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（由申请人提供）：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同工型，APOE2，APOE3和APOE4。 APOE促进了从循环中促进脂蛋白残留物的受体介导的清除，导致脂质稳态，并保护动脉粥样硬化。干扰受体结合的APOE中的缺乏或特定点突变阻碍了循环中动脉粥样硬化性脂蛋白的清除，并导致III型高脂蛋白血症与人类和实验动物的早产动脉粥样硬化有关。 APOE的APOE4同工型也被认为是晚期家族性阿尔茨海默氏病的危险因素。而在生理范围内APOE的表达清除了脂蛋白残留物，APOE2，APOE或APOE4的高水平表达会引起高甘油三酯血症。我们最近确定，高甘油三酯血症是由位于羧基末端区域261至269氨基酸之间的疏水残基在很大程度上介导的。这些残基还会影响含有APOE的HDL颗粒的形成。 APOE受体结合结构域的LDL受体的缺乏或突变降低了小鼠诱导高甘油三酸酯血症所需的APOE阈值。体外和体内实验表明，APOE与ABCA1的功能相互作用，并促进了含ApoE的HDL的生物发生。此外，APOE与SR-BI功能相互作用并促进脂质外排。在此应用程序中，我们建议利用过去四年中获得的新知识，以解决与APOE功能及其在血脂异常中的作用有关的三个重要问题。我们的具体目的是：1：研究单个APOE残基L261，W264，F265，L268，V269在APOE的体内功能中的贡献，包括甘油三酯血症的发展，免受动脉粥样硬化的保护和HDL的形成。最终目标是生成动脉保护性并改善生物学功能的重组APOE形式。 2：研究APOE羧基末端结构域在受体识别中的相对贡献，对高甘油三酸酯血症的敏感性以及对APOE突变体中动脉粥样硬化的敏感性，这些敏感性与III型高脂蛋白质蛋白血症的主要形式相关。这些研究可以鉴定APOE功能与有助于其抗动脉粥样硬化特性的LDL受体结合不同。 3：为了阐明APOE和ABCA1之间的功能相互作用如何促进类似HDL的含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的相互作用及其在整体胆固醇稳态中的作用来成熟。这些研究将采用用于APOA-L，APOE，SR-BI和生化分析的单个或双基因敲除小鼠的基因转移。