University Paris Descartes, Center for Research and Interdisciplinarity (CRI), 8bis Rue Charles V, Paris, France.
Soft Matter. 2019 Dec 4;15(47):9647-9653. doi: 10.1039/c9sm01902b.
Global changes of cell shape under mechanical or osmotic external stresses are mostly controlled by the mechanics of the cortical actin cytoskeleton underlying the cell membrane. Some aspects of this process can be recapitulated in vitro on reconstituted actin-and-membrane systems. In this paper, we investigate how the mechanical properties of a branched actin network shell, polymerized at the surface of a liposome, control membrane shape when the volume is reduced. We observe a variety of membrane shapes depending on the actin thickness. Thin shells undergo buckling, characterized by a cup-shape deformation of the membrane that coincides with the one of the actin network. Thick shells produce membrane wrinkles, but do not deform their outer layer. For intermediate micrometer-thick shells, wrinkling of the membrane is observed, and the actin layer is slightly deformed. Confronting our experimental results with a theoretical description, we determine the transition between buckling and wrinkling, which depends on the thickness of the actin shell and the size of the liposome. We thus unveil the generic mechanism by which biomembranes are able to accommodate their shape against mechanical compression, through thickness adaptation of their cortical cytoskeleton.
在机械或渗透外部压力下，细胞形状的全局变化主要由细胞膜下的皮质肌动球蛋白细胞骨架的力学控制。这个过程的某些方面可以在体外重新构建的肌动蛋白和膜系统中再现。在本文中，我们研究了当体积减小时，聚合在脂质体表面的分支肌动蛋白网络壳的机械性能如何控制膜的形状。我们观察到了各种取决于肌动蛋白厚度的膜形状。薄壳会发生屈曲，其特征是膜的杯状变形与肌动蛋白网络的变形一致。厚壳会产生膜皱纹，但不会使外膜层变形。对于中间的微米厚的壳，观察到膜的起皱，并且肌动蛋白层略有变形。将我们的实验结果与理论描述进行对比，我们确定了从屈曲到起皱的转变，这取决于肌动蛋白壳的厚度和脂质体的大小。因此，我们揭示了生物膜通过其皮质细胞骨架的厚度适应来适应机械压缩的通用机制。
