Chen Yalei, Hancock William O
Department of Biomedical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Interdisciplinary Graduate Degree Program in Cell and Developmental Biology, Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Nat Commun. 2015 Oct 6;6:8160. doi: 10.1038/ncomms9160.
Kinesin-5 slides antiparallel microtubules during spindle assembly, and regulates the branching of growing axons. Besides the mechanical activities enabled by its tetrameric configuration, the specific motor properties of kinesin-5 that underlie its cellular function remain unclear. Here by engineering a stable kinesin-5 dimer and reconstituting microtubule dynamics in vitro, we demonstrate that kinesin-5 promotes microtubule polymerization by increasing the growth rate and decreasing the catastrophe frequency. Strikingly, microtubules growing in the presence of kinesin-5 have curved plus ends, suggesting that the motor stabilizes growing protofilaments. Single-molecule fluorescence experiments reveal that kinesin-5 remains bound to the plus ends of static microtubules for 7 s, and tracks growing microtubule plus ends in a manner dependent on its processivity. We propose that kinesin-5 pauses at microtubule plus ends and enhances polymerization by stabilizing longitudinal tubulin-tubulin interactions, and that these activities underlie the ability kinesin-5 to slide and stabilize microtubule bundles in cells.
驱动蛋白-5在纺锤体组装过程中使反平行微管滑动，并调节生长轴突的分支。除了其四聚体结构所赋予的机械活性外，驱动蛋白-5的特定运动特性构成其细胞功能的基础仍不清楚。在这里，通过构建一个稳定的驱动蛋白-5二聚体并在体外重建微管动力学，我们证明驱动蛋白-5通过提高生长速率和降低灾变频率来促进微管聚合。令人惊讶的是，在驱动蛋白-5存在的情况下生长的微管具有弯曲的正端，这表明该运动蛋白稳定了正在生长的原丝。单分子荧光实验表明，驱动蛋白-5在静态微管的正端保持结合7秒，并以依赖其持续性的方式追踪生长的微管正端。我们提出，驱动蛋白-5在微管正端暂停，并通过稳定纵向微管蛋白-微管蛋白相互作用来增强聚合，并且这些活性构成了驱动蛋白-5在细胞中滑动和稳定微管束的能力的基础。
