Microtubule-associated proteins control the kinetics of microtubule nucleation
Microtubule-associated proteins control the kinetics of microtubule nucleation
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DOI：
10.1038/ncb3188
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发表时间：
2015-07-01
影响因子：
21.3
通讯作者：
Brouhard, Gary J.
中科院分区：
文献类型：
--
作者：
Wieczorek, Michal;Bechstedt, Susanne;Brouhard, Gary J.
微管不断地产生和再生，即使在静止期也是如此。这些聚合物由模板成核，即γ-微管蛋白环复合物（γ -TuRCs）和切断的微管末端。利用单分子生物物理学，我们表明从γ -TuRCs、轴丝和种子微管的成核需要微管蛋白浓度远高于临界浓度。我们测量了微管蛋白到达和稳态伸长开始之间相当长的时间滞后。微管相关蛋白（MAPs）改变了这些时间滞后。灾变因子（MCAK和EB1）抑制成核，而聚合酶（XMAP215）和抗灾变因子（TPX2）促进成核。我们在细胞中观察到了类似的现象。我们得出结论，GTP水解通过使持续伸长所需的新生正端不稳定来抑制微管成核。我们的结果解释了MAPs如何建立微管成核的时空分布。
Microtubules are born and reborn continuously, even during quiescence. These polymers are nucleated from templates, namely gamma-tubulin ring complexes (gamma-TuRCs) and severed microtubule ends. Using single-molecule biophysics, we show that nucleation from gamma-TuRCs, axonemes and seed microtubules requires tubulin concentrations that lie well above the critical concentration. We measured considerable time lags between the arrival of tubulin and the onset of steady-state elongation. Microtubule-associated proteins (MAPs) alter these time lags. Catastrophe factors (MCAK and EB1) inhibited nucleation, whereas a polymerase (XMAP215) and an anti-catastrophe factor (TPX2) promoted nucleation. We observed similar phenomena in cells. We conclude that GTP hydrolysis inhibits microtubule nucleation by destabilizing the nascent plus ends required for persistent elongation. Our results explain how MAPs establish the spatial and temporal profile of microtubule nucleation.