Changes in Coenzyme A Levels are a Key Mechanism Regulating Metabolic Pathways

项目摘要 辅酶A（Coenzyme A，CoA）是哺乳动物细胞中一种重要的辅因子，也是酰基的主要载体. CoA扮演一个 在能量代谢中的中心和调节作用，因为其酰基辅酶A衍生物是数百种 代谢反应和组蛋白和关键代谢酶的翻译后修饰。CoA- 依赖性过程发生在多个亚细胞区室中，CoA的主要池存在于 线粒体、过氧化物酶体和胞质溶胶。在整个组织水平上，CoA的浓度受到严格的调节 并根据代谢状态的变化进行动态调整。严格控制CoA的重要性 水平是强调的事实，基因操纵，迫使浓度CoA以外的 稳态范围导致代谢调节和器官功能丧失。例如，无法增加 禁食期间的辅酶A水平减弱了肝脏中的脂肪酸氧化和脂肪生成， 低血糖另一方面，骨骼肌中异常高浓度的CoA与 减少肌肉质量，ATP水平和运动表现，突出了机制的重要性， 防止这种辅因子积累到毒性水平。CoA的浓度通过平衡其 合成和降解。CoA降解过程的表征较差。而且 调节不同亚细胞CoA库的机制还不完全清楚。前一 资金周期，我们已经表征了两种CoA降解酶的生化和调节特性， NUDT 7和NUDT 19，它们分别存在于肝脏和肾脏过氧化物酶体中。我们出版和未出版的 观察结果支持这些酶调节过氧化物酶体脂质代谢的结论。此外，委员会认为， Nudt19的缺失导致3-羟基-3-甲基戊二酰辅酶A在肾脏中的积累，这表明 与胆固醇合成有关。我们还鉴定了第一种哺乳动物CoA降解酶NUDT 8， 它存在于线粒体中，我们最近制造了Nudt8-/-小鼠。CoA的存在- 过氧化物酶体和线粒体中的降解酶表明，这些酶有助于 调节这些细胞器内的CoA池。我们研究计划的长期目标是了解 调节组织CoA水平的机制，并利用它们来操纵代谢网络， 代谢紊乱的治疗或预防。为了实现这一目标，我们建议：1）确定 NUDT 19调节肾脏脂质代谢和肾功能的机制，以及2）确定 NUDT 8在调节线粒体CoA库和线粒体代谢中所起的作用。这 研究计划将促进我们对调节过氧化物酶体的机制的理解， 线粒体CoA池。此外，确定由每种CoA降解酶调节的过程将 帮助制定针对和纠正代谢中特定CoA依赖性途径的策略， 紊乱

Project Summary Coenzyme A (CoA) is an essential cofactor and the major acyl group carrier in mammalian cells. CoA plays a central and regulatory role in energy metabolism, as its acyl-CoA derivatives are substrates for hundreds of metabolic reactions and the posttranslational modification of histones and key metabolic enzymes. CoA- dependent processes occur in multiple subcellular compartments, and major pools of CoA are found in the mitochondria, peroxisomes and cytosol. At the whole tissue level, the concentration of CoA is tightly regulated and dynamically adjusted to changes in the metabolic state. The importance of such a tight control over CoA levels is underscored by the fact that genetic manipulations that force the concentration of CoA outside of its homeostatic range result in loss of metabolic regulation and organ function. For example, the inability to increase CoA levels during a fast blunts fatty acid oxidation and gluconeogenesis in the liver, causing fasting hypoglycemia. On the other hand, an abnormally high concentration of CoA in skeletal muscle is associated with decreased muscle mass, ATP levels and exercise performance, highlighting the importance of mechanisms that prevent the accumulation of this cofactor to toxic levels. The concentration of CoA is regulated by balancing its synthesis and degradation. The process of CoA degradation is poorly characterized. Furthermore, the mechanisms that regulate the different subcellular CoA pools are incompletely understood. During the previous funding cycle, we have characterized the biochemical and regulatory properties of two CoA-degrading enzymes, NUDT7 and NUDT19, which reside in liver and kidney peroxisomes, respectively. Our published and unpublished observations support the conclusion that these enzymes regulate peroxisomal lipid metabolism. Furthermore, deletion of Nudt19 leads to the accumulation of 3-hydroxy-3-methylglutaryl-CoA in the kidneys, suggesting a connection to cholesterol synthesis. We also identified the first mammalian CoA-degrading enzyme, NUDT8, which resides in the mitochondria, and we have recently generated Nudt8-/- mice. The existence of CoA- degrading enzymes in both peroxisomes and mitochondria suggests that these enzymes contribute to the regulation of the CoA pools within these organelles. The long-term goal of our research program is to understand the mechanisms that regulate tissue CoA levels and to harness them to manipulate the metabolic network for the treatment or prevention of metabolic disorders. To move toward this goal, we propose to 1) determine the mechanisms through which NUDT19 regulates kidney lipid metabolism and kidney function and 2) determine the role played by NUDT8 in the regulation of the mitochondrial CoA pool and mitochondrial metabolism. This research program will advance our understanding of the mechanisms that regulate the peroxisomal and mitochondrial CoA pools. Furthermore, identifying the processes regulated by each CoA-degrading enzyme will aid in the development of strategies to target and correct specific CoA-dependent pathways in metabolic disorders.