Mitochondrial-dependent Mechanisms of Apolipoprotein E Gene Expression in the Mammalian Brain

项目总结 阿尔茨海默病(AD)是一种使人衰弱和常见的痴呆症，也是老年人死亡的主要原因之一。 美国。淀粉样蛋白假说的检验一直是AD研究的重点。 根据这一假说，阿尔茨海默病前体蛋白(APP)的致病处理导致 斑块中含有淀粉样β蛋白，这是阿尔茨海默病的标志和明显的原因。尽管有很多 经过努力，基于这一假说的研究尚未为AD提供有效的治疗靶点。因此，替代方案 线粒体、脂类和胆固醇代谢在AD发病机制中的因果作用假说 也被提出了。虽然这些假说已经与淀粉样蛋白假说进行了测试，但 在确定线粒体和胆固醇/脂质是否起因果作用方面仍然存在关键的机制差距 AD发病机制中的代谢可能是相互关联的。脂和胆固醇代谢在糖尿病中的作用 载脂蛋白E(ApoE)基因的一个等位基因编码主要携带者的事实支持AD 大脑中的血脂和胆固醇是散发性AD最强的遗传风险因素。相比之下，研究 研究线粒体在AD中的因果作用主要集中在生物能量学和氧化应激上，尽管 线粒体在胆固醇和脂肪代谢中也扮演着已知的角色。线粒体是否影响载脂蛋白E 阿尔茨海默病背景下的表达和/或胆固醇稳态仍未被探索，并将成为这一研究的焦点 求婚。我们的初步数据表明线粒体膜转运蛋白的表达减少 SLC25A1可提高载脂蛋白E和APP水平。SLC25A1将代谢产物柠檬酸从线粒体运送到 细胞质，在那里它被转化为乙酰辅酶A，这是脂肪和胆固醇合成所必需的。中环 本提案将检验的假设是SLC25A1相互作用体(SLC25A1)的遗传中断 以及与其物理相互作用的蛋白质网络)会增加ApoE的表达和改变 胆固醇动态平衡，从而影响下游APP的生产和加工。在目标1中， 受训者将确定ApoE表达增加是否是表明功能障碍的特定读数 SLC25A1相互作用体的组成部分，或者是对线粒体功能障碍的一般反应，使用 免疫印迹、定量聚合酶链式反应(RT-qPCR)和脂类组学分析 神经胶质细胞。在目标2中，受训者将确定SLC25A1基因剂量是否调节小鼠的AD病理 AD模型，采用平板免疫分析和免疫细胞化学方法。这些目标的完成将揭示 线粒体是否通过载脂蛋白E和/或胆固醇依赖机制参与AD的发病。 以及这种影响是否特定于与脂质/胆固醇有关的线粒体蛋白的某个中枢 新陈代谢。这些发现将提高我们对阿尔茨海默病发病机制的理解，并提出新的 针对这种毁灭性疾病的药物靶点。

PROJECT SUMMARY Alzheimer’s disease (AD) is a debilitating and common form of dementia, and a leading cause of death in the United States. Testing of the amyloid hypothesis has overwhelmingly been the focus of research on AD. According to this hypothesis, pathogenic processing of the Alzheimer’s precursor protein (APP) leads to accumulation of plaques containing amyloid beta that are a hallmark, and apparent cause, of AD. Despite much effort, research based on this hypothesis has yet to provide effective therapeutic targets for AD. Thus, alternative hypotheses invoking causal roles for mitochondria and metabolism of lipids and cholesterol in AD pathogenesis have also been proposed. While these hypotheses have been tested in relation to the amyloid hypothesis, a critical mechanistic gap remains in determining whether causal roles for mitochondria and cholesterol/lipid metabolism in AD pathogenesis may be linked with one another. A role for lipid and cholesterol metabolism in AD is supported by the fact that an allele of the ApolipoproteinE (ApoE) gene, encoding the primary carrier of lipids and cholesterol in the brain, is the strongest genetic risk factor for sporadic AD. In contrast, research examining causal roles for mitochondria in AD has focused on bioenergetics and oxidative stress, although mitochondria also play known roles in cholesterol and lipid metabolism. Whether mitochondria influence ApoE expression and/or cholesterol homeostasis in the context of AD remains unexplored and will be the focus of this proposal. Our preliminary data indicates that reduced expression of the mitochondrial membrane transporter SLC25A1 increases levels of ApoE and APP. SLC25A1 shuttles the metabolite citrate from mitochondria to the cytoplasm, where it gets converted to acetyl-CoA that is required for lipid and cholesterol synthesis. The central hypothesis that will be tested in this proposal is that genetic disruption of the SLC25A1 interactome (SLC25A1 and the network of proteins with which it physically interacts) drives increased ApoE expression and changes in cholesterol homeostasis, consequently impacting downstream APP production and processing. In Aim 1, the trainee will determine whether increased ApoE expression is a specific readout indicating dysfunction of components of the SLC25A1 interactome, or is instead a general response to mitochondrial dysfunction, using immunoblots, quantitative polymerase chain reaction (RT-qPCR), and lipidomics profiling in primary neurons and glia. In Aim 2, the trainee will determine whether Slc25a1 gene dosage modulates AD pathology in a mouse model of AD, using plate-based immunoassays and immunocytochemistry. Completion of these aims will reveal whether mitochondria contribute to AD pathogenesis through ApoE and/or cholesterol-dependent mechanisms, as well as whether this influence is specific to a certain hub of mitochondrial proteins involved in lipid/cholesterol metabolism. These findings will improve our understanding of mechanisms contributing to AD and suggest novel drug targets for this devastating disease.