Prestress and Area Compressibility of Actin Cortices Determine the Viscoelastic Response of Living Cells.,Physical Review Letters

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Prestress and Area Compressibility of Actin Cortices Determine the Viscoelastic Response of Living Cells.
Physical Review Letters ( IF 8.1 ) Pub Date : 2020-08-06 , DOI: 10.1103/physrevlett.125.068101
Andrea Cordes ₁ , Hannes Witt ₂ , Aina Gallemí-Pérez ₂ , Bastian Brückner ₁ , Florian Grimm _{1,

3} , Marian Vache ₁ , Tabea Oswald ₄ , Jonathan Bodenschatz ₁ , Daniel Flormann ₅ , Franziska Lautenschläger _{5,

6} , Marco Tarantola ₂ , Andreas Janshoff ₁

Affiliation

Shape, dynamics, and viscoelastic properties of eukaryotic cells are primarily governed by a thin, reversibly cross-linked actomyosin cortex located directly beneath the plasma membrane. We obtain time-dependent rheological responses of fibroblasts and MDCK II cells from deformation-relaxation curves using an atomic force microscope to access the dependence of cortex fluidity on prestress. We introduce a viscoelastic model that treats the cell as a composite shell and assumes that relaxation of the cortex follows a power law giving access to cortical prestress, area-compressibility modulus, and the power law exponent (fluidity). Cortex fluidity is modulated by interfering with myosin activity. We find that the power law exponent of the cell cortex decreases with increasing intrinsic prestress and area-compressibility modulus, in accordance with previous finding for isolated actin networks subject to external stress. Extrapolation to zero tension returns the theoretically predicted power law exponent for transiently cross-linked polymer networks. In contrast to the widely used Hertzian mechanics, our model provides viscoelastic parameters independent of indenter geometry and compression velocity.

中文翻译：

肌动蛋白皮质的预应力和区域可压缩性决定了活细胞的粘弹性响应。

真核细胞的形状，动力学和粘弹性主要受直接位于质膜正下方的薄的，可逆交联的肌动球蛋白皮层支配。我们使用原子力显微镜从皮层流动性对预应力的依赖关系中，从松弛松弛曲线获得了成纤维细胞和MDCK II细胞的时间依赖性流变响应。我们介绍了一种粘弹性模型，该模型将细胞视为复合壳，并假设皮质的松弛遵循幂定律，从而可以访问皮层预应力，面积可压缩模量和幂律指数（流动性）。皮质流动性通过干扰肌球蛋白活性来调节。我们发现，细胞皮质的幂律指数随固有预应力和面积压缩模量的增加而减小，根据先前发现的受外界压力影响的孤立肌动蛋白网络。外推至零张力可返回理论上预测的瞬态交联聚合物网络的幂律指数。与广泛使用的赫兹力学相反，我们的模型提供了与压头几何形状和压缩速度无关的粘弹性参数。

更新日期：2020-08-06

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