Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois 606037, USA.
James Franck Institute, University of Chicago, Chicago, Illinois 606037, USA.
Nat Commun. 2017 Jun 12;8:15817. doi: 10.1038/ncomms15817.
Cytoskeletal mechanics regulates cell morphodynamics and many physiological processes. While contractility is known to be largely RhoA-dependent, the process by which localized biochemical signals are translated into cell-level responses is poorly understood. Here we combine optogenetic control of RhoA, live-cell imaging and traction force microscopy to investigate the dynamics of actomyosin-based force generation. Local activation of RhoA not only stimulates local recruitment of actin and myosin but also increased traction forces that rapidly propagate across the cell via stress fibres and drive increased actin flow. Surprisingly, this flow reverses direction when local RhoA activation stops. We identify zyxin as a regulator of stress fibre mechanics, as stress fibres are fluid-like without flow reversal in its absence. Using a physical model, we demonstrate that stress fibres behave elastic-like, even at timescales exceeding turnover of constituent proteins. Such molecular control of actin mechanics likely plays critical roles in regulating morphodynamic events.
细胞骨架力学调节细胞形态动力学和许多生理过程。虽然收缩性在很大程度上依赖于 RhoA，但局部生化信号如何转化为细胞水平的反应尚不清楚。在这里，我们结合 RhoA 的光遗传学控制、活细胞成像和牵引力显微镜来研究基于肌动球蛋白的力产生的动力学。局部激活 RhoA 不仅刺激肌动蛋白和肌球蛋白的局部募集，还增加了牵引力，这些力通过应力纤维迅速在细胞内传播，并驱动肌动蛋白流增加。令人惊讶的是，当局部 RhoA 激活停止时，这种流动会反转方向。我们确定了黏着斑蛋白（zyxin）是应力纤维力学的调节剂，因为在没有它的情况下，应力纤维是类液体的，没有流动反转。使用物理模型，我们证明了即使在组成蛋白周转时间超过的情况下，应力纤维也表现出弹性样行为。这种对肌动蛋白力学的分子控制可能在调节形态动力学事件中发挥关键作用。
