The Arp2/3 complex nucleates actin filament branches from the sides of pre-existing filaments
The Arp2/3 complex nucleates actin filament branches from the sides of pre-existing filaments
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DOI：
10.1038/35060104
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发表时间：
2001-03-01
影响因子：
21.3
通讯作者：
Pollard, TD
中科院分区：
文献类型：
--
作者：
Amann, KJ;Pollard, TD
肌动蛋白丝网络的调节组装提供了推动运动真核细胞（1）和细胞内致病细菌（2）和病毒（3）前沿的机械力。当通过与肌动蛋白丝和Wiskott-Aldrich综合征蛋白（WASP）/Scar蛋白的WA结构域结合而激活时，Arp 2/3复合物使从其倒刺末端生长的新丝成核（4-8）。Arp 2/3复合物与肌动蛋白丝的侧边（9）和尖端（10，11）结合，定位于存在于层中的独特的70度肌动蛋白丝分支（12），并在体外形成类似的分支（6，8，10）。这些观察结果产生了肌动蛋白网络组装的树枝状成核模型（10，13），其中Arp 2/3复合物在较老的细丝的侧面引发分支。然而，最近有人提出了另一种形成分支的机制（8）。在“倒刺末端成核”模型中，Arp 2/3复合物结合到细丝的自由倒刺末端，随后从分支生长出两个细丝。在这里，我们报告使用动力学和微观实验来区分这些模型。我们的研究结果表明，激活的Arp 2/3复合物优先直接在预先存在的细丝的侧面上成核细丝分支。
Regulated assembly of actin-filament networks provides the mechanical force that pushes forward the leading edge of motile eukaryotic cells(1) and intracellular pathogenic bacteria(2) and viruses(3). When activated by binding to actin filaments and to the WA domain of Wiskott-Aldrich syndrome protein (WASP)/Scar proteins, the Arp2/3 complex nucleates new filaments that grow from their barbed ends(4-8). The Arp2/3 complex binds to the sides(9) and pointed ends(10,11) of actin filaments, localizes to distinctive 70 degrees actin-filament branches present in lamellae(12), and forms similar branches in vitro(6,8,10). These observations have given rise to the dendritic nucleation model for actin-network assembly(10,13) in which the Arp2/3 complex initiates branches on the sides of older filaments. Recently, however, an alternative mechanism for branch formation has been proposed(8). In the 'barbed-end nucleation' model, the Arp2/3 complex binds to the free barbed end of a filament and two filaments subsequently grow from the branch. Here we report the use of kinetic and microscopic experiments to distinguish between these models. Our results indicate that the activated Arp2/3 complex preferentially nucleates filament branches directly on the sides of pre-existing filaments.