Immunochemical Structure/Function of Apolipoprotein A-I

描述(申请人提供)：低水平的高密度脂蛋白(高密度脂蛋白)是一个强大的预测指标，以确定谁有动脉粥样硬化的风险。此外，高密度脂蛋白是药物干预降低这种风险的重要靶点。这笔赠款将专注于高密度脂蛋白的主要蛋白质--载脂蛋白AI(ApoAI)的细胞外流特性。血浆高密度脂蛋白水平并不控制细胞胆固醇外流的速度。相反，外流发生在细胞外空间。2个事件决定了胆固醇移出外周细胞的速度：依赖能量的胆固醇移出细胞的过程，这是由ABCA1执行的过程；以及这种转运的胆固醇的低脂受体的可用性，一种两亲性的阿尔法螺旋载脂蛋白。体外研究已经证实，许多载脂蛋白，包括载脂蛋白AI、ALL、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。这一提议将检验这样一种假设，即ApoAI的体内特异性是ApoAI从球形α迁移高密度脂蛋白解离并形成瞬时稳定的、缺乏脂质的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-/-)小鼠身上进行的，涉及三个特定的目标。第一个目的是确定磷脂转移蛋白(PLTP)在体内和体外产生低脂载脂蛋白AI中的作用。第二个目的是确定胆固醇酯转移蛋白(CETP)在这一过程中所起的作用。这两种转移蛋白都在Mphi中表达，都能从球形高密度脂蛋白中产生无脂的载脂蛋白AI，并通过连接肝X受体(LXR)来诱导。第三个目的是确定脂蛋白脂酶(LPL)和肝脂酶(HL)在低脂载脂蛋白AI产生中的作用。这些脂肪酶也由Mphi表达，并受LXR调节。我们认为，通过甘油三酯水解降低核心脂质，以及通过PLTP和CETP重塑，可以从高密度脂蛋白释放低脂载脂蛋白AI，以促进动脉粥样硬化病变内Mphi泡沫细胞的外流。

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.