CHOLESTEROL EFFECTS ON HUMAN ApoE AND APP INTERACTIONS

该项目旨在验证apoE和胆固醇以同型型依赖的方式改变β沉积的假设，其中apoE4等位基因以显性模式起作用。淀粉样蛋白前体蛋白（APP）的罕见突变是一些早发性常染色体显性阿尔茨海默病（AD）病例的原因。AD易感基因载脂蛋白（apo） E位点的异构体差异影响迟发性AD的发病年龄，可能影响所有病例的15-50%。在人类中，有三种主要的载脂蛋白e异构体，分别是apoE2， E3和E4，它们的区别仅在于一个氨基酸。ApoE的功能是维持胆固醇和脂肪的体内平衡。ApoE异构体也直接或间接地与APP相互作用，调节与AD病理一维相关的β沉积程度。目前的人体研究表明，高胆固醇会增加患阿尔茨海默病的风险。动物研究显示，胆固醇对大脑中APP和apoE代谢以及β沉积有显著影响，并提示主要环境因素（即膳食脂肪和胆固醇）可能改变AD病理。我们有转基因动物模型来验证这一假设，人类apoE靶向替代小鼠，人类apoE转基因小鼠和人类APPV717F转基因小鼠。ApoE亚型特异性启动子对脑ApoE水平的影响将在基础和高胆固醇条件下进行测量。通过将apoE靶向替代动物与携带人类APP突变的小鼠杂交，以Abeta沉积和APP代谢为终点，研究ad相关病理。最后，建立人类常见杂合子APOE3/4的动物模型的能力，将允许测试人类apoE亚型的显性阳性或显性阴性效应。模拟可能调节APP和apoE的饮食因素将促进对影响AD发病和进展的环境和遗传相互作用的理解。

This project proposes to test the hypothesis that apoE and cholesterol modify Abeta deposition in an isoform-dependent fashion with the apoE4 allele acting in a dominant mode. Rare mutations in amyloid precursor protein (APP) are responsible for some cases of early onset autosomal dominant Alzheimer's disease (AD). Isoform differences at the AD susceptibility gene apolipoprotein (apo) E locus affect age of onset for late on-set AD, and may influence from 15-50% of all cases. In humans, there are three major apoE isoforms designated apoE2, E3, and E4 that differ by a single amino acid. ApoE functions to maintain cholesterol and fat homeostasis. ApoE isoforms also interact either directly or indirectly with APP to modulate the extent of Abeta deposition associated with one dimension of AD pathology. Current human studies suggest that high cholesterol increases the risk of AD. Animal studies reveal significant effects of cholesterol on APP and apoE metabolism in the brain, and on Abeta deposition, and suggest a major environmental (i.e. dietary fat and cholesterol) may modify AD pathology. We have transgenic animal models to test this hypothesis, human apoE targeted replacement mice, human apoE transgenic mice and the human APPV717F transgenic mouse. ApoE isoform-specific promoter effects on brain apoE levels will be measured under basal and high cholesterol conditions. AD-related pathology will be examined by crossing the apoE targeted replacement animals to mice bearing a human APP mutation using Abeta deposition and APP metabolism as endpoints. Finally, the ability to create animal models of the common human heterozygote, APOE3/4, will allow testing for dominant-positive or dominant-negative effects of human apoE isoforms. Modeling dietary factors that may modulate APP and apoE will advance the understanding of environmental and genetic interactions that influence the onset and progression of AD.