CHOLESTEROL EFFECTS ON HUMAN ApoE AND APP INTERACTIONS

本项目旨在验证apoE和胆固醇以亚型依赖的方式修饰Abeta沉积，apoE 4等位基因以显性模式起作用的假设。淀粉样前体蛋白（APP）的罕见突变是早发性常染色体显性阿尔茨海默病（AD）的原因。AD易感基因载脂蛋白（apo）E位点的亚型差异影响晚发性AD的发病年龄，并可能影响15-50%的病例。在人类中，有三种主要的apoE同种型，称为apoE 2、E3和E4，它们仅相差一个氨基酸。ApoE的功能是维持胆固醇和脂肪的稳态。ApoE同种型也直接或间接地与APP相互作用，以调节与AD病理学的一个维度相关的Abeta沉积的程度。目前的人类研究表明，高胆固醇会增加AD的风险。动物研究揭示了胆固醇对脑中APP和apoE代谢以及对Abeta沉积的显著影响，并表明主要环境（即膳食脂肪和胆固醇）可能改变AD病理学。我们有转基因动物模型来验证这一假设，人apoE靶向替代小鼠，人apoE转基因小鼠和人APPV 717 F转基因小鼠。将在基础和高胆固醇条件下测量ApoE亚型特异性启动子对脑apoE水平的影响。通过将apoE靶向替代动物与携带人APP突变的小鼠交叉，使用Abeta沉积和APP代谢作为终点，检查AD相关病理学。最后，建立人类常见杂合子APOE 3/4的动物模型的能力将允许检测人类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.