Presenilin dysfunction in the brain

描述（由申请人提供）：阿尔茨海默病（AD）是神经变性和痴呆的最常见原因。早老素1 （PS1）和早老素2 （PS2）突变占家族性AD （FAD）所有已发现的致病突变的约90%，突出了早老素（PS）在AD发病机制中的重要性。然而，在FAD中，PS突变导致神经元功能障碍和死亡的分子机制是一个尚未解决的关键问题。已发现致病性突变损害PS功能并促进？-淀粉样蛋白肽在细胞培养系统中的作用，但功能丧失和功能获得机制对FAD发病机制的相对贡献尚未完全确定。通过生成和分析成年脑中缺乏PS功能的条件敲除小鼠，我们先前确定了PS在成年脑突触功能、记忆和神经元存活中的重要作用。基于这些和其他观察结果，我们最近提出PS基本神经元功能的丧失可能是FAD痴呆和神经退行性变的主要原因。在这个新的竞争性R01应用中，我们通过检查FAD突变对发育和成人大脑中基本PS功能的影响来验证这一假设。我们最近在一个早发性FAD家系中发现了一个PS1突变（L435F），并发现该突变导致几乎完全丧失？ps缺陷小鼠胚胎成纤维细胞分泌酶活性。此外，我们最近发现，携带致病突变的PS1可以以显性负向方式调节野生型PS1的活性。在第一个特异性目标中，我们提出了PS1 L435F突变对发育中的小鼠大脑神经发生以及成年大脑突触功能、记忆和神经元存活的影响的多学科分析。特别是，我们将确定该突变是否可以挽救由于PS完全失活而导致的这些过程中的缺陷，我们还将评估PS基因剂量在确定突变的表型后果中的作用。在第二个特定目标中，我们将研究携带L435F突变的突变体PS1是否可以调节野生型PS1在发育和成年大脑中的活性。我们将比较PS1 L435F和零突变对？-分泌酶活性A？生产和A？沉积在培养的神经元和/或成人大脑中的然后我们将我们的分析扩展到额外的FAD突变对？原代神经元培养系统中分泌酶活性与突触功能的关系。完成我们提出的特异性目标将为致病突变对大脑中PS功能的影响提供机制见解，AD的发病机制最终发生在大脑中。我们的长期目标是了解致病性突变如何改变PS功能，从而引发AD患者痴呆和神经退行性变，并揭示PS功能丧失导致突触功能障碍、认知能力下降和神经退行性变的机制。

DESCRIPTION (provided by applicant): Alzheimer's disease (AD) is the most common cause of neurodegeneration and dementia. Mutations in presenilin 1 (PS1) and presenilin 2 (PS2) account for ~90% of all identified causative mutations in familial AD (FAD), highlighting the importance of presenilins (PS) in AD pathogenesis. However, the molecular mechanisms by which PS mutations lead to neuronal dysfunction and death in FAD is a key unresolved question. Pathogenic mutations have been found to impair PS function and promote overproduction of ?-amyloid peptides in cell culture systems, but the relative contributions of loss-of-function and gain-of-function mechanisms to FAD pathogenesis have not been fully defined. Through the generation and analysis of conditional knockout mice lacking PS function in the adult brain, we previously identified essential roles for PS in synaptic function, memory and neuronal survival in the adult brain. Based on these and other observations, we recently proposed that loss of essential neuronal functions of PS may be a primary cause of dementia and neurodegeneration in FAD. In this new competing R01 application, we test this hypothesis by examining the impact of FAD mutations on essential PS functions in the developing and adult brains. We recently identified a PS1 mutation (L435F) in an early-onset FAD pedigree with cotton wool plaque neuropathology, and found that this mutation causes a nearly complete loss of ?-secretase activity in PS-deficient mouse embryo fibroblasts. Moreover, we recently found that PS1 harboring pathogenic mutations can modulate the activity of wild-type PS1 in a dominant-negative manner. In the first Specific Aim, we propose a multidisciplinary analysis of the effects of the PS1 L435F mutation on neurogenesis in the developing mouse brain and synaptic function, memory and neuronal survival in the adult brain. In particular, we will determine whether this mutation can rescue the defects in these processes caused by complete PS inactivation, and we will also assess the role of PS gene dosage in determining the phenotypic consequences of the mutation. In the second Specific Aim, we will investigate whether the mutant PS1 bearing the L435F mutation can modulate the activity of wild-type PS1 in the developing and adult brains. We will compare the relative effects of PS1 L435F and null mutations on ?-secretase activity, A? production and A? deposition in cultured neurons and/or the adult brain. We will then extend our analysis to the effects of additional FAD mutations on ?-secretase activity and synaptic function in a primary neuronal culture system. Completion of our proposed Specific Aims will provide mechanistic insight into the effects of pathogenic mutations on PS function in the brain, where the pathogenesis of AD ultimately occurs. Our long-term goal is to understand how pathogenic mutations alter PS function to provoke dementia and neurodegeneration in AD, and to unravel the mechanisms by which loss of PS function produces synaptic dysfunction, cognitive decline and neurodegeneration.