Department of Cell Biology, Erasmus Medical Center, PO Box 2040, 3000 CA Rotterdam, The Netherlands.
Curr Biol. 2010 Oct 12;20(19):1717-22. doi: 10.1016/j.cub.2010.08.020. Epub 2010 Sep 16.
The kinesin-13 family member mitotic centromere-associated kinesin (MCAK) is a potent microtubule depolymerase. Paradoxically, in cells it accumulates at the growing, rather than the shortening, microtubule plus ends. This plus-end tracking behavior requires the interaction between MCAK and members of the end-binding protein (EB) family, but the effect of EBs on the microtubule-destabilizing activity of MCAK and the functional significance of MCAK accumulation at the growing microtubule tips have so far remained elusive. Here, we dissect the functional interplay between MCAK and EB3 by reconstituting EB3-dependent MCAK activity on dynamic microtubules in vitro. Whereas MCAK alone efficiently blocks microtubule assembly, the addition of EB3 restores robust microtubule growth, an effect that is not dependent on the binding of MCAK to EB3. At the same time, EB3 targets MCAK to growing microtubule ends by increasing its association rate with microtubule tips, a process that requires direct interaction between the two proteins. This EB3-dependent microtubule plus-end accumulation does not affect the velocity of microtubule growth or shortening but enhances the capacity of MCAK to induce catastrophes. The combination of MCAK and EB3 thus promotes rapid switching between microtubule growth and shortening, which can be important for remodeling of the microtubule cytoskeleton.
驱动蛋白-13 家族成员有丝分裂着丝粒相关驱动蛋白（MCAK）是一种有效的微管解聚酶。矛盾的是，在细胞中，它积累在生长的微管的正端，而不是缩短的微管的正端。这种正端追踪行为需要 MCAK 与末端结合蛋白（EB）家族成员之间的相互作用，但 EB 对 MCAK 的微管解稳定活性的影响以及 MCAK 在生长中的微管尖端的积累的功能意义迄今仍不清楚。在这里，我们通过在体外重建 EB3 依赖性 MCAK 活性在动态微管上来剖析 MCAK 和 EB3 之间的功能相互作用。虽然 MCAK 本身可以有效地阻止微管组装，但添加 EB3 可以恢复强大的微管生长，而这种效果并不依赖于 MCAK 与 EB3 的结合。同时，EB3 通过增加 MCAK 与微管尖端的结合速率将 MCAK 靶向生长中的微管末端，这一过程需要两种蛋白质之间的直接相互作用。这种 EB3 依赖性微管正端积累不会影响微管生长或缩短的速度，但增强了 MCAK 诱导灾难的能力。因此，MCAK 和 EB3 的组合促进了微管生长和缩短之间的快速切换，这对于微管细胞骨架的重塑可能很重要。
