p75NTR-Ceramide Signaling in Alzheimer?s Disease

描述（由申请人提供）： 问题：老龄化是阿尔茨海默病（AD）最重要的风险因素，AD是世界上最常见的痴呆症原因。这种疾病优先影响65岁以上的人，并且在我们老龄化的退伍军人中越来越普遍。 初步数据：在初步研究部分，我们表明，p75 NTR和神经酰胺是所需的年龄相关的激活A（代。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IGF 1-R介导）的过度激活导致早期TrkA到p75 NTR的转换，A β、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度产生和BACE 1的分子稳定化有关。当被改造成表达APP 695/swe时，p44+/+小鼠发生了严重形式的AD样神经病理学和早期死亡。值得强调的是，由p44+/+小鼠显示的IGF 1-R信号传导的超活化是由p44转基因产生的PTEN的显著下调的结果。这是特别重要的，因为AD脑的特征还在于降低的PTEN水平、IGF 1-R信号传导的过度活化、增加的p75 NTR表达/活性和增加的神经酰胺水平。这些相似性加强了p44+/+模型用于AD病理学研究的相关性。最后，我们还报告了成功鉴定p75 SMI，一种负责p75 NTR依赖性激活nSMase的分子相互作用。 假设：该建议的中心假设是，p75 NTR-神经酰胺信号系统在AD神经病理学的发病机制和进展中起着重要作用，并且代表了预防这种可怕疾病的潜在治疗靶点。 研究设计：具体目标1将分析p75 NTR-神经酰胺信号传导的超活化对p44+/+; APP 695/swe小鼠中AD病理学的过程和发展产生的影响。为了解决这一目标，我们已经描述了一系列的生化，组织学和认知方法。此外，我们还将用manumycin A治疗p44+/+; APP 695/swe动物，以评估这是否是阻断/延迟神经病理学所有方面的有效策略。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p75 SMI的作用，这是p75 NTR介导的神经酰胺激活所必需的。为了解决上述目标，我们描述了生物化学，细胞和遗传学方法的组合，在原代神经元和神经元细胞系。生物化学方法包括体外测定、体外亲和力结合、IP/co-IP研究和药理学抑制剂，而遗传学方法包括突变神经元细胞系、p75 NTR缺失突变克隆、反义寡核苷酸、siRNA和p75 SMI缺失突变体。 公共卫生相关性： 叙述（相关性声明）对兽医保健的潜在影响：我们的研究发现了衰老和AD之间的一种新的分子联系，并将该领域引向新的方向，如果成功，将对预防一种预计到2050年将影响近1500万美国人的疾病产生直接影响。这个特殊的项目是重要的，我们了解的基本分子事件的特点都正常老化的大脑和AD神经病理学。它与该部门的研究和临床优先事项直接相关。这将对我们增加老龄化基本知识的能力产生影响，以应对老龄化退伍军人人口中与年龄相关的疾病的急剧增加，并提高老年人护理的质量。最后，本项目的长期目标与退伍军人医院老年医学研究、教育和临床中心（GRECC）的使命一致。

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.