Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA.
Biophysics Graduate Group, University of California Berkeley, Berkeley, CA, USA.
Nat Commun. 2022 Jun 22;13(1):3578. doi: 10.1038/s41467-022-31207-5.
Actin assembly facilitates vesicle formation in several trafficking pathways, including clathrin-mediated endocytosis (CME). Interestingly, actin does not assemble at all CME sites in mammalian cells. How actin networks are organized with respect to mammalian CME sites and how assembly forces are harnessed, are not fully understood. Here, branched actin network geometry at CME sites was analyzed using three different advanced imaging approaches. When endocytic dynamics of unperturbed CME sites are compared, sites with actin assembly show a distinct signature, a delay between completion of coat expansion and vesicle scission, indicating that actin assembly occurs preferentially at stalled CME sites. In addition, N-WASP and the Arp2/3 complex are recruited to one side of CME sites, where they are positioned to stimulate asymmetric actin assembly and force production. We propose that actin assembles preferentially at stalled CME sites where it pulls vesicles into the cell asymmetrically, much as a bottle opener pulls off a bottle cap.
肌动蛋白组装有助于几种运输途径中的囊泡形成，包括网格蛋白介导的内吞作用（CME）。有趣的是，在哺乳动物细胞中，肌动蛋白根本不会在所有 CME 部位组装。关于哺乳动物 CME 部位的肌动蛋白网络如何组织以及如何利用组装力，目前还不完全清楚。在这里，使用三种不同的先进成像方法分析了 CME 部位分支肌动蛋白网络的几何形状。当比较未受干扰的 CME 部位的内吞动力学时，显示出肌动蛋白组装的部位具有明显的特征，即在衣壳扩展完成和囊泡分裂之间存在延迟，这表明肌动蛋白组装优先发生在停滞的 CME 部位。此外，N-WASP 和 Arp2/3 复合物被募集到 CME 部位的一侧，在那里它们的位置被定位以刺激不对称肌动蛋白组装和力的产生。我们提出，肌动蛋白优先在停滞的 CME 部位组装，在这些部位，它将囊泡不对称地拉入细胞中，就像开瓶器拉开瓶盖一样。
