Molecular intersection between neuronal apoptosis and axon degeneration

描述(申请人提供)：选择性轴突变性发生在神经元发育过程中，也见于许多神经退行性变的情况。然而，神经元如何激活和分割这条退化的路径，以在不危及细胞其余部分的情况下摧毁其轴突，目前尚不清楚。了解轴突丢失的分子机制对于开发新的治疗措施来治疗病理条件下的轴突变性具有重要意义。这个项目将探索破坏整个神经元的凋亡通路和介导轴突特异性退化的通路之间的分子交叉点。Caspase-6最近被证明在退化轴突中是活跃的。这一提议将检验Caspase-6通过刺激依赖的机制积极促进轴突特异性死亡的假设，该机制涉及内在(线粒体)凋亡途径的组成部分。第一个目标是研究Caspase-6作为轴突变性的一种普遍机制的重要性。具体地说，Caspase-6的激活将在体外和体内的多种轴突变性模型中进行检测。重要的是，微流控技术将被用来定位对轴突的损伤，因此可以在不影响神经元细胞体的情况下研究轴突特异性变性。第二个目的是研究已知的凋亡成分(如Bax、细胞色素c、Caspase-9、Apaf-1、Caspase-3)在轴突特异性退变过程中对Caspase-6激活的重要性。这一目标也将检验一种假说，即Caspase的内源性抑制物XIAP在轴突变性期间通过将Caspase活性限制在轴突来保护神经元细胞体。 与公共健康相关：神经元能够选择性地摧毁它们的轴突--神经元功能所需的细胞体的大范围延伸--而不会使细胞的其余部分处于危险之中。这项拨款中提议的实验将有助于确定轴突退化的分子机制，并确定神经元如何能够在保持细胞其余部分完好无损的同时将破坏轴突的机制分开。这些信息可能导致新的治疗方法，专门防止神经元损伤或疾病期间的轴突退化。

DESCRIPTION (provided by applicant): Selective degeneration of axons occurs during neuronal development and is also seen in many neurodegenerative situations. However, exactly how a neuron can activate and compartmentalize this degenerative pathway to destroy its axon without putting the rest of the cell at risk is unclear. Understanding the molecular mechanism of axonal loss is important for developing new therapeutic interventions to treat axon degeneration in pathological conditions. This project will explore the molecular intersection between apoptotic pathways that destroy an entire neuron and pathways that mediate axon-specific degeneration. Caspase-6 was recently shown to be active in degenerating axons. This proposal will test the hypothesis that Caspase-6 actively contributes to axon-specific demise through a stimulus-dependent mechanism that involves components of the intrinsic (mitochondrial) apoptotic pathway. The first aim will investigate the importance of Caspase-6 as a generalized mechanism of axon degeneration. Specifically, Caspase-6 activation will be examined in multiple models of axon degeneration in vitro and in vivo. Importantly, microfluidic technology will be utilized to localize insults to axons, therefore allowing the study of axon-specific degeneration without affecting the neuronal cell body. The second aim will examine the importance of known apoptotic components (e.g., Bax, cytochrome c, Caspase-9, Apaf-1, Caspase-3) in Caspase-6 activation during axon-specific degeneration. This aim will also test the hypothesis that XIAP, an endogenous inhibitor of caspases, protects the neuronal cell body by restricting caspase activity to the axon during axonal degeneration. PUBLIC HEALTH RELEVANCE: Neurons are able to selectively destroy their axons - a large extension from the cell body that is required for neuron function - without putting the rest of the cell at risk. The experiments proposed in this grant will help identify the molecular mechanism by which axons degenerate and determine how neurons are able to compartmentalize destructive mechanisms to axons while keeping the rest of the cell intact. This information could lead to new therapies that specifically prevent axon degeneration during neuronal injury or disease.