Phua Donovan Y Z, Sun Xiaoyu, Alushin Gregory M
Laboratory of Structural Biophysics and Mechanobiology, The Rockefeller University, New York, NY 10065, USA.
Laboratory of Structural Biophysics and Mechanobiology, The Rockefeller University, New York, NY 10065, USA.
Curr Biol. 2025 Feb 24;35(4):854-870.e9. doi: 10.1016/j.cub.2025.01.042. Epub 2025 Feb 13.
As the cytoskeleton sustains cell and tissue forces, it incurs physical damage that must be repaired to maintain mechanical homeostasis. The LIN-11, Isl-1, and Mec-3 (LIM)-domain protein zyxin detects force-induced ruptures in actin-myosin stress fibers, coordinating downstream repair factors to restore stress fiber integrity through unclear mechanisms. Here, we reconstitute stress fiber repair with purified proteins, uncovering detailed links between zyxin's force-regulated binding interactions and cytoskeletal dynamics. In addition to binding individual tensed actin filaments (F-actin), zyxin's LIM domains form force-dependent assemblies that bridge broken filament fragments. Zyxin assemblies engage repair factors through multivalent interactions, coordinating nucleation of new F-actin by VASP and its crosslinking into aligned bundles by ɑ-actinin. Through these combined activities, stress fiber repair initiates within the cores of micron-scale damage sites in cells, explaining how these F-actin-depleted regions are rapidly restored. Thus, zyxin's force-dependent organization of actin repair machinery inherently operates at the network scale to maintain cytoskeletal integrity.
由于细胞骨架承受着细胞和组织的作用力，它会遭受物理损伤，而这种损伤必须得到修复以维持机械稳态。LIN-11、Isl-1和Mec-3（LIM）结构域蛋白桩蛋白可检测肌动蛋白-肌球蛋白应力纤维中力诱导的断裂，通过尚不清楚的机制协调下游修复因子以恢复应力纤维的完整性。在这里，我们用纯化的蛋白质重建应力纤维修复过程，揭示了桩蛋白的力调节结合相互作用与细胞骨架动力学之间的详细联系。除了结合单个紧张的肌动蛋白丝（F-肌动蛋白）外，桩蛋白的LIM结构域还形成力依赖性组装体，连接断裂的丝片段。桩蛋白组装体通过多价相互作用与修复因子结合，协调VASP介导的新F-肌动蛋白的成核及其由α-辅肌动蛋白交联成排列的束状结构。通过这些联合活动，应力纤维修复在细胞内微米级损伤部位的核心区域启动，解释了这些F-肌动蛋白耗尽区域是如何迅速恢复的。因此，桩蛋白对肌动蛋白修复机制的力依赖性组织本质上在网络尺度上起作用，以维持细胞骨架的完整性。
