Regulation of Energy Metabolism by PDP1 and PDP2

描述（由申请人提供）：本项目的长期目标是了解负责线粒体丙酮酸脱氢酶复合物（PDC）调节的分子机制。由PDC催化的反应在一般代谢中起核心作用，为主要的能量产生和生物合成途径（例如柠檬酸循环、脂肪生成和胆固醇的生物合成）提供碳源。哺乳动物PDC的活性通过丙酮酸脱氢酶激酶和丙酮酸脱氢酶磷酸酶催化的可逆磷酸化/去磷酸化循环来调节。越来越多的证据强烈表明，控制PDC的磷酸化状态在饥饿、代谢性酸中毒、缺血和糖尿病中变得至关重要。本申请的主要目的是了解磷酸酶反应中PDC重新激活的分子机制。以前，我们已经证明，PDC的去磷酸化是由两个密切相关的磷酸酶（PDP 1和PDP 2），这是显着不同的组织分布，酶活性和调节催化。我们还发现，PDP 2蛋白在糖尿病中下调，从而导致PDC的不希望的失活，这阻止了碳水化合物燃料的有氧氧化。最近，我们获得了第一个证据表明，在线粒体中，PDP 1和PDP 2与不同的辅助或靶向亚基相互作用。基于这些初步的数据，我们假设，在体内的磷酸酶活性的调节主要是通过特定的蛋白质-蛋白质相互作用。在本申请中，将通过以下具体目标来研究这一主要工作假设：1）分离和鉴定PDP 1和PDP 2的相互作用配偶体; 2）建立靶向和调节PDP 1的分子机制; 3）建立靶向和调节PDP 2的分子机制;阐明糖尿病中PDP 2长期调控的分子机制。丙酮酸脱氢酶复合物由于其过度磷酸化而失活，在代谢性酸中毒、缺血和糖尿病中具有有害作用。揭示负责丙酮酸脱氢酶磷酸酶1和2进行的丙酮酸脱氢酶复合物的再活化的分子机制对于开发新的治疗剂至关重要。

DESCRIPTION (provided by applicant): The long-term goal of this project is to understand the molecular mechanisms responsible for the regulation of mitochondrial pyruvate dehydrogenase complex (PDC). The reaction catalyzed by PDC plays a central role in general metabolism providing a source of carbon for the major energy-generating and biosynthetic pathways such as the Citric Acid Cycle, lipogenesis, and the biosynthesis of cholesterol. The activity of mammalian PDC is regulated through a reversible phosphorylation/dephosphorylation cycle catalyzed by pyruvate dehydrogenase kinase and pyruvate dehydrogenase phosphatase. Growing evidence strongly suggests that control over the phosphorylation state of PDC becomes critically important in starvation, metabolic acidosis, ischemia, and diabetes. The major thrust of this application is to understand the molecular mechanisms responsible for the re-activation of PDC in phosphatase reaction. Previously, we have demonstrated that dephosphorylation of PDC is catalyzed by two closely related phosphatases (PDP1 and PDP2) that are markedly different with respect to their tissue distribution, enzymatic activities and regulation. We have also found that PDP2 protein is down-regulated in diabetes thereby contributing to the unwanted inactivation of PDC, which prevents the aerobic oxidation of carbohydrate fuels. Recently, we obtained the first evidence indicating that, in mitochondria, PDP1 and PDP2 interact with different accessory or targeting subunits. Based on these preliminary data, we hypothesize that the regulation of phosphatase activity in vivo occurs largely through specific protein-protein interactions. In the present application, this major working hypothesis will be investigated through the following specific aims: 1) to isolate and identify the interacting partners of PDP1 and PDP2; 2) to establish the molecular mechanisms of targeting and regulation of PDP1; 3) to establish the molecular mechanisms of targeting and regulation of PDP2; and 4) to elucidate the molecular mechanism of long-term regulation of PDP2 in diabetes. Inactivation of pyruvate dehydrogenase complex due to its hyperphosphorylation has detrimental effect in metabolic acidosis, ischemia, and diabetes. Uncovering the molecular mechanisms responsible for the reactivation of pyruvate dehydrogenase complex carried out by pyruvate dehydrogenase phosphatases 1 and 2 is critical for development of new therapeuticals.