Roles of Cdk5 in neurodevelopment and neurodegeneration

Cdk5 在神经发育和神经变性中的作用

• 批准号: 8746837
• 负责人: edward giniger
• 金额: $ 76.03万
• 依托单位: NATIONAL INSTITUTE OF NEUROLOGICAL DISORDERS AND STROKE
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/8746837
• 关键词: Action Potentials; Acute; Adult; Age; Aging-Related Process; Axon; Cell physiology; Cells; Characteristics; Data; Defect; Dendrites; Development; Disease; Disease Progression; Drosophila genus; Event; Gene Expression; Gene Expression Profiling; Genes; Genomics; Homeostasis; Homologous Gene; Human; Investigation; Ions; Maintenance; Microarray Analysis; Mitochondria; Modeling; Molecular Target; Mus; Nerve Degeneration; Neurodegenerative Disorders; Neurofibrillary Tangles; Neurons; Neurophysiology - biologic function; Oxidation-Reduction; Pathologic Processes; Pathway interactions; Phosphotransferases; Physiological Processes; Play; Process; Protein Kinase; Proteins; Proteomics; Publishing; RNA; Role; Sensory; Stress; Structure; Swelling; Synaptic Transmission; Syndrome; System; Testing; Time; Tissues; Validation; base; fly; genome-wide; inhibitor/antagonist; mutant; neurodevelopment; neuron development; neuron loss; novel; prevent; tau-1

We seek to answer two questions: how do neurons become connected during development, and why do they become disconnected during neurodegenerative disease? We previously developed a potential Drosophila model of mammalian neurodegenerative disease by inactivating the protein kinase Cdk5. This is the fly homolog of one of the two main proteins responsible for phosphorylating tau into the form found in the neurofibrillary tangles that are characteristic of many forms of human neurodegeneration. This year, we published data documenting many phenotypic similarities between the neurodegenerative syndrome in this endogenous process of flies and that observed in humans and mice, thus validating our Drosophila mutant as a model of the mammalian disease process. We also extended our analysis of a novel pathological process that occurs early in disease progression in our fly model that had not previously been described in studies of the mammalian diseases. Last year, we found that lack of Cdk5 activity prevents a neuron from segregating the portion of the cell where action potentials initiate (the axon initial segment). This is apt to be relevant to the mechanism of neurodegeneration, since we find that the defective initial segment domain becomes prone to development of gross axonal swellings as the fly ages, and later is the focus of histological abnormalities such as large, vacuolated holes in the tissue. We now find that this is not just a developmental function of Cdk5. This year, we showed that Cdk5 is required chronically for maintenance of the initial segment, as introduction of pharmacologic inhibitors of Cdk5 cause acute loss of the initial segment even after it has formed. We also initiated systematic, genome-wide investigations into the consequences of Cdk5 inactivation. We have used microarrays to perform gene expression profiling of adult flies having, or lacking, Cdk5 activity. We have focused our efforts on early events in degeneration by isolating RNA from young flies, at a time before the onset of overt cellular or organismal defects in the mutants. Preliminary analysis reveals two classes of gene expression changes in mutants lacking Cdk5 activity. We observe alterations in genes directly important for neural function, including sensory transduction, synaptic transmission and ion homeostasis. We also observe changes in the expression of genes associated with a variety of organismal physiological processes we had previously hypothesized to be associated with Cdk5 function, based on our phenotypic analysis. These include proteostasis, redox state, mitochondrial structure and function and stress-sensitivity. The microarray analysis, therefore, serves as a powerful independent validation of the phenotypic analysis. Moreover, as this unbiased, genome-wide array analysis failed to identify major classes of genes not predicted by the earlier studies, these data suggest that we have identified the major functional pathways downstream of Cdk5 that are responsible for its pathological consequences.

我们试图回答两个问题：在发育过程中神经元如何联系，为什么它们在神经退行性疾病期间断开了连接？ 我们先前通过灭活蛋白激酶CDK5来开发了哺乳动物神经退行性疾病的潜在果蝇模型。这是两种主要蛋白之一的苍蝇同源物，负责将tau磷酸化的形式磷酸化，这是许多形式的人类神经变性的特征。今年，我们发表了数据，记录了神经退行性综合征在这种苍蝇过程中的许多表型相似性，并且在人类和小鼠中观察到，从而验证了我们的果蝇突变体是哺乳动物疾病过程的模型。我们还扩展了对一种新型病理过程的分析，该过程在疾病进展早期发生的苍蝇模型中发生，该过程以前在哺乳动物疾病的研究中没有描述过。去年，我们发现缺乏CDK5活性阻止神经元隔离动作电位启动的细胞部分（轴突初始段）。这很容易与神经退行性的机理相关，因为我们发现随着苍蝇的年龄，有缺陷的初始段结构域很容易发育，后来是组织学异常的重点，例如组织中大型的，吸水的孔。现在，我们发现这不仅是CDK5的发展函数。今年，我们表明CDK5是长期以来需要进行初始段所必需的，因为CDK5的药物抑制剂的引入即使在形成后也会导致初始部分的急性损失。 我们还对CDK5失活的后果进行了系统的全基因组研究。我们已经使用微阵列对具有或缺乏CDK5活性的成年果蝇进行基因表达分析。在突变体中明显的细胞或生物缺陷发作之前，我们通过将RNA从幼体中分离出来，将精力集中在早期事件上。初步分析揭示了缺乏CDK5活性的突变体中的两类基因表达变化。我们观察到对神经功能直接重要的基因的改变，包括感觉转导，突触传递和离子稳态。我们还根据我们的表型分析，观察到与以前假设与CDK5功能相关的各种有机生理过程相关的基因表达变化。这些包括蛋白质，氧化还原状态，线粒体结构以及功能以及应力敏感性。因此，微阵列分析是对表型分析的强大独立验证。此外，由于这种公正的全基因组阵列分析未能识别出早期研究未预测的主要基因类别，因此这些数据表明，我们已经确定了CDK5下游的主要功能途径，这些途径是其病理后果的原因。