Understanding essential roles of microtubule regulators during synapse formation and maintenance

了解微管调节器在突触形成和维持过程中的重要作用

• 批准号: BB/M007456/1
• 负责人: Natalia Sanchez-Soriano
• 金额: $ 52.2万
• 依托单位: University of Liverpool
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2015
• 资助国家: 英国
• 起止时间: 2015 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FM007456%2F1
• 关键词: Understanding; essential; roles; microtubule; regulators

A key prerequisite for nervous system function is the capability of neurons to communicate with other cells via specialised cell junctions called synapses. Synapses contain complex machinery for rapid transmission of signals to partner cells. Once formed, synapses have to be maintained in a plastic state, and precocious loss of synapses is considered a potential cause of neuronal decay in ageing and in neurodegenerative diseases. However, in spite of this importance, the mechanisms underlying synaptic maintenance are very little understood. The overarching aim of this project is to deliver such understanding, thus bridging an important gap in our knowledge about processes of ageing and degeneration in the brain.During a neuron's life, its synaptic machinery is constantly recycled. To this end, its building blocks have to be efficiently transported between the neuronal cell body and the very distant synapses (up to a meter away in humans), connected only by a cable-like neuronal protrusion called the axon. Such precise movement of synaptic proteins along the axon is achieved by motor proteins which bind to transport vesicles containing synaptic proteins and trail along highways made out of parallel bundles of microtubules (MTs). MTs are dynamic filamentous polymers which are continuously built and degraded throughout a neuron's life, and these processes have to be regulated to sustain proper axonal transport. The number of MTs needs to be well controlled, they have to bear the right posttranslational modifications (PTMs) to promote the right motor protein interactions, and they have to maintain their bundled organisation - all so that blockage or slowdown of transport is prevented. For this, MTs are regulated through MT-binding proteins (MTBPs) which can control MT de/polymerisation, stabilisation, cross-linkage and PTMs. It seems therefore obvious that MTBPs, through controlling MT networks, can regulate axonal transport and consequently also synaptic maintenance and neuronal survival, and this causative chain could provide important explanations for why a number of MTBPs are associated with neurodegenerative disease. However, MTBP-based mechanisms of synaptic maintenance remain poorly understood. For example, the MTBP Tau was discovered several decades ago. It has been associated with Alzheimer's Disease and Frontotemporal Dementia and has therefore been intensely researched. However, its function in health and disease remains surprisingly poorly understood. This is due to the complexity and robustness of the regulatory networks underpinning MT regulation which are experimentally difficult to decipher. To tackle this problem I am using a genetic model organism, the fruit fly Drosophila, I have extensive experience with this system and the role and regulation of the neuronal cytoskeleton therein. I have provided substantial proof of principle that regulatory mechanisms can be deciphered and applied to higher animals. Apart from the enormous amenability and speed of experimentation, the fundamental advantage for cytoskeletal research in Drosophila is the efficiency with which genes can be manipulated and investigated in combination. Thus, on this project, I capitalise on my finding that functions of tau become apparent when combined with loss of a second MTBP, called Shot. Only upon combined deletion does a new phenotype occur consisting in dramatic loss of synapses caused by collapse of axonal transport of synaptic proteins. This phenotype provides robust readouts to decipher the underlying mechanisms, which will be one key objective of this project. In addition, I will study the relevance of these mechanisms for neuronal survival and assess their potential conservation in mouse neurons. This work will unlock important new mechanistic understanding that will advance research on brain development, ageing and degeneration.

神经系统功能的一个关键前提是神经元通过称为突触的特殊细胞连接与其他细胞交流的能力。突触包含向配对细胞快速传输信号的复杂机制。一旦形成，突触必须保持在可塑性状态，突触的早熟丢失被认为是衰老和神经退行性疾病中神经元衰退的潜在原因。然而，尽管这很重要，人们对突触维持的机制却知之甚少。这个项目的总体目标是提供这种理解，从而弥合我们对大脑老化和退化过程的知识中的一个重要缺口。在神经元的生命过程中，它的突触机制不断循环。为此，它的构件必须在神经元细胞体和非常远的突触(在人类中最远距离为一米)之间有效地运输，只有被称为轴突的缆状神经元突起才能连接起来。突触蛋白沿着轴突的这种精确运动是由马达蛋白实现的，马达蛋白结合到运输含有突触蛋白的囊泡和由平行的微管束(MTS)组成的高速公路上的TRAIL。MTS是一种动态的丝状聚合物，在神经元的整个生命过程中不断构建和降解，这些过程必须受到调节才能维持适当的轴突运输。MT的数量需要得到很好的控制，它们必须承受正确的翻译后修饰(PTM)以促进正确的马达蛋白质相互作用，它们必须保持其捆绑的组织-所有这些都是为了防止运输受阻或减速。为此，MT通过MT结合蛋白(MTBP)进行调节，MTBP可以控制MT的解聚、稳定、交联和PTMS。因此，很明显，MTBPs通过控制MT网络，可以调节轴突的运输，从而调节突触的维持和神经元的存活，这一原因链可以为为什么许多MTBPs与神经退行性疾病相关提供重要的解释。然而，基于MTBP的突触维持机制仍然知之甚少。例如，MTBP Tau是几十年前发现的。它与阿尔茨海默病和额颞痴呆有关，因此得到了深入的研究。然而，它在健康和疾病中的作用仍然令人惊讶地知之甚少。这是由于支持MT监管的监管网络的复杂性和健壮性，这些监管网络在实验上很难破译。为了解决这个问题，我使用了一种遗传模式生物--果蝇，我对这个系统以及其中神经元细胞骨架的作用和调节有丰富的经验。我已经提供了大量的原则性证据，证明监管机制可以被破译并应用于高等动物。除了实验的巨大改善性和速度之外，果蝇细胞骨架研究的根本优势是可以组合操作和研究基因的效率。因此，在这个项目中，我利用我的发现，当结合第二个MTBP的损失时，tau的功能变得明显，称为Sort。只有在联合缺失的情况下，才会出现新的表型，包括突触蛋白轴突运输崩溃导致的突触急剧丧失。这种表型提供了强大的读数来破译潜在的机制，这将是该项目的一个关键目标。此外，我将研究这些机制与神经元存活的相关性，并评估它们在小鼠神经元中的潜在保守性。这项工作将开启重要的新机制理解，将推动对大脑发育、衰老和退化的研究。

项目成果

Tau, XMAP215 and Eb1 act as a functional trio to regulate microtubule polymerisation and organisation in neurons. Microtubules

Tau、XMAP215 和 Eb1 作为功能三重奏来调节神经元中的微管聚合和组织。

• 发表时间: 2018
• 作者: Hahn I,

Understanding the microtubule regulation that underlies neuronal cell biology

了解神经元细胞生物学基础的微管调节

• 发表时间: 2018
• 作者: Hahn I

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

Functional and Genetic Analysis of Spectraplakins in Drosophila.

• DOI: 10.1016/bs.mie.2015.06.022
• 发表时间: 2015-08
• 期刊: Methods in enzymology
• 作者: Ines Hahn;M. Ronshaugen;N. Sánchez-Soriano;A. Prokop

Understanding the formation and maintenance of microtubule bundles in neurons

了解神经元微管束的形成和维持

• 发表时间: 2018
• 作者: Hahn I