Regulation of Cellular Cholesterol Homeostasis

描述（由申请人提供）：需要细胞脂质稳态来维持双层流动性、膜不渗透性和细胞器身份。全身脂质稳态紊乱是冠状动脉疾病和肥胖相关II型糖尿病病理的核心。这项研究的长期目标是将细胞调节事件的知识转化为整个生物体的知识，并推进我们对这些日益广泛的疾病的理解。作为实现这一目标的第一步，我们将使用胆固醇作为模型脂质，以了解细胞如何测量这些大部分不溶性分子的水平，并进而调节它们的产生。哺乳动物细胞中的胆固醇稳态是由一种反馈机制调节的，该机制监测细胞膜中的胆固醇水平，并改变胆固醇供应所需基因的转录。这些基因的转录是由内质网膜结合的转录因子SREBP控制的，该转录因子在甾醇耗尽的细胞中通过蛋白水解被激活并从膜上释放出来。为了加速甾醇稳态调节因子的发现，我们正在研究分裂酵母的SREBP通路。酵母SREBP，称为Sre1，在一种新的氧感应途径中起作用，该途径介导细胞对低氧的适应。有趣的是，在裂变酵母中，甾醇通过一种新机制调节Sre1的活性，并且有证据表明Sre1的裂解是由一种独特的蛋白水解系统介导的。在本项目中，将使用遗传、分子和生化方法的结合来实现以下具体目标：1)使用遗传选择鉴定Sre1切割所需的基因；2)确定Sre1解理机制；3)明确甾醇调控Sre1切割的机制。该项目的长期目标是利用S. pombe作为遗传模型来了解细胞如何测量不溶性、膜内嵌的胆固醇水平。期望这些研究将描述脂质传感和蛋白质水解的新机制，这将促进我们对哺乳动物SREBP途径和真核细胞生物学的理解。公共卫生相关性：心脏病是美国成年人的主要杀手。适当调节细胞胆固醇稳态对心血管健康是不可或缺的。在这个项目中，我们将使用酵母作为遗传模式生物来定义胆固醇稳态调节的新机制，目的是确定降低血清胆固醇和预防心脏病的改进治疗策略。

DESCRIPTION (provided by applicant): Cellular lipid homeostasis is required to maintain bilayer fluidity, membrane impermeability, and organelle identity. Disturbances in systemic lipid homeostasis lie at the core of the pathologies for both coronary artery disease and obesity related type II diabetes. The long-term goal of this research is to translate knowledge of cellular regulatory events to that of the whole organism and to advance our understanding of these increasingly widespread diseases. As a first step toward this goal, we will use cholesterol as a model lipid to understand how cells measure levels of these largely insoluble molecules and in turn modulate their production. Cholesterol homeostasis in mammalian cells is regulated by a feedback mechanism that monitors the level of cholesterol in membranes and alters transcription of genes required for cholesterol supply. Transcription of these genes is controlled by the ER membrane-bound transcription factor called SREBP that is activated and released from the membrane by proteolysis in sterol-depleted cells. To accelerate discovery of sterol homeostasis regulators, we are studying the SREBP pathway in the fission yeast Schizosaccharomyces pombe. Yeast SREBP, called Sre1, functions in a new oxygen sensing pathway that mediates adaptation of cells to low oxygen. Interestingly, sterols regulate Sre1 activity through a novel mechanism in fission yeast, and evidence also indicates that Sre1 cleavage is mediated by a unique proteolytic system. In this project, a combination of genetic, molecular, and biochemical approaches will be used to accomplish the following specific aims: 1) To identify genes required for Sre1 cleavage using a genetic selection; 2) To define the machinery for Sre1 cleavage; and 3) To define the mechanism of sterol-regulated Sre1 cleavage. The long-term goal of this project is to use S. pombe as a genetic model to understand how cells measure levels of insoluble, membrane-embedded cholesterol. The expectation is that these studies will describe new mechanisms for lipid sensing and proteolysis that will advance our understanding of the mammalia SREBP pathway and eukaryotic cell biology. PUBLIC HEALTH RELEVANCE: Heart disease is a leading killer of adults in the United States. Proper regulation of cellular cholesterol homeostasis is integral to cardiovascular health. In this project, we will use yeast as a genetic model organism to define new mechanisms for regulation of cholesterol homeostasis with the goal of identifying improved therapeutic strategies for lowering serum cholesterol and preventing heart disease.