Axonal transport of neurofilaments

描述(申请人提供)：这是一份修订后的申请，旨在更新我们的神经丝研究计划，神经丝是神经元的中间丝。神经丝是大轴突中最丰富的结构，其主要功能是增加轴突口径，这是决定轴突传导速度的关键因素。神经丝也是临床上感兴趣的，因为神经丝蛋白突变可以导致周围神经病变，因为在许多神经退行性疾病中神经丝异常堆积。虽然神经丝是轴突的结构成分，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，神经丝的堆积可能是由神经丝运输障碍引起的。因此，我们的长期目标是了解神经丝运输的机制，以及它在健康和疾病中是如何调节的。在过去的几年里，我们发现了神经细丝的两个显著行为，即它们可以通过端到端的融合来延长，也可以通过切断机制来缩短。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，这对调节神经丝运输以及其他类型细胞中的中间丝动力学具有一定的意义。我们已经开发了工具和策略来分析神经丝断裂的机制以及神经丝长度对轴突中神经丝运输的影响，我们还获得了神经丝马达可能与这些聚合物的头端形成特殊联系的证据。目前的提议建立在这一进展的基础上，以解决三个目标：在目标1中，我们将测试神经细丝切断是神经元中一种健壮而有效的现象的假设，我们将测试切断机制的特定假设。这些实验将确定神经丝断裂的流行程度，这是以前没有描述过的中间丝的新现象，它们将阐明调节神经丝长度的新机制。在目标2中，我们将检验这样一种假设，即马达蛋白与神经丝的前端形成特殊的连接。这些实验将确定发动机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。在目标3中，我们将检验神经丝运输受神经丝长度调节的假设。这些实验将定义一种调节神经丝运输的新机制，并将确立轴突中神经丝切断和退火的功能意义。总体而言，该项目将阐明轴突中神经丝动力学的新方面，这些方面可能代表未来治疗干预的目标，以减轻神经丝的堆积或疾病中的改变。

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.