Mechanisms of ER stress - induced fatty liver

项目6.项目摘要/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，以及急性接触肝毒素。FLD可从单纯性脂肪变性进展为脂肪性肝炎 这会损害肝功能，导致炎症、纤维化、肝硬化，最终导致肝功能衰竭。而当 FLD很可能反映了脂肪合成、储存、氧化和/或分泌之间的失衡， 这种不平衡的潜在分子原因只被部分了解。作为酒精性肝病和酒精性肝病 非酒精来源是非常常见的，确定其病因可能是不同的，将提示途径 预防肝功能衰竭的治疗。这项研究建议是基于强有力的初步数据论证 内质网应激导致参与维持的基因转录抑制 脂质稳态；内质网应激敏感蛋白ATF6基因缺陷的小鼠无法克服内质网 压力，并在挑战时变得非常脂肪。这些动物，在其他地方是正常的 未损伤状态，为剖析内质网应激与肝脂之间的关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电流变微扰是如何促进 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 要了解内质网应激反应如何与脂类稳态在 抄写。基因调控事件将根据体内的能力被放入一个层次中 过表达关键代谢转录因子以部分或完全挽救ATF6基因缺失小鼠的脂肪变性。在……里面 由内质网应激调节的转录因子对基因的平行、直接调控将由两个无偏见的 和有针对性的染色质免疫沉淀。最后，连接新陈代谢转录的机制 对未解决的内质网应激的调节将被确定。第二个目标是确定如何监管 内质网应激反应引起的脂质代谢进而影响内质网功能。这一目标将通过以下方式实现 找出在内质网应激期间导致脂肪变性的脂肪代谢途径，并测试 当这些途径发生变化时，内质网折叠和处理客户蛋白的能力(即“内质网功能”)就会改变 不受内质网压力的影响。第三个目标是确定慢性内质网应激对 病理性脂肪变性，尤其是酒精性脂肪肝。我们将使用ATF6缺失的小鼠来测试 内质网功能受损使小鼠在长期饮酒过程中对脂肪变性敏感。我们还将 确定慢性酒精摄入如何通过内质网应激调节改变细胞内稳态 在基因表达上。这项工作提供了几个独立的途径来解决开发的一个方面 目前对脂肪变性知之甚少，并将确定可能 代表了未来预防肝功能衰竭的治疗干预的有吸引力的目标。

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.