APOE orchestrated ''molecular signatures'' in aging brain and AD - the contribution of APOE2

载脂蛋白E(ApoE)是19号染色体上apoE/apoC基因簇的一部分，编码3种蛋白质 异构体-APOE2、APOE3和APOE4。载脂蛋白E在外周转运胆固醇和磷脂 大脑。载脂蛋白E亚型的脂质和受体结合能力不同，其作用与清除有关 低密度脂蛋白、极低密度脂蛋白和乳糜粒。载脂蛋白4等位基因的遗传性增加，载脂蛋白2降低患糖尿病的风险 迟发性AD(LOAD)，但其机制尚不清楚。虽然APOE参与了关键的细胞 氧化过程、炎症、胶质细胞和神经元动态平衡等功能，这些都不能 解离异构体特异性结合，将胆固醇和磷脂运输和输送到不同的细胞 类型。最近的报道表明，在小胶质细胞中可能存在不同的apoE-亚型特异性效应。 脑内表达的免疫受体的吞噬作用和功能。我们的初步数据显示APOE 异构体影响免疫受体Dectin-1/Clec7a、Siglec1、Siglech、OSCAR的表达 炎症反应和吞噬作用。大力支持APOE和免疫发挥相互关联的作用 受体介导的吞噬作用是我们的多维质谱猎枪脂组学结果 AD患者的大脑样本，我们发现在磷脂分子形态上有显著差异 主要的磷脂类。我们假设APOE异构体对吞噬功能的特异性影响是由 载脂蛋白脂粒的不同磷脂组成和/或载脂蛋白异构体的差异效应 在小胶质细胞转录组上。我们提出了三个具体的目标来检验这一假说：目标1.建立异构体- 载脂蛋白Eε2等位基因对阿尔茨海默病患者脑实质及线粒体脂质体和转录组的依赖作用 患者和非痴呆症对照组。其目标是整合脂质和转录图谱，并揭示 APOE等位基因控制SA3中额外功能分析的表型和脂类分子种类。目标2. 检测载脂蛋白E基因对小鼠脑内脂肪和转录组的同型和年龄效应 表达人APOE2、APOE3或APOE4亚型的小鼠。我们将测定其磷脂含量。 星形胶质细胞条件培养液中的天然载脂蛋白、脑间质液中的脂质颗粒及其在脑中的差异 表达APOE2、APOE3或APOE4亚型的小鼠脑实质和线粒体脂体 不同的年龄。目的3.检测载脂蛋白E纳米粒对β细胞吞噬功能的影响 在活体内。我们的目标是应用关于AD和小鼠脂肪成分差异的知识 并检测磷脂分子种类对小胶质细胞介导的Aβ吞噬功能的影响 Aβ寡聚体在体外和体内实验系统中的清除

APOE (Apolipoprotein E) is part of APOE/APOC gene cluster on chromosome 19 and codes for 3 protein isoforms – APOE2, APOE3 and APOE4. APOE transports cholesterol and phospholipids in the periphery and brain. APOE isoforms differ in their lipid and receptor binding capacity and their role is associated with clearance of LDL, VLDL and chylomicrons. The inheritance of APOE4 allele increases and APOE2 decreases the risk for late onset AD (LOAD), but the mechanism is poorly understood. While APOE is involved in critical cellular functions such as oxidative processes, inflammation, glial cell and neuronal homeostasis, none of those can be dissociated from isoform specific binding, transport and delivery of cholesterol and phospholipids to different cell types. Recent reports suggest there might be a differential APOE-isoform specific effect on microglia mediated phagocytosis and function of immune receptors expressed in brain. Our preliminary data demonstrate APOE isoforms influence expression of immune receptors Dectin-1/Clec7a, Siglec1, Siglech, Oscar - involved in inflammatory response and phagocytosis. A strong support to an interconnected role for APOE and immune receptor mediated phagocytosis are our results of Multi-Dimensional Mass Spectrometry Shotgun Lipidomics of brain samples from AD patients, where we find significant differences in phospholipid molecular speciation in major phospholipid classes. We hypothesize the APOE isoform-specific effects on phagocytosis are driven by the different phospholipid composition of APOE lipid particles and/or by the differential effect of APOE isoforms on microglial transcriptome. We are proposing 3 Specific Aims to test the hypothesis: Aim 1. Establish isoform- dependent effect of APOEε2 allele on brain parenchymal and mitochondrial lipidome and transcriptome in AD patients and non-demented controls. The goal is to integrate lipid and transcriptional profiles and to reveal APOE allele controlled phenotypes and lipid molecular species for additional functional assays in SA3. Aim 2. Determine isoform- and age-dependent effect of APOE genotype on brain lipidome and transcriptome in mice expressing human APOE2, APOE3 or APOE4 isoforms. We will determine phospholipid content of native APOE in Astrocyte Conditioned media, lipid particles in brain interstitial fluid (ISF) and differences in brain parenchyma and mitochondrial lipidomes between mice expressing APOE2, APOE3 or APOE4 isoforms at 2 different ages. Aim 3. To test the effect of APOE-containing nanoparticles on Aβ phagocytosis in vitro and in vivo. The goals are to apply the knowledge about differences in lipid compositions of AD and mouse brains and to test the effect of phospholipid molecular species on microglia mediated Aβ phagocytosis and clearance of Aβ oligomeric species in in vitro and in vivo experimental systems.