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The Poisson ratio of the cellular actin cortex is frequency-dependent
Biophysical Journal ( IF 3.4 ) Pub Date : 2020-04-01 , DOI: 10.1016/j.bpj.2020.03.002
Marcel Mokbel 1 , Kamran Hosseini 2 , Sebastian Aland 1 , Elisabeth Fischer-Friedrich 2
Affiliation  

Cell shape changes are vital for many physiological processes such as cell proliferation, cell migration, and morphogenesis. They emerge from an orchestrated interplay of active cellular force generation and passive cellular force response, both crucially influenced by the actin cytoskeleton. To model cellular force response and deformation, cell mechanical models commonly describe the actin cytoskeleton as a contractile isotropic incompressible material. However, in particular at slow frequencies, there is no compelling reason to assume incompressibility because the water content of the cytoskeleton may change. Here, we challenge the assumption of incompressibility by comparing computer simulations of an isotropic actin cortex with tunable Poisson ratio to measured cellular force response. Comparing simulation results and experimental data, we determine the Poisson ratio of the cortex in a frequency-dependent manner. We find that the Poisson ratio of the cortex decreases in the measured frequency regime analogous to trends reported for the Poisson ratio of glassy materials. Our results therefore indicate that actin cortex compression or dilation is possible in response to acting forces at sufficiently fast timescales. This finding has important implications for the parameterization in active gel theories that describe actin cytoskeletal dynamics.

中文翻译:

细胞肌动蛋白皮层的泊松比是频率依赖性的

细胞形状变化对许多生理过程至关重要,例如细胞增殖、细胞迁移和形态发生。它们来自主动细胞力产生和被动细胞力反应的协调相互作用,两者都受到肌动蛋白细胞骨架的关键影响。为了模拟细胞力响应和变形,细胞力学模型通常将肌动蛋白细胞骨架描述为可收缩的各向同性不可压缩材料。然而,特别是在低频率下,没有令人信服的理由假设不可压缩性,因为细胞骨架的水含量可能会发生变化。在这里,我们通过将具有可调泊松比的各向同性肌动蛋白皮层的计算机模拟与测量的细胞力响应进行比较来挑战不可压缩性的假设。比较模拟结果和实验数据,我们以频率相关的方式确定皮层的泊松比。我们发现皮层的泊松比在测量的频率范围内降低,类似于玻璃材料泊松比报告的趋势。因此,我们的结果表明,肌动蛋白皮质压缩或扩张是可能的,以响应足够快的时间尺度的作用力。这一发现对描述肌动蛋白细胞骨架动力学的活性凝胶理论中的参数化具有重要意义。因此,我们的结果表明,肌动蛋白皮质压缩或扩张是可能的,以响应足够快的时间尺度的作用力。这一发现对描述肌动蛋白细胞骨架动力学的活性凝胶理论中的参数化具有重要意义。因此,我们的结果表明,肌动蛋白皮质压缩或扩张是可能的,以响应足够快的时间尺度的作用力。这一发现对描述肌动蛋白细胞骨架动力学的活性凝胶理论中的参数化具有重要意义。
更新日期:2020-04-01
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