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: 10018413
• 负责人: edward giniger
• 金额: $ 60.84万
• 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/10018413
• 关键词: Acceleration; Adult; Age; Aging; Ankyrins; Autophagocytosis; Axon; Cause of Death; Cell physiology; Cells; Cytoskeleton; Data; Data Set; Defect; Dendrites; Development; Dominant-Negative Mutation; Drosophila genus; Event; Expression Profiling; Genes; Genetic Predisposition to Disease; Genomic approach; Goals; Immune; Immunity; Individual; Innate Immune Response; Measures; Methods; Modeling; Mus; Mutation; Nerve Degeneration; Neurodegenerative Disorders; Neurons; Paper; Pathology; Pathway interactions; Phenotype; Phosphotransferases; Physiological; Play; Population; Process; Proteins; Proteomics; Publishing; Reporting; Role; Structure; Synapses; System; Tauopathies; Testing; Work; antimicrobial peptide; dopaminergic neuron; fly; inhibition of autophagy; metabolomics; mitochondrial dysfunction; mutant; neurodevelopment; neuron development; neuron loss; neuronal excitability; neurotoxic; paralogous gene

A primary goal of our work in neurodegeneration has been to dissect the relationships among the various mechanisms of pathology. In the past year, we have made significant advances in this effort (published in three papers). In the previous year, we had developed a method for measuring the physiological age of an individual or population by quantitative expression profiling and used this method to show that one mechanism of degeneration in our fly model is acceleration of the onset of aging. (The method we developed has since been used by a large number of labs in the aging field, and its principles have been applied to proteomic and metabolomic datasets, as well.) Given that this provided us with a way to account quantitatively for the contribution of aging to degeneration, it also gave us the ability to subtract that effect from expression profiles of our degeneration mutant and thus isolate non-aging components of degeneration. This revealed the existence of a second pathway, orthogonal to aging, by which inhibition of autophagy causes neurotoxic activation of the innate immune response, and that it is the resulting hyperexpression of immune effector proteins, such as antimicrobial peptides, that actually cause the death of a sensitive neuronal population (dopamine neurons; reported in Shukla, 2019 a and b). In parallel to our identification of an autophagy/immunity pathway of degeneration, we also identified yet a third pathway. In characterizing the phenotype of our neurodegeneration mutant (a null mutant of the gene encoding the Cdk5 activating subunit, p35), we previously demonstrated that the mutation causes severe disruption of the axonal cytoskeleton, and in particular of the axon initial segment (AIS), that is correlated with cell degeneration. Since we published this, other labs have shown that the same correlation is observed in other models of degeneration, such as a tauopathy model in the mouse. However, neither their work nor our previous work could provide evidence as to whether AIS defects are causal for degeneration, or simply correlated. In our new work we disrupted AIS structure directly, by expression of a dominant-negative form of the Ankyrin paralog that nucleates the AIS, and found that this was sufficient to cause axon fragmentation and neuron loss. We further showed that the mechanism of ankyrin-induced AIS loss is genetically separate from the mechanism of Cdk5/p35-dependent AIS disruption. Together, these data therefore provide strong evidence that disruption of the axonal cytoskeleton, and of neuronal excitability through dysregulation of the AIS, are indeed a third, distinguishable, causal pathway of neurodegeneration in our tauopathy model in the fly (Spurrier, et al. 2019). We now plan to extend our analysis of the three-way relationship of aging, immunity and degeneration; investigate how mitochondrial dysfunction and synapse loss fit into the picture of degeneration that we have developed, and begin efforts to screen for mutants that can modulate the onset of degeneration in flies that are genetically predisposed to this pathology.

我们在神经退行性变研究中的一个主要目标是剖析各种病理机制之间的关系。在过去的一年里，我们在这方面取得了重大进展（发表在三篇论文中）。 在过去的一年中，我们开发了一种通过定量表达谱来测量个体或群体生理年龄的方法，并使用这种方法来证明我们的果蝇模型中的一种退化机制是加速衰老的开始。(The我们开发的方法已经被衰老领域的大量实验室使用，其原理也已应用于蛋白质组学和代谢组学数据集。鉴于这为我们提供了一种定量解释衰老对退化的贡献的方法，它也使我们能够从我们的退化突变体的表达谱中减去这种影响，从而分离出退化的非衰老成分。这揭示了与衰老正交的第二种途径的存在，通过该途径，自噬的抑制导致先天免疫反应的神经毒性激活，并且正是由此产生的免疫效应蛋白（如抗菌肽）的过度表达实际上导致敏感神经元群体的死亡（多巴胺神经元; Shukla，2019 a和B报道）。 在我们鉴定变性的自噬/免疫途径的同时，我们还鉴定了第三种途径。在表征我们的神经变性突变体的表型（编码Cdk 5激活亚基，p35的基因的无效突变体），我们以前证明，突变导致轴突细胞骨架的严重破坏，特别是轴突起始段（AIS），这是与细胞变性。自从我们发表这篇文章以来，其他实验室已经表明，在其他变性模型中也观察到了同样的相关性，例如小鼠中的tau蛋白病模型。然而，他们的工作和我们以前的工作都不能提供证据证明AIS缺陷是否是变性的原因，或者只是相关的。在我们的新工作中，我们通过表达成核AIS的显性负性形式的Ankyrin parkyrin直接破坏AIS结构，并发现这足以导致轴突断裂和神经元丢失。我们进一步表明，强直性脊柱炎诱导的AIS损失的机制与Cdk 5/p35依赖性AIS破坏的机制在遗传上是分开的。总之，这些数据因此提供了强有力的证据，证明轴突细胞骨架的破坏和通过AIS失调引起的神经元兴奋性的破坏确实是我们在果蝇中的tau蛋白病模型中神经变性的第三个可区分的因果途径（Spurrier，et al. 2019）。 我们现在计划扩展我们对衰老、免疫和退化三方面关系的分析;研究线粒体功能障碍和突触丧失如何与我们已经开发的退化相适应，并开始努力筛选可以调节遗传上易患这种病理学的果蝇的退化发作的突变体。