Institute of Molecular Biology and Genetics, Seoul National University, Seoul, Republic of Korea.
Center for Nanomedicine, Institute for Basic Science (IBS) and Yonsei-IBS Institute, Yonsei University, Seoul, Republic of Korea.
Sci Rep. 2020 Feb 10;10(1):2301. doi: 10.1038/s41598-020-59030-2.
Despite the importance in various cellular processes, the nanomechanical responses of the living cell membrane have been elusive due to complexities in the membrane associated with the hidden architecture of multiple molecular components, including the lipid bilayer. Here, combined experimental and theoretical frameworks that can probe and interpret nanomechanical responses of the cell membrane are demonstrated. A magnetic tweezer assay was introduced to apply pico-Newton scale forces to lipids and E-cadherin molecules at the living cell surface. Two unique classes of force-extension curves were identified: one with a deflection transition (Type I) and another with a discontinuous transition (Type II). The repeated observations of these responses, regardless of cell type and targeted cell surface molecule, suggest the Type I and II curves are the primary nanomechanical responses of cell membranes. To reproduce these responses in vitro, a model system using synthetic lipid vesicles was also developed. Together with a finite element model of lipid bilayers, the reproduced responses suggest that the confined fluidity and curvature constraints imposed on the lipid bilayer components of the cell membrane are the main parameters responsible for the generation of these responses. This work provides an insight into how forces on membrane molecules propagate to the lipid bilayer components to generate specific nanomechanical responses. In addition, the consistent results obtained using different methodologies demonstrate that the presented force-probing assays and the theoretical model can serve a combined testbed to investigate nanoscale mechanics of the living cell membrane.
尽管活细胞膜的纳米力学响应在各种细胞过程中都很重要，但由于与隐藏的多个分子成分（包括脂质双层）相关的膜复杂性，这些响应一直难以捉摸。本文展示了可以探测和解释细胞膜纳米力学响应的组合实验和理论框架。引入了磁镊测定法，以在活细胞表面向脂质和 E-钙黏蛋白分子施加皮牛顿级别的力。确定了两种独特的力-延伸曲线类型：一种具有挠度转变（I 型），另一种具有不连续转变（II 型）。无论细胞类型和靶向细胞表面分子如何，这些响应的重复观察表明，I 型和 II 型曲线是细胞膜的主要纳米力学响应。为了在体外重现这些响应，还开发了使用合成脂质囊泡的模型系统。与脂质双层的有限元模型一起，重现的响应表明，对细胞膜脂质双层成分施加的受限流动性和曲率约束是产生这些响应的主要参数。这项工作深入了解了膜分子上的力如何传递到脂质双层成分以产生特定的纳米力学响应。此外，使用不同方法学获得的一致结果表明，所提出的力探测测定法和理论模型可以作为一个联合测试平台，用于研究活细胞膜的纳米力学。
