Regulation and function of plasma lipid transfer proteins

血浆脂质转运蛋白的调节和功能

• 批准号: 6602445
• 负责人: ALAN richard TALL
• 金额: $ 26.82万
• 依托单位: ROCKEFELLER UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-07-01 至 2003-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6602445
• 关键词: apolipoproteins; atherosclerosis; blood lipoprotein metabolism; blood lipoprotein transport; cholesterol esters; dietary lipid; gene targeting; genetic promoter element; genetic regulation; genetically modified animals; high density lipoproteins; laboratory mouse; low density lipoprotein; nuclear receptors; nutrition related tag; protein structure function; tissue /cell culture; transport proteins

Low HDL levels are a major atherogenic risk factor for which no specific treatment is yet available. The plasma liquid transfer proteins, cholestryl ester transfer protein (CETP) and phospholipid transfer protein (PLTP), play a an important part in HDL homeostasis. CETP transfers HDL CE to triglyceride-rich lipoproteins which are then taken up in the liver, in a process of reverse cholesterol or endogenous hypercholesterolemia. We have used natural flanking region CETP transgenic (Tg) mice, and reporter gene constructs, to localize the CETP response to a novel element in the gene proximal promoter, and we have shown that this positive response is mediated in vitro by the nuclear receptor, LXR. Since LXRalpha is known to mediate sterol up-regulation of cyp7a, the rate- limiting enzyme in the conversion of cholesterol into bile salts, our findings suggest that LXRs may help to coordinate the response of a variety of genes involved in cholesterol removal from the body. In Aim 1 we will use LXRalpha and beta knock-out mice to evaluate the role of LXRs in lipid transfer protein gene regulation in vivo and to explore the overall role of these transcription factors in regulating genes involved in reverse cholesterol transport; these mice will also be crossed onto atherosclerosis-susceptible backgrounds in order to evaluate their role in atherogenesis. Aim 2 we will use recently developed PLTP knockout-out (PLTP0) mice to explore the role of PLTP in lipoprotein metabolism and atherogenesis. We will investigate possible redundancy of CETP and PLTP activities by crossing CETP into the LTP0 background. PLTP0 mice will also be crossed with apoB Tg mice and atherosclerosis studies performed. These studies will evaluated the hypothesis that phospholipid/apoA-IV/apoE vesicles accumulating in PLTP0 mice on a high fat diet may have anti-atherogenic PLTP in adding phospholipids to nascent HDL. This project is likely to provide definitive information on the molecular mechanism of lipid transfer protein regulation by sterols. It will also test the novel hypothesis that LXRs coordinate a program of reverse cholesterol transport with anti-atherogenic consequences. Finally, it will evaluate a new idea concerning PLTP deficiency as an anti- atherogenic state. This project will have strong interactions with Project 4, investigating mechanisms of HDL-mediated cholesterol efflux from macrophages, and will provide information on novel genes and pathways regulated by LXRs, which may be relevant to studies in Projects 1 and 2.

低高密度脂蛋白水平是导致动脉粥样硬化的主要危险因素，目前还没有特效的治疗方法。胆固醇酯转移蛋白(CETP)和磷脂转移蛋白(PLTP)这两种血浆液体转移蛋白在高密度脂蛋白稳态中起着重要作用。CETP将HDLCE转移到富含甘油三酯的脂蛋白，然后在逆转胆固醇或内源性高胆固醇血症的过程中被肝脏吸收。我们使用天然侧翼区CETP转基因(TG)小鼠和报告基因构建物来定位CETP对基因近端启动子中一个新元件的反应，我们已经证明这种阳性反应是由核受体LXR在体外介导的。由于LXRpha是已知的调节胆固醇转化为胆盐的限速酶cyp7a的激素，我们的发现提示LXRs可能有助于协调参与体内胆固醇清除的各种基因的反应。在目标1中，我们将使用LXRAlpha和Beta基因敲除小鼠来评估LXRs在体内脂转移蛋白基因调控中的作用，并探索这些转录因子在调控胆固醇反向运输相关基因中的整体作用；这些小鼠也将被交叉到动脉粥样硬化易感背景中，以评估它们在动脉粥样硬化形成中的作用。目的2利用新近建立的PLTP基因敲除(PLTP0)小鼠，探讨PLTP在脂蛋白代谢和动脉粥样硬化形成中的作用。我们将通过将CETP进入LTP0背景来调查CETP和PLTP活动可能的冗余。PLTP0小鼠也将与apoB TG小鼠杂交，并进行动脉粥样硬化研究。这些研究将评估磷脂/apoA-IV/apoE囊泡在高脂饮食中积累在PLTP0小鼠体内的假设，即在新生的高密度脂蛋白中添加磷脂可能具有抗动脉粥样硬化的作用。该项目很可能为甾醇调节脂转移蛋白的分子机制提供明确的信息。它还将检验新的假设，即LXRs协调一项具有抗动脉粥样硬化作用的反向胆固醇运输程序。最后，对PLTP缺乏作为抗动脉粥样硬化状态的新观点进行评价。这个项目将与项目4有很强的相互作用，研究高密度脂蛋白介导的胆固醇从巨噬细胞流出的机制，并将提供有关LXRs调控的新基因和途径的信息，这可能与项目1和2中的研究相关。