Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan.
J Cell Biol. 2012 Nov 26;199(5):849-62. doi: 10.1083/jcb.201206101.
Dynamic microtubules (MTs) are essential for various intracellular events, such as mitosis. In Drosophila melanogaster S2 cells, three MT tip-localizing proteins, Msps/XMAP215, EB1, and Sentin (an EB1 cargo protein), have been identified as being critical for accelerating MT growth and promoting catastrophe events, thus resulting in the formation of dynamic MTs. However, the molecular activity of each protein and the basis of the modulation of MT dynamics by these three factors are unknown. In this paper, we showed in vitro that XMAP215(msps) had a potent growth-promoting activity at a wide range of tubulin concentrations, whereas Sentin, when recruited by EB1 to the growing MT tip, accelerated growth and also increased catastrophe frequency. When all three factors were combined, the growth rate was synergistically enhanced, and rescue events were observed most frequently, but frequent catastrophes restrained the lengthening of the MTs. We propose that MT dynamics are promoted by the independent as well as the cooperative action of XMAP215(msps) polymerase and the EB1-Sentin duo.
动态微管（MTs）对于各种细胞内事件是必不可少的，例如有丝分裂。在黑腹果蝇 S2 细胞中，已经鉴定出三种 MT 尖端定位蛋白，Msps/XMAP215、EB1 和 Sentin（EB1 货物蛋白），它们对于加速 MT 生长和促进灾难事件至关重要，从而形成动态 MTs。然而，每种蛋白质的分子活性以及这三种因素调节 MT 动力学的基础尚不清楚。在本文中，我们在体外表明，XMAP215（msps）在广泛的微管蛋白浓度范围内具有很强的促进生长活性，而当 Sentin 被 EB1 招募到生长的 MT 尖端时，它会加速生长并增加灾难频率。当这三个因素结合在一起时，生长速度呈协同增强，并且观察到最频繁的拯救事件，但频繁的灾难会限制 MT 的延长。我们提出，MT 动力学是由 XMAP215（msps）聚合酶和 EB1-Sentin 二聚体的独立和协同作用来促进的。
