Immunochemical Structure/Function of Apolipoprotein A-I

描述（由申请人提供）：低水平的高密度脂蛋白（HDL）是识别动脉粥样硬化风险人群的有力预测指标。此外，HDL是降低这种风险的药物干预的重要目标。这项资助将集中在HDL的主要蛋白质载脂蛋白AI（apoAI）的细胞外排特性。血浆HDL水平不控制细胞胆固醇流出的速率。相反，外排发生在细胞外空间。2个事件决定了胆固醇从外周细胞中移出的速率：胆固醇从细胞中的能量依赖性转运，这是由ABCA 1进行的过程;以及这种转运的胆固醇的脂质贫乏受体，即两亲性α螺旋脱辅基蛋白的可用性。体外研究已经证实，许多载脂蛋白包括载脂蛋白AI、AIV和E都是细胞胆固醇的良好受体。只有载脂蛋白AI将介导巨噬细胞（Mphi）介导的脂质从动脉粥样硬化病变内的泡沫细胞流出。该提议将检验这样的假设，即apoAI的这种体内特异性是apoAI从球形α-迁移HDL中解离并形成瞬时稳定的、脂质贫乏的apoAI的能力的函数。我们的研究是在低密度脂蛋白受体缺陷（LDLr-/-）小鼠中进行的，涉及3个具体目标。第一个目标是确定磷脂转移蛋白（PLTP）在体内和体外产生脂质贫乏的apoAI中的作用。第二个目标将确定胆固醇酯转移蛋白（CETP）在这一过程中发挥的作用。这两种转移蛋白都在Mphi中表达，可以从球形HDL产生贫脂apoAI，并通过连接核肝X受体（LXR）诱导。第三个目标是确定脂蛋白脂肪酶（LpL）和肝脂肪酶（HL）在产生低脂载脂蛋白AI中的作用。这些脂肪酶也由Mphi表达并受LXR调节。我们认为，核心脂质减少甘油三酯水解和重塑PLTP和CETP释放脂质贫载脂蛋白AI从HDL，促进流出的Mphi泡沫细胞内动脉粥样硬化病变。

DESCRIPTION (provided by applicant): Low levels of high density lipoprotein (HDL) are a powerful predictor for identifying persons who are at risk for atherosclerosis. Moreover HDL is an important target for pharmacologic intervention to reduce this risk. This grant will focus on the cellular efflux properties of the major protein of HDL, apolipoprotein AI (apoAI). Plasma HDL levels do not control the rate of cellular cholesterol efflux. Instead, efflux occurs in extracellular spaces. 2 events dictate the rate of movement of cholesterol out of peripheral cells: an energy-dependent transport of cholesterol out of the cell, a process carried out by ABCA1; and the availability of a lipid-poor acceptor of this transported cholesterol, an amphipathic alpha helical apoprotein. Studies in vitro have verified that many apoproteins including apoproteins AI, All, AIV and E are equally good acceptors of cellular cholesterol. Only apoAI will mediate macrophage (Mphi)-mediated lipid efflux from foam cells within atherosclerotic lesions. This proposal will test the hypothesis that this in vivo specificity for apoAI is a function of the ability of apoAI to dissociate from spherical alpha-migrating HDL and form transiently stable, lipid-poor apoAI. Our studies are performed in low density lipoprotein receptor-deficient (LDLr-/-) mice and involve 3 specific aims. The first aim will identify the role of phospholipid transfer protein (PLTP) in the generation of lipid-poor apoAI in vivo and in vitro. The second aim will identify the role played by cholesterol ester transfer protein (CETP) in this same process. Both of these transfer proteins are expressed in Mphi, can generate lipid-poor apoAI from spherical HDL and are induced by ligation of nuclear liver X receptors (LXR). The third aim will identify the role of lipoprotein lipase (LpL) and hepatic lipase (HL) in the generation of lipid-poor apo AI. These lipases also are expressed by Mphi and regulated by LXR. We propose that core lipid reduction by triglyceride hydrolysis and remodeling by PLTP and CETP release lipid-poor apoAI from HDL to facilitate efflux from Mphi foam cells within atherosclerotic lesions.