Hundreds of mRNAs are transported into neurites to provide templates for the assembly of local protein networks. These networks enable a neuron to configure different cellular domains for specialized functions. According to current evidence, mRNAs are mostly transported in rather small packages of one to three copies, rarely containing different transcripts. This opens a fascinating logistic problem: how are hundreds of different mRNA cargoes sorted into distinct packages and how are they coupled to and released from motor proteins to produce the observed mRNA distributions? Are all mRNAs transported by the same transport machinery or are there different adaptors or motors for different transcripts or classes of mRNAs? A variety of often indirect evidence exists for the involvement of proteins in mRNA localization but relatively little is known about the essential activities required for the actual transport process. Here, we summarize the different types of available evidence for interactions that connect mammalian mRNAs to motor proteins to highlight at which point further research is needed to uncover critical missing links. We further argue that a combination of discovery approaches reporting direct interactions, in vitro reconstitutions and fast perturbations in cells is an ideal future strategy to unravel essential interactions and specific functions of proteins in mRNA transport processes.

中文翻译：

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哺乳动物神经元mRNA转运复合物：鲜为人知的许多未知

数百种mRNA被转运到神经突中，以提供用于组装局部蛋白质网络的模板。这些网络使神经元能够为专用功能配置不同的蜂窝域。根据目前的证据，mRNA大多以较小的一到三个拷贝的包装运输，很少包含不同的转录本。这带来了一个令人着迷的后勤​​问题：如何将数百种不同的mRNA货物分类到不同的包装中，以及它们如何与运动蛋白偶联并从中释放出来以产生观察到的mRNA分布？是所有的mRNA都是通过相同的运输工具运输的，还是存在针对不同转录本或类别的mRNA的不同衔接子或驱动子？存在许多通常间接的证据来证明蛋白质参与mRNA定位，但对实际运输过程所需的基本活性的了解相对较少。在这里，我们总结了将哺乳动物mRNA与运动蛋白连接的相互作用的不同可用证据类型，以突出说明需要进一步研究才能发现关键的缺失环节的证据。我们进一步认为，发现方法的组合报告了直接的交互作用，