Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany.
Proc Natl Acad Sci U S A. 2013 Sep 3;110(36):14670-5. doi: 10.1073/pnas.1218053110. Epub 2013 Aug 20.
The generation of pulling and pushing forces is one of the important functions of microtubules, which are dynamic and polarized structures. The ends of dynamic microtubules are able to form relatively stable links to cellular structures, so that when a microtubule grows it can exert a pushing force and when it shrinks it can exert a pulling force. Microtubule growth and shrinkage are tightly regulated by microtubule-associated proteins (MAPs) that bind to microtubule ends. Given their localization, MAPs may be exposed to compressive and tensile forces. The effect of such forces on MAP function, however, is poorly understood. Here we show that beads coated with the microtubule polymerizing protein XMAP215, the Xenopus homolog of Dis1 and chTOG, are able to link stably to the plus ends of microtubules, even when the ends are growing or shrinking; at growing ends, the beads increase the polymerization rate. Using optical tweezers, we found that tensile force further increased the microtubule polymerization rate. These results show that physical forces can regulate the activity of MAPs. Furthermore, our results show that XMAP215 can be used as a handle to sense and mechanically manipulate the dynamics of the microtubule tip.
产生推拉力量是微管的重要功能之一，微管是动态和极化的结构。动态微管的末端能够与细胞结构形成相对稳定的连接，因此当微管生长时，它可以施加推力，当它收缩时，它可以施加拉力。微管相关蛋白（MAPs）通过与微管末端结合来紧密调节微管的生长和收缩。鉴于它们的定位，MAPs 可能会受到压缩和拉伸力的影响。然而，这些力对 MAP 功能的影响知之甚少。在这里，我们表明，涂有微管聚合蛋白 XMAP215 的珠子，即 Dis1 和 chTOG 的非洲爪蟾同源物，即使在微管末端生长或收缩时，也能够稳定地连接到微管的正极；在生长的末端，珠子会增加聚合速率。我们使用光镊发现，张力进一步增加了微管的聚合速率。这些结果表明物理力可以调节 MAP 的活性。此外，我们的结果表明，XMAP215 可用作一种工具，用于感知和机械操纵微管尖端的动力学。
