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

APOE（载脂蛋白 E）是 19 号染色体上 APOE/APOC 基因簇的一部分，编码 3 种蛋白质 同种型 – APOE2、APOE3 和 APOE4。 APOE 在外周转运胆固醇和磷脂， 大脑。 APOE 亚型的脂质和受体结合能力不同，其作用与清除有关 LDL、VLDL 和乳糜微粒。 APOE4 等位基因的遗传增加，APOE2 降低风险 迟发性AD（LOAD），但其机制知之甚少。虽然 APOE 参与关键的细胞 氧化过程、炎症、神经胶质细胞和神经元稳态等功能，这些都不能被 与胆固醇和磷脂同种型特异性结合、运输和递送至不同细胞分离 类型。最近的报告表明，APOE 亚型对小胶质细胞介导的特异性作用可能存在差异 大脑中表达的免疫受体的吞噬作用和功能。我们的初步数据表明 APOE 同工型影响免疫受体 Dectin-1/Clec7a、Siglec1、Siglech、Oscar 的表达 - 参与 炎症反应和吞噬作用。对 APOE 和免疫的相互关联作用的有力支持 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 AD 患者的大脑样本中，我们发现磷脂分子形态存在显着差异 主要磷脂类别。我们假设 APOE 异构体对吞噬作用的特异性影响是由以下因素驱动的 APOE 脂质颗粒的不同磷脂组成和/或 APOE 亚型的差异效应 关于小胶质细胞转录组。我们提出 3 个具体目标来检验这一假设： 目标 1. 建立异构体- APOEε2 等位基因对 AD 脑实质和线粒体脂质组和转录组的依赖性影响 患者和非痴呆对照。目标是整合脂质和转录谱并揭示 APOE 等位基因控制表型和脂质分子种类，用于 SA3 中的其他功能测定。目标2。 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 APOE2、APOE3 或 APOE4 亚型的小鼠。我们将测定磷脂含量 星形胶质细胞条件培养基中的天然 APOE、脑间质液 (ISF) 中的脂质颗粒以及大脑中的差异 2 表达 APOE2、APOE3 或 APOE4 亚型的小鼠之间的实质和线粒体脂质组 不同的年龄。目的3. 体外测试含APOE纳米粒子对Aβ吞噬作用的影响 和体内。目标是应用有关 AD 和小鼠脂质成分差异的知识 大脑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 在体外和体内实验系统中清除 Aβ 寡聚体。

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.