Apolipoprotein E in Alzheimer's Disease: Cellular Mechanisms

载脂蛋白E4（Apolipoprotein，apo）是阿尔茨海默病（Alzheimer's disease，AD）的主要危险因子或易感基因。 虽然致病机制尚不清楚，但我们在前一个资助期的发现， 其他人报道的研究结果表明，apoE 4具有多种细胞来源和多种结构， 生物物理特性通过各种途径与不同因素相互作用而导致AD， 其中一些是淀粉样蛋白-（3（A|（3）其他人不依赖。虽然A| apoE 4的3依赖性作用 在AD发病机制中的作用已被广泛研究，并产生了许多有价值的信息，|3-独立 apoE 4的作用是目前建议的焦点，但引起的关注较少，研究也不足。 在中枢神经系统（CNS）中，apoE由几种类型的细胞产生，包括星形胶质细胞， 激活了小胶质细胞和受损的神经元新出现的证据表明，神经元产生的apoE和 星形细胞产生的apoE在生理和病理生理途径中具有独特的作用，包括AD 发病机制因此，了解apoE在CNS神经元中的表达是如何调节的， 对apoE亚型在神经生物学和神经变性中的不同作用的基本见解。 本提议以上一个供资期间的四项调查结果为基础。首先，CNS神经元表达 apoE对损伤的反应。第二，损伤后apoE的神经元表达受星形胶质细胞源性 控制apoE基因内含子-3保留/剪接的因子。第三，apoE 4比 比apoES对神经元特异性蛋白水解敏感，并且产生的片段引起AD样 神经变性和行为缺陷。第四，在转基因小鼠中， apoE 4或其片段的表达导致学习和记忆缺陷和早期神经元缺陷， 内嗅皮层、下托和海马，提示特定CNS神经元的选择性脆弱性。 本课题的目的是研究apoE在中枢神经元表达的调控， apoE在AD发病机制中的亚型特异性作用具体来说，我们将探讨 CNS神经元apoE表达的调节（目的1）;确定蛋白水解的抑制是否减少或 消除转基因小鼠中apoE 4相关的有害作用（目的2）;并探讨其机制 不同类型的CNS神经元对apoE 4及其片段的选择性脆弱性的基础（目的3）。 这些研究，包括在体外和体内的方法，将提供深入了解的调控和作用， apoE 4在健康和疾病中的作用，并可能为apoE 4相关的 神经退行性疾病，特别是AD。

Apolipoprotein (apo) E4 is a major risk factor or susceptibility gene for Alzheimer's disease (AD). Although the pathogenic mechanisms are unclear, our findings during the preceding funding period, and findings reported by others, suggest that apoE4¿with its multiple cellular origins and multiple structural and biophysical properties¿contributes to AD by interacting with different factors through various pathways, some of which are amyloid-(3 (A|3) dependent and others are not. Although the A|3-dependent roles of apoE4 in AD pathogenesis have been widely studied and much valuable information generated, the A|3-independent roles of apoE4¿the focus of the current proposal¿have drawn less attention and have been understudied. In the central nervous system (CNS), apoE is produced by several types of cells, including astrocytes, activated microglia, and injured neurons. Emerging evidence suggests that neuron-generated apoE and astroycte-generated apoE have distinct roles in physiological and pathophysiological pathways, including AD pathogenesis. Thus, understanding how apoE expression is regulated in CNS neurons should provide fundamental insights into the varied effects of apoE isoforms in neurobiology and neurodegeneration. This proposal builds on four findings during the preceding funding period. First, CNS neurons express apoE in response to injury. Second, neuronal expression of apoE after injury is regulated by an astrocytederived factor (or factors) that controls intron-3 retention/splicing of the apoE gene. Third, apoE4 is more susceptible than apoES to neuron-specific proteolysis, and the resulting fragments cause AD-like neurodegeneration and behavioral deficits in transgenic mice. Fourth, in transgenic mice, pan-neuronal expression of apoE4 or its fragment causes learning and memory deficits and early neuronal deficits in the entorhinal cortex, subiculum, and hippocampus, suggesting selective vulnerability of specific CNS neurons. The goal of this project is to study the regulation of apoE expression in CNS neurons and to explore Apindependent, isoform-specific roles of apoE in the pathogenesis of AD. Specifically, we will explore the regulation of apoE expression in CNS neurons (Aim 1); determine if inhibition of proteolysis reduces or abolishes apoE4-related detrimental effects in transgenic mice (Aim 2); and explore the mechanisms underlying the selective vulnerability of different types of CNS neurons to apoE4 and its fragments (Aim 3). These studies, involving both in vitro and in vivo approaches, will provide insights into the regulation and role of apoE4 in both health and disease and may identify new therapeutic targets for apoE4-associated neurodegenerative disorders, particularly AD.