Cell Biology of Presenilin 1 and Associated Proteins

描述(申请人提供)：脑部沉积的β-淀粉样多肽(AB)是阿尔茨海默病的病理特征之一。AB是由淀粉样前体蛋白(APP)在BACE1和g-分泌酶的作用下连续蛋白分解而产生的。G-分泌酶是由四个主要亚基组成的多聚体蛋白质复合体，即PS1(或PS2)、NICAXTIN、PEN2和APH-1，以及CD147和p23(也称为TMP21)等少数调节亚基。PS1被认为是g-分泌酶复合体的催化亚单位。G-分泌酶四个核心亚单位的翻译后成熟和稳定性是相互调节的，它们对功能酶的活性都是不可或缺的。另一方面，CD147或p23表达的减少增加了AB的产生，表明这些蛋白负向调节APP的g-分泌酶的加工。P23调控APP的g-分泌酶切割的具体机制尚不清楚。这项研究概述了p23在培养细胞和小鼠脑内APP转运和g-分泌酶加工中的作用。具体地说，我们建议阐明p23和g-分泌酶亚基之间的功能相互作用，以便更好地理解p23负性调节AB产生的机制。我们将定义p23‘S影响APP运输和AB产生的结构域，并使用p23转基因小鼠和p23条件基因敲除小鼠研究p23对AB沉积的调控。最后，我们将详细研究p23‘S在APP分泌和内吞转运中的作用，并探讨高尔基体形态与AB产生的关系。我们的研究结合了生化、分子和细胞生物学技术来实现以下具体目标。目的1：研究p23与G-分泌酶的功能相互作用。目的：研究p23蛋白对小鼠脑内AB产生和沉积的调节作用。目的3：探讨p23功能与APP转运和G-分泌酶加工的联系机制。我们的研究解决了阿尔茨海默病分子发病机制的核心问题。我们试图研究p23调节g-分泌酶的一个新方面，它影响AB的产生。我们的研究有可能揭示p23对APP贩运和AB产生的调节方面的重要见解，并可能导致基于p23的新治疗策略的开发，旨在通过选择性失活APP处理中的g-分泌酶功能来减少AB负担。与公共卫生相关：阿尔茨海默病(AD)是导致老年人痴呆的主要原因，80岁以上的人口中有50%以上患有这种疾病；目前有510万美国人患有这种毁灭性的疾病。AD患者和老年人都会在大脑中积聚β-淀粉样多肽，称为老年斑。使用培养细胞、转基因小鼠和条件性基因敲除小鼠作为实验模型，我们研究了一种名为p23的蛋白质在调节β-淀粉样蛋白产生和沉积中的功能。我们的研究将对开发旨在减少大脑中β-淀粉样蛋白负担的新型合理AD疗法至关重要。

DESCRIPTION (provided by applicant): Cerebral deposition of beta-amyloid peptides (AB) is one of the pathological hallmarks of Alzheimer's disease. AB is generated by sequential proteolysis of amyloid precursor protein (APP) by BACE1 and g-secretase. g-secretase is a multimeric protein complex made of four main subunits, namely PS1 (or PS2), nicastrin, PEN2 and APH-1, and a few regulatory subunits including CD147 and p23 (also referred to asTMP21). PS1 is thought to function as the catalytic subunit of g-secretase complex. Post-translational maturation and stability of the four core subunits of g-secretase are mutually regulated, and each of them is indispensable for functional enzyme activity. On the other hand, diminution of CD147 or p23 expression increases AB production, suggesting that these proteins negatively regulate g-secretase processing of APP. The specific mechanisms by which p23 modulates g-secretase cleavage of APP remain undetermined. Studies outlined in this proposal address the function of p23 in trafficking and g-secretase processing of APP in cultured cells and in mouse brains Specifically, we propose to elucidate the functional interaction between p23 and g-secretase subunits so that we can better understand the mechanisms by which p23 negatively regulates AB production. We will define the structural domains essential for p23's influence on APP trafficking and AB production, and investigate p23 modulation of AB deposition using p23 transgenic mice and p23 conditional knockout mice. Finally, we will investigate the details on p23's role in secretory and endocytic trafficking of APP and examine the relationship between Golgi morphology and AB production. Our investigation uses a combination of biochemical, molecular and cell biology techniques to accomplish the following specific aims. Aim 1: To study the functional interaction between p23 and g-secretase. Aim 2: To investigate p23 regulation of AB production and deposition in mouse brain. Aim 3: To determine the mechanisms linking p23 function with APP trafficking and g-secretase processing. Our studies address issues that are central to molecular Alzheimer's disease pathogenesis. We seek to investigate a novel aspect of g-secretase modulation by p23 that impacts on AB production. Our studies have the potential to uncover significant insights on p23 regulation of APP trafficking and AB production, and may lead to the development of p23-based novel therapeutic strategies aimed reducing AB burden by selective inactivation of g-secretase function in APP processing. PUBLIC HEALTH RELEVANCE: Alzheimer's disease (AD) is the major cause of dementia in the elderly, afflicting more than 50% of the population over 80 years of age; presently 5.1 million Americans suffer from this devastating disorder. AD patients as well as aged individuals accumulate beta-amyloid peptides as deposits in brain, called senile plaques. Using cultured cells, transgenic mice, and conditional knockout mice as experimental models we investigate the function a protein called p23 in regulating beta-amyloid production and deposition. Our studies will be critical to develop novel rational AD therapeutics aimed at reducing beta-amyloid burden in the brain.