Defining the Function of APOE in Autophagy and Neurodegeneration

项目总结/摘要 阿尔茨海默氏病（AD）是痴呆症的最常见原因，在65岁以上的老年人中， 美国的AD是使人衰弱和致命的，并且没有有效的治疗方法。自噬失调， 将细胞废物转运至内-溶酶体系统进行降解的过程，已被提出为 一种与AD和许多其他神经退行性疾病有关的机制。自噬可以被下调 正常衰老和具有自噬功能的蛋白质突变。最大的遗传风险因素， AD发病是APOE。我推测APOE作为一种选择性自噬受体蛋白发挥作用， 疾病相关的APOE 4亚型失调自噬，导致疾病。APOE 4损害自噬 在小鼠星形胶质细胞中，减少人胶质母细胞瘤细胞系中的自噬基因转录，并导致 在AD的早期阶段内体显著增大。载脂蛋白E运输大脑的大部分脂质， 脂质蓄积是AD的病理标志之一，提示脂质清除可能是AD的重要病理机制之一。 受损APOE是否会直接影响自噬功能，这一点尚未得到证实。 自噬机制APOE具有已建立的自噬受体的几个特性，包括定位 在酸性隔室和低聚反应中。最近发现APOE与哺乳动物Atg 8 s相互作用， 在自噬过程中，这是自噬受体的一个关键特征。蛋白质序列比对数据表明， APOE可能与酵母自噬蛋白Atg 39有一些相似之处，Atg 39是最近发现的一种针对APOE的受体。 脂质和内质网的自噬。这项建议的目的如下。目标1：评估 APOE与自噬机制的相互作用。我将研究APOE作为自噬受体的功能 蛋白质部分通过定义其与自噬机制蛋白质的相互作用。目标2：检查 自噬底物。在这里，我将确定是否APOE是必需的选择性 脂质和内质网的自噬。目的3：评估APOE亚型对自噬的影响 降解为此，我将评估致病的APOE 4等位基因是否可以影响自噬， APOE的周转、自噬体的形成和自噬底物的积累。这些目标将开始 以确定APOE是否具有作为自噬货物受体的新功能。调查的职能 APOE在自噬中的作用，以及APOE 4亚型是否会损害或增强这些功能，可能会提供一些见解。 自噬修饰疗法可以使数百万AD患者受益。

PROJECT SUMMARY/ABSTRACT Alzheimer's Disease (AD) is the most common cause of dementia, affecting 1 in 10 over the age of 65 in the United States. AD is debilitating and fatal, and no effective treatments are available. Dysregulation of autophagy, the process of transporting cellular waste to the endo-lysosomal system for degradation, has been proposed as a mechanism involved in AD and many other neurodegenerative diseases. Autophagy can be down-regulated by both normal aging and mutation of proteins with autophagic functions. The greatest genetic risk factor for late onset AD is APOE. I hypothesize that APOE functions as a selective autophagic receptor protein, and that the disease-associated APOE4 isoform dysregulates autophagy, contributing to disease. APOE4 impairs autophagy in mouse astrocytes, reduces autophagy gene transcription in a human glioblastoma cell line, and results in dramatic endosomal enlargement in the early stages of AD. APOE transports the majority of the brain's lipids, and lipid accumulation is one of the pathological hallmarks of AD, suggesting that lipid clearance may be impaired. It has not yet been tested whether APOE may impact autophagic function directly as part of the autophagy machinery. APOE has several properties of established autophagy receptors, including localization in acidic compartments and oligomerization. It was recently shown that APOE interacts with mammalian Atg8s during autophagy, a key characteristic of autophagy receptors. Protein sequence alignment data suggests that APOE may have some similarity to the yeast autophagy protein Atg39, a recently discovered receptor for the autophagy of lipids and the endoplasmic reticulum. The Aims of this proposal are as follows. Aim 1: Assess APOE interactions with the autophagy machinery. I will investigate APOE's function as an autophagic receptor protein in part by defining its interactions with autophagy machinery proteins. Aim 2: Examine accumulation of autophagic substrates upon APOE knockdown. Here, I will determine whether APOE is required for selective autophagy of lipids and endoplasmic reticulum. Aim 3: Assess impact of APOE isoforms on autophagic degradation. For this aim, I will assess whether the disease-causing APOE4 allele can impact autophagic turnover of APOE, autophagosome formation, and accumulation of autophagic substrates. These aims will begin to determine whether APOE has a novel function as an autophagic cargo receptor. Investigating the functions of APOE in autophagy, and whether the APOE4 isoform impairs or enhances those functions, may offer insight into the types of autophagy modifying therapies that could benefit millions of patients with AD.