Mechanosensitivity of Membrane-Actin Cortex Adhesion

由人类或动物细胞产生或施加于细胞的物理力几乎参与了细胞的所有基本功能，包括分裂、形状控制、体积和内压控制、分化和迁移，以及细胞死亡。这些力量必须穿过细胞表面，细胞表面由外部的薄脂膜和内部的机械坚韧的生物聚合物网络--肌动蛋白皮质组成。细胞仔细地感知和调节这些力量。正如将帐篷织物与支撑框架捆绑在一起的带子是监测风对帐篷影响的最佳位置一样，细胞中的力感应机械的最佳位置是肌动蛋白皮质和类脂膜之间的交界处。单个细胞如何对力做出反应并产生自己的细胞，对于组织和器官发育、癌症进展和转移、伤口愈合和组织再生等生物体中的大规模动力学非常重要。然而，细胞如何感知和对力做出反应在很大程度上仍不清楚。在这个项目中，该团队将开发和使用一套创新的生物传感器来研究一种重要的膜肌动蛋白连接蛋白Ezrin，它已知调节干细胞分化和细胞迁移，并与癌症进展有关。研究人员将使用传感器来探测蛋白质在哪里积累，它可以以什么构象存在，以及当细胞受到物理操作时它经历了什么力。研究人员将把这些分子探针的结果与我们所知的细胞表面更大范围的力学知识结合起来，并使用激光、磁性颗粒和弹性微悬臂进行微机械探测。计算模型将被用来模拟Ezrin动力学并解释这些实验的结果。这项工作提出了一个创新的概念，将细胞膜和底层机械骨架之间的蛋白质视为一种感觉机制，提供关键信号来控制细胞行为。这项研究旨在发现重要的分子参与者，并确定它们如何与整个细胞的更大范围的机制联系在一起。该项目还推动了技术创新，因为它将提供一套新的生物传感器，探测蛋白质所经历的定位、构象和分子力，可以观察到并直接与标准荧光显微镜进行比较。细胞机械传感是生命系统物理学的核心部分，新的见解将对基础细胞和发育生物学以及生物技术和医学产生广泛影响。机械传感和机械调节对再生医学和包括癌症和纤维化在内的各种突出的人类病理学特别相关。通过将分子工程与细胞生物物理学和理论建模相结合，该项目将提供新的方法来培训未来在这一跨学科领域工作的各级科学家和工程师。通过教育和公众宣传，这项研究将吸引来自不同社区的新一代年轻科学家，并激励他们参与生命系统物理学广泛领域的研究。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Physical forces generated by, or applied to, human or animal cells are involved in almost every fundamental cellular function, including division, shape control, volume and internal pressure control, differentiation, and migration, as well as cell death. These forces must pass through the surface of the cell, which consists of a thin lipid membrane on the outside and a mechanically tough biopolymer network, the actin cortex, on the inside. Cells meticulously sense and regulate these forces. In the same way that the straps that tie the fabric of a tent to its supporting frame would be the best place to monitor what the wind is doing to the tent, the prime location for force-sensing machinery in the cell is at the interface between the actin cortex and the lipid membrane. How single cells react to forces and produce their own is important for large-scale dynamics in living organisms, such as tissue and organ development, cancer progression and metastasis, wound healing, and tissue regeneration. However, it remains largely unknown how cells sense and respond to forces.In this project, the team will develop and use a suite of innovative biosensors to study a prominent membrane actin linker protein, ezrin, which is known to regulate stem cell differentiation and cell migration and is implicated in cancer progression. The investigators will use the sensors to probe where the protein accumulates, what conformations it can be in, and what forces it experiences as cells are physically manipulated. The investigators will combine the results from these molecular probes with what we know about the larger-scale mechanics of the cell surface and use manipulation with laser beams, magnetic particles, and elastic micro-cantilevers for micromechanical probing. Computational modeling will be used to simulate ezrin kinetics and interpret the results of these experiments. This work develops an innovative concept, considering the proteins at the interface between the cell membrane and the underlying mechanical skeleton as a sensory machinery supplying crucial signals to control cell behavior. The research aims to discover the important molecular players and determine how they tie into the larger-scale mechanics of the whole cell. The project also drives technical innovation in that it will provide a new suite of biosensors that probe the localization, conformation, and molecular force experienced by a protein that can be observed and directly compared with standard fluorescence microscopy.Cellular mechanosensing is a central part of the physics of living systems, and new insights will have a broad impact on fundamental cell and developmental biology as well as biotechnology and medicine. Mechanosensing and mechanoregulation are particularly relevant for regenerative medicine and for various prominent human pathologies, including cancer and fibrosis. By combining molecular engineering with cell biophysics and theoretical modeling, the project will provide new ways of training future scientists and engineers working in this interdisciplinary area at all levels. Through educational and public outreach, the research will engage new generations of young scientists from diverse communities and stimulate them to participate in research in the broad area of the physics of living systems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.