Mechanisms of ER stress - induced fatty liver

项目6.项目总结/摘要 脂肪肝（FLD）有多种原因，包括慢性饮酒，肥胖，病毒感染， 营养不良和急性暴露于肝毒素。FLD可从单纯脂肪变性发展为脂肪性肝炎 损害肝功能，导致炎症，纤维化，肝硬化，最终肝衰竭。而 FLD很可能反映了脂质合成、储存、氧化和/或分泌之间的不平衡， 这种不平衡的潜在分子原因只是部分了解。作为酒精和 非酒精性起源是非常常见的，确定其病因，这可能是不同的，将建议的途径， 治疗以防止肝衰竭。这项研究建议是基于强有力的初步数据， 内质网（ER）应激导致参与维持细胞内 脂质稳态; ER应激感应蛋白ATF 6基因缺陷的小鼠未能克服ER 压力，并在挑战中变得极度脂肪化。这些动物，在其他方面是正常的， 未损伤状态下，为解剖ER应激与肝脏脂质之间的联系提供了有价值的工具 新陈代谢.这项工作的长期目标是了解ER扰动如何有助于 脂肪肝这一目标将通过三个相辅相成的调查领域来实现。第一个目标是 为了了解ER应激反应如何在机制上与脂质稳态在水平上联系起来， 转录。基因调控事件将被放置到一个层次的基础上的能力，在体内 关键代谢转录因子的过度表达以部分或完全挽救Atf 6缺失小鼠的脂肪变性。在 平行的，ER应激调节转录因子对基因的直接调节将通过两个无偏的 和靶向染色质免疫沉淀。最后，联系代谢转录的机制 将确定对未解决的ER应激的调节。第二个目标是确定如何监管 ER应激反应引起的脂质代谢反过来影响ER功能。这一目标将通过以下方式实现： 精确定位ER应激期间导致脂肪变性的脂质代谢途径，并测试 ER折叠和加工客户蛋白的能力（即，当这些通路被阻断时， 独立于ER应激进行操作。第三个目的是确定慢性内质网应激如何有助于 病理性脂肪变性，特别是酒精性脂肪肝病。我们将使用Atf 6基因敲除小鼠来测试 ER功能的损伤使小鼠在慢性乙醇消耗期间对脂肪变性敏感。我们还将 确定慢性乙醇消耗如何通过ER应激调节改变细胞内稳态 in gene基因expression表达.这项工作提供了几个独立的途径，以解决发展的一个方面， 脂肪变性，目前了解甚少，并将确定新的关键调控途径， 代表未来治疗干预以预防肝衰竭的有吸引力的靶点。

Item 6. Project Summary/Abstract Fatty liver disease (FLD) has a variety of causes including chronic alcohol consumption, obesity, viral infection, malnutrition, and acute exposure to hepatotoxins. FLD can progress from simple steatosis to steatohepatitis that compromises liver function, leading to inflammation, fibrosis, cirrhosis, and ultimately liver failure. While FLD most likely reflects an imbalance between lipid synthesis, storage, oxidation, and/or secretion, the underlying molecular causes of this imbalance are only partially understood. As FLD of both alcoholic and nonalcoholic origins is very common, identifying its etiologies, which are likely varied, will suggest avenues of treatment to prevent liver failure. This research proposal is based upon strong preliminary data demonstrating that endoplasmic reticulum (ER) stress leads to transcriptional suppression of genes involved in maintaining lipid homeostasis; mice genetically deficient in the ER stress-sensing protein ATF6¿ fail to overcome ER stress, and become profoundly steatotic upon challenge. These animals, which are otherwise normal in the uninjured state, provide a valuable tool for dissecting the connections between ER stress and liver lipid metabolism. The long-term objective of this work is to understand how ER perturbation contributes to fatty liver disease. This goal will be achieved by three complementary areas of investigation. The first aim is to understand how the ER stress response is mechanistically connected to lipid homeostasis at the level of transcription. Gene regulatory events will be placed into a hierarchy based on the ability of in vivo overexpression of key metabolic transcription factors to partially or fully rescue steatosis in Atf6¿-null mice. In parallel, direct regulation of genes by ER stress-regulated transcription factors will be probed by both unbiased and targeted chromatin immunoprecipitation. Finally, the mechanism that ties metabolic transcriptional regulation to unresolved ER stress will be determined. The second aim is to determine how the regulation of lipid metabolism by the ER stress response in turn impacts ER function. This aim will be achieved by pinpointing the pathways of lipid metabolism that contribute to steatosis during ER stress, and testing how the ability of the ER to fold and process client proteins (i.e., "ER function") is altered when these pathways are manipulated independent of ER stress. The third aim is to determine how chronic ER stress contributes to pathological steatosis, in particular alcoholic fatty liver disease. We will use Atf6¿-null mice to test whether impairment of ER function sensitizes mice to steatosis during chronic ethanol consumption. We will also determine how chronic ethanol consumption alters cellular homeostasis through ER stress-regulated changes in gene expression. This work provides several independent avenues to address an aspect of the development of steatosis that is currently poorly understood, and will identify novel key regulatory pathways that might represent attractive targets for future therapeutic intervention to prevent liver failure.