McKenney Richard J, Huynh Walter, Vale Ronald D, Sirajuddin Minhajuddin
Department of Cellular and Molecular Pharmacology, the Howard Hughes Medical Institute University of California, San Francisco, CA, USA.
Department of Cellular and Molecular Pharmacology, the Howard Hughes Medical Institute University of California, San Francisco, CA, USA
EMBO J. 2016 Jun 1;35(11):1175-85. doi: 10.15252/embj.201593071. Epub 2016 Mar 11.
Post-translational modifications (PTMs) of α/β-tubulin are believed to regulate interactions with microtubule-binding proteins. A well-characterized PTM involves in the removal and re-ligation of the C-terminal tyrosine on α-tubulin, but the purpose of this tyrosination-detyrosination cycle remains elusive. Here, we examined the processive motility of mammalian dynein complexed with dynactin and BicD2 (DDB) on tyrosinated versus detyrosinated microtubules. Motility was decreased ~fourfold on detyrosinated microtubules, constituting the largest effect of a tubulin PTM on motor function observed to date. This preference is mediated by dynactin's microtubule-binding p150 subunit rather than dynein itself. Interestingly, on a bipartite microtubule consisting of tyrosinated and detyrosinated segments, DDB molecules that initiated movement on tyrosinated tubulin continued moving into the segment composed of detyrosinated tubulin. This result indicates that the α-tubulin tyrosine facilitates initial motor-tubulin encounters, but is not needed for subsequent motility. Our results reveal a strong effect of the C-terminal α-tubulin tyrosine on dynein-dynactin motility and suggest that the tubulin tyrosination cycle could modulate the initiation of dynein-driven motility in cells.
α/β-微管蛋白的翻译后修饰（PTMs）被认为可调节与微管结合蛋白的相互作用。一种特征明确的PTM涉及α-微管蛋白C末端酪氨酸的去除和重新连接，但这种酪氨酸化-去酪氨酸化循环的目的仍不清楚。在这里，我们研究了与动力蛋白激活蛋白和BicD2（DDB）复合的哺乳动物动力蛋白在酪氨酸化和去酪氨酸化微管上的持续运动性。在去酪氨酸化微管上，运动性降低了约四倍，这是迄今为止观察到的微管蛋白PTM对运动功能的最大影响。这种偏好是由动力蛋白激活蛋白的微管结合p150亚基介导的，而不是动力蛋白本身。有趣的是，在由酪氨酸化和去酪氨酸化片段组成的二分微管上，在酪氨酸化微管上开始运动的DDB分子会继续移动到由去酪氨酸化微管组成的片段中。这一结果表明，α-微管蛋白酪氨酸促进了动力蛋白与微管的初始接触，但后续运动并不需要它。我们的结果揭示了α-微管蛋白C末端酪氨酸对动力蛋白-动力蛋白激活蛋白运动性的强烈影响，并表明微管蛋白酪氨酸化循环可能调节细胞中动力蛋白驱动运动的起始。
