Department of Physics and Astronomy, Institute for the Physics of Living Systems, University College London, London, United Kingdom; MRC Laboratory for Molecular Cell Biology, University College London, London, United Kingdom.
Laboratoire Physico-Chimie Curie, Institut Curie, PSL Research University, CNRS UMR168, Paris, France; Sorbonne Université, Paris, France; Institut Curie, PSL Research University CNRS UMR 144, Paris, France.
Biophys J. 2021 Feb 16;120(4):598-606. doi: 10.1016/j.bpj.2020.12.028. Epub 2021 Jan 16.
The cell membrane is an inhomogeneous system composed of phospholipids, sterols, carbohydrates, and proteins that can be directly attached to underlying cytoskeleton. The protein linkers between the membrane and the cytoskeleton are believed to have a profound effect on the mechanical properties of the cell membrane and its ability to reshape. Here, we investigate the role of membrane-cortex linkers on the extrusion of membrane tubes using computer simulations and experiments. In simulations, we find that the force for tube extrusion has a nonlinear dependence on the density of membrane-cortex attachments: at a range of low and intermediate linker densities, the force is not significantly influenced by the presence of the membrane-cortex attachments and resembles that of the bare membrane. For large concentrations of linkers, however, the force substantially increases compared with the bare membrane. In both cases, the linkers provided membrane tubes with increased stability against coalescence. We then pulled tubes from HEK cells using optical tweezers for varying expression levels of the membrane-cortex attachment protein Ezrin. In line with simulations, we observed that overexpression of Ezrin led to an increased extrusion force, while Ezrin depletion had a negligible effect on the force. Our results shed light on the importance of local protein rearrangements for membrane reshaping at nanoscopic scales.
细胞膜是一个不均匀的系统，由磷脂、固醇、碳水化合物和蛋白质组成，可以直接附着在下面的细胞骨架上。膜和细胞骨架之间的蛋白质连接物被认为对细胞膜的机械性能及其重塑能力有深远的影响。在这里，我们使用计算机模拟和实验研究了膜皮质连接物在膜管挤出中的作用。在模拟中，我们发现管挤出的力与膜皮质附着的密度呈非线性关系：在低和中等附着密度范围内，力不受膜皮质附着的存在的显著影响，类似于裸膜的力。然而，对于较大浓度的连接物，力与裸膜相比显著增加。在这两种情况下，连接物都增加了膜管对聚结的稳定性。然后，我们使用光学镊子从 HEK 细胞中提取管，以改变膜皮质附着蛋白 Ezrin 的表达水平。与模拟结果一致，我们观察到 Ezrin 的过表达导致挤出力增加，而 Ezrin 的耗竭对力几乎没有影响。我们的结果揭示了局部蛋白质重排对纳米尺度下细胞膜重塑的重要性。
