Loading history determines the velocity of actin-network growth
Loading history determines the velocity of actin-network growth
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DOI：
10.1038/ncb1336
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发表时间：
2005-12-01
影响因子：
21.3
通讯作者：
Fletcher, DA
中科院分区：
文献类型：
--
作者：
Parekh, SH;Chaudhuri, O;Fletcher, DA
肌动蛋白细丝在分支网络中的定向聚合是真核细胞中最强大的力生成系统之一。紧密连接的肌动蛋白网络的生长驱动细胞爬行(2)、囊泡和细胞器的细胞内运输(3、4)以及细胞内病原体的移动，如单核细胞增多性李斯特氏菌。使用改进的原子力显微镜(AFM)，我们获得了在体外生长的肌动蛋白网络的力-速度(Fv)测量，直到网络延伸在失速力停止。我们发现，分支肌动蛋白网络的增长速度在很大的力范围内是与载荷无关的，然后凸起下降到失速。令人惊讶的是，当不断增长的网络上的力减小时，速度增加到比以前的速度更大的值，这样在一个载荷下可以存在两个或更多稳定的增长速度。这些结果表明，与细胞中的其他分子马达不同，单一的FV关系不能捕捉到该系统的完整行为，因为生长速度取决于加载历史，而不仅仅是瞬时加载。
Directional polymerization of actin filaments in branched networks is one of the most powerful force-generating systems in eukaryotic cells(1). Growth of densely cross-linked actin networks drives cell crawling(2), intracellular transport of vesicles and organelles(3,4) and movement of intracellular pathogens such as Listeria monocytogenes'. Using a modified atomic force microscope (AFM), we obtained force-velocity (Fv) measurements of growing actin networks in vitro until network elongation ceased at the stall force. We found that the growth velocity of a branched actin network against increasing forces is load-independent over a wide range of forces before a convex decline to stall. Surprisingly, when force was decreased on a growing network, the velocity increased to a value greater than the previous velocity, such that two or more stable growth velocities can exist at a single load. These results demonstrate that a single Fv relationship does not capture the complete behaviour of this system, unlike other molecular motors in cells, because the growth velocity depends on loading history rather than solely on the instantaneous load.