Functions of apoE in cholesterol and triglyceride homeostasis

apoE 在胆固醇和甘油三酯稳态中的功能

• 批准号: 7090402
• 负责人: VASSILIS I ZANNIS
• 金额: $ 36.34万
• 依托单位: BOSTON UNIVERSITY MEDICAL CAMPUS
• 依托单位国家: 美国
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-09-01 至 2011-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7090402
• 关键词: apolipoprotein E; atherosclerosis; blood lipoprotein metabolism; blood lipoprotein transport; cardiovascular disorder therapy; cholesterol; gene therapy; genetically modified animals; laboratory mouse; nonhuman therapy evaluation; protein structure function; transfection; triglycerides

DESCRIPTION (provided by applicant): Apolipoprotein E is an important protein of the cholesterol transport system which has three common isoforms, apoE2, apoE3, and apoE4 in the general population. ApoE promotes receptor-mediated clearance of lipoprotein remnants from the circulation, contributes to lipid homeostasis, and protects from atherosclerosis. Deficiency or specific point mutations in apoE that interfere with receptor binding impede the clearance of atherogenic lipoproteins from the circulation, and result in type III hyperlipoproteinemia which is associated with premature atherosclerosis in humans and experimental animals. The apoE4 isoforms of apoE has been also implicated as a risk factor in late-onset familial Alzheimer's disease. Whereas expression of apoE within a physiological range clears lipoprotein remnants, high levels of expression of apoE2, apoES, or apoE4 causes hypertriglyceridemia. We have established recently that the hypertriglyceridemia is mediated to a large extent by hydrophobic residues located between amino acids 261 to 269 of the carboxy terminal region. These residues also influence the formation of apoE-containing HDL particles. Deficiency of the LDL receptor or mutations in the receptor binding domain of apoE decreases the threshold of apoE required for induction of hypertriglyceridemia in mice. In vitro and in vivo experiments have shown that apoE interacts functionally with ABCA1 and promotes the biogenesis of apoE-containing HDL. In addition, apoE interacts functionally with SR-BI and promotes lipid efflux. In this application, we propose to capitalize on the new knowledge we have acquired during the last four years to address three important questions pertinent to the functions of apoE and its role in dyslipidemia, in atherogenesis and the biogenesis of HDL-like apoE-containing lipoproteins. Our specific aims are: 1: To investigate the contribution of individual apoE residues L261, W264, F265, L268, V269 in the in vivo functions of apoE, including the development ofhypertriglyceridemia, protection from atherogenesis, and formation of HDL. The ultimate goal is to generate recombinant apoE forms that are atheroprotective and have improved biological functions. 2: To investigate the relative contribution of the carboxy terminal domain of apoE in receptor recognition, sensitivity to hypertriglyceridemia and susceptibility to atherosclerosis in apoE mutants that are associated with dominant forms of type III hyperlipoproteinemia. These studies may identify apoE functions different from the LDL receptor binding that contribute to its anti-atherogenic properties. 3: To elucidate how functional interactions between apoE and ABCA1 contribute to the de novo biogenesis of HDL-like apoE- containing lipoprotein particles, the maturation of these particles by subsequent interactions with LCAT and SR-BI, and their role in the overall cholesterol homeostasis. Gene transfer in single or double knockout mice for apoA-l, apoE, SR-BI and biochemical analyses will be employed in these studies.

描述（申请人提供）： 载脂蛋白E是胆固醇转运系统的重要蛋白质，在一般人群中具有三种常见的亚型：apoE2、apoE3和apoE4。 ApoE 促进受体介导的脂蛋白残余物从循环中的清除，有助于脂质稳态，并防止动脉粥样硬化。 apoE 的缺陷或特定点突变会干扰受体结合，从而阻碍动脉粥样硬化脂蛋白从循环中的清除，并导致 III 型高脂蛋白血症，这与人类和实验动物的过早动脉粥样硬化有关。 apoE 的 apoE4 亚型也被认为是晚发家族性阿尔茨海默病的危险因素。虽然 apoE 在生理范围内的表达可以清除脂蛋白残余物，但 apoE2、apoES 或 apoE4 的高水平表达会导致高甘油三酯血症。我们最近已经确定，高甘油三酯血症在很大程度上是由位于羧基末端区域的氨基酸261至269之间的疏水残基介导的。这些残基也会影响含有 apoE 的 HDL 颗粒的形成。 LDL 受体的缺陷或 apoE 受体结合域的突变会降低诱导小鼠高甘油三酯血症所需的 apoE 阈值。体外和体内实验表明，apoE 与 ABCA1 发生功能性相互作用，并促进含有 apoE 的 HDL 的生物发生。此外，apoE 与 SR-BI 发生功能性相互作用，促进脂质流出。在本申请中，我们建议利用过去四年中获得的新知识来解决与apoE的功能及其在血脂异常、动脉粥样硬化形成和含有类HDL的apoE脂蛋白的生物发生中的作用相关的三个重要问题。我们的具体目标是： 1：研究单个apoE残基L261、W264、F265、L268、V269在apoE体内功能中的贡献，包括高甘油三酯血症的发生、防止动脉粥样硬化形成和HDL形成。最终目标是产生具有动脉粥样硬化保护作用并具有改善的生物学功能的重组apoE形式。图2：研究与III型高脂蛋白血症的主要形式相关的apoE突变体中apoE的羧基末端结构域在受体识别、对高甘油三酯血症的敏感性和对动脉粥样硬化的易感性中的相对贡献。这些研究可能会鉴定出 apoE 功能不同于 LDL 受体结合，从而有助于其抗动脉粥样硬化特性。图 3：阐明 apoE 和 ABCA1 之间的功能相互作用如何促进含 apoE 的类 HDL 脂蛋白颗粒的从头生物发生、这些颗粒通过随后与 LCAT 和 SR-BI 的相互作用而成熟，以及它们在总体胆固醇稳态中的作用。这些研究将采用单敲除或双敲除小鼠中的 apoA-1、apoE、SR-BI 基因转移和生化分析。