Integration of linear and dendritic actin nucleation in Nck-induced actin comets.
Integration of linear and dendritic actin nucleation in Nck-induced actin comets.
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DOI：
10.1091/mbc.e14-11-1555
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发表时间：
2016-01-15
影响因子：
3.3
通讯作者：
Mayer BJ
中科院分区：
文献类型：
--
作者：
Borinskaya S;Velle KB;Campellone KG;Talman A;Alvarez D;Agaisse H;Wu YI;Loew LM;Mayer BJ
评估了NCK接头蛋白在平衡彗星尾部线形和分支肌动蛋白成核中的作用。NCK招募了线形和分枝成核促进因子，这两种因子都是肌动蛋白彗星形成所必需的。这一发现突显了Nck在病原体样肌动蛋白运动中的新角色。NCK接头蛋白招募胞浆效应物，如N-WASP，诱导局部肌动蛋白聚合。NCK SH3结构域在膜上的实验性聚集诱导肌动蛋白彗尾--动态的、细长的肌动蛋白结构，类似于驱动微生物病原体(如痘苗病毒)移动的结构。在这里，我们展示了对未分支成核/分支成核之间的平衡的实验操作改变了NCK诱导的肌动蛋白彗星的形态和动力学。用小分子抑制剂SMIFH2抑制基于福尔明的线性成核或福尔明FH1结构域的过度表达会导致形成以圆形为主的低迁移率的肌动蛋白结构(肌动蛋白斑点)。这些结果表明，基于福尔明的线性肌动蛋白聚合对于NCK依赖的肌动蛋白彗星尾巴的形成和维持至关重要。与此一致的是，一个独有的分枝成核促进因子(N-WASP的VCA结构域)的聚集，其密度和周转类似于N-WASP在NCK彗星中的密度和周转，并没有重建动态的、拉长的肌动蛋白彗星。此外，N-WASP过表达增强了分支Arp2/3介导的成核，导致了NCK聚集导致的典型肌动蛋白彗星尾部形状的丧失。因此，线状和树枝状成核活性的比率可能有助于区分不同病毒和细菌病原体诱导的肌动蛋白结构的性质。
The role of the Nck adaptor protein in balancing linear versus branched actin nucleation in comet tails is evaluated. Nck recruits both linear and branched nucleation-promoting factors, both of which are necessary for the formation of actin comets. The findings highlight a novel role for Nck in pathogen-like actin motility. The Nck adaptor protein recruits cytosolic effectors such as N-WASP that induce localized actin polymerization. Experimental aggregation of Nck SH3 domains at the membrane induces actin comet tails—dynamic, elongated filamentous actin structures similar to those that drive the movement of microbial pathogens such as vaccinia virus. Here we show that experimental manipulation of the balance between unbranched/branched nucleation altered the morphology and dynamics of Nck-induced actin comets. Inhibition of linear, formin-based nucleation with the small-molecule inhibitor SMIFH2 or overexpression of the formin FH1 domain resulted in formation of predominantly circular-shaped actin structures with low mobility (actin blobs). These results indicate that formin-based linear actin polymerization is critical for the formation and maintenance of Nck-dependent actin comet tails. Consistent with this, aggregation of an exclusively branched nucleation-promoting factor (the VCA domain of N-WASP), with density and turnover similar to those of N-WASP in Nck comets, did not reconstitute dynamic, elongated actin comets. Furthermore, enhancement of branched Arp2/3-mediated nucleation by N-WASP overexpression caused loss of the typical actin comet tail shape induced by Nck aggregation. Thus the ratio of linear to dendritic nucleation activity may serve to distinguish the properties of actin structures induced by various viral and bacterial pathogens.