The mechanistic basis and potential disease relevance of microtubule disorganisation in axons

轴突微管紊乱的机制基础和潜在疾病相关性

• 批准号: BB/P020151/1
• 负责人: Andreas Prokop
• 金额: $ 63.16万
• 依托单位: University of Manchester
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2018
• 资助国家: 英国
• 起止时间: 2018 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FP020151%2F1
• 关键词: mechanistic; basis; potential; disease; relevance

Here we will study the properties of the microtubule (MT) cytoskeleton of neuronal axons to gain a better understanding of the important roles that MTs play during the formation, maintenance and degeneration of neurons. Axons are the slender, cable-like, up to several meter long protrusions of neurons which form the nerves that electrically wire our bodies. They can usually not be replaced, hence need to be maintained for up to a century in humans. Unsurprisingly, we gradually lose ~50% of our axons towards old age - and far more in neurodegenerative diseases (ND). In spite of their enormous importance, we know far too little about the mechanisms that maintain these delicate structures long-term or lead to their premature decay in neurodegeneration. Axon formation and maintenance essentially depends on the microtubule (MT) cytoskeleton. MTs consist of filamentous protein polymers arranged into 25nm thick tubules. In axons, MTs form continuous parallel bundles, serving as structural backbones and highways for life sustaining cargo/organelle transport. In ageing and ND, axons often form swellings where MT bundles become disorganised into criss-crossing curls, which trap organelles and are believed to trigger axonal loss. For the study of MT disorganisation, we developed the working model of axonal homeostasis based on our experimental data obtained in Drosophila neurons; this model involves three steps (details in CfS pt. 1): (1) MTs have to undergo constant polymerisation/depolymerisation to self-renew. (2) Each MT polymerisation event poses a risk of MT disorganisation, particularly in axons where high densities of MTs and molecular motors generate shear forces which can induce MT curling. (3) Order is imposed by a range of different mechanisms mediated by MT-binding proteins (e.g. by guiding MTs into parallel bundles, or eliminating MTs that have gone off-track). We propose that loss of single (or multiple) of these order-imposing mechanisms increases the risk of MT disorganisation leading to axon swellings - thereby providing potential explanations for late-onset axon degeneration linked genetically to various MT regulators. So far we have tested and refined this model primarily through experimental work in cultured fly and mouse neurons, by focusing on mechanisms regarding step 3 of our model (i.e. order-imposing MT regulators). Here we will focus on the mechanisms involved in step 2 (i.e. causing the curling of MTs), and compare our knowledge in cultured neurons to the situation in the nervous system in vivo. This work is important for several reasons: First, data obtained here will reveal the degree to which observations made in the highly efficient model of cultured neurons, reflect mechanisms underlying axon swellings in vivo. This will give important direction for experimental work aiming to unravel how axon swellings form and can be prevented. Second, we will generate important data concerning MT dynamics and their spatial arrangements in axons. These data will provide important information for the mathematical models of MT behaviours (see support letters) which we are developing in parallel projects - aiming to eventually perform long-term in silico experiments that can test pathological roles of MTs in late-onset neurodegeneration.Third, our data will provide important understanding, descriptions and concepts of axonal MTs that will aid worldwide research into axonal transport, organelle dynamics and MT regulation, thus promoting general advances in our understanding of axon biology during development, ageing, regeneration and degeneration.

在这里，我们将研究神经元轴突的微管（MT）细胞骨架的特性，以更好地了解MT在神经元的形成，维持和退化过程中发挥的重要作用。轴突是细长的，电缆状的，长达几米的神经元突起，形成了连接我们身体的神经。它们通常不能被替换，因此需要在人类中维持长达世纪。不出所料，我们逐渐失去了约50%的轴突对老年-和更多的神经退行性疾病（ND）。尽管它们非常重要，但我们对长期维持这些微妙结构或导致其在神经退行性疾病中过早衰退的机制知之甚少。轴突的形成和维持基本上依赖于微管（MT）细胞骨架。MT由排列成25 nm厚的小管的丝状蛋白质聚合物组成。在轴突中，MT形成连续的平行束，作为维持生命的货物/细胞器运输的结构骨干和高速公路。在衰老和ND中，轴突通常形成轴突，其中MT束变得混乱成纵横交错的卷曲，其捕获细胞器并被认为引发轴突损失。对于MT解体的研究，我们根据我们在果蝇神经元中获得的实验数据开发了轴突稳态的工作模型;该模型包括三个步骤（详见CfS pt.（1）MT必须经历不断的聚合/解聚以自我更新。(2)每个MT聚合事件都有MT解体的风险，特别是在轴突中，高密度的MT和分子马达产生剪切力，这可能会诱导MT卷曲。(3)秩序是由MT结合蛋白介导的一系列不同机制强加的（例如，通过引导MT进入平行束，或消除偏离轨道的MT）。我们提出，这些命令施加机制的单个（或多个）的损失增加了MT紊乱导致轴突slogan的风险，从而为遗传上与各种MT调节剂相关的迟发性轴突变性提供了潜在的解释。到目前为止，我们主要通过培养的苍蝇和小鼠神经元的实验工作来测试和完善这个模型，重点是我们模型第3步的机制（即命令强加MT调节器）。在这里，我们将重点关注步骤2中涉及的机制（即引起MT卷曲），并将我们在培养神经元中的知识与体内神经系统中的情况进行比较。这项工作很重要，原因有几个：首先，这里获得的数据将揭示在培养神经元的高效模型中进行的观察在多大程度上反映了体内轴突轴突再生的机制。这将为旨在揭示轴突肉瘤形成和预防的实验工作提供重要方向。其次，我们将产生重要的数据MT动态和它们的空间安排在轴突。这些数据将为MT行为的数学模型提供重要信息（见支持信），我们正在平行项目中开发-旨在最终进行长期的计算机实验，可以测试MT在迟发性神经变性中的病理作用。第三，我们的数据将提供重要的理解，描述和轴突MT的概念，这将有助于世界范围内对轴突运输的研究，细胞器动力学和MT调节，从而促进我们对轴突生物学在发育、衰老、再生和退化过程中的理解的普遍进步。

项目成果

Tau, XMAP215/Msps and Eb1 co-operate interdependently to regulate microtubule polymerisation and bundle formation in axons.

• DOI: 10.1371/journal.pgen.1009647
• 发表时间: 2021-07
• 期刊: PLoS genetics
• 影响因子: 4.5
• 作者: Hahn I;Voelzmann A;Parkin J;Fülle JB;Slater PG;Lowery LA;Sanchez-Soriano N;Prokop A
• 通讯作者: Prokop A

ALFRED: Automated image analysis of microtubule networks in nerve cells

ALFRED：神经细胞微管网络的自动图像分析

• 发表时间: 2018
• 作者: Costa-Gomes, B

A new concept explaining axonal cell biology, ageing and pathology

解释轴突细胞生物学、衰老和病理学的新概念

• 发表时间: 2021
• 作者: Hahn I

The model of local axon homeostasis - explaining the role and regulation of microtubule bundles in axon maintenance and pathology

局部轴突稳态模型 - 解释微管束在轴突维持和病理学中的作用和调节

• DOI: 10.1101/577320
• 发表时间: 2019
• 作者: Hahn I

ALFRED: automated image analysis application to inform mathematical modelling of microtubule networks in nerve cells

ALFRED：自动图像分析应用程序，为神经细胞中微管网络的数学建模提供信息

• 发表时间: 2018
• 作者: Costa-Gomes, B.