Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA.
Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA.
Dev Cell. 2022 May 9;57(9):1132-1145.e5. doi: 10.1016/j.devcel.2022.04.012. Epub 2022 May 2.
Actin assembly provides force for a multitude of cellular processes. Compared to actin-assembly-based force production during cell migration, relatively little is understood about how actin assembly generates pulling forces for vesicle formation. Here, cryo-electron tomography identified actin filament number, organization, and orientation during clathrin-mediated endocytosis in human SK-MEL-2 cells, showing that force generation is robust despite variance in network organization. Actin dynamics simulations incorporating a measured branch angle indicate that sufficient force to drive membrane internalization is generated through polymerization and that assembly is triggered from ∼4 founding "mother" filaments, consistent with tomography data. Hip1R actin filament anchoring points are present along the entire endocytic invagination, where simulations show that it is key to pulling force generation, and along the neck, where it targets filament growth and makes internalization more robust. Actin organization described here allowed direct translation of structure to mechanism with broad implications for other actin-driven processes.
肌动蛋白组装为多种细胞过程提供力。与细胞迁移过程中基于肌动蛋白组装的力产生相比，人们对肌动蛋白组装如何产生用于囊泡形成的拉力知之甚少。在这里，低温电子断层扫描确定了人 SK-MEL-2 细胞中网格蛋白介导的内吞作用过程中的肌动蛋白丝数量、组织和方向，表明尽管网络组织存在差异，但力的产生是稳健的。包含测量的分支角度的肌动蛋白动力学模拟表明，足以驱动膜内化的力是通过聚合产生的，并且组装是从大约 4 个原始的“母”丝触发的，这与断层扫描数据一致。Hip1R 肌动蛋白丝锚定点存在于整个内陷的整个过程中，模拟表明它是产生拉力的关键，并且沿着颈部，它靶向丝的生长并使内化更稳健。此处描述的肌动蛋白组织允许将结构直接转化为机制，这对其他肌动蛋白驱动的过程具有广泛的意义。
