W. M. Keck Science Department, Scripps College, Pitzer College, and Claremont McKenna College, 925 N. Mills Ave., Claremont, California 91711, United States.
Department of Physics and Biophysics, University of San Diego, 5998 Alcala Park, San Diego, California 92110, United States.
ACS Macro Lett. 2021 Sep 21;10(9):1151-1158. doi: 10.1021/acsmacrolett.1c00500. Epub 2021 Sep 3.
The composite cytoskeleton, comprising interacting networks of semiflexible actin and rigid microtubules, generates forces and restructures by using motor proteins such as myosins to enable key processes including cell motility and mitosis. Yet, how motor-driven activity alters the mechanics of cytoskeleton composites remains an open challenge. Here, we perform optical tweezers microrheology and confocal imaging of composites with varying actin-tubulin molar percentages (25-75, 50-50, and 75-25), driven by light-activated myosin II motors, to show that motor activity increases the elastic plateau modulus by over 2 orders of magnitude by active restructuring of both actin and microtubules that persists for hours after motor activation has ceased. Nonlinear microrheology measurements show that motor-driven restructuring increases the force response and stiffness and suppresses actin bending. The 50-50 composite exhibits the most dramatic mechanical response to motor activity due to the synergistic effects of added stiffness from the microtubules and sufficient motor substrate for pronounced activity.
复合细胞骨架由相互作用的半刚性肌动蛋白和刚性微管网络组成，通过肌球蛋白等动力蛋白产生力并进行重构，从而实现细胞运动和有丝分裂等关键过程。然而，马达驱动活动如何改变细胞骨架复合材料的力学性质仍然是一个悬而未决的挑战。在这里，我们通过光激活肌球蛋白 II 马达驱动的具有不同肌动蛋白-微管摩尔百分比（25-75、50-50 和 75-25）的复合材料的光镊微流变学和共聚焦成像，表明马达活性通过肌动蛋白和微管的主动重构将弹性平台模量增加了两个数量级以上，这种重构在马达激活停止后持续数小时。非线性微流变学测量表明，马达驱动的重构增加了力响应和刚度，并抑制了肌动蛋白弯曲。由于微管增加的刚度和显著活性的足够的马达底物的协同效应，50-50 复合材料表现出最显著的机械响应。
