Exploring FOXO Signaling in Promoting Neurodegeneration in AD

探索 FOXO 信号传导促进 AD 神经退行性变

• 批准号: 8680567
• 负责人: Kavita Shah
• 金额: $ 21.25万
• 依托单位: PURDUE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-07-01 至 2016-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8680567
• 关键词: APP-PS1; Acetylcholinesterase Inhibitors; Alzheimer disease prevention; Alzheimer' s Disease; Amyloid; Apoptosis; Area; Biological Markers; Brain; Calcineurin; Cell Death; Cell Death Process; Cell physiology; Cessation of life; Clinical; Combined Modality Therapy; Coupled; Cyclin-Dependent Kinase 5; Data; Development; Diagnostic; Disease; Disease Progression; Drug Targeting; Enzymes; Failure; Functional disorder; Genetic Screening; Glutamates; Goals; Health; Human; In Vitro; Insulin; Lead; Link; Mediating; Molecular; Molecular Target; Mus; N-Methyl-D-Aspartate Receptors; Nerve Degeneration; Neurons; Oxidative Stress; Pathogenesis; Pathology; Pathway interactions; Pharmaceutical Preparations; Phase III Clinical Trials; Phosphorylation; Phosphotransferases; Post-Translational Protein Processing; Process; Protein Dephosphorylation; Proteins; Rattus; Regulation; Resistance; Role; Sampling; Signal Transduction; Site; Synapses; Testing; Therapeutic; Tissues; Transgenic Mice; Up-Regulation; Work; base; chemical genetics; clinically relevant; fetal; forkhead protein; in vivo; inhibitor/antagonist; innovation; mimetics; mouse model; mutant; nervous system disorder; neuroprotection; neurotoxic; neurotoxicity; novel; novel therapeutic intervention; prevent; research study; secretase; therapeutic target; tool; transcription factor

DESCRIPTION (provided by applicant): Our long-term goal is to identify effective therapeutic targets for preventing neurodegeneration in Alzheimer's disease (AD). In this proposal, we investigate a novel mechanism of AD pathogenesis following our discovery of transcription factors FOXO1 and FOXO3a as novel Cyclin Dependent Kinase-5 (Cdk5) substrates. FOXO1 and FOXO3a are highly expressed in the brain, specifically in areas susceptible to neurodegeneration in AD. However, the roles and regulation of FOXOs in AD are unclear. The activation of FOXOs and their post- translational modifications have not been analyzed in human clinical samples. We show that the activation of FOXOs occurs early in AD clinical tissues and is highly neurotoxic in b-amyloid-mediated signaling. Further, our data suggest that FOXOs are activated by two independent mechanisms: (i) Cdk5-mediated phosphorylation (FOXO1 at S249, FOXO3a at S173); (ii) calcineurin-mediated dephosphorylation of FOXOs at Akt sites. Akt is known to phosphorylate FOXO1 and FOXO3a, rendering them inactive. Hypothesis: Cdk5 and calcineurin synergistically promote FOXOs' activation, which leads to neurotoxic b- amyloid processing and cell death, two hallmarks of AD. The impact of this work is that its successful completion will provide retrospective biomarkers and potential new strategies for AD treatment. This hypothesis will be tested by pursuing three specific aims: Aim 1: Dissect the molecular mechanism by which FOXOs are activated by Cdk5 and calcineurin in rat and human fetal neurons. Aim 2: Determine the roles of active FOXOs in promoting b-amyloid processing and neurotoxicity in rat and human fetal neurons. Aim 3: Investigate the clinical relevance of FOXOs' phosphorylation in two AD mouse models (APP/PS1 and p25-transgenic mice) and human clinical tissues. While APP/PS1 mice will confirm a global role of Ab in FOXO signaling, p25-mice will specifically demonstrate Cdk5's role in activating FOXOs and their correlation with neurodegeneration. Innovation: The hypothesis is formulated based on novel Cdk5 substrates FOXO1 and FOXO3a, discovered using a highly innovative chemical genetic approach. Second, this study suggests that inhibiting FOXOs directly or targeting the upstream regulators of FOXO signaling will provide novel therapeutic intervention points for preventing neurodegeneration in AD. Third, our study provides a novel molecular link between insulin depletion (a cause for AD), Akt inhibition, activation of FOXOs and neurodegeneration in Ab1-42 neurotoxicity. Significance: We propose that activating Akt or inhibiting calcineurin and Cdk5 will abrogate FOXO signaling, causing neuroprotection in AD. Analysis of FOXO post-translational modifications coupled with Cdk5, CaN and Akt activation levels in AD mouse models and human clinical samples will aid in the development of novel tools for retrospective analysis to better understand AD pathogenesis. Thus, we expect that determining the molecular mechanisms by which FOXO transcriptional pathway contributes to disease pathogenesis will be an important step forward in AD prevention and treatment.

描述（由申请人提供）：我们的长期目标是确定预防阿尔茨海默病（AD）神经变性的有效治疗靶点。在本提案中，我们发现转录因子 FOXO1 和 FOXO3a 作为新型细胞周期蛋白依赖性激酶 5 (Cdk5) 底物后，研究了 AD 发病机制的新机制。 FOXO1 和 FOXO3a 在大脑中高度表达，特别是在 AD 中易发生神经退行性变的区域。然而，FOXO 在 AD 中的作用和调节尚不清楚。 FOXO 的激活及其翻译后修饰尚未在人类临床样本中进行分析。我们发现 FOXO 的激活发生在 AD 临床组织的早期，并且在 b-淀粉样蛋白介导的信号传导中具有高度神经毒性。此外，我们的数据表明 FOXO 由两种独立的机制激活：（i）Cdk5 介导的磷酸化（FOXO1 在 S249，FOXO3a 在 S173）； (ii) 钙调神经磷酸酶介导的 FOXO 在 Akt 位点的去磷酸化。已知 Akt 可使 FOXO1 和 FOXO3a 磷酸化，使它们失活。假设：Cdk5 和钙调神经磷酸酶协同促进 FOXO 的激活，从而导致神经毒性 b-淀粉样蛋白加工和细胞死亡，这是 AD 的两个标志。这项工作的影响在于，其成功完成将为 AD 治疗提供回顾性生物标志物和潜在的新策略。该假设将通过追求三个具体目标来检验： 目标 1：剖析大鼠和人类胎儿神经元中 Cdk5 和钙调神经磷酸酶激活 FOXO 的分子机制。目标 2：确定活性 FOXO 在促进大鼠和人类胎儿神经元中的 β-淀粉样蛋白加工和神经毒性中的作用。目标 3：研究 FOXO 磷酸化在两种 AD 小鼠模型（APP/PS1 和 p25 转基因小鼠）和人类临床组织中的临床相关性。 APP/PS1 小鼠将证实 Ab 在 FOXO 信号传导中的整体作用，而 p25 小鼠将具体证明 Cdk5 在激活 FOXO 中的作用及其与神经变性的相关性。创新：该假设是基于采用高度创新的化学遗传方法发现的新型 Cdk5 底物 FOXO1 和 FOXO3a 制定的。其次，这项研究表明，直接抑制 FOXO 或靶向 FOXO 信号传导的上游调节因子将为预防 AD 神经变性提供新的治疗干预点。第三，我们的研究提供了 Ab1-42 神经毒性中胰岛素耗竭（AD 的一个原因）、Akt 抑制、FOXO 激活和神经变性之间的新分子联系。意义：我们建议激活 Akt 或抑制钙调神经磷酸酶和 Cdk5 将 消除 FOXO 信号传导，导致 AD 中的神经保护。对 AD 小鼠模型和人类临床样本中的 FOXO 翻译后修饰以及 Cdk5、CaN 和 Akt 激活水平进行分析将有助于开发用于回顾性分析的新工具，以更好地了解 AD 发病机制。因此，我们期望确定 FOXO 转录途径促进疾病发病机制的分子机制将成为 AD 预防和治疗的重要一步。