Cholesterol and Sphingolipid Metabolism in Alzheimer's Disease

 描述(由申请人提供)：本申请的目标是在细胞培养和完整的动物水平上提供更多证据，以支持酰基辅酶A：胆固醇酰基转移酶1(ACAT1)作为阿尔茨海默病(AD)治疗的潜在新治疗靶点的特征。ACAT1是一种催化游离胆固醇转化为胆固醇酯的酶，在全身组织和大脑中的胆固醇动态平衡中发挥着重要作用。此前，我们的实验室表明，在AD的小鼠模型中，Acat1的基因敲除(KO)减少了淀粉样变性并挽救了认知缺陷。在这项资助的最后一个周期中，我们表明，表达针对Acat1的microRNAs的腺相关病毒直接传递到有症状的AD小鼠的大脑中，将大脑淀粉样β蛋白和全长人类淀粉样前体蛋白的水平降低到类似于完全基因切除Acat1的水平。我们还发现，在小胶质细胞和神经元中，Acat1基因KO或ACAT1特异性抑制剂K604刺激自噬小体的形成和转录因子EB介导的溶酶体蛋白分解，从而增加溶酶体Aü1-42的降解。阻断ACAT1对自噬的增强作用不依赖于雷帕霉素(MTOR)信号转导靶点和内质网应激反应。这些结果提示，阻断小胶质细胞和神经元的ACAT1可能是治疗AD的有效方法。为了在细胞培养和体内水平上提供更多的证据来支持ACAT1阻断的治疗潜力，我们在当前的应用中提出了两个特定的目标：特定的目标1：验证ACAT1阻断通过改变线粒体相关膜内的富含胆固醇/神经酰胺的结构域而增加自噬小体形成的假设。具体目的2：验证ACAT1阻断小胶质细胞和神经元延缓AD神经细胞丢失和记忆障碍的假说。相关性：这项应用的结果将提供证据支持一种潜在的新的治疗方法，以靶向小胶质细胞和神经元中的ACAT1来治疗AD。

 DESCRIPTION (provided by applicant): The goal of the current application is to provide more evidence at the cell culture and intact animal levels to support the characterization of acyl-CoA: cholesterol acyltransferase1 (ACAT1) as a potential new therapeutic target for Alzheimer's disease (AD) treatment. ACAT1 is an enzyme that catalyzes the conversion of free cholesterol to cholesterol esters, and that plays an important role in cholesterol homeostasis in systemic tissues and the brain. Previously, our laboratory showed that in a mouse model for AD, gene knockout (KO) of Acat1 decreased amyloidopathy and rescued cognitive deficits. During the last cycle of this grant, we showed that adeno-associated viruses expressing microRNAs targeting Acat1 delivered directly to the brains of symptomatic AD mice decreased the levels of brain amyloid-beta and full-length human amyloid precursor protein to levels similar to complete genetic ablation of Acat1. We also showed that in microglia and neurons, Acat1 gene KO or an ACAT1-specific inhibitor K604 stimulated autophagosome formation and transcription factor EB-mediated lysosomal proteolysis, thereby resulting in an increase in lysosomal Aß1-42 degradation. The enhancing effect of ACAT1 blockage on autophagy was independent of mammalian target of rapamycin (mTOR) signaling and the endoplasmic reticulum stress response. These results suggest that ACAT1 blockage in microglia and neurons may be effective in the treatment of AD. To provide more evidence at the cell culture and in vivo levels to support the therapeutic potential of ACAT1 blockage, we propose two specific aims in the current application: Specific Aim 1: To test the hypothesis that ACAT1 blockage increases autophagosome formation by altering the cholesterol-rich/ceramide-rich domain within the mitochondrial- associated membrane. Specific Aim 2: To test the hypothesis that ACAT1 blockage in microglia and neurons delays neuronal cell loss and memory deficits in AD. Relevance The outcome of this application will offer evidence to support a potential new therapeutic approach to target ACAT1 in microglia and neurons for AD treatment.