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

项目摘要 辅酶A(CoA)是一种重要的辅因子，也是哺乳动物细胞中主要的酰基载体。CoA扮演着一个 在能量代谢中的中心和调节作用，因为它的酰基-CoA衍生物是数百种 代谢反应以及组蛋白和关键代谢酶的翻译后修饰。CoA- 依赖过程发生在多个亚细胞隔室中，主要的CoA池位于 线粒体、过氧化物体和胞浆。在整个组织水平上，辅酶A的浓度受到严格的调控 并根据代谢状态的变化进行动态调整。对CoA进行如此严格控制的重要性 强调这一水平的是这样一个事实，即迫使CoA集中在其 体内平衡范围会导致代谢调节和器官功能的丧失。例如，无法增加 快速钝化期间CoA水平降低肝脏中的脂肪酸氧化和糖异生，从而导致禁食 低血糖症。另一方面，骨骼肌中CoA的异常高浓度与 肌肉质量、三磷酸腺苷水平和运动成绩下降，突显了 防止这种辅因子积累到有毒的水平。辅酶A的浓度是通过平衡其 合成和降解。CoA的降解过程没有得到很好的描述。此外， 调节不同亚细胞CoA池的机制尚不完全清楚。在上一次 在资金周期中，我们已经表征了两种CoA降解酶的生化和调节特性， Nudt7和Nudt19，分别存在于肝脏和肾脏的过氧化物体中。我们出版的和未出版的 观察结果支持这一结论，即这些酶调节过氧酶体的脂肪代谢。此外， Nudt19的缺失导致3-羟基-3-甲基戊二酰辅酶A在肾脏中积累，这表明 与胆固醇合成有关。我们还鉴定了第一个哺乳动物CoA降解酶Nudt8， 它驻留在线粒体中，我们最近产生了nudt8-/-小鼠。CoA的存在-- 过氧化物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水平并利用它们来操纵代谢网络的机制 新陈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 Nudt19调节肾脏脂代谢和肾功能的机制及2)决定 Nudt8在调节线粒体CoA池和线粒体代谢中的作用。这项研究 该计划将促进我们对调节过氧化物体和线粒体的机制的理解 可口可乐泳池。此外，确定每个CoA降解酶调节的过程将有助于 制定策略以针对和纠正代谢紊乱中特定的辅酶A依赖途径。

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.