Molecular mechanism for direct actin force-sensing by α-catenin.
Molecular mechanism for direct actin force-sensing by α-catenin.
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DOI：
10.7554/elife.62514
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发表时间：
2020-09-24
期刊：
影响因子：
7.7
通讯作者：
Alushin GM
中科院分区：
文献类型：
--
作者：
Mei L;Espinosa de Los Reyes S;Reynolds MJ;Leicher R;Liu S;Alushin GM
肌动蛋白细胞骨架介导细胞与其组织微环境之间的机械耦合。肌动蛋白网络的结构和组成是由力调节的;然而，目前还不清楚肌动蛋白丝（F-肌动蛋白）和相关蛋白之间的相互作用是如何机械调节的。在这里，我们采用光学捕获和生化重建与肌球蛋白马达蛋白显示单一的皮牛顿力单独应用于F-肌动蛋白增强结合的人类版本的基本细胞-细胞粘附蛋白α E-连环蛋白，而不是它的同系物黏着斑蛋白。冷冻电子显微镜结构的两种蛋白质结合F-肌动蛋白揭示独特的重排，促进其灵活的C-末端重折叠，从事不同的接口。截断α-连环蛋白的C-末端消除了力激活的F-肌动蛋白结合，并且将该基序添加到黏着斑蛋白中赋予力激活的结合，表明α-连环蛋白的C-末端是F-肌动蛋白张力的模块化检测器。我们的研究表明，F-actin上的微微牛顿力可以增强伴侣结合，我们提出通过α-catenin机械地调节细胞粘附。我们身体中的所有细胞都依赖于周围环境的提示来改变它们的行为。除了相互发送化学信号，如激素，细胞还可以检测周围细胞施加的压力和物理力。这些物理相互作用由称为细胞骨架的蛋白质网络协调，细胞骨架提供维持细胞形状的内部支架。然而，目前还不清楚通过细胞骨架传递的力如何转化为控制细胞行为的机械信号。细胞骨架主要由称为肌动蛋白的蛋白质细丝组成，这些蛋白质细丝经常处于外力和内力对细胞的推拉作用下。许多蛋白质直接与肌动蛋白结合，包括允许细胞“粘”到周围环境的粘附蛋白。一种可能性是，当肌动蛋白丝感受到张力时，它们通过改变与其他蛋白质结合的方式将其转化为机械信号。为了验证这一理论，Mei等人分离并研究了一种称为α-catenin的粘附蛋白，已知它与肌动蛋白相互作用。这表明，当微小的力--类似于体内细胞所经历的量--作用于肌动蛋白丝时，这会导致α-连环蛋白和肌动蛋白更牢固地结合在一起。然而，施加相同水平的物理力并没有改变肌动蛋白与一种类似的粘附蛋白（称为黏着斑蛋白）结合的程度。进一步的实验表明，这是由于在两种蛋白质上发现的小的柔性区域的差异。操纵这个区域揭示了当存在力时，它有助于α-连环蛋白附着到肌动蛋白上，因此被命名为“力探测器”。与肌动蛋白结合的蛋白质在所有动物中都是必不可少的，这使得力检测器可能是一种常见的机制。科学家们现在可以利用这一发现来识别和操纵不同细胞和动物中其他蛋白质中的力探测器。这可能有助于开发针对机械信号过程的药物，尽管这将需要进一步了解力检测器如何在分子水平上工作。
The actin cytoskeleton mediates mechanical coupling between cells and their tissue microenvironments. The architecture and composition of actin networks are modulated by force; however, it is unclear how interactions between actin filaments (F-actin) and associated proteins are mechanically regulated. Here we employ both optical trapping and biochemical reconstitution with myosin motor proteins to show single piconewton forces applied solely to F-actin enhance binding by the human version of the essential cell-cell adhesion protein αE-catenin but not its homolog vinculin. Cryo-electron microscopy structures of both proteins bound to F-actin reveal unique rearrangements that facilitate their flexible C-termini refolding to engage distinct interfaces. Truncating α-catenin’s C-terminus eliminates force-activated F-actin binding, and addition of this motif to vinculin confers force-activated binding, demonstrating that α-catenin’s C-terminus is a modular detector of F-actin tension. Our studies establish that piconewton force on F-actin can enhance partner binding, which we propose mechanically regulates cellular adhesion through α-catenin. All of the cells in our bodies rely on cues from their surrounding environment to alter their behavior. As well sending each other chemical signals, such as hormones, cells can also detect pressure and physical forces applied by the cells around them. These physical interactions are coordinated by a network of proteins called the cytoskeleton, which provide the internal scaffold that maintains a cell’s shape. However, it is not well understood how forces transmitted through the cytoskeleton are converted into mechanical signals that control cell behavior. The cytoskeleton is primarily made up protein filaments called actin, which are frequently under tension from external and internal forces that push and pull on the cell. Many proteins bind directly to actin, including adhesion proteins that allow the cell to ‘stick’ to its surroundings. One possibility is that when actin filaments feel tension, they convert this into a mechanical signal by altering how they bind to other proteins. To test this theory, Mei et al. isolated and studied an adhesion protein called α-catenin which is known to interact with actin. This revealed that when tiny forces – similar to the amount cells experience in the body – were applied to actin filaments, this caused α-catenin and actin to bind together more strongly. However, applying the same level of physical force did not alter how well actin bound to a similar adhesion protein called vinculin. Further experiments showed that this was due to differences in a small, flexible region found on both proteins. Manipulating this region revealed that it helps α-catenin attach to actin when a force is present, and was thus named a ‘force detector’. Proteins that bind to actin are essential in all animals, making it likely that force detectors are a common mechanism. Scientists can now use this discovery to identify and manipulate force detectors in other proteins across different cells and animals. This may help to develop drugs that target the mechanical signaling process, although this will require further understanding of how force detectors work at the molecular level.