Chaperoning Drp1 mediated fission in neurons

陪伴 Drp1 介导的神经元裂变

• 批准号: BB/L02294X/1
• 负责人: Paul Chapple
• 金额: $ 41.29万
• 依托单位: Queen Mary University of London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2014
• 资助国家: 英国
• 起止时间: 2014 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FL02294X%2F1
• 关键词: Chaperoning; Drp1; mediated; fission; neurons

Problems with mitochondria, the cellular 'power plants', have recently been linked to multiple neurodegenerative diseases. Cells need energy to function and mitochondria convert energy into a form that can fuel cellular processes. Because of this and other important cellular roles healthy mitochondria are essential. In cells, mitochondria undergo continuous cycles of division (fission) and fusion that regulate their organisation into networks. This dynamic nature is key to regulating mitochondrial function, maintaining healthy mitochondria and removing damaged parts of the mitochondrial network. This is particularly important in neurons because if mitochondria are the wrong size they cannot be effectively transported along thin branching dendrites. Indeed, there is significant evidence that structural and functional abnormalities in mitochondria are involved in ageing and age-related neurodegenerative diseases, such as Alzheimer's, Parkinson's, Huntington's and amyotrophic lateral sclerosis.Given this context it is essential that we understand the mechanisms that regulate mitochondrial fission in neurons. The principle driver of this process has been identified as dynamin related protein-1 (Drp1). For fission to occur Drp1 must be recruited to future sites of mitochondrial division where it polymerises into spirals that act to constrict and pinch off parts of the network. In mammalian cells the recruitment and activation of Drp1 is not fully understood.We have identified an interaction between Drp1 and another protein called sacsin. Mutations in sacsin cause the inherited neurodegenerative disease Autosomal Spastic Ataxia of Charlevoix Saguenay (ARSACS). Defects in mitochondrial dynamics and function are features of ARSACS with loss of sacsin causing mitochondrial networks to become more interconnected. Moreover, cells lacking sacsin had a reduced incidence of Drp1 associated with their mitochondria even after fission is induced. Drp1 also functions in biogenesis of another organelle, the peroxisomes. Consistent with sacsin functioning in a common pathway with Drp1 we observed loss of sacsin correlates with a decrease in peroxisome number. Sacsin is one of the largest proteins ever identified and contains a number of regions with homology to other proteins of known function. These include domains that are found in molecular chaperone and cochaperone proteins. Chaperones and their cochaperone partners work together in the folding of other proteins and assembly of protein complexes. The presence of a J-domain in sacsin indicates that it functions with an Hsp70 protein, potentially recruiting Hsp70 action to a specific cellular role. Together these data suggest a requirement for chaperone activity in Drp1 mediated fission.To comprehend how Drp1 mediated fission is modulated by sacsin we looked for additional proteins that interact with sacsin. This identified dynactin-6, which has been suggested to play a role in mitochondrial biogenesis and is part of a complex involved in transport of Drp1 to mitochondria. We found dynactin-6 and Drp1 also interact and that reducing dynactin-6 levels in cells lead to a more interconnected mitochondrial network while increasing Drp1 levels caused mitochondrial fragmentation. In combination these data are consistent with Drp1 mediated fission being modulated by a novel protein complex that utilises Hsp70 chaperone action. We hypothesise that sacsin represents the core component or scaffold of such a complex, which is required for Drp1 to be fully active in neurons. The research outlined in this proposal will test these concepts through a comprehensive series of experiments designed to identify how sacsin and dynactin-6 function in Drp1 mediated fission. The main outcome of this research will be the elucidation of the cellular mechanisms controlling mitochondrial fission and the requirement for molecular chaperone action.

线粒体的问题，细胞的“发电厂”，最近被链接到多种神经退行性疾病。细胞需要能量来运作，线粒体将能量转化为可以为细胞过程提供燃料的形式。由于这一点和其他重要的细胞作用，健康的线粒体是必不可少的。在细胞中，线粒体经历连续的分裂（裂变）和融合循环，将其组织调节成网络。这种动态性质是调节线粒体功能、维持健康线粒体和去除线粒体网络受损部分的关键。这在神经元中特别重要，因为如果线粒体的大小不对，它们就不能有效地沿着沿着细的分支树突运输。事实上，有大量证据表明，线粒体的结构和功能异常与衰老和年龄相关的神经退行性疾病有关，如阿尔茨海默氏症、帕金森氏症、亨廷顿舞蹈症和肌萎缩性侧索硬化症。这一过程的主要驱动因素已被确定为动力蛋白相关蛋白-1（Drp 1）。为了使裂变发生，Drp 1必须被募集到线粒体分裂的未来位点，在那里它聚合成螺旋，从而收缩和夹断网络的一部分。在哺乳动物细胞中，Drp 1的募集和激活还不完全清楚，我们已经确定了Drp 1和另一种叫做sacsin的蛋白质之间的相互作用。sacsin的突变导致遗传性神经退行性疾病常染色体痉挛性共济失调（ARSACS）。线粒体动力学和功能的缺陷是ARSACS的特征，其中sacsin的缺失导致线粒体网络变得更加互连。此外，细胞缺乏sacsin有一个减少的发病率Drp 1与他们的线粒体，即使在分裂诱导。drp 1还在另一种细胞器过氧化物酶体的生物发生中起作用。与在与Drp 1的共同途径中起作用的sacsin一致，我们观察到sacsin的损失与过氧化物酶体数量的减少相关。Sacsin是迄今为止发现的最大的蛋白质之一，并且含有许多与已知功能的其他蛋白质具有同源性的区域。这些包括在分子伴侣和辅伴侣蛋白中发现的结构域。分子伴侣和它们的辅分子伴侣在其他蛋白质的折叠和蛋白质复合物的组装中一起工作。囊蛋白中J结构域的存在表明它与Hsp 70蛋白一起发挥功能，潜在地将Hsp 70作用募集到特定的细胞作用。这些数据表明，在Drp 1介导的fistation.To理解如何Drp 1介导的裂变是由sacsin调制的伴侣活性的要求，我们寻找额外的蛋白质与sacsin相互作用。这确定了dynactin-6，它被认为在线粒体生物发生中起作用，并且是参与Drp 1转运到线粒体的复合物的一部分。我们发现dynactin-6和Drp 1也相互作用，降低细胞中dynactin-6的水平会导致线粒体网络更加互连，而增加Drp 1水平会导致线粒体碎片化。结合这些数据是一致的Drp 1介导的裂变被调制的一种新的蛋白质复合物，利用Hsp 70分子伴侣的行动。我们假设sacsin代表了这种复合物的核心成分或支架，这是Drp 1在神经元中完全活跃所必需的。本提案中概述的研究将通过一系列全面的实验来测试这些概念，这些实验旨在确定囊蛋白和dynactin-6在Drp 1介导的裂变中的功能。这项研究的主要成果将是阐明控制线粒体分裂的细胞机制和分子伴侣作用的要求。

项目成果

Altered organization of the intermediate filament cytoskeleton and relocalization of proteostasis modulators in cells lacking the ataxia protein sacsin.

• DOI: 10.1093/hmg/ddx197
• 发表时间: 2017-08-15
• 期刊: Human molecular genetics
• 影响因子: 3.5
• 作者: Duncan EJ;Larivière R;Bradshaw TY;Longo F;Sgarioto N;Hayes MJ;Romano LEL;Nethisinghe S;Giunti P;Bruntraeger MB;Durham HD;Brais B;Maltecca F;Gentil BJ;Chapple JP
• 通讯作者: Chapple JP

A reduction in Drp1-mediated fission compromises mitochondrial health in autosomal recessive spastic ataxia of Charlevoix Saguenay.

• DOI: 10.1093/hmg/ddw173
• 发表时间: 2016-08-01
• 期刊: Human molecular genetics
• 影响因子: 3.5
• 作者: Bradshaw TY;Romano LE;Duncan EJ;Nethisinghe S;Abeti R;Michael GJ;Giunti P;Vermeer S;Chapple JP
• 通讯作者: Chapple JP