Huang Derek L, Bax Nicolas A, Buckley Craig D, Weis William I, Dunn Alexander R
Biophysics Program, Stanford University, Stanford, CA 94305, USA.
Department of Structural Biology, Stanford University, Stanford, CA 94305, USA.
Science. 2017 Aug 18;357(6352):703-706. doi: 10.1126/science.aan2556.
Vinculin is an actin-binding protein thought to reinforce cell-cell and cell-matrix adhesions. However, how mechanical load affects the vinculin-F-actin bond is unclear. Using a single-molecule optical trap assay, we found that vinculin forms a force-dependent catch bond with F-actin through its tail domain, but with lifetimes that depend strongly on the direction of the applied force. Force toward the pointed (-) end of the actin filament resulted in a bond that was maximally stable at 8 piconewtons, with a mean lifetime (12 seconds) 10 times as long as the mean lifetime when force was applied toward the barbed (+) end. A computational model of lamellipodial actin dynamics suggests that the directionality of the vinculin-F-actin bond could establish long-range order in the actin cytoskeleton. The directional and force-stabilized binding of vinculin to F-actin may be a mechanism by which adhesion complexes maintain front-rear asymmetry in migrating cells.
纽蛋白是一种肌动蛋白结合蛋白，被认为可增强细胞间和细胞与基质的黏附。然而，机械负荷如何影响纽蛋白与丝状肌动蛋白（F-肌动蛋白）的结合尚不清楚。通过单分子光镊测定法，我们发现纽蛋白通过其尾部结构域与F-肌动蛋白形成一种力依赖性的捕获键，但其寿命在很大程度上取决于所施加力的方向。向肌动蛋白丝的尖端（-）端施加力会导致一种键，该键在8皮牛顿（pN）时最为稳定，其平均寿命（12秒）是向肌动蛋白丝的倒刺（+）端施加力时平均寿命的10倍。板状伪足肌动蛋白动力学的计算模型表明，纽蛋白与F-肌动蛋白结合的方向性可在肌动蛋白细胞骨架中建立长程有序结构。纽蛋白与F-肌动蛋白的定向和力稳定结合可能是黏附复合物在迁移细胞中维持前后不对称性的一种机制。
