The role of netrin-1 as an APP ligand in Alzheimer disease

描述(申请人提供)：阿尔茨海默病(AD)是最常见的与年龄相关的痴呆形式，部分特征是认知和情感脑区中由β-淀粉样蛋白组成的老年斑。AD神经发病机制的研究主要集中在其前体蛋白APR(β-淀粉样前体蛋白)产生β-淀粉样蛋白。然而，对APP的潜在配体的了解有限，这些配体可能介导APP信号转导和随后的β-淀粉样蛋白产生。最近，与P.Mehlen博士(大学)合作。，我们已经确定了APP的一个新的神经营养配体netrin-1，并提出了一个导致净β-淀粉样蛋白水平显著下降的APP信号转导模型。为了建立阿尔茨海默病治疗操作的框架，本提案试图进一步研究netrin-1作为APP配体在改善AD表型某些元素方面的潜在作用。考虑到这一目标，具体目标提出了以下计划：1)通过建立可诱导表达Netrin-1的AD转基因小鼠模型，在体内验证Netrin-1‘S调节β-淀粉样蛋白产生和其他AD样特征(即齿状回萎缩、突触丢失和Y迷宫中的工作记忆)的能力；2)利用缺失突变设计，我计划鉴定并纯化与全长Netrin-1类似的最低APP结合和生物活性区域的Netrin-1。我们假设，通过与APP结合，netrin-1的表达将降低大脑中的β-淀粉样蛋白水平，并相关地改善AD样特征。此外，如果发现Netrin-1衍生的片段在机械上与Netrin-1相似，那么它作为治疗AD的化合物可能是可行的。

DESCRIPTION (provided by applicant): Alzheimer disease (AD) is the most common form of age-related dementia, in part characterized by senile plaques composed of beta-amyloid protein in cognitive and affective brain regions. Much research in the area of AD neuropathogenesis has focused on the production of beta-amyloid from its precursor protein APR (beta-amyloid precursor protein). However, limited knowledge exists on the potential ligands of APP, which may mediate APP signal transduction and subsequent beta-amyloid production. Recently, in collaboration with Dr. P. Mehlen (Univ. of Lyon), we have identified a novel neurotrophic ligand for APP, netrin-1, and posited a model of APP signal transduction that results in a significant decrease in net beta- amyloid levels. In order to establish a framework for the therapeutic manipulation of AD, this proposal seeks to further investigate the potential role of netrin-1 as an APP ligand in amelioration of certain elements of the AD phenotype. With this goal in mind, the specific aims present a plan to 1) validate netrin-1's ability to modulate beta-amyloid production and other AD-like traits (i.e., dentate gyral atrophy, synapse loss, and working memory in a Y-maze) in vivo by establishing an AD transgenic mouse model that inducibly expresses netrin-1; and 2) using deletion mutant designs, I plan to identify, and then purify the minimum APP-binding and biologically active domain of netrin-1 that suppresses net beta-amyloid production like full- length netrin-1. We hypothesize that netrin-1 expression, through binding with APP, will decrease beta- amyloid levels in brain, with a related amelioration of AD-like features. Furthermore, if a netrin-1-derived fragment is discovered that is mechanistically similar to netrin-1, then it may be feasible as a therapeutic compound in the treatment of AD.