Tensile properties of single desmin intermediate filaments
Tensile properties of single desmin intermediate filaments
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DOI：
10.1529/biophysj.107.119826
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发表时间：
2008-04-01
影响因子：
3.4
通讯作者：
Aebi, Ueli
中科院分区：
文献类型：
--
作者：
Kreplak, Laurent;Herrmann, Harald;Aebi, Ueli
在肌纤维内，结蛋白中间丝（IFs）是肌节外细胞骨架的主要成分。然而，它们对肌细胞力学特性的贡献一直不清楚。我们提出一种实验方法来测量体外重构并吸附在固体支持物上的结蛋白中间丝的伸展性和抗张强度。原子力显微镜（AFM）的尖端被用于垂直于丝轴推动单根丝。在推动过程中监测原子力显微镜悬臂的扭矩，以估算弯曲和拉伸丝所需的侧向力。结蛋白中间丝被拉伸至3.4倍，最大力约为3.5纳牛。通过原子力显微镜和电子显微镜观察，完全拉伸的丝直径比天然中间丝小得多，即约为3.5纳米，而天然中间丝为12.6纳米。此外，我们结合形态学和侧向力数据来计算单根结蛋白丝的平均应力 - 应变曲线。主要特征是在伸长超过50%时出现明显的应变硬化区域，抗张强度至少为240兆帕。由于这些非线性的拉伸特性，结蛋白中间丝可能会耗散机械能，并在大变形过程中作为连续肌节之间的物理连接。
Within muscle fibers, desmin intermediate filaments (IFs) are major constituents of the extrasarcomeric cytoskeleton. However, their contribution to the mechanical properties of myocytes has remained elusive. We present an experimental approach to measure the extensibility and the tensile strength of in vitro reconstituted desmin IFs adsorbed to a solid support. The tip of an atomic force microscope (AFM) was used to push on single filaments perpendicular to the filament axis. The torque of the AFM cantilever was monitored during the pushing events to yield an estimate of the lateral force necessary to bend and stretch the filaments. Desmin IFs were stretched up to 3.4-fold with a maximum force of similar to 3.5 nN. Fully stretched filaments exhibited a much smaller diameter than did native IFs, i.e., similar to 3.5 nm compared to 12.6 nm, both by AFM and electron microscopy. Moreover, we combined the morphological and lateral force data to compute an average stress-strain curve for a single desmin filament. The main features were a pronounced strain-hardening regime above 50% extension and a tensile strength of at least 240 MPa. Because of these nonlinear tensile properties, desmin IFs may dissipate mechanical energy and serve as a physical link between successive sarcomeres during large deformation.