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（如心肌梗死和中风）下遇到的环境应激。在高等真核生物中，细胞内在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，HIF-1和HIF-2对生存至关重要，这是小鼠基因消融研究的结果所表明的。尽管HIF-1和HIF-2在蛋白水平上具有相似性，但它们具有不同的生物学作用。HIF-2是一种特异性的HIF因子，在成年小鼠中负责诱导促红细胞生成素和主要抗氧化酶（AOE），从而分别调节细胞存活和抗氧化应激的保护性细胞反应。我们最近证明，在缺氧过程中，HIF-2而非HIF-1的信号被Sirt1选择性地增强，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信号是哺乳动物抵抗缺氧诱导损伤的重要信号通路。本研究的初步数据显示，Sirt1水平在缺氧时升高，HIF-2在缺氧时被特定的细胞乙酰转移酶乙酰化，心肌细胞特异性HIF-2消融在小鼠心肌梗死后会导致更差的结果。本实验旨在通过试管、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在缺氧期间激活的促生存机制，并利用这一知识开发治疗心肌梗死和中风的新型治疗药物，这是当今美国成年人发病率和死亡率的主要原因。本提案的具体目的如下：目的1：确定缺氧时HIF信号在Sirt1激活中的作用；目的2：确定乙酰化在Sirt1/HIF-2信号传导中的作用；目的3：确定HIF-2在心肌梗死后心脏生理中的作用

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