Regulation of Energy Metabolism by PDP1 and PDP2

描述（由申请人提供）：该项目的长期目标是了解线粒体丙酮酸脱氢酶复合物（PDC）调控的分子机制。PDC催化的反应在一般代谢中起核心作用，为主要的能量生成和生物合成途径（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的活性是通过丙酮酸脱氢酶激酶和丙酮酸脱氢酶催化的可逆磷酸化/去磷酸化循环来调节的。越来越多的证据强烈表明，对PDC磷酸化状态的控制在饥饿、代谢性酸中毒、缺血和糖尿病中至关重要。该应用程序的主要目的是了解在磷酸酶反应中PDC再激活的分子机制。之前，我们已经证明PDC的去磷酸化是由两种密切相关的磷酸酶（PDP1和PDP2）催化的，这两种磷酸酶在组织分布、酶活性和调控方面明显不同。我们还发现，PDP2蛋白在糖尿病中下调，从而导致PDC失活，从而阻止碳水化合物燃料的有氧氧化。最近，我们首次获得证据表明，在线粒体中，PDP1和PDP2与不同的辅助或靶向亚基相互作用。基于这些初步数据，我们假设体内磷酸酶活性的调节主要是通过特定的蛋白质-蛋白质相互作用发生的。在本应用中，我们将通过以下具体目标来研究这一主要的工作假设：1)分离和识别PDP1和PDP2的相互作用伙伴；2)建立PDP1靶向调控的分子机制；3)建立靶向调控PDP2的分子机制；4)阐明PDP2在糖尿病中长期调控的分子机制。丙酮酸脱氢酶复合物因其过度磷酸化而失活，对代谢性酸中毒、缺血和糖尿病有不利影响。揭示丙酮酸脱氢酶磷酸酶1和2进行丙酮酸脱氢酶复合体再激活的分子机制对新疗法的开发至关重要。

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.