Dendritic organization of actin comet tails
Dendritic organization of actin comet tails
复制标题
DOI：
10.1016/s0960-9822(01)00022-7
复制
发表时间：
2001-01-23
期刊：
影响因子：
9.2
通讯作者：
Borisy, GG
中科院分区：
文献类型：
--
作者：
Cameron, LA;Svitkina, TM;Borisy, GG
肌动蛋白丝的聚合对于爬行细胞前沿的突出以及某些细胞内病原体的推进都是必需的[1]，并且足以在体外为细菌的运动产生力[2]。运动性细胞内病原体与富含肌动蛋白的彗尾相关联，彗尾包含许多与片足中相同的分子成分[3]，这表明这两个系统使用相似的运动机制。然而，现有的结构证据表明彗尾的组织与片足不同。片足中的肌动蛋白丝形成分支阵列[4]，据认为是由Arp2/3复合物介导的树突状成核产生的[5,6]。相比之下，彗尾被不同地描述为由短的、随机取向的丝组成[7]，在周边有更高程度的排列[8]，或者包含长而直的轴向丝以及少量斜向丝[9]。由于病原体相关彗尾的组装已被用作片足突出的模型系统，解决这种明显的差异是很重要的。在这里，我们使用铂复制方法表明，彗尾中的肌动蛋白丝阵列实际上具有树突状组织，Arp2/3复合物像在片足中一样定位于Y形连接处[10]。因此，彗尾和片足似乎共享一种用于突出运动的常见树突状成核机制。然而，彗尾与片足的不同之处在于它们的肌动蛋白丝通常是扭曲的，并且似乎处于显著的扭转应力之下。
Polymerization of actin filaments is necessary for both protrusion of the leading edge of crawling cells and propulsion of certain intracellular pathogens [1], and it is sufficient for generating force for bacterial motility in vitro [2]. Motile intracellular pathogens are associated with actin-rich comet tails containing many of the same molecular components present in lamellipodia [3], and this suggests that these two systems use a similar mechanism for motility. However, available structural evidence suggests that the organization of comet tails differs from that of lamellipodia. Actin filaments in lamellipodia form branched arrays [4], which are thought to arise by dendritic nucleation mediated by the Arp2/3 complex [5, 6]. In contrast, comet tails have been variously described as consisting of short, randomly oriented filaments [7], with a higher degree of alignment at the periphery [8], or as containing long, straight axial filaments with a small number of oblique filaments [9]. Because the assembly of pathogen-associated comet tails has been used as a model system for lamellipodial protrusion, it is important to resolve this apparent discrepancy. Here, using a platinum replica approach, we show that actin filament arrays in comet tails in fact have a dendritic organization with the Arp2/3 complex localizing to Y-junctions as in lamellipodia [10]. Thus, comet tails and lamellipodia appear to share a common dendritic nucleation mechanism for protrusive motility. However, comet tails differ from lamellipodia in that their actin filaments are usually twisted and appear to be under significant torsional stress.