Mechanism of cholesterol regulation by the mitochondrial translocator protein (TSPO)

项目总结 游离胆固醇是膜双层完整性和流动性所必需的结构成分 对细胞信号和脂类代谢的调节很重要。游离胆固醇也是 类固醇激素和胆汁酸的合成。游离胆固醇与酯化贮藏之间的平衡 形态受到体内所有细胞的严格调控，对于预防高胆固醇血症和 伴发的疾病。直到最近，人们还认为转位蛋白(TSPO)存在于外周血细胞 线粒体膜是胆固醇进入线粒体进行类固醇激素的转运体 制作。我们在最近的工作中推翻了这一假设，证明TSPO没有参与其中 进程。这一空白使人们的注意力重新集中在阐明TSPO行动的作用上。这是极端的 重要的是因为TSPO的上调在多种人类病理中都可以看到，目前有24 用于治疗或诊断目的的针对TSPO的人体临床试验。通过重新审视两国关系 利用不同的TSPO基因缺失模型发现TSPO与胆固醇之间存在一种新的联系 TSPO和胆固醇酯化之间的关系。这个应用程序的目的是阐明 TSPO：(目标1)定义TSPO介导的胆固醇酯化机制，并(目标2)了解 TSPO基因敲除(TSPO-/-)小鼠体内脂质稳态的变化。这个项目的实验计划 从TSPO的分子表征扩展到利用体内代谢研究其功能相关性 模特们。利用体外模型，我们研究了胆固醇结合和蛋白质相互作用对 TSPO通过评估假定结合部位的特定氨基酸突变；我们还进行代谢组学以 评估细胞反应并确定与已知胆固醇调节途径的功能整合 在牢房里。利用活体模型，我们研究了TSPO对肝脏和白色脂肪中脂代谢的影响 组织及其对血脂的相关影响。这些研究的结果将提供新的见解。 TSPO对血脂的调节，这可能解释了动脉粥样硬化中观察到的特定病理功能障碍， 非酒精性脂肪性肝病(NAFLD)和非酒精性脂肪性肝炎(NASH)。此外，了解 TSPO功能将与描述其参与病理的基础和定义 TSPO用于促进人类医学的药理靶向的基本原理。

PROJECT SUMMARY Free cholesterol is an essential structural component required for integrity and fluidity of membrane bilayers important for cell signaling and regulation of lipid metabolism. Free cholesterol is also the precursor for the synthesis of steroid hormones and bile acids. The balance between free cholesterol and its esterified storage form is tightly regulated by all cells in the body, and is crucial for preventing hypercholesterolemia and associated disorders. Until recently, it was believed that the translocator protein (TSPO) present in the outer mitochondrial membrane was a transporter for cholesterol to enter the mitochondria for steroid hormone production. We overturned this assumption in recent work demonstrating that TSPO is not involved in this process. This void has refocused attention on elucidating the role of TSPO action. This is of extreme importance because upregulation of TSPO is seen in multiple human pathologies, and there are currently 24 human clinical trials targeting TSPO for therapeutic or diagnostic purposes. By reexamining the relationship between TSPO and cholesterol using different Tspo gene deleted models we have identified a novel link between TSPO and cholesterol esterification. The objective of this application is to elucidate the precise role of TSPO: (Aim 1) Define the TSPO-mediated mechanism in cholesterol esterification, and (Aim 2) Understand the in vivo changes to lipid homeostasis in Tspo knockout (Tspo-/-) mice. The experimental plans for this project extend from molecular characterization of TSPO to studying its functional relevance using in vivo metabolism models. Using in vitro models, we investigate the importance of cholesterol binding and protein interactions to TSPO by evaluating specific amino acid mutations to putative binding sites; we also perform metabolomics to evaluate cellular responses and determine functional integration with known pathways of cholesterol regulation in cells. Using in vivo models, we examine TSPO effects on lipid metabolism in the liver and white adipose tissue and the associated impact on plasma lipids. Results from these studies are poised to offer novel insights into lipid regulation by TSPO that might explain specific pathological dysfunctions observed in atherosclerosis, non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH). In addition, knowledge of TSPO function will be highly relevant to describing the basis of its involvement in pathologies and defining the principles underlying pharmacological targeting of TSPO for advancing human medicine.