ATP-Binding Cassette Transporter-2 Regulates Amyloid Precursor Protein Dynamics

描述（由申请人提供）：项目概述：本项目的长期目标是将ATP结合盒转运蛋白2（ABCA 2）作为淀粉样前体蛋白（APR）蛋白水解加工的新型调节剂。APP的淀粉样蛋白生成加工导致A-β肽裂解产物的产生，所述A-β肽裂解产物与阿尔茨海默病（AD）的病因有关。调节APP加工和Ap生产的机制尚未完全阐明。调节APP加工的一种机制是APP和介导其在膜隔室中的蛋白水解裂解的关键酶的胆固醇运输依赖性定位。ABCA 2可能具有调节外源脂蛋白衍生的胆固醇从晚期内体/溶酶体到膜隔室的细胞内胆固醇运输的功能。我们确定ABCA 2作为APP加工和A-β生产的调节剂在体外。我们确定，在稳定共表达ABCA 2和携带APP“瑞典”突变的APP的非神经元HEK 293细胞中，细胞APP全蛋白水平和A-β分泌增加。我们还使用微阵列分析在稳定表达ABCA 2的HEK 293细胞中检测到许多与AD相关的基因的表达增加。尽管有证据表明ABCA 2可能是APP代谢的关键调节因子，可能通过调节细胞内胆固醇的运输和分布，我们还没有检测ABCA 2功能在神经元细胞或表达APP突变形式的转基因小鼠的脑中的作用。我们最近生产的ABCA 2敲除小鼠和ABCA 2转基因小鼠在脑特异性Thy-1启动子将允许在AD转基因小鼠模型中研究ABCA 2转运蛋白在体内调节APP加工和A-β产生中的这种新功能。我们的初步结果使我们提出了一个新的假设，即ABCA 2通过调节细胞内胆固醇运输依赖性APP和膜室中关键加工酶的定位来调节APP加工和A-β产生。 公共卫生相关性：这些研究可能提供胆固醇代谢和APP加工之间的新的和机制的联系，可能是直接的临床相关性。深入了解ABCA 2转运蛋白调节APP加工的作用机制可能为开发预防和治疗AD的治疗策略提供基础。

DESCRIPTION (provided by applicant): Project Summary: The long-term goals of this project focus on establishing the ATP-binding cassette transporter-2 (ABCA2) as a novel regulator of proteolytic processing of the amyloid precursor protein (APR). Amyloidogenic processing of APP results in the generation of A-beta peptide cleavage products that are implicated in the etiology of Alzheimer's disease (AD). The complete elucidation of the mechanisms that regulate APP processing and Ap production has not been realized. One mechanism that regulates APP processing is the cholesterol trafficking-dependent localization of APP and key enzymes that mediate its proteolytic cleavage in membrane compartments. ABCA2 may function to modulate intracellular cholesterol trafficking of exogenous llpoprotein-derived cholesterol from late-endosomes/lysosomes to membrane compartments. We identified ABCA2 as a regulator of APP processing and A-beta production in vitro. We determined that cellular APP holoprotein levels and A-beta secretion were increased in non-neuronal HEK293 cells that stably co-expressed ABCA2 and APP bearing the APP "Swedish" mutation. We also detected increased expression of a number of genes associated with AD using microarray analysis in HEK293 cells that stably expressed ABCA2. Although evidence suggests that ABCA2 may be a key regulator of APP metabolism, perhaps by regulation of intracellular cholesterol trafficking and distribution, we have not examined the effects of ABCA2 function in either neuronal cells or in the brains of transgenic mice expressing mutant forms of APP. Our recent production of ABCA2 knockout mice and ABCA2 transgenic mice under the control of the brain-specific Thy-1 promoter will permit the investigation of this novel function of the ABCA2 transporter in regulating APP processing and A-beta production in vivo in transgenic mouse models of AD. Our preliminary results have led us to the novel hypothesis that ABCA2 acts to regulate APP processing and A-beta production through modulation of intracellular cholesterol trafficking-dependent localization of APP and key processing enzymes in membrane compartments. Public Health Relevance: These studies may provide novel and mechanistic links between cholesterol metabolism and APP processing that could be of direct clinical relevance. In depth knowledge of the mechanisms of action of the ABCA2 transporter on regulation of APP processing may provide a basis for the development of therapeutic strategies in prevention and treatment of AD.