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

描述(由申请人提供)：项目摘要：该项目的长期目标集中在建立ATP结合盒转运体-2(ABCA2)作为淀粉样前体蛋白(APR)蛋白分解过程的新调节子。APP的淀粉样变性处理导致A-β多肽裂解产物的产生，这些裂解产物与阿尔茨海默病(AD)的病因有关。调控APP加工和AP产生的机制尚未完全阐明。调节APP加工的一种机制是APP的胆固醇转运依赖的定位和关键酶，这些酶介导APP在膜室中的蛋白水解性切割。ABCA2可能调节外源性脂蛋白衍生的胆固醇在细胞内的运输，使其从晚期内体/溶酶体转移到细胞膜。我们发现ABCA2在体外是APP加工和A-β产生的调节因子。我们确定，在稳定共表达ABCA2和APP的非神经性HEK293细胞中，细胞APP全蛋白水平和A-β分泌增加，这些细胞携带APP“瑞典”突变。我们还使用微阵列分析在稳定表达ABCA2的HEK293细胞中检测到与AD相关的一些基因的表达增加。尽管有证据表明ABCA2可能是APP代谢的关键调节因子，可能是通过调节细胞内胆固醇的运输和分布，但我们尚未研究ABCA2功能在神经细胞或表达APP突变形式的转基因小鼠大脑中的影响。我们最近在大脑特异性Thy-1启动子的控制下获得了ABCA2基因敲除小鼠和ABCA2转基因小鼠，这将使我们能够研究ABCA2转运蛋白在调节AD转基因小鼠模型体内APP加工和A-β产生方面的这一新功能。我们的初步结果使我们得出了一个新的假设，即ABCA2通过调节细胞内依赖胆固醇运输的APP和膜中关键加工酶的定位来调节APP的加工和A-β的产生。 公共卫生相关性：这些研究可能提供胆固醇代谢和APP处理之间的新的和机械的联系，这可能具有直接的临床相关性。深入了解ABCA2转运蛋白在APP加工调控中的作用机制，可能为制定防治AD的治疗策略提供依据。

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.