Age Impaired ER Homeostasis in Wake-Active Neurons: BiP/Nox2 Crosstalk

描述(申请人提供)：正常的衰老会导致睡眠和清醒状态的持续恶化。在许多与年龄相关的神经退化过程中，这两种行为状态的损害都变得更加明显。失眠会干扰数百万美国老年人的认知功能和生活质量。拟议的研究是两个实验室之间的合作努力，以合并每个实验室已经确定的与年龄相关的神经损伤的途径。奈杜博士最近证明，长时间清醒会激活大脑中未折叠的蛋白质反应。幼鼠通过增加Bip和减弱蛋白质翻译来维持蛋白质的动态平衡。相比之下，老年动物BIP反应不足，表现为ER代谢紊乱，GADD153/CHOP增加。她的实验室将利用全球和部分觉醒神经元组中Bip水平改变的小鼠模型，探索Bip在延长清醒状态下与年龄相关的ER稳态反应下降中所起的作用(目标1)。维西博士的实验室发现，在氧化损伤模型中，神经元NADPH氧化酶是造成蛋白质损伤的主要因素。这些NADPH氧化酶阳性神经元(去甲肾上腺素能和多巴胺能)比非NADPH氧化酶觉醒神经元更早形成与年龄相关的内质网稳态受损。她的研究小组发现内质网(ER)损伤增加，GADD153/CHOP激活，核糖体解聚和蛋白质聚集在NADPH氧化酶阳性的觉醒神经元中。选择具有不同年龄相关损伤的觉醒活性神经元组，为识别衰老损害觉醒功能的机制提供了一个有价值的工具。我们假设，在整个生命周期中，儿茶酚胺能神经元中重复的NADPH氧化酶激活会破坏这些神经元中的内质网稳态，从而导致不可逆转的错误折叠蛋白的逐渐积累(目标2)。这些研究旨在确定为什么特定群体的觉醒神经元更容易受到与年龄相关的损伤，并将两种与蛋白质稳态老化有关的致病机制联系起来，以解释神经元功能对衰老的不同易感性。觉醒障碍可能会导致新的治疗方法，以增强健康老年人和那些有神经退行性过程的人的白天功能。这项拟议的研究考察了衰老损害觉醒的机制。我们假设觉醒神经元中的一种氧化酶会逐渐破坏内质网中的陪伴系统。因此，蛋白质的动态平衡被破坏，有毒的蛋白质聚集体积累。

DESCRIPTION (provided by applicant): Normal aging results in a relentless deterioration of both sleep and wakefulness. Impairments in both behavioral states become more pronounced in many age-dependent neurodegenerative processes. Impaired wakefulness interferes with cognitive function and quality of life for millions of older Americans. The proposed studies are a collaborative effort between two labs to merge pathways of age-related neural injury that each lab has identified. Dr. Naidoo has recently demonstrated that prolonged wakefulness activates the unfolded protein response in the brain. Young mice maintain protein homeostasis, in part, by increasing BiP and attenuating protein translation. In contrast, aged animals mount an insufficient BiP response and manifest ER dyshomeostasis with increased GADD153/CHOP. Her lab will explore the role BiP plays in age-related declines in ER homeostatic response to prolonged wakefulness using murine models with altered BiP levels globally and in select wake neuronal groups (Aim 1). Dr. Veasey's laboratory has identified neuronal NADPH oxidase as a major contributor to protein damage in a model of oxidative injury. These NADPH oxidase-positive neurons (noradrenergic and dopaminergic) develop age-related impaired ER homeostasis earlier than in non-NADPH oxidase wake neurons. Her group has identified increased endoplasmic reticulum (ER) injury with GADD153/CHOP activation, ribosomal disaggregation and protein aggregation in the NADPH oxidase-positive wake neurons. Having select groups of wake-active neurons with differential age-related injury presents a valuable tool with which to identify mechanisms by which aging impairs wake function. We hypothesize that repeated NADPH oxidase activation in catecholaminergic neurons across the lifetime disrupts ER homeostasis in these neurons sufficiently to result in a progressive accumulation of irreversibly misfolded proteins (Aim 2). The studies are designed to determine why select populations of wake neurons are more susceptible to age-related injury and will link two pathogenic mechanisms implicated in the aging of protein homeostasis to explain differential susceptibility to aging decline in neuronal function. Wake impairments may lead to novel therapeutic approaches to enhance daytime functioning in healthy elderly and those with neurodegenerative processes. The proposed studies examine mechanisms by which aging impairs wakefulness. We hypothesize that an oxidase enzyme in wake neurons progressively disrupts the chaperoning system in the endoplasmic reticulum. Consequently protein homeostasis is compromised and toxic protein aggregates accumulate.