Nicastrin and Presenilin-dependent gamma-secretase

描述（由申请人提供）：阿尔茨海默病（AD）是一种老年人进行性神经退行性疾病，其特征是海马和大脑皮质中β-淀粉样蛋白（ABeta）沉积和神经原纤维缠结。分泌酶对淀粉样前体蛋白（APP）的内切蛋白水解裂解导致产生被认为具有神经毒性的ABeta肽。早老素（PS1和PS2），当突变引起家族性阿尔茨海默病，是重要的几种蛋白质，包括APP和Notch 1的膜内蛋白水解。早老素是含有γ-分泌酶的高分子量复合物的一部分。对这种γ 7-分泌酶复合物至关重要的是另一种I型跨膜糖蛋白，称为nicastrin，其结合APP和Notch 1，并且是glp-1/notch信号传导所需的。最近在nicastrin缺陷果蝇中的研究表明，nicastrin的缺失废除了早老蛋白依赖的Notch膜内蛋白水解。因此，我们假设nicastrin是必需的Notch 1在哺乳动物中的蛋白水解加工和信号。我们计划首先通过产生nicastrin缺陷小鼠来确定nicastrin水平降低是否会影响哺乳动物中早老蛋白介导的Notch信号传导，并表征nicastrin减少的表型后果。其次，由于研究表明nicastin在APP加工中起重要作用，我们将使用nicastin敲除细胞测试nicastin在早老蛋白介导的APP γ-分泌酶切割中的作用。此外，我们将确定机制，从而nicastrin的影响早老素，以促进跨膜切割的Notch和APP。最后，检查在体内的作用nicastrin在成人大脑中，我们将产生和表征nicastrin条件性基因敲除小鼠。总之，这些努力的结果将对我们理解nicastrin影响早老素促进早老素依赖性γ-分泌酶在几个关键途径（包括Notch和APP）上的活动的机制以及nicastrin作为阿尔茨海默病的潜在治疗靶点具有重要意义。

DESCRIPTION (provided by applicant): Alzheimer's disease (AD), a progressive neurodegenerative disorder of the elderly, is characterized by the deposition of Beta-amyloid (ABeta) and neurofibrillary tangles in the hippocampus and cerebral cortex. Endoproteolytic cleavages of amyloid precursor protein (APP) by secretases result in the generation of ABeta peptides that are believed to be neurotoxic. The presenilins (PS1 and PS2), which when mutated cause familial Alzheimer's disease, are important for the intramembraneous proteolysis of several proteins, including APP and Notch1. The presenilins is part of a high molecular weight complex that contains the gamma-secretase. Critical to this gamma7-secretase complex is another type I transmembrane glycoprotein, termed nicastrin that binds to both APP and Notch1 and is required for glp-1/notch signaling. Recent studies in nicastrin-deficient Drosophila demonstrate that the loss of nicastrin abolishes the presenilin-dependent intramembraneous proteolysis of Notch. Thus, we hypothesize that nicastrin is required for proteolytic processing and signaling of Notch1 in mammals. We plan first to determine whether reduced levels of nicastrin impact on presenilin-mediated Notch signaling in mammals by generating nicastrin-deficient mice and characterize the phenotypic consequences of reduction in nicastrin. Secondly, because studies indicated that nicastion plays an important role in APP processing, we will test the role of nicastrin in presenilin-mediated gamma-secretase cleavage of APP using nicastrin knockout cells. In addition, we will determine the mechanism whereby nicastrin influences presenilins to facilitate transmembrane cleavage of Notch and APP. Finally, to examine the in vivo role of nicastrin in adult brain, we will generate and characterize nicastrin conditional knockout mice. Taken together, outcomes from these efforts will have important implications toward our understanding of the mechanism whereby nicastrin influences presenilins in facilitating the presenilin-dependent gamma-secretase activities on several critical pathways, including Notch and APP, as well as for nicastrin as a potential therapeutic target in Alzheimer's disease.