Focal adhesions (FAs) strengthen their link with the actin cytoskeleton to resist force. Talin-vinculin association could reinforce actin anchoring to FAs by controlling actin polymerization. However, the actin polymerization activity of the talin-vinculin complex is not known because it requires the reconstitution of the mechanical and biochemical activation steps that control the association of talin and vinculin and the exposure of their actin-binding domains. By combining kinetic and binding assays with single actin filament observations in TIRF microscopy, we show that the association of talin and vinculin mutants, mimicking different degrees of activation, results in a variety of activities. In particular, mechanically stretched talin and activated vinculin combine to stimulate actin assembly synergistically through a sequential mechanism in which filaments are nucleated, capped and released to elongate. Our findings suggest a versatile mechanism for the regulation of actin assembly in FAs subjected to various combinations of biochemical and mechanical cues.

中文翻译：

---

Talin 和 vinculin 结合它们的活动来触发肌动蛋白组装

粘着斑 (FAs) 加强了它们与肌动蛋白细胞骨架的联系以抵抗力。Talin-vinculin 结合可以通过控制肌动蛋白聚合来加强肌动蛋白对 FA 的锚定。然而，talin-vinculin 复合物的肌动蛋白聚合活性尚不清楚，因为它需要重建机械和生化激活步骤，这些步骤控制 talin 和 vinculin 的结合以及它们的肌动蛋白结合域的暴露。通过将动力学和结合测定与 TIRF 显微镜中的单肌动蛋白丝观察相结合，我们表明 talin 和 vinculin 突变体的关联，模拟不同程度的激活，导致各种活动。尤其是，机械拉伸的踝关节蛋白和激活的纽蛋白结合起来，通过细丝成核、加帽和释放以伸长的顺序机制协同刺激肌动蛋白组装。我们的研究结果表明，在受到各种生化和机械线索组合的影响下，FA 中肌动蛋白组装的调节机制多种多样。