The plasma membrane and the underlying cytoskeletal cortex constitute active platforms for a variety of cellular processes. Recent work has shown that the remodeling acto-myosin network modifies local membrane organization, but the molecular details are only partly understood because of difficulties with experimentally accessing the relevant time and length scales. Here, we use interferometric scattering microscopy to investigate a minimal acto-myosin network linked to a supported lipid bilayer membrane. Using the magnitude of the interferometric contrast, which is proportional to molecular mass, and fast acquisition rates, we detect and image individual membrane-attached actin filaments diffusing within the acto-myosin network and follow individual myosin II filament dynamics. We quantify myosin II filament dwell times and processivity as functions of ATP concentration, providing experimental evidence for the predicted ensemble behavior of myosin head domains. Our results show how decreasing ATP concentrations lead to both increasing dwell times of individual myosin II filaments and a global change from a remodeling to a contractile state of the acto-myosin network.

中文翻译：

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干涉散射显微镜揭示肌动蛋白网络中的肌球蛋白 II 丝动力学

质膜和下面的细胞骨架皮层构成了各种细胞过程的活跃平台。最近的工作表明，重塑肌动蛋白网络改变了局部膜组织，但由于难以通过实验获得相关的时间和长度尺度，因此只能部分了解分子细节。在这里，我们使用干涉散射显微镜来研究与支持的脂质双层膜相关联的最小肌动蛋白网络。使用与分子质量成正比的干涉对比度的大小和快速采集速率，我们检测和成像单个膜附着肌动蛋白丝在肌动蛋白网络内扩散，并跟踪单个肌球蛋白 II 丝动力学。我们将肌球蛋白 II 细丝停留时间和持续合成能力作为 ATP 浓度的函数进行量化，为肌球蛋白头部域的预测整体行为提供了实验证据。我们的结果表明，降低 ATP 浓度如何导致单个肌球蛋白 II 细丝的停留时间增加以及肌动蛋白网络从重构到收缩状态的全局变化。