Role of phosphoinositides in neuronal membrane traffic and neurodegeneration

描述(申请人提供)：细胞内信号脂控制多种细胞过程，包括膜运输、细胞骨架动力学、跨膜运输和信号转导。毫不奇怪，脂质信号及其变化与人类疾病的联系越来越大。阿尔茨海默病(AD)是一种脂质代谢紊乱和膜转运缺陷被认为起关键作用的疾病。这个概念很容易与这样一个事实相一致，即AD中的主要分子角色，包括淀粉样前体蛋白(APP)和β-、β-和β-分泌酶，都是跨膜蛋白(或蛋白复合体)，它们在细胞内运输并在细胞膜上或细胞膜内发挥功能。我们的工作假设是，特定的血脂变化可能驱动或介导AD发病的基本方面。以系统为基础的方法，如“脂质组学”，正在成为描述处于患病状态的细胞、组织或生物体的强大工具，提供了一幅可能与致病性有关的脂质变化的公正和全面的图景。为了更好地了解脂信号缺陷与AD发病机制之间的联系，我们最近对来自三个家族性AD转基因动物模型的大脑样本以及来自晚发性AD患者的三个独立的脑区进行了脂质组学分析。我们发现，在分析的330种脂类中，只有一种脂类在受AD影响的小鼠(前脑)和人类(内嗅觉和前额叶皮质)的大脑区域显著减少：磷脂酰肌醇-3-磷酸(PI3P)。PI3P是一种主要由脂蛋白激酶Vps34合成的磷脂酰肌醇，是内噬和自噬途径的主要调节者。PI3P控制含有PI3P结合模块的各种隔室特异性效应器的招募，如FYVE或PX结构域。我们发现，敲除/敲除Vps34概括了与AD发病相关的显著特征，即：(I)内小体增大；(Ii)淀粉样前体蛋白(APP)的内体异常运输和加工；以及(Iii)自噬底物的积累。此外，其他人的研究表明，神经元中Vps34的慢性缺乏会导致神经退化。综上所述，我们的结果证实PI3P缺乏是AD发病的关键因素。这项建议侧重于解决干扰PI3P信号在AD发病机制中的两个关键过程中的后果，即APP的内体运输和加工(AIM 1)和神经元自噬(AIM 2)。它还将评估PI3P缺乏对A？和Tau活体病理学(Aim 3)。我们期待我们的研究将为APP和Tau的生物学提供关键的见解，并更好地理解脂质失调在AD发病机制中的作用。

DESCRIPTION (provided by applicant): Intracellular signaling lipids control a large variety of cellular processes, including membrane trafficking, cytoskeletal dynamics, transport across membranes and signal transduction. Not surprisingly, lipid signaling and alterations thereof are increasingly linked to human disease. Alzheimer's disease (AD) is one such disorder in which lipid dyshomeostasis and membrane trafficking defects are believed to play a critical role. This concept is easily reconciled with the fact that the main molecular players in AD, including amyloid precursor protein (APP) and the ?-, ?- and ?-secretases, are all transmembrane proteins (or protein complexes) that traffic in cells and exert their functions at or within cellulr membranes. Our working hypothesis is that specific lipid changes may drive or mediate fundamental aspects of AD pathogenesis. Systems-based approaches, such as "lipidomics", are emerging as a powerful tool to profile cells, tissues or organisms in a diseased state, providing both an unbiased and comprehensive picture of lipid alterations potentially linked to pathogenicity. To better understand the link between lipid signaling defects and AD pathogenesis, we have recently conducted a lipidomic analysis of brain samples derived from three transgenic animal models of familial AD as well as three independent brain regions from patients with late-onset AD. We found that out of 330 lipid species analyzed, only one lipid species was significantly reduced in AD-affected brain regions in mice (forebrain) and men (entorhinal and prefrontal cortex): phosphatidylinositol-3-phosphate (PI3P). PI3P is a phosphoinositide primarily synthesized by lipid kinase Vps34 and acts as a master regulator of the endosomal and autophagy pathways. PI3P controls the recruitment of a variety of compartment-specific effectors harboring PI3P binding modules, such as FYVE or PX domains. We found that knocking down/out Vps34 recapitulates salient features linked to AD pathogenesis, namely (i) enlarged endosomes; (ii) aberrant endosomal trafficking and processing of the amyloid precursor protein (APP); and (iii) accumulation of autophagy substrates. Additionally, work from others shows that chronic lack of Vps34 in neurons produces neurodegeneration. Altogether, our results have identified PI3P deficiency as a key factor in AD pathogenesis. This proposal focuses on addressing the consequences of disrupting PI3P signaling on two processes that emerge as critical in AD pathogenesis, namely the endosomal trafficking and processing of APP (Aim 1) and neuronal autophagy (Aim 2). It will also assess the impact of PI3P deficiency on the A? and Tau pathologies in vivo (Aim 3). We anticipate that our studies will provide key insights into the biology of APP and Tau as well as a better understanding of the role of lipid dysregulation in AD pathogenesis.