Role of ABeta-Degrading Proteases in Alzheimer's Disease

描述(申请人提供)：尽管大量研究支持淀粉样β蛋白(Aβ)在阿尔茨海默病(AD)发病机制中的核心作用，但在绝大多数情况下，这种多肽积累的根本原因尚不清楚。只有几个病例(5%)涉及Aβ的过度产生，新产生的AB迅速从大脑中清除，这表明Aβ降解蛋白酶可能在调节大脑多肽水平方面发挥重要作用。虽然许多工作都集中在Aβ蛋白的产生上，但对Aβ蛋白分解的了解相对较少，它在AD的发病机制和/或潜在的治疗中可能同样重要，甚至更重要。研究最多的两种A-β降解酶是奈普利辛(NEP)和胰岛素降解酶(IDE)。有人类遗传证据表明，在一些人群中，染色体10q的IDE区域与阿尔茨海默病和2型糖尿病(DM2)都有关联，这一点很有趣，因为越来越多的证据表明DM2和高胰岛素血症与发展为AD的风险增加有关。这一建议的中心假设是，IDE和NEP是体内Aβ水平的重要调节因子，这些蛋白酶的缺陷可能是某些AD病例的基础。我的目标是：1)利用两种动物模型确定IDE功能障碍是否导致体内Aβ和胰岛素分解代谢降低；2)通过培育基因缺失的小鼠和人APP转基因小鼠，评估IDE和NEP在体内对人Aβ亚型代谢的相对作用；3)通过量化转录本和使用报告结构来确定AD家系中已知的IDE基因5‘非翻译区(UTR)的生物学意义，并通过量化转录本和使用报告结构来确定与该区域等位基因关联的IDE；4)检测IDE正常细胞生物学的几个方面，如可能的GPI锚，脑脊液和血清中的异构体，并寻找天然结合伙伴。这份K08提案的目标是在细胞和分子生物学、动物育种策略和统计分析方面获得必要的科学培训，以允许候选人检验上述假设，并在这样做的过程中，允许候选人发展成为一名成功和独立的内科科学家，拥有帮助神经退行性痴呆患者的技能。应聘者的职业发展计划，世界级的培训环境，以及他所在部门的承诺将有助于实现这一目标。

DESCRIPTION (provided by applicant): Although an impressive number of studies support a central role for amyloid beta-protein (A beta) in the pathogenesis of Alzheimer's disease (AD), in the vast majority of cases, the underlying causes for the peptide's accumulation are unknown. Overproduction of A beta has been implicated in only a few cases (<5%), and newly generated AB is rapidly cleared from the brain, suggesting that A beta-degrading proteases could play a vital role in regulating cerebral levels of the peptide. Although much work has focused on the generation of A beta, relatively little is known about A beta proteolysis, which could be equally or even more important in the pathogenesis and/or potential treatments of AD. The two best-studied A beta-degrading proteases are neprilysin (NEP) and insulin-degrading enzyme (IDE). There is human genetic evidence showing linkage of the IDE region of chromosome 10q to both AD and type 2 diabetes mellitus (DM2) in some populations, which is intriguing in light of the growing evidence that DM2 and hyperinsulinemia are associated with an increased risk of developing AD. The central hypothesis of this proposal is that IDE and NEP are important regulators of A beta levels in vivo and defects in these proteases may underlie some cases of AD. My Aims are to: 1) Determine whether dysfunction of IDE leads to decreased A beta and insulin catabolism in vivo using two animal models, 2) Assess the relative roles in vivo of IDE and NEP in the metabolism of the human isoform of A beta by breeding gene-deleted mice to human APP transgenic mice, 3) Determine the biological significance of the known polymorphisms in the 5' un-translated region (UTR) of the IDE gene in AD families with allelic association to this region of chromosome 10q by quantifying transcripts and using reporter constructs and 4) Examine several aspects of the normal cell biology of IDE, such as a possible GPI-anchor, isoforms in the CSF and serum, and search for natural binding partners. The goal of this K08 proposal is to obtain the necessary scientific training in cell and molecular biology, animal breeding strategies, and statistical analysis to allow the candidate to test the above hypothesis as outlined, and in doing so, allow the candidate to develop into a successful and independent physician-scientist with the skills to help individuals with neurodegenerative dementias. The candidate's career development plan, world-class training environment, and commitment from his Department will allow the realization of this goal.