School of Biological and Biomedical Sciences, University of Durham, South Road, Durham DH1 3LE, UK.
J Cell Sci. 2010 Sep 1;123(Pt 17):3019-28. doi: 10.1242/jcs.071126. Epub 2010 Aug 10.
Spatial-temporal flexibility of the actin filament network (F-actin) is essential for all basic cellular functions and is governed by a stochastic dynamic model. In this model, actin filaments that randomly polymerise from a pool of free actin are bundled with other filaments and severed by ADF/cofilin. The fate of the severed fragments is not known. It has been proposed that the fragments are disassembled and the monomeric actin recycled for the polymerisation of new filaments. Here, we have generated tobacco cell lines and Arabidopsis plants expressing the actin marker Lifeact to address the mechanisms of F-actin reorganisation in vivo. We found that F-actin is more dynamic in isotropically expanding cells and that the density of the network changes with a periodicity of 70 seconds. The depolymerisation rate, but not the polymerisation rate, of F-actin increases when microtubules are destabilised. New filaments can be assembled from shorter free cytoplasmic fragments, from the products of F-actin severing and by polymerisation from the ends of extant filaments. Thus, remodelling of F-actin might not require bulk depolymerisation of the entire network, but could occur via severing and end-joining of existing polymers.
肌动蛋白丝网络（F-actin）的时空灵活性对于所有基本细胞功能都是必不可少的，并且受到随机动态模型的控制。在该模型中，从游离肌动蛋白池中随机聚合的肌动蛋白丝与其他纤维丝捆绑在一起，并被 ADF/cofilin 切断。但是，对于被切断的片段的命运尚不清楚。据推测，这些片段被解体，单体肌动蛋白被回收，用于新纤维丝的聚合。在这里，我们生成了表达肌动蛋白标记物 Lifeact 的烟草细胞系和拟南芥植物，以解决体内 F-actin 重组的机制问题。我们发现，在各向同性扩展的细胞中，F-actin 更加动态，并且网络的密度随 70 秒的周期而变化。当微管不稳定时，F-actin 的解聚速率而不是聚合速率增加。新的纤维丝可以从较短的细胞质游离片段组装而成，也可以从 F-actin 切断的产物以及通过现存纤维丝末端的聚合来组装。因此，F-actin 的重塑可能不需要整个网络的大量解聚，而是可以通过现有聚合物的切断和末端连接来实现。
