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

载脂蛋白E（Apolipoprotein E，APOE）是位于19号染色体上的APOE/APOC基因簇的一部分，编码3种蛋白质 APOE 2、APOE 3和APOE 4。APOE在外周转运胆固醇和磷脂， 个脑袋APOE亚型在脂质和受体结合能力方面不同，其作用与清除有关 低密度脂蛋白极低密度脂蛋白和乳糜微粒APOE 4等位基因的遗传增加，APOE 2降低了 迟发性AD（LOAD），但其机制知之甚少。虽然APOE参与了关键的细胞 功能，如氧化过程，炎症，神经胶质细胞和神经元的稳态，没有一个可以被 与胆固醇和磷脂到不同细胞同种型特异性结合、转运和递送分离 类型最近的报道表明，可能存在差异APOE亚型特异性作用于小胶质细胞介导的 吞噬作用和脑中表达的免疫受体的功能。我们的初步数据表明， 同种型影响免疫受体Dectin-1/Clec 7a、Siglec 1、Siglech、Oscar的表达， 炎症反应和吞噬作用。对APOE和免疫的相互作用的有力支持 受体介导的吞噬作用是我们的多维质谱鸟枪脂质组学的结果， 从AD患者的大脑样本中，我们发现磷脂分子形态的显着差异， 主要的磷脂类。我们假设APOE亚型对吞噬作用的特异性作用是由以下因素驱动的： APOE脂质颗粒的不同磷脂组成和/或APOE同种型的差异效应 在小胶质细胞转录组上我们提出了3个具体目标来检验假设：目标1。建立亚型- AD患者APOEε2等位基因对脑实质和线粒体脂质组及转录组依赖性影响 患者和非痴呆对照。目标是整合脂质和转录谱，并揭示 APOE等位基因控制的表型和脂质分子种类，用于SA 3中的其他功能测定。目标二。 确定APOE基因型对脑脂质组和转录组的亚型和年龄依赖性影响， 表达人APOE 2、APOE 3或APOE 4同种型的小鼠。我们将测定 星形胶质细胞条件培养基中的天然APOE，脑间质液（ISF）中的脂质颗粒和脑内 表达APOE 2、APOE 3或APOE 4亚型的小鼠之间的实质和线粒体脂质体的差异 不同年龄目标3。检测载脂蛋白E纳米粒对体外Aβ吞噬功能的影响 和体内。目的是应用有关AD和小鼠脂质组成差异的知识， 并测试磷脂分子种类对小胶质细胞介导的Aβ吞噬作用的影响， 体外和体内实验系统中Aβ寡聚物的清除。

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.