Transcriptional Control of Mitochondrial Bioenergetic Function

描述(申请人提供)：能量消耗(体重的主要组成部分)通过控制生物能量/代谢功能的信号和转录成分组成的复杂调控网络来调节。骨骼肌和米色/棕色脂肪是占能量消耗很大一部分的关键组织。肾上腺素能/cAMP信号通路是影响能量平衡和细胞生物能量学的重要途径之一。信号/转录和线粒体生物能量系统组件的缺陷足以促进肥胖和相关的疾病，如2型糖尿病和动脉粥样硬化。重要的是，线粒体生物能量功能的维持和激活严格依赖于编码线粒体蛋白的核基因的基础和调控转录。在这些线粒体过程的转录调控因子中，有PGC1家族的辅助激活因子和转录因子，包括核呼吸因子、激素核受体和YY1。在过去的几年里，我们的实验室已经确定转录因子YY1是核线粒体基因的关键调节因子，在培养细胞和动物中都对线粒体的生物能量能力有重要影响。依赖于YY1在特定位置的磷酸化，磷酸化的YY1通过招募PGCl1在线粒体基因上形成一个活性复合体。相反，去磷-YY1通过与多梳蛋白相互作用形成抑制复合体，抑制线粒体基因的表达。重要的是，控制YY1依赖的磷酸化相互作用的信号之一是cAMP途径。基于这些发现，这项建议的主要目标是确定通过YY1转录复合体驱动线粒体基因表达的调控机制，并使用体内肥胖和糖尿病小鼠模型评估其功能。我们有三个具体的目标：目标1建议对YY1转录复合体如何控制线粒体功能进行分子机制分析。目的2致力于在骨骼和脂肪培养细胞中进行YY1转录蛋白复合体介导的细胞和功能线粒体的生物能量和代谢分析。目的3在骨骼肌和脂肪组织中进行YY1转录因子介导的体内代谢和能量分析。我们将使用遗传小鼠模型，在这些组织中YY1的功能获得和丧失。这些研究的结果将提供YY1转录复合体调节线粒体生物能量能力的分子机制，以及该复合体中的缺陷如何导致线粒体功能和能量平衡失调。基于这些途径在肥胖和糖尿病等代谢性疾病中发生改变的事实，这项拨款申请中提议的研究可能会转化为潜在的治疗方法。

DESCRIPTION (provided by applicant): Energy expenditure (a major component of body weight) is regulated through a complex regulatory network formed by signaling and transcriptional components that control bioenergetic/metabolic function. Skeletal muscle and beige/brown adipose are key tissues that account for a large fraction of energy expenditure. Adrenergic/cAMP signaling is one of the powerful pathways that affect energy balance and cellular bioenergetics. Defects in components of the signaling/transcriptional and mitochondrial bioenergetic system is sufficient to promote obesity and associated disorders such as type 2 diabetes and atherosclerosis. Importantly, maintenance and activation of mitochondrial bioenergetic function strictly depend on basal and regulated transcription of nuclear genes encoding for mitochondrial proteins. Among the transcriptional regulators of these mitochondrial processes are the PGC1 family of coactivators and transcription factors including Nuclear Respiratory Factors, Hormone Nuclear Receptors and YY1. In the last years, our laboratory has identified the transcription factor YY1 as a key regulator of nuclear mitochondrial genes that has a major impact in mitochondrial bioenergetic capacity, both in cultured cells and in animals. Depending on YY1 phosphorylation at specific sites, phospho-YY1 forms an active complex on mitochondrial genes through recruitment of PGC1¿. In contrast, dephospho-YY1 forms a repressor complex through interacting with Polycomb Proteins that suppresses the expression of mitochondrial genes. Importantly, one of the signals that govern YY1-dependent phosphorylation interaction is the cAMP pathway. Based on these findings, the major goal of this proposal is to identify the regulatory mechanisms driving mitochondrial gene expression through YY1 transcriptional complex and to assess the functionality using in-vivo mouse models of obesity and diabetes. We have three Specific Aims: Aim 1 proposes to perform molecular mechanistic analysis of how the YY1 transcriptional complex controls mitochondrial function. Aim 2 is devoted to carry out cellular and functional mitochondrial bioenergetic and metabolic analysis mediated by the YY1 transcriptional protein complex in skeletal and adipose cultured cells. Aim 3 is focused to perform in-vivo metabolic and energetic analysis mediated by the YY1 transcription factor in skeletal muscle and adipose tissues. We will use genetic mouse models with gain and loss-of-function of YY1 in these tissues. The outcomes of these studies will provide the identification of the molecular mechanisms by which the YY1 transcriptional complex regulates mitochondrial bioenergetic capacities and how defects in this complex result in dysregulated mitochondrial function and energy balance. Based on the fact that these pathways are altered in metabolic diseases such as obesity and diabetes, studies proposed in this grant application might translate into potential therapies.