Cholesterol and Sphingolipid Metabolism in Alzheimer's Disease

 描述（由申请人提供）：本申请的目的是在细胞培养和完整动物水平提供更多证据，以支持酰基辅酶A：胆固醇酰基转移酶1（ACAT 1）作为阿尔茨海默病（AD）治疗的潜在新治疗靶点的表征。ACAT 1是一种催化游离胆固醇转化为胆固醇酯的酶，在全身组织和大脑的胆固醇稳态中起重要作用。以前，我们的实验室表明，在AD小鼠模型中，Acat 1的基因敲除（KO）减少了淀粉样蛋白病并挽救了认知缺陷。在该资助的最后一个周期中，我们发现，表达靶向Acat 1的microRNA的腺相关病毒直接递送到有症状的AD小鼠的大脑中，将大脑淀粉样蛋白β和全长人类淀粉样蛋白前体蛋白的水平降低到与Acat 1的完全基因消融相似的水平。我们还发现，在小胶质细胞和神经元中，Acat 1基因KO或ACAT 1特异性抑制剂K604刺激自噬体形成和转录因子EB介导的溶酶体蛋白水解，从而导致溶酶体A β 1 -42降解增加。ACAT 1阻断对自噬的增强作用不依赖于哺乳动物雷帕霉素靶蛋白（mTOR）信号传导和内质网应激反应。这些结果表明，在小胶质细胞和神经元中阻断ACAT 1可能在治疗AD中有效。为了在细胞培养和体内水平提供更多证据以支持ACAT 1阻断的治疗潜力，我们在本申请中提出了两个具体目的：具体目的1：为了测试ACAT 1阻断通过改变线粒体相关膜内的富含胆固醇/富含神经酰胺的结构域来增加自噬体形成的假设。具体目的2：检验小胶质细胞和神经元中的ACAT 1阻断延迟AD中的神经元细胞损失和记忆缺陷的假设。相关性本申请的结果将提供证据支持一种潜在的新治疗方法，靶向小胶质细胞和神经元中的ACAT 1用于AD治疗。

 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.