Dendritic actin networks develop from a first actin filament through branching by the Arp2/3 complex. At the surface of endosomes, the WASH complex activates the Arp2/3 complex and interacts with the Capping Protein for unclear reasons. Here we show that that the WASH complex interacts with Dynactin and uncaps it through its FAM21 subunit. In vitro, the uncapped Arp1/11 minifilament elongates an actin filament, which then primes the WASH-induced Arp2/3 branching reaction. In Dynactin-depleted cells or in cells where the WASH complex is reconstituted with a FAM21 mutant that cannot uncap Dynactin, formation of branched actin at the endosomal surface is impaired. Our results reveal the importance of the WASH complex in coordinating two complexes containing actin-related proteins.

中文翻译：

---

Dynactin的Arp1 / 11细丝引发内体Arp2 / 3复杂。

树突状肌动蛋白网络从第一个肌动蛋白丝通过Arp2 / 3复合物分支形成。在内体的表面，WASH复合物激活Arp2 / 3复合物，并与盖蛋白相互作用，原因尚不清楚。在这里，我们显示WASH复合物与Dynactin相互作用，并通过其FAM21亚基对其进行脱帽。在体外，未封端的Arp1 / 11细丝拉长了肌动蛋白丝，然后引发WASH诱导的Arp2 / 3分支反应。在缺乏Dynactin的细胞中或在WASH复合物被无法解旋Dynactin的FAM21突变体重构的细胞中，在内体表面上分支肌动蛋白的形成受到损害。我们的结果揭示了WASH复合物在协调包含肌动蛋白相关蛋白的两种复合物中的重要性。