SR-BI: INFLUENCE OF APOA-II

描述：（改编自研究者摘要）：HDL和apoA-I血浆 水平与冠状动脉疾病呈负相关。两个主要子类 高密度脂蛋白的主要成分是仅含有apoA-I（LpAI）的高密度脂蛋白和同时含有apoA-I 和apoA-II（LpAI/AII）。而apoA-1通常被认为是 抗动脉粥样硬化，证据表明apoA-II是促动脉粥样硬化的。的HDL 受体SR-BI在HDL代谢中起重要作用。SR-BI 介导胆固醇酯从HDL进入细胞的选择性摄取， 增强细胞游离胆固醇向HDL的流出。尽管SR-BI 被认为表现出广泛的脂蛋白结合特异性， PI在未发表的研究中发现，LpAI/AII明显缺乏其 结合SR-BI的能力。本提案中要检验的中心假设是 载脂蛋白AII通过抑制HDL发挥调节功能 与SR-BI结合，从而SR-BI介导的HDL和HDL之间的脂质通量 细胞apoA-II的这种调节功能将对以下方面产生重大影响： HDL代谢，包括其在胆固醇逆向转运中的作用。这 因此，一项提案试图研究apoA-II对SR-BI介导的 高密度脂蛋白代谢和高密度脂蛋白和细胞之间的胆固醇流量。具体目标 主要是：1）确定apoA-II对SR-BI介导的胆固醇流量的影响 HDL和细胞之间的联系这将通过研究 人apoA-II对人HDL的结合和代谢的影响 转染的CHO细胞。仅ApoA-I和含有apoAI/apoAII的颗粒将 以及增加重组中apoA-II水平的作用。 2）评估apoA-II对HDL水平和对 小鼠肝选择性胆固醇酯摄取。为实现这些目标将 测定肝选择性胆固醇酯摄取的相对速率， apoA-1-/-小鼠LpAI和LpAI/AII的表达及腺病毒介导的LpAI/AII的影响 人或小鼠apoA-II的血浆水平增加对HDL水平的表达 在人apoA-I转基因小鼠或C57 BL/6小鼠中，以及3）研究 apoA-II的结构要求是apoA-I作为一种免疫调节剂调节apoA-II所必需的。 SR-BI配体。这将通过研究体内和体内 培养的细胞，一系列的结构变异和突变的影响， apoA-II对HDL与SR-BI结合和选择性胆固醇酯摄取的影响。

DESCRIPTION: (Adapted from the Investigator's Abstract):HDL and apoA-I plasma levels are inversely related to coronary artery disease. Two major subclasses of HDL are those containing only apoA-I (LpAI) and those containing both apoA-I and apoA-II (LpAI/AII). Whereas apoA-1 is considered to be generally anti-atherogenic, evidence points to apoA-II being pro-atherogenic. The HDL receptor, SR-BI, plays an important role in the metabolism in HDL. SR-BI mediates the selective uptake of cholesterol esters from HDL into cells and enhances the efflux of cellular free cholesterol to HDL. Although SR-BI is considered to exhibit a broad lipoprotein binding specificity, the group of the PI has found in unpublished studies that LpAI/AII is markedly deficient in its ability to bind SR-BI. The central hypothesis to be examined in this proposal is that apolipoprotein AII exerts a regulatory function by inhibiting HDL binding to SR-BI and consequently SR-BI-mediated lipid flux between HDL and cells. Such a regulatory function of apoA-II would have major implications for HDL metabolism, including its role in reverse cholesterol transport. This proposal therefore seeks to examine the influence of apoA-II on SR-BI-mediated HDL metabolism and on cholesterol flux between HDL and cells. The specific aims are: 1) to determine the effect of apoA-II on SR-BI-mediated cholesterol flux between HDL and cells. This will be accomplished by studying the influence of human apoA-II on the binding and metabolism of human HDL by SR-BI expressed in transfected CHO cells. ApoA-I only and apoAI/apoAII-containing particles will be compared and the effect of increasing apoA-II levels in reconstituted particles studied, 2) to assess the effect of apoA-II on HDL levels and on hepatic selective cholesterol ester uptake in mice. This will be achieved by determining relative rates of hepatic selective cholesterol ester uptake from LpAI and LpAI/AII in apoA-1-/- mice and the effect of adenovirus-mediated expression of increasing plasma levels of human or mouse apoA-II on HDL levels in human apoA-I transgenic mice or C57BL/6 mice and 3) to investigate the structural requirements of apoA-II necessary for the modulation of apoA-I as an SR-BI ligand. This will be accomplished by studying both in vivo and in cultured cells, the effects of a series of structural variants and mutations of apoA-II on HDL binding to SR-BI and on selective cholesterol ester uptake.