Institute of Molecular Biology, 1229 University of Oregon, Eugene, Oregon 97403, USA.
Nat Cell Biol. 2010 Dec;12(12):1235-41. doi: 10.1038/ncb2128. Epub 2010 Nov 14.
Microtubules are polymers of tubulin heterodimers that exhibit dynamic instability: periods of growth followed by periods of shrinkage. However, the molecular regulation of dynamic instability remains elusive. Here, we show that EFA-6, a cortically-localized protein, limits the growth of microtubules near the cell cortex of early embryonic cells from Caenorhabditis elegans, possibly by inducing microtubule catastrophes. Compared with wild type, embryos lacking EFA-6 had abnormally long and dense microtubules at the cell cortex, and growing microtubule plus ends resided at the cortex for up to five-fold longer. Loss of EFA-6 also caused excess centrosome separation and displacement towards the cell cortex early in mitosis, and subsequently a loss of anaphase spindle-pole oscillations and increased rates of spindle elongation. The centrosome separation phenotype was dependent on the motor protein dynein, suggesting a possible link between the modulation of microtubule dynamics at the cortex and dynein-dependent force production. EFA-6 orthologues activate ARF6-type GTPases to regulate vesicle trafficking. However, we show that only the C. elegans EFA-6 amino-terminus is both necessary and sufficient to limit microtubule growth along the cortex, and that this function is independent of ARF-6.
微管是由微管蛋白异二聚体组成的聚合物，表现出动态不稳定性：生长期后紧接着是收缩期。然而，动态不稳定性的分子调节仍然难以捉摸。在这里，我们表明，EFA-6，一种皮质定位的蛋白质，可能通过诱导微管灾难，限制秀丽隐杆线虫早期胚胎细胞靠近质膜的微管生长。与野生型相比，缺乏 EFA-6 的胚胎在质膜处具有异常长而密集的微管，并且生长中的微管正极端在质膜处停留的时间长达五倍。EFA-6 的缺失还导致有丝分裂早期中心体分离和向质膜的过度位移，随后失去后期纺锤体极的摆动和增加纺锤体伸长的速度。中心体分离表型依赖于动力蛋白 dynein，这表明质膜处微管动力学的调节和 dynein 依赖性力的产生之间可能存在联系。EFA-6 同源物激活 ARF6 型 GTP 酶来调节囊泡运输。然而，我们表明，只有线虫的 EFA-6 氨基末端既需要又足以限制微管沿着质膜生长，并且该功能独立于 ARF-6。
