Cell Biology of Presenilin 1 and Associated Proteins

描述（由申请人提供）：大脑中β -淀粉样肽（AB）的沉积是阿尔茨海默病的病理标志之一。AB是由BACE1和g-分泌酶对淀粉样蛋白前体蛋白（APP）进行顺序蛋白水解而产生的。g-secretase是一种多聚体蛋白复合物，由四个主要亚基组成，即PS1（或PS2）、nicastrin、PEN2和APH-1，以及一些调节亚基包括CD147和p23（也称为asTMP21）。PS1被认为是g-分泌酶复合物的催化亚基。g-secretase的四个核心亚基在翻译后的成熟和稳定是相互调控的，每一个亚基对于功能酶的活性都是不可或缺的。另一方面，CD147或p23表达的减少会增加AB的产生，这表明这些蛋白负向调节APP的g分泌酶加工。p23调节APP的g分泌酶裂解的具体机制尚不确定。本研究概述了p23在培养细胞和小鼠大脑中转运和g-分泌酶加工APP中的功能，我们建议阐明p23与g-分泌酶亚基之间的功能相互作用，以便我们更好地了解p23负性调节AB产生的机制。我们将定义p23对APP运输和AB产生影响所必需的结构域，并使用p23转基因小鼠和p23条件敲除小鼠研究p23对AB沉积的调节。最后，我们将详细研究p23在APP分泌和内吞运输中的作用，并研究高尔基体形态与AB产生的关系。我们的研究结合了生物化学、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2：探讨p23对小鼠脑内AB生成和沉积的调控作用。目的3：确定p23功能与APP贩运和g-分泌酶加工之间的联系机制。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分泌酶对AB产生影响的一个新方面。我们的研究有可能揭示p23调控APP运输和AB产生的重要见解，并可能导致基于p23的新型治疗策略的发展，旨在通过选择性失活APP加工中的g分泌酶功能来减少AB负担。公共卫生相关性：阿尔茨海默病（AD）是老年人痴呆的主要原因，困扰着超过50%的80岁以上人口；目前有510万美国人患有这种毁灭性的疾病。阿尔茨海默病患者和老年人都会在大脑中积聚β -淀粉样肽，称为老年斑。我们使用培养细胞、转基因小鼠和条件敲除小鼠作为实验模型，研究了一种名为p23的蛋白在调节β -淀粉样蛋白产生和沉积中的功能。我们的研究将对开发新的合理的阿尔茨海默病治疗方法至关重要，旨在减少大脑中的β -淀粉样蛋白负担。

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.