Redox Regulation of O-GlcNAcylation Signaling in the Pathogenesis of Alcoholic Fatty Liver Disease

项目总结 酒精性脂肪肝(AFLD)是慢性肝病的主要病因。在全球范围内，AFLD占0.9% 占总死亡率和伤残调整寿命年的0.6%，仍然是全世界的公共卫生问题。 尽管对健康和经济产生了深远的影响，但由于缺乏，AFLD的管理仍然具有挑战性 详细了解其发病和发展的决定因素。这个项目的目标是 阐明氧化还原调节的肝脏O-GlcNAc信号在酒精性肝损伤中的新作用 从而确定针对AFLD的潜在新的预防、诊断和/或治疗靶点。氧化 应激被认为在AFLD的发生和发展的许多途径中发挥核心作用。 肝脏谷胱甘肽(GSH)在维持细胞氧化还原动态平衡中的作用。耐人寻味的是，慢性GSH 谷氨酸-半胱氨酸连接酶修饰亚单位(Gclm)基因整体缺失的小鼠 对酒精引起的脂肪变性有保护作用。分子和代谢组学研究表明， 低GSH的保肝作用与激活AMPK信号通路和NRF2抗氧化剂有关 反应和肝脏代谢的重新编程，有利于维持细胞氧化还原和 代谢动态平衡。多重组学分析表明，转录后机制起着重要作用 在介导低GSH诱导的酒精暴露的代谢适应中。蛋白质的O-GlcN酰化是一种 翻译后修饰(PTM)的普遍形式，其中单个O-连接的N-乙酰氨基葡萄糖(O- GlcNAc)部分添加到核蛋白、细胞质蛋白和线粒体蛋白中。此过程由一个 一对O-GlcNAc循环酶，O-GlcNAc转移酶(OGT)和O-GlcNAcase(OGA)。在肝脏中，O- GlcNAc信号已被证明是营养和胁迫感知的重要机制，并 随后调节肝脏细胞的动态平衡。肝脏中存在异常的O-GlcN酰化 胰岛素抵抗、脂肪肝和相关的纤维化。到目前为止，人们对O-的作用知之甚少。 GlcN酰化在AFLD发病机制中的作用我们的初步研究表明，在GSH缺陷的Gclm缺失小鼠中 肝脏，长期酗酒导致全局O-GlcNA化和相关的有益变化 细胞通路和信号蛋白。该项目将对这些具有挑衅性的发现进行扩展，并测试 假设预测慢性氧化应激(由于GSH)驱动的适应性O-GlcNAc信号 肝虚)可保护肝脏免受酒精引起的肝损伤。我们建议(1)利用GCLM-NULL 小鼠模型研究乙醇对O-GlcN酰化和磷酸化修饰的影响 O-GlcNAc循环酶的肝脏蛋白质组和底物靶向性，以及(2)功能评价 最佳候选蛋白-O-GlcN酰化对人HepaRG乙醇相关应激反应的影响 细胞。这项拟议的研究将是第一次检查体内肝脏氧化还原状态与氧还原态的相互作用。 酒精性肝损伤背景下的谷氨酰化信号转导。

PROJECT SUMMARY Alcoholic fatty liver disease (AFLD) is a major cause of chronic liver disease. Globally, AFLD accounts for 0.9% of total mortality and 0.6% of disability-adjusted life years and remains a public health problem worldwide. Despite its profound health and economic impact, the AFLD management remains challenging due to the lack of detailed understanding of determinants of its pathogenesis and progression. The goal of this project is to elucidate a novel role of redox-modulated hepatic O-GlcNAc signaling in alcohol-induced liver injury, and thereby identify potential novel preventive, diagnostic and/or therapeutic targets against AFLD. Oxidative stress is implicated to play a central role in many pathways involved in the initiation and progression of AFLD. Hepatic glutathione (GSH) functions in maintaining cellular redox homeostasis. Intriguingly, chronic GSH deficiency in mice harboring a global disruption of the glutamate-cysteine ligase modifier subunit (Gclm) gene confers protection against alcohol-induced steatosis. Molecular and metabolomics studies indicate that the hepatoprotective effect of low GSH is linked to activations of AMPK signaling pathway and NRF2 antioxidant response, and reprogramming of hepatic metabolism that benefits the maintenance of cellular redox and metabolic homeostasis. Multiomics analyses imply that post-transcriptional mechanisms play a significant role in mediating low GSH-elicited metabolic adaptation upon ethanol exposure. O-GlcNAcylation of protein is a prevalent form of post-translational modification (PTM), where a single O-linked N-acetylglucosamine (O- GlcNAc) moiety is added to nuclear, cytoplasmic and mitochondrial proteins. This process is controlled by a pair of O-GlcNAc cycling enzymes, O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA). In the liver, O- GlcNAc signaling has been shown to serve as an important mechanism for nutrient and stress sensing and subsequent regulation of liver cellular homeostasis. Aberrant O-GlcNAcylation has been implicated in hepatic insulin resistance, fatty liver disease and associated fibrosis. To date, little is known about the role of O- GlcNAcylation in AFLD pathogenesis. Our preliminary studies show that, in GSH-deficient Gclm-null mouse livers, chronic-binge ethanol feeding induced beneficial changes in global O-GlcNAylation and associated cellular pathways and signaling proteins. This project will expand upon these provocative findings and test the hypothesis predicting that adaptive O-GlcNAc signaling driven by chronic oxidative stress (due to GSH deficiency) in the liver protects against alcohol-induced liver injury. We propose to (1) utilize the Gclm-null mouse model to examine ethanol-induced changes in O-GlcNAcylation and phosphorylation modifications of the liver proteome and substrate targeting of O-GlcNAc cycling enzymes, and (2) evaluate the functional impacts of top candidate protein-O-GlcNAcylations in ethanol-associated stress response in human HepaRG cells. The proposed study will be the first examination of in vivo interplay between hepatic redox status and O- GlcNAcylation signaling in the context of alcohol induced liver injury.