Domains of neuronal microtubule-associated proteins and flexural rigidity of microtubules.
Domains of neuronal microtubule-associated proteins and flexural rigidity of microtubules.
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DOI：
10.1083/jcb.138.5.1067
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发表时间：
1997-09-08
期刊：
影响因子：
--
通讯作者：
Schliwa M
中科院分区：
文献类型：
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作者：
Felgner H;Frank R;Biernat J;Mandelkow EM;Mandelkow E;Ludin B;Matus A;Schliwa M
微管是一种柔性聚合物，其力学性能是决定细胞结构和功能的重要因素。两种最突出的神经元微管相关蛋白（MAPs）， tau和MAP2，其微管结合区域在很大程度上是同源的，对神经元过程的形成和维持做出了重要贡献，推测是通过增加微管的刚性。使用光学镊子操纵单个微管，我们测量了它们在tau和MAP2c的各种结构存在下的弯曲刚度。结果显示，在野生型tau或MAP2c存在下，微管刚性分别增加了三倍或四倍。出乎意料的是，即使低浓度的MAPs也能促进微管刚性的大幅增加。因此，当全长tau蛋白达到~ 20%饱和时，微管的硬度为接近饱和浓度时的80%。使用tau或MAP2的几种不同结构来确定微管结合区域中某些子结构域的相对贡献。所有测试的结构都增加了微管刚性，尽管程度不同。因此，单独的重复结构域仅略微增加微管刚性，而重复结构域的侧翼则有显著的贡献。总的来说，MAP结构与微管的结合强度（由其解离常数kd表示）与微管刚性的增加之间存在良好的相关性。这些发现表明，神经元map及其衍生的结构体增加了微管刚性，并且不同结构体观察到的刚性变化与其他生化和生理参数密切相关。
Microtubules are flexible polymers whose mechanical properties are an important factor in the determination of cell architecture and function. It has been proposed that the two most prominent neuronal microtubule-associated proteins (MAPs), tau and MAP2, whose microtubule binding regions are largely homologous, make an important contribution to the formation and maintenance of neuronal processes, putatively by increasing the rigidity of microtubules. Using optical tweezers to manipulate single microtubules, we have measured their flexural rigidity in the presence of various constructs of tau and MAP2c. The results show a three- or fourfold increase of microtubule rigidity in the presence of wild-type tau or MAP2c, respectively. Unexpectedly, even low concentrations of MAPs promote a substantial increase in microtubule rigidity. Thus at ∼20% saturation with full-length tau, a microtubule exhibits >80% of the rigidity observed at near saturating concentrations. Several different constructs of tau or MAP2 were used to determine the relative contribution of certain subdomains in the microtubule-binding region. All constructs tested increase microtubule rigidity, albeit to different extents. Thus, the repeat domains alone increase microtubule rigidity only marginally, whereas the domains flanking the repeats make a significant contribution. Overall, there is an excellent correlation between the strength of binding of a MAP construct to microtubules (as represented by its dissociation constant K d) and the increase in microtubule rigidity. These findings demonstrate that neuronal MAPs as well as constructs derived from them increase microtubule rigidity, and that the changes in rigidity observed with different constructs correlate well with other biochemical and physiological parameters.