Molecular mechanisms dictating Sirt1/HIF-2 signaling during hypoxia

描述（由申请人提供）：识别和应对环境压力的能力是所有生物体的基本特征。低氧状态或缺氧是在生理和病理生理疾病状态（例如心肌梗塞和中风）下遇到的环境应激。在高等真核生物中，细胞固有的转录缺氧反应包括缺氧诱导因子（HIF）转录因子介导的作用。在脊椎动物中，HIF 家族由三个成员组成，其中 HIF-1 和 HIF-2 对于生存至关重要，小鼠遗传消融研究的结果表明。尽管 HIF-1 和 HIF-2 在蛋白质水平上相似，但它们具有不同的生物学作用。 HIF-2 是负责诱导成年小鼠促红细胞生成素和主要抗氧化酶 (AOE) 的特定 HIF 因子，从而分别调节细胞存活和针对氧化应激的保护性细胞反应。我们最近证明，缺氧期间的 HIF-2（而非 HIF-1）信号传导会被 Sirtuin 1 (Sirt1) 选择性增强，Sirt1 是一种脱乙酰酶，也与衰老、营养感知和基因毒性应激反应有关。我们的中心假设是 Sirt1/HIF-2 信号传导是保护哺乳动物免受缺氧引起的损伤的重要信号传导途径。该提案中的初步数据表明，缺氧期间 Sirt1 水平增加，缺氧期间 HIF-2 被特定的细胞乙酰转移酶乙酰化，小鼠心肌细胞特异性 HIF-2 消融会导致心肌梗塞后的结果更差。拟议的实验旨在通过试管、细胞培养和动物模型研究阐明哺乳动物中 Sirt1/HIF-2 信号传导的机制和生物学作用。我们的长期目标是确定缺氧期间激活的促生存机制，并利用这些知识开发新的治疗药物来治疗心肌梗塞和中风，这是当今美国成年人发病和死亡的主要原因。该提案的具体目标如下： 目标 1：定义缺氧期间 HIF 信号传导在 Sirt1 激活中的作用 目标 2：定义乙酰化在 Sirt1/HIF-2 信号传导中的作用 目标 3：定义 HIF-2 在心肌梗死后心脏生理学中的作用

DESCRIPTION (provided by applicant): The ability to recognize and respond to environmental stress is an essential characteristic of all living organisms. A low oxygen state, or hypoxia, is an environmental stress encountered under physiological as well as pathophysiological disease states such as myocardial infarction and stroke. In higher eukaryotes, the cell-intrinsic transcriptional hypoxia response includes actions mediated by Hypoxia Inducible Factor (HIF) transcription factors. In vertebrates, the HIF family is comprised of three members with HIF-1 and HIF-2 being essential for survival as indicated by results from genetic ablation studies in mice. Despite their similarity at the protein level, HIF-1 and HIF-2 have distinct biological roles. HIF-2 is the specific HIF factor responsible for induction of erythropoietin and of major antioxidant enzymes (AOE) in adult mice, thereby regulating cell survival and protective cellular responses against oxidative stress, respectively. We recently demonstrated that HIF-2, but not HIF-1, signaling during hypoxia is selectively augmented by Sirtuin 1 (Sirt1), a deacetylase also implicated in aging, nutrient sensing, and genotoxic stress response. Our central hypothesis is that Sirt1/HIF-2 signaling is an essential signaling pathway for protection against hypoxia-induced damage in mammals. Preliminary data within this proposal reveal that Sirt1 levels increase during hypoxia, HIF-2 is acetylated by specific cellular acetyltransferases during hypoxia, and cardiomyocyte-specific HIF-2 ablation in mice results in worse outcome following myocardial infarction. The experiments proposed are aimed at elucidating the mechanism and biological role for Sirt1/HIF-2 signaling in mammals using test tube, cell culture, and animal model studies. Our long-term goals are to identify the prosurvival mechanisms activated during hypoxia and to leverage this knowledge to develop novel therapeutic agents for treatment of myocardial infarction and stroke, the leading causes of morbidity and mortality in US adults today. The Specific Aims of this proposal are as follows: Aim 1: Define the role of HIF signaling in Sirt1 activation during hypoxia Aim 2: Define the role of acetylation in Sirt1/HIF-2 signaling Aim 3: Define the role of HIF-2 in cardiac physiology after myocardial infarction