Role of apoE structure and metabolism in neurodegeneration

性状（由申请方提供）：载脂蛋白（apo）E在血浆和中枢神经系统的脂质代谢和转运中起关键作用。人类三种主要apoE亚型之一apoE 4是阿尔茨海默病的主要危险因素，其机制尚未明确。我们的长期目标是采用结构-功能方法来建立这些机制，以确定潜在的治疗干预措施。本建议侧重于与这一目标有关的两个主要领域。首先，我们将扩展我们的x-射线衍射和小角x-射线散射模型结合磷脂的apoE 4的分辨率和比较apoE 4和apoE 3结合脂质的结构。其次，我们将继续我们的研究，我们联系的apoE 4结构域相互作用的特性，神经变性和功能和认知缺陷。人apoE同种型敲入小鼠的脑和我们的Arg-61 apoE小鼠模型（其中引入了结构域相互作用）分别含有较低水平的apoE 4和Arg-61小鼠apoE（与apoE 3和小鼠野生型apoE相比）。较低水平是由于星形胶质细胞分泌减少，其中Arg-61 apoE被选择性降解，诱导未折叠蛋白应激反应。基于这些研究，我们假设域相互作用通过对星形胶质细胞的两种作用促进神经退行性变。1)结构域相互作用被认为是一种异常折叠的蛋白质，导致内质网应激反应，导致对支持神经元完整性的关键生化途径的下游影响。2)apoE 4分泌减少导致胆固醇水平降低，以支持突触形成和神经元维持。这一假说代表了一种新的范式，其中apoE 4结构域相互作用有助于神经变性和功能和认知缺陷，涉及星形胶质细胞在没有额外的应激源。我们认为这些效应是apoE 4携带者的早期事件，并为增加脑应激源（例如年龄，缺血或A2毒性）而产生更显著的反应奠定了基础。这种范式将apoE结构与神经变性和功能后果联系起来，并表明干扰结构域相互作用是一种可行的治疗方法。这些研究有可能确定apoE 4与阿尔茨海默病和其他形式的神经退行性疾病的高风险相关的机制，并确定降低这种风险的治疗方法。公共卫生相关性：载脂蛋白E4（apoE 4）是一种脑蛋白，是阿尔茨海默病的主要遗传危险因素，尽管这种关联的基础尚不清楚。基于我们的apoE 4结构研究，我们提出了一种新的机制，这种关联涉及星形胶质细胞，星形胶质细胞是大脑中支持和维持神经细胞的细胞。这些研究有可能确定新的治疗方法来逆转apoE 4对阿尔茨海默病的影响。

DESCRIPTION (provided by applicant): Apolipoprotein (apo) E plays a key role in lipid metabolism and transport in plasma and the central nervous system. One of the three major human apoE isoforms, apoE4, is a major risk factor for Alzheimer's disease by as yet undefined mechanisms. Our long-range objective is to employ a structure-function approach to establish these mechanisms with the goal of identifying potential therapeutic interventions. This proposal focuses on two major areas related to this goal. First, we will extend the resolution of our x-ray diffraction and small-angle x- ray scattering model of apoE4 bound to phospholipids and compare the structures of apoE4 and apoE3 bound to lipid. Secondly, we will continue our studies in which we link the apoE4 structural property of domain interaction to neurodegeneration and functional and cognitive deficits. The brains of human apoE isoform knock in mice and our Arg-61 apoE mouse model in which domain interaction was introduced, contain lower levels of apoE4 and Arg-61 mouse apoE compared to apoE3 and mouse wild-type apoE, respectively. The lower levels were due to decreased secretion by astrocytes, in which the Arg-61 apoE was selectively degraded, inducing an unfolded protein stress response. Based on these studies, we hypothesize that domain interaction contributes to neurodegeneration through two effects on astrocytes. 1) Domain interaction is recognized as an abnormally folded protein, resulting in an endoplasmic reticulum stress response that leads to downstream effects on key biochemical pathways supporting neuronal integrity. 2) Decreased secretion of apoE4 results in lower levels of cholesterol to support synapse formation and neuronal maintenance. This hypothesis represents a novel paradigm in which apoE4 domain interaction contributes to neurodegeneration and functional and cognitive deficits, involving astrocytes in the absence of additional stressors. We believe that these effects are early events in apoE4 carriers and set the stage for more dramatic responses with the addition of brain stressors (e.g. age, ischemia or A2 toxicity). This paradigm links apoE structure with neurodegeneration and functional consequences and suggests that interference with domain interaction is a viable therapeutic approach. These studies hold the potential to determine the mechanisms by which apoE4 is associated with a high risk for Alzheimer's disease and other forms of neurodegeneration and for identifying therapeutic approaches to reduce this risk. PUBLIC HEALTH RELEVANCE: Apolipoprotein E4 (apoE4) a brain protein, is the major genetic risk factor for Alzheimer's disease although the basis for this association is unknown. Based on our apoE4 structure studies, we propose a new mechanism for this association involving astrocytes, which are cells in the brain that support and maintain nerve cells. These studies hold the potential to identify new therapeutic approaches to reverse the effects of apoE4 on Alzheimer's disease.