The influence of dynein processivity control, MAPs, and microtubule ends on directional movement of a localising mRNA.
The influence of dynein processivity control, MAPs, and microtubule ends on directional movement of a localising mRNA.
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DOI：
10.7554/elife.01596
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发表时间：
2014-04-15
期刊：
影响因子：
7.7
通讯作者：
Bullock SL
中科院分区：
文献类型：
--
作者：
Soundararajan HC;Bullock SL
许多细胞成分与马达蛋白的多个拷贝一起沿着微管行进。在货物分拣过程中，这些电机的活动是如何调节的，人们知之甚少。在这项研究中，我们使用一种新的体外实验来定位与天然动力蛋白-动力蛋白复合物结合的果蝇mrna的运动性。高精度跟踪显示，群体中的个体RNPs沿着微管进行弥漫性或高度进行性的负端定向运动。RNA定位信号刺激过程运动，与调节动力蛋白-动力蛋白的活性，而不是其每个RNP的总拷贝数，负责这种效果。我们的数据支持一种新的多运动易位机制，该机制基于离散货物相关特征对动力蛋白加工能力的调节。研究RNPs对微管相关蛋白（MAPs）和微管末端的体外反应，可以深入了解RNA群体如何导航细胞骨架网络并锚定在细胞中的目的地。DOI: http://dx.doi.org/10.7554/eLife.01596.001一个单元要完成它的工作，它内部的不同组件需要移动到不同的位置。这是通过精密的细胞运输系统实现的。为了将一个成分移动到它需要的地方，运动蛋白通常在其他“辅助”蛋白质的帮助下与它结合。然后，这个货物-马达复合体沿着细胞内的轨道网络移动。病毒也利用这种运输系统，以便在其生命周期中被运送到细胞的特定部位。许多货物沿着微管轨道移动。多个微管马达蛋白通常附着在同一货物上，但它们在运输过程中如何协同工作尚不清楚。以前的研究试图通过将运动蛋白附着在人工货物上来解决这个问题，比如合成珠子。然而，这些实验没有包括一些被认为在活细胞内运输过程中起作用的辅助蛋白。Soundararajan和Bullock现在研究了包含多个马达的复合物如何与辅助蛋白结合，将信使RNA分子移动到细胞内的特定位置。通过可视化果蝇mRNA沿着附着在玻璃表面的微管移动，可以详细研究运输过程。这些复合物似乎有两种移动方式：它们要么沿着微管扩散，它们可以在任何一个方向上扩散，要么沿着微管为自己提供能量，它们只能在一个方向上移动。虽然先前的人工货物实验表明，复合体中马达的数量决定了单向运输的可能性，但似乎在mRNA运输过程中，一个或多个辅助蛋白实际上是受控制的。Soundararajan和Bullock还记录了mRNA-motor复合物如何对微管高速公路上的路障和死角做出反应。在遇到这种情况时，复合物不会放开微管，而是会沿着轨道反向而下。这种行为可以帮助它们找到通往目的地的新路线。DOI: http://dx.doi.org/10.7554/eLife.01596.002
Many cellular constituents travel along microtubules in association with multiple copies of motor proteins. How the activity of these motors is regulated during cargo sorting is poorly understood. In this study, we address this issue using a novel in vitro assay for the motility of localising Drosophila mRNAs bound to native dynein-dynactin complexes. High precision tracking reveals that individual RNPs within a population undergo either diffusive, or highly processive, minus end-directed movements along microtubules. RNA localisation signals stimulate the processive movements, with regulation of dynein-dynactin’s activity rather than its total copy number per RNP, responsible for this effect. Our data support a novel mechanism for multi-motor translocation based on the regulation of dynein processivity by discrete cargo-associated features. Studying the in vitro responses of RNPs to microtubule-associated proteins (MAPs) and microtubule ends provides insights into how an RNA population could navigate the cytoskeletal network and become anchored at its destination in cells. DOI: http://dx.doi.org/10.7554/eLife.01596.001 For a cell to do its job, the different components inside it need to be moved to different locations. This is achieved by an elaborate cellular transport system. To move a component to where it needs to be, motor proteins bind to it, often with the assistance of other ‘accessory’ proteins. This cargo-motor complex then moves along a network of tracks within the cell. Viruses also exploit this transport system in order to be trafficked to specific parts of the cell during their life cycles. Many cargos are moved along microtubule tracks. Multiple microtubule motor proteins often attach to the same cargo, but it is unclear how they work together during transport. Previous studies have attempted to address this issue by attaching motor proteins to artificial cargoes, such as synthetic beads. However, these experiments did not include some of the accessory proteins that are thought to play a role during transport within the living cell. Soundararajan and Bullock have now examined how complexes containing multiple motors bound to accessory proteins move molecules of messenger RNA to specific sites within cells. By visualising fruit fly mRNA moving along microtubules attached to a glass surface, the transport process can be studied in detail. It appears that the complexes travel using one of two methods: they either diffuse along the microtubules, which they can do in either direction, or they power themselves along the microtubules, which they can only do in one direction. Although previous experiments with artificial cargos suggested that the number of motors in the complex determines the likelihood of one-way traffic, it appears that one or more accessory proteins are actually in control during mRNA transport. Soundararajan and Bullock also documented how the mRNA-motor complexes react to roadblocks and dead-ends on the microtubule highway. Rather than letting go of the microtubule upon such an encounter, the complexes can reverse back down the track. This behaviour may help them to find a new route to their destination. DOI: http://dx.doi.org/10.7554/eLife.01596.002