Ghasemi Foad, Cao LuYan, Mladenov Miroslav, Guichard Bérengère, Way Michael, Jégou Antoine, Romet-Lemonne Guillaume
Université Paris Cité, CNRS, Institut Jacques Monod, F-75013 Paris, France.
The Francis Crick Institute, London, UK.
Sci Adv. 2024 Jan 26;10(4):eadj7681. doi: 10.1126/sciadv.adj7681.
Branched actin filaments are found in many key cellular structures. Branches are nucleated by the Arp2/3 complex activated by nucleation-promoting factor (NPF) proteins and bound to the side of preexisting "mother" filaments. Over time, branches dissociate from their mother filament, leading to network reorganization and turnover, but this mechanism is less understood. Here, using microfluidics and purified proteins, we examined the dissociation of individual branches under controlled biochemical and mechanical conditions. We observe that the Arp2/3 complex remains bound to the mother filament after most debranching events, even when accelerated by force. Strikingly, this surviving Arp2/3 complex readily nucleates a new actin filament branch, without being activated anew by an NPF: It simply needs to exchange its nucleotide and bind an actin monomer. The protein glia maturation factor (GMF), which accelerates debranching, prevents branch renucleation. Our results suggest that actin filament renucleation can provide a self-repair mechanism, helping branched networks to sustain mechanical stress in cells over extended periods of time.
分支状肌动蛋白丝存在于许多关键的细胞结构中。分支由成核促进因子（NPF）蛋白激活的Arp2/3复合体成核，并与预先存在的“母”丝的侧面结合。随着时间的推移，分支会从其母丝上解离，导致网络重组和更新，但这种机制尚不太清楚。在这里，我们使用微流控技术和纯化蛋白，在可控的生化和机械条件下研究了单个分支的解离。我们观察到，在大多数去分支事件后，Arp2/3复合体仍与母丝结合，即使在力的作用下加速解离也是如此。令人惊讶的是，这种留存的Arp2/3复合体很容易成核形成新的肌动蛋白丝分支，而无需被NPF重新激活：它只需要交换其核苷酸并结合一个肌动蛋白单体。加速去分支的蛋白神经胶质成熟因子（GMF）可阻止分支重新成核。我们的结果表明，肌动蛋白丝重新成核可以提供一种自我修复机制，帮助分支网络在细胞中长期承受机械应力。
