p75NTR-Ceramide Signaling in Alzheimer?s Disease

描述(由申请人提供)： 问题：衰老是阿尔茨海默病(AD)的唯一最重要的危险因素，AD是世界上最常见的痴呆症原因。这种疾病优先影响65岁以上的个人，并在我们日益老龄化的退伍军人中日益流行。初步数据：在初步研究部分，我们表明p75NTR和神经酰胺是年龄相关的A(代)激活所必需的。我们还发现，在p44+/+转基因小鼠(一种加速衰老的模型)中，衰老程序(由胰岛素样生长因子1受体(IGF1-R)介导)的过度激活会导致TrkA到p75NTR的早期切换，A(，tau)过度磷酸化的产生增加，以及记忆障碍。上述事件与神经酰胺的过量生产和BACE1的分子稳定有关。当被设计为表达APP695/Swe时，p44+/+小鼠出现了严重的AD样神经病理和早期死亡。值得强调的是，p44+/+小鼠表现出的IGF1-R信号的过度激活是p44转基因产生的PTEN显著下调的结果。这一点尤其重要，因为AD脑内PTEN水平降低，IGF1-R信号过度激活，p75NTR表达/活性增加，神经酰胺水平增加。这些相似性加强了p44+/+模型与AD病理研究的相关性。最后，我们还报道了p75SMI的成功鉴定，它是一种负责p75NTR依赖的nSMase激活的分子相互作用因子。假设：这一建议的中心假设是p75NTR-神经酰胺信号系统在AD神经病理的发生和发展中发挥重要作用，并代表着预防这一可怕疾病的潜在治疗靶点。研究设计：特定目的1分析p75NTR神经酰胺信号过度激活在p44+/+APP695/Swe小鼠AD病理过程中的作用。为了解决这一目标，我们描述了一系列生化、组织学和认知方法。此外，我们还将用manumycin A治疗p44+/+；APP695/Swe动物，以评估这是否是一种有效的策略来阻断/延迟神经病理的所有方面。最后，我们将分析衰老程序如何影响tau代谢和小鼠的学习/认知功能。具体目标2将分析p75SMI的作用，这是p75NTR介导的神经酰胺激活所必需的。为了解决上述目标，我们描述了生化、细胞和遗传方法在原代神经元和神经元细胞系中的组合。生化方法包括体外分析、体外亲和结合、IP/co-IP研究和药物抑制，而遗传学方法包括突变型神经元细胞系、p75NTR缺失突变克隆、反义寡核苷酸、siRNA和p75SMI缺失突变。 公共卫生相关性： 叙述(相关陈述)对退伍军人医疗保健的潜在影响：我们的研究发现了衰老和阿尔茨海默病之间的新的分子联系，并正在引领该领域走向新的方向，如果成功，将对预防这一疾病产生直接影响，预计到2050年，这一疾病将影响近1500万美国人。这个特殊的项目对于我们理解大脑正常衰老和AD神经病理的基本分子事件都很重要。它与该部门的研究和临床优先事项有直接关系。退伍军人事务部，并将对我们的能力产生影响，以增加关于老龄化的基本知识，应对与年龄相关的疾病在老年退伍军人中急剧上升，并提高护理老年人的质量。最后，该项目的长期目标与该退伍军人医院老年研究、教育和临床中心(GRECC)的使命是一致的。

DESCRIPTION (provided by applicant): PROBLEM: Aging is the single most important risk factor for Alzheimer's disease (AD), which represents the most common cause of dementia in the World. The disease preferentially affects individuals who are older than 65 years of age and is becoming increasingly prevalent among our aging veteran population. PRELIMINARY DATA: In the Preliminary Studies section, we show that p75NTR and ceramide are required for the age-associated activation of A( generation. We also show that hyperactivation of the aging program (mediated by the insulin-like growth factor 1 receptor, IGF1-R) in p44+/+ transgenic mice, a model of accelerated aging, leads to early TrkA-to-p75NTRswitch, increased production of A(, tau hyperphosphorylation, and memory impairment. The above events were linked to overproduction of ceramide and molecular stabilization of BACE1. When engineered to express APP695/swe, p44+/+ mice developed a severe form of AD-like neuropathology and early death. It is worth stressing that the hyperactivation of IGF1-R signaling displayed by p44+/+ mice is a consequence of the marked down-regulation of PTEN produced by the p44 transgene. This is particularly important because AD brains are also characterized by decreased levels of PTEN, hyperactivation of IGF1-R signaling, increased expression/activity of p75NTR, and increased levels of ceramide. These similarities strengthen the relevance of the p44+/+ model for the study of AD pathology. Finally, we also report the successful identification of p75SMI, a molecular interactor responsible for the p75NTR-dependent activation of nSMase. HYPOTHESIS: The central hypothesis of this proposal is that the p75NTR-ceramide signaling system plays an important role in the pathogenesis and progression of AD neuropathology, and represents a potential therapeutic target for the prevention of this terrible disease. STUDY DESIGN: Specific Aim 1 will analyze the effects produced by the hyperactivation of p75NTR- ceramide signaling on the course and development of AD pathology in p44+/+;APP695/swe mice. To address this objective, we have described a battery of biochemical, histological, and cognitive approaches. In addition, we will also treat p44+/+;APP695/swe animals with manumycin A to assess whether this is an effective strategy to block/delay all the aspects of the neuropathology. Finally, we will analyze how the aging program affects tau metabolism and the learning/cognitive functions of the mice. Specific Aim 2 will analyze the role of p75SMI, which is required for the p75NTR-mediated activation of ceramide. To address the above objectives, we described a combination of biochemical, cellular, and genetic approaches in both primary neurons and neuronal cell lines. The biochemical approaches include in vitro assays, in vitro affinity binding, IP/co-IP studies, and pharmacological inhibitors, whereas the genetic approaches include mutant neuronal cell lines, deletion mutant clones of p75NTR, antisense oligonucleotides, siRNA, and deletion mutants of p75SMI. PUBLIC HEALTH RELEVANCE: Narrative (Relevance Statement) POTENTIAL IMPACT ON VETERANS' HEALTH CARE: Our studies have uncovered a novel molecular link between aging and AD, and are leading the field toward new directions that, if successful, will have direct impact on the prevention of a disease that is projected to affect nearly 15 million Americans by the year 2050. This particular project is important for our understanding of basic molecular events that characterize both normal aging of the brain and AD neuropathology. It has direct relevance for the research and clinical priorities of the Dept. of Veterans Affairs, and will have impact on our abilities to increase basic knowledge of aging, to respond to the dramatic rise of age-associated pathologies among the aging veteran population, and to improve the quality of care to the aged. Finally, the long-term goal of this project is consistent with the mission of the Geriatric Research, Education and Clinical Center (GRECC) of this VA Hospital.