Analysis of chemomechanical behavior of stress fibers by continuum mechanics-based FRAP
Analysis of chemomechanical behavior of stress fibers by continuum mechanics-based FRAP
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基于连续介质力学的 FRAP 分析应力纤维的化学力学行为
DOI：
10.1016/j.bpj.2022.06.032
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发表时间：
2022
影响因子：
3.4
通讯作者：
S.
中科院分区：
文献类型：
--
作者：
Saito;T.;Matsunaga;D.;Deguchi;S.
光漂白后荧光恢复（FRAP）是分析活细胞中分子周转的常用技术。已经开发了许多物理化学模型来定量评估由化学反应和扩散驱动的周转率，这些反应和扩散发生在几秒钟到几分钟内。另一方面，它们在解释长期FRAP反应方面存在局限性，因为细胞内的活跃运动不可避免地为靶分子结构提供了化学反应和扩散以外的额外效应，即定向运输和结构变形。为了克服这些限制，我们开发了一个基于连续介质力学的模型，该模型允许将FRAP响应解耦到固有周转率和亚细胞力学特征（如位移矢量和应变张量）中。我们的方法在肌动球蛋白介导的收缩装置（称为应力纤维）中使用荧光标记的β-肌动蛋白进行了验证，揭示了多物理化学事件的空间不同模式，其中代表β-肌动蛋白有效脱落率的周转率在细胞中心明显更高。我们还发现，周转率与沿应力纤维的位移率或速度呈负相关，但有趣的是，与应变的绝对大小无关。此外，应力纤维受到向心流动的影响，这是由肌动蛋白分子的循环促进的。总之，这个长期FRAP分析的新框架允许揭示被忽视的微观力学对活细胞分子更新的贡献。
Fluorescence recovery after photobleaching (FRAP) is a common technique to analyze the turnover of molecules in living cells. Numerous physicochemical models have been developed to quantitatively evaluate the rate of turnover driven by chemical reaction and diffusion that occurs in a few seconds to minutes. On the other hand, they have limitations in interpreting long-term FRAP responses where intracellular active movement inevitably provides target molecular architectures with additional effects other than chemical reaction and diffusion, namely directed transport and structural deformation. To overcome the limitations, we develop a continuum mechanics-based model that allows for decoupling FRAP response into the intrinsic turnover rate and subcellular mechanical characteristics such as displacement vector and strain tensor. Our approach was validated using fluorescently labeledβ-actin in an actomyosin-mediated contractile apparatus called stress fibers, revealing spatially distinct patterns of the multi-physicochemical events, in which the turnover rate, which represents effective off-rate ofβ-actin, was significantly higher at the center of the cell. We also found that the turnover rate is negatively correlated with the rate of displacement or velocity along stress fibers but, interestingly, not with the absolute magnitude of strain. Moreover, stress fibers are subjected to centripetal flow that is facilitated by the circulation of actin molecules. Taken together, this novel framework for long-term FRAP analysis allows for unveiling the contribution of overlooked microscopic mechanics to molecular turnover in living cells.