Axonal transport of neurofilaments

描述（由申请人提供）：这是我们关于神经丝的研究项目的修订申请，神经丝是神经元的中间纤维。神经丝是大轴突中最丰富的结构，其主要功能是增加轴突直径，而轴突直径是轴突传导速度的关键决定因素。由于神经丝蛋白突变可引起周围神经病变，并且神经丝在许多神经退行性疾病中异常积聚，因此神经丝也具有临床意义。虽然神经丝是轴突的结构组成部分，但我们已经证明它们也是轴突运输的货物。细丝移动得很快，但总体速度很慢，因为它们大部分时间都在停顿。对实验动物的研究表明，神经丝积聚可由神经丝运输受损引起。因此，我们的长期目标是了解神经丝转运的机制，以及它在健康和疾病中是如何调节的。在过去的几年里，我们发现了神经丝的两种显著行为，一种是它们可以通过端到端融合而延长，另一种是它们也可以通过切断机制而缩短。我们对这些发现感到兴奋，因为它们提出了一种调节神经丝长度的新机制，这对其他细胞类型的神经丝运输和中间丝动力学的调节具有重要意义。我们已经开发了工具和策略来分析神经丝切断的机制和神经丝长度对神经丝在轴突运输的影响，我们也获得了证据，神经丝马达可能与这些聚合物的前端形成特殊的关联。目前的建议建立在这一进展的基础上，以解决三个目标：在目标1中，我们将测试神经丝切断是神经元中一个强大而有效的现象的假设，我们将测试一个关于切断机制的特定假设。这些实验将确定神经丝断裂的普遍性，这是一种以前没有描述过的中间丝的新现象，它们将阐明神经丝长度调节的新机制。在目标2中，我们将测试运动蛋白与神经丝的前端形成特殊附着的假设。这些实验将确定马达与中间细丝相互作用的新机制，这对这些独特的细胞内货物的运动机制和调节具有有趣的意义。在Aim 3中，我们将检验神经丝运输受神经丝长度调节的假设。这些实验将为神经丝转运的调控提供新的机制，并将确立神经丝在轴突中的切断和退火的功能意义。总的来说，这个项目将阐明轴突中神经丝动力学的新方面，这可能代表未来治疗干预的目标，以减轻疾病中神经丝的积累或改变。

DESCRIPTION (provided by applicant): This is a revised application to renew our program of research on neurofilaments, which are the intermediate filaments of neurons. Neurofilaments are the most abundant structure in large axons and their principal function is to increase axonal caliber, which is a critical determinant of axonal conduction velocity. Neurofilaments are also of clinical interest because neurofilament protein mutations can cause peripheral neuropathy and because neurofilaments accumulate abnormally in many neurodegenerative diseases. Though neurofilaments are structural components of axons, we have demonstrated that they are also cargoes of axonal transport. The filaments move rapidly but the overall rate is slow because they spend most of their time pausing. Studies on laboratory animals have shown that neurofilament accumulations can be caused by an impairment of neurofilament transport. Thus our long-term goal is to understand the mechanism of neurofilament transport and how it is regulated in health and disease. In the past few years we have discovered two remarkable behaviors for neurofilaments, which is that they can lengthen by fusing end-to-end and that they can also be shortened by a severing mechanism. We are excited about these findings because they suggest a novel mechanism for the regulation of neurofilament length that has implications for the regulation of neurofilament transport as well as intermediate filament dynamics in other cell types. We have developed tools and strategies to analyze the mechanism of neurofilament severing and the influence of neurofilament length on neurofilament transport in axons, and we have also obtained evidence that neurofilament motors may form special associations with the leading ends of these polymers. The current proposal builds on this progress to address three aims: In Aim 1 we will test the hypothesis that neurofilament severing is a robust and efficient phenomenon in neurons and we will test a specific hypothesis for the severing mechanism. These experiments will establish the prevalence of neurofilament severing, which is a novel phenomenon not previously described for intermediate filaments, and they will elucidate a novel mechanism for the regulation of neurofilament length. In Aim 2 we will test the hypothesis that motor proteins form special attachments with the leading ends of neurofilaments. These experiments will identify a novel mechanism for the interaction of motors with intermediate filaments that has intriguing implications for the mechanism and regulation of the movement of these unique intracellular cargoes. In Aim 3 we will test the hypothesis that neurofilament transport is regulated by neurofilament length. These experiments will define a novel mechanism for the regulation of neurofilament transport and they will establish the functional significance of neurofilament severing and annealing in axons. Overall this project will elucidate novel aspects of neurofilament dynamics in axons that may represent targets for future therapeutic intervention to alleviate neurofilament accumulations or alterations in disease.