Novel mechanisms of mitochondrial regulation by sirtuin deacetylases

描述（由申请人提供）：线粒体是在真核细胞中执行许多关键功能的细胞质细胞器，其中包括产生大多数细胞ATP。线粒体功能障碍涉及多种病理学，如2型糖尿病、肌肉减少症、神经变性和癌症。尽管它们对人类健康至关重要，但线粒体功能调节的机制仍不完全清楚。这种应用的基本原理是，对这种机制的更深入的了解可以允许开发调节线粒体功能的治疗剂，作为对各种人类疾病的治疗。本申请集中于sirtuin蛋白在调节关键线粒体功能中的新作用。Sirtuins是一个脱乙酰基酶家族，在无脊椎动物模型中促进寿命延长，并调节哺乳动物的多种过程。该应用程序是基于两个新的观察。首先，线粒体sirtuin SIRT 5在丙酮酸脱氢酶复合物（PDC）的脱乙酰化和抑制活性中起迄今未描述的作用，所述丙酮酸脱氢酶复合物是在调节哺乳动物细胞中的葡萄糖氧化中起主要作用的线粒体全酶。PDC功能障碍与2型糖尿病、癌症和心脏缺血有关。刺激PDC活性的新方法-如通过SIRT 5抑制-在这些和其他临床环境中将是有益的。其次，sirtuin SIRT 6在刺激线粒体呼吸中具有意想不到的作用。脂肪组织特异性SIRT 6敲除（S6 AKO）小鼠显示出显著的肥胖，这可能部分归因于棕色脂肪组织（BAT）中的线粒体呼吸缺陷。本申请的总体目标是阐明沉默调节蛋白的线粒体调节的新机制，从而解决线粒体生物学中的关键知识缺口。本申请的假设是双重的。第一个假设是SIRT 5通过减弱PDC活性来抑制葡萄糖氧化。第二个假设是SIRT 6促进线粒体呼吸以促进细胞和生物体的稳态。这些假设将在两个具体目标中得到检验。首先，SIRT 5在调节PDC中的作用将通过质谱、诱变、体内通量分析和高脂喂养的组合在机制水平上阐明。其次，SIRT 6在促进线粒体呼吸中的作用将被机械地定义。SIRT 6在抑制肥胖中的功能将通过S6 AKO小鼠的详细表征和通过产生BAT特异性SIRT 6敲除来阐明。这种应用是创新的，因为它专注于sirtuins在调节线粒体能量方面的新功能。各种尖端技术将被用来测试这些假设。该应用是重要的，因为它将在sirtuins和线粒体之间建立新的联系，可能为未来sirtuin定向治疗奠定基础，以调节葡萄糖氧化和/或线粒体呼吸。因此，这项工作福尔斯属于国家地理、气象和科学研究所的总体使命。

DESCRIPTION (provided by applicant): Mitochondria are cytoplasmic organelles that perform many crucial functions in eukaryotic cells, among them generation of most cellular ATP. Mitochondrial dysfunction is implicated in diverse pathologies such as type 2 diabetes, sarcopenia, neurodegeneration, and cancer. Despite their central importance to human health, mechanisms by which mitochondrial functions are regulated remain incompletely understood. The rationale for this application is that improved insights into such mechanisms may permit development of therapeutics to modulate mitochondrial functions as treatments for a wide variety of human diseases. This application focuses on novel roles for sirtuin proteins in regulating key mitochondrial functions. Sirtuins are a family of deacetylases that promote increased longevity in invertebrate models and modulate diverse processes in mammals. The application is based on two novel observations. First, the mitochondrial sirtuin SIRT5 plays a hitherto undescribed role in deacetylating and suppressing activity of Pyruvate Dehydrogenase Complex (PDC), a mitochondrial holoenzyme with a major role in regulating glucose oxidation in mammalian cells. PDC dysfunction is implicated in type 2 diabetes, cancer, and cardiac ischemia. Novel means of stimulating PDC activity - as by SIRT5 inhibition - would be beneficial in these and other clinical settings. Second, the sirtuin SIRT6 has an unexpected role in stimulating mitochondrial respiration. Adipose tissue- specific SIRT6 knockout (S6AKO) mice show marked adiposity, potentially due in part to mitochondrial respiratory defects in brown adipose tissue (BAT). The overall objective of this application is to elucidate novel mechanisms of mitochondrial regulation by sirtuin proteins, thus addressing a key knowledge gap in mitochondrial biology. The hypotheses of this application are two-fold. The first hypothesis is that SIRT5 inhibits glucose oxidation by attenuating PDC activity. The second hypothesis is that SIRT6 promotes mitochondrial respiration to promote cellular and organismal homeostasis. These hypotheses will be tested in two specific aims. First, the roles of SIRT5 in regulating PDC will be elucidated at a mechanistic level through a combination of mass spectrometry, mutagenesis, in vivo flux analysis, and high fat feeding. Second, the role of SIRT6 in promoting mitochondrial respiration will be defined mechanistically. The function of SIRT6 in suppressing adiposity will be elucidated through detailed characterization of S6AKO mice, and through generation of BAT-specific SIRT6 knockouts. This application is innovative, since it focuses on novel functions for sirtuins in regulating mitochondrial energetics. A variety of cutting-edge techniques will be brought to bear to test these hypotheses. The application is significant, since it will establish novel links between sirtuins and mitochondria, potentially laying the groundwork for future sirtuin-directed therapies to modulate glucose oxidation and/or mitochondrial respiration. Hence this work falls within the overall mission of NIGMS.