Role of apoE structure and metabolism in neurodegeneration

描述（申请人提供）：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。人类三种主要载脂蛋白e亚型之一，载脂蛋白e4，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相关的两个主要领域。首先，我们将扩大apoE4与磷脂结合的x射线衍射和小角度x射线散射模型的分辨率，并比较apoE4与apoE3与脂质结合的结构。其次，我们将继续我们的研究，将apoE4结构域相互作用的结构特性与神经变性和功能和认知缺陷联系起来。在小鼠和我们的Arg-61 apoE小鼠模型中，引入域相互作用的人类apoE亚型敲除小鼠的大脑中，apoE4和Arg-61小鼠apoE的水平分别低于apoE3和小鼠野生型apoE。较低的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，诱导未折叠的蛋白应激反应。基于这些研究，我们假设区域相互作用通过对星形胶质细胞的两种作用来促进神经退行性变。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，导致下游对支持神经元完整性的关键生化途径的影响。2) apoE4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。这一假设代表了apoE4结构域相互作用导致神经变性、功能和认知缺陷的新范式，涉及星形胶质细胞在缺乏额外应激源的情况下。我们认为这些影响是apoE4携带者的早期事件，并为添加脑应激源（例如年龄，缺血或A2毒性）时更剧烈的反应奠定了基础。这种范式将apoE结构与神经退行性变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apoE4与阿尔茨海默病和其他形式的神经退行性疾病高风险相关的机制，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 （apoE4）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。基于我们对apoE4结构的研究，我们提出了一种涉及星形胶质细胞的新机制，星形胶质细胞是大脑中支持和维持神经细胞的细胞。这些研究有可能找到新的治疗方法来逆转apoE4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.