Schepers Anna V, Lorenz Charlotta, Köster Sarah
Institute for X-Ray Physics, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany.
Nanoscale. 2020 Jul 23;12(28):15236-15245. doi: 10.1039/d0nr02778b.
The cytoskeleton is formed by three types of filamentous proteins - microtubules, actin filaments, and intermediate filaments (IFs) - and enables cells to withstand external and internal forces. Vimentin is the most abundant IF protein in humans and assembles into 10 nm diameter filaments with remarkable mechanical properties, such as high extensibility and stability. It is, however, unclear to which extent these properties are influenced by the electrostatic environment. Here, we study the mechanical properties of single vimentin filaments by employing optical trapping combined with microfluidics. Force-strain curves, recorded at varying ion concentrations and pH values, reveal that the mechanical properties of single vimentin IFs are influenced by pH and ion concentration. By combination with Monte Carlo simulations, we relate these altered mechanics to electrostatic interactions of subunits within the filaments. We thus suggest possible mechanisms that allow cells to locally tune their stiffness without remodeling the entire cytoskeleton.
细胞骨架由三种丝状蛋白——微管、肌动蛋白丝和中间丝（IFs）——构成，使细胞能够承受外部和内部的作用力。波形蛋白是人类中最丰富的中间丝蛋白，组装成直径为10纳米的细丝，具有显著的机械性能，如高延展性和稳定性。然而，目前尚不清楚这些特性在多大程度上受静电环境的影响。在这里，我们通过结合光镊和微流控技术来研究单个波形蛋白丝的机械性能。在不同离子浓度和pH值下记录的力-应变曲线表明，单个波形蛋白中间丝的机械性能受pH值和离子浓度的影响。通过与蒙特卡罗模拟相结合，我们将这些改变的力学性能与细丝内亚基的静电相互作用联系起来。因此，我们提出了一些可能的机制，使细胞能够在不重塑整个细胞骨架的情况下局部调节其硬度。
