即乙醇暴露会损害 通过破坏信号级联反应，肝细胞中的脂肪分解和脂肪吞噬机制 膜运输事件，导致肝脂肪变性。指导该项目的两位主要研究员 优势互补：Casey 博士是一位生物化学家，其专长是酒​​精性肝病 损害。麦克尼文博士是一位细胞生物学家，其专业是膜细胞骨架动力学。这种独特的 事实证明，合作努力对酒精性肝病领域非常有益，并将继续带来 个人努力无法达到的结果。拟议的调查将利用最先进的技术 膜运输和成像技术可量化导致酒精的特定分子事件 诱发脂肪肝。这些研究的成功完成将为乙醇如何影响提供新的见解 肝细胞中的 LD 动态以及旨在减少或消除的治疗策略的重要信息 脂肪变性的严重程度并阻止其进一步发展为酒精性脂肪性肝炎、纤维化和肝硬化。