CD73 is a multi-functional protein that regulates liver injury

抽象的。 它们对肝脏的合成、分泌和代谢功能的核心重要性使肝细胞 特别容易受伤。增强肝细胞对破坏性侮辱的抵抗力有可能阻止 肝脏疾病早期进展，与病因无关。为此，胞外-5‘-核苷酸酶(CD73)是一种 很有希望成为新的肝病靶点，因为它在多种小鼠肝损伤模型中发挥关键作用，并且是 多种病因慢性肝病患者的肝脏调节失调。CD73的经典功能 是细胞外一磷酸腺苷(AMP)向腺苷的代谢。我们发现全球CD73-/-小鼠 对化学诱导的肝细胞损伤具有抵抗力，考虑到肝损伤会导致 野生型小鼠细胞表面CD73 AMPase活性几乎完全丧失。这指向可供选择的功能， 这也得到了我们在晚期发现的一种新的催化失活的CD73亚型(CD73S)的支持 人类肝病。我们观察到在原代肝细胞中表达的凋亡相关信号的差异 两种不同的人类CD73亚型。CD73在体外结合了两种生物活性脂类，表明它可能调节 脂质动态平衡。我们的中心假设是，非酶和替代的异构体相关的机制 肝细胞CD73促进肝损伤和疾病进展。这一假设将通过两个具体的 目的：(I)确定CD73在肝细胞中的非酶和异构体特异性功能；(Ii)研究 CD73缺失时的体内和组织水平的保肝机制。我们对目标1的方法将 将高通量配基筛选、高含量成像和蛋白质组学与详细的生化相结合， 分子和细胞生物学评估以确定CD73是脂质敏感受体还是内质网调节因子 并确定非催化CD73S变异体在肝细胞抵抗 压力。对于目标2，我们将使用酒精和酒精的两种模型在体内检测CD73对肝脏的特异性贡献。 高脂饮食诱导的损伤和我们新产生的肝脏特异性CD73-/-小鼠。我们将利用重组 体内酶和精密切割的肝脏切片，以执行机械性抢救和功能丧失研究。这 这项工作将导致CD73功能在肝细胞中的彻底整合，并有可能产生新的 保护肝脏的机械性方法。

Abstract. Their central importance to the synthetic, secretory and metabolic functions of the liver renders hepatocytes particularly vulnerable to injury. Reinforcing hepatocyte resilience to damaging insults holds potential to block liver disease progression at early stages, independent of etiology. To that end, ecto-5’-nucleotidase (CD73) is a promising novel liver disease target, as it plays critical roles in multiple mouse liver injury models, and is dysregulated in livers of patients with chronic liver diseases of multiple etiologies. The classical function of CD73 is metabolism of extracellular adenosine monophosphate (AMP) to adenosine. We found that global CD73-/- mice are resistant to chemically-induced hepatocellular injury, an unexpected finding given that liver injury induces near-complete loss of cell surface CD73 AMPase activity in wild-type mice. This points to alternative functions, which is also supported by our identification of a novel, catalytically-inactive CD73 isoform (CD73S) in advanced human liver disease. We observe differences in apoptosis-related signaling in primary hepatocytes expressing the two different human CD73 isoforms. CD73 binds two bioactive lipids in vitro, suggesting that it may regulate lipid homeostasis. Our central hypothesis is that non-enzymatic and alternative isoform-related mechanisms of hepatocyte CD73 promote liver injury and disease progression. The hypothesis will be addressed via two specific aims: (i) Define the non-enzymatic and isoform-specific functions of CD73 in hepatocytes and (ii) Examine the in vivo and tissue-level mechanisms of hepatoprotection in the absence of CD73. Our approach for Aim 1 will couple high throughput ligand screening, high content imaging, and proteomics with detailed biochemical, molecular and cell-biological assessments to determine if CD73 is a lipid-sensing receptor or a regulator of ER stress, and to determine the specific function of the non-catalytic CD73S variant in hepatocyte resistance to stress. For Aim 2, we will examine liver-specific contributions of CD73 in vivo using two models of alcohol and high fat diet-induced injury and our newly-generated liver-specific CD73-/- mice. We will utilize recombinant enzyme in vivo and precision-cut liver slices to perform mechanistic rescue and loss-of-function studies. This work will lead to a thorough integration of CD73 function in hepatocytes with the potential to yield novel mechanistic approaches for hepatoprotection.