Regulation of Cellular Cholesterol Through Oxysterol-Membrane Interactions

描述（由申请人提供）：细胞和血浆胆固醇的严格调节对于正常的细胞功能至关重要，因为过量的游离胆固醇对细胞有毒，并与动脉粥样硬化和心脏病相关。细胞胆固醇稳态由酶促形成的氧化胆固醇衍生物（称为氧固醇）调节。氧固醇可以抑制负责胆固醇从头合成和脂蛋白胆固醇摄取的基因的表达，并作为核受体的内源性配体，其激活胆固醇分解代谢和流出途径。虽然氧化固醇在胆固醇稳态的急性调节中的重要性是已知的，但氧化固醇发挥其作用的精确分子机制仍有待阐明。我的中心假设是氧固醇通过非对映选择性膜无序效应发挥其胆固醇调节作用。为了验证这一假设，我将（1）合成天然（nat）和对映体（ent）形式的LY 295427-一种已知的25-HC拮抗剂，（2）检查nat和ent-LY 295427-膜相互作用的对映体选择性以及LY 295427对25-HC膜无序特性的影响，和（3）测定LY 295427抑制培养细胞中25-HC介导的甾醇稳态应答的对映体选择性。该项目的长期目标是阐明维持细胞胆固醇平衡的分子机制，并深入了解膜结构的改变如何用于传递调节信号。拟议的研究可能有助于确定操纵胆固醇的细胞处理和动脉粥样硬化治疗的药理学靶点。 公共卫生相关性：血浆脂蛋白胆固醇水平高（例如，以低密度脂蛋白（LDL）的形式存在，与动脉粥样硬化和心脏病有关。了解细胞和全身胆固醇水平调节的机制将为开发降胆固醇治疗提供新的方法，并可能减少心血管疾病。

DESCRIPTION (provided by applicant): Tight regulation of cellular and plasma cholesterol is crucial to proper cellular functioning, as excess free cholesterol is toxic to cells and is associated with atherosclerosis and heart disease. Cellular cholesterol homeostasis is regulated by enzymatically formed oxygenated cholesterol derivatives called oxysterols. Oxysterols can suppress expression of genes responsible for de novo cholesterol synthesis and lipoprotein cholesterol uptake, and serve as endogenous ligands for nuclear receptors, which activate cholesterol catabolic and efflux pathways. While the importance of oxysterols in the acute regulation of cholesterol homeostasis is known, the precise molecular mechanisms through which oxysterols exert their effects remain to be elucidated. My central hypothesis is that oxysterols exert their cholesterol-regulatory effects through non- enantioselective membrane-disordering effects. To test this hypothesis, I will (1) synthesize both the natural (nat) and enantiomeric (ent) forms of LY295427-a known antagonist of 25-HC, (2) examine the enantioselectivity of nat- and ent-LY295427-membrane interactions and the effect of LY295427 on the membrane-disordering properties of 25-HC, and (3) determine the enantioselectivity of LY295427 inhibition of 25-HC-mediated sterol homeostatic responses in cultured cells. The long-term objectives of this project are to elucidate the molecular mechanisms underlying the maintenance of cellular cholesterol balance, and to provide insight into how alteration in membrane structure can be used to relay regulatory signals. The proposed studies may help to identify pharmacological targets for manipulation of the cellular handling of cholesterol and treatment of atherosclerosis. PUBLIC HEALTH RELEVANCE: High levels of plasma lipoprotein cholesterol (e.g., in the form low-density lipoproteins (LDL), are associated with atherosclerosis and heart disease. Understanding the mechanisms through which cellular and whole-body cholesterol levels are regulated will provide new approaches to developing cholesterol-lowering treatments, and may reduce cardiovascular disease.