Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore.
Department of Physics, National University of Singapore, Singapore 117542, Singapore.
J Am Chem Soc. 2023 Jul 12;145(27):14670-14678. doi: 10.1021/jacs.3c02303. Epub 2023 Jun 27.
Filamin C (FLNC), a large dimeric actin-binding protein in muscle cells, plays a critical role in transmitting force in the cytoskeleton and that between membrane receptors and the cytoskeleton. It performs crucial mechanosensing and downstream mechanotransduction functions via force-dependent interactions with signaling proteins. Mutations in FLNC have been linked to muscle and heart diseases. The mechanical responses of the force-bearing elements in FLNC have not been determined. This study investigated the mechanical responses of FLNC domains and their dimerization interface using magnetic tweezers. Results showed high stability of the N-terminal domains in the rod-1 segment but significant changes in the rod-2 domains in response to forces of a few piconewtons (pN). The dimerization interface, formed by the R24 domain, has a lifetime of seconds to tens of seconds at pN forces, and it dissociates within 1 s at forces greater than 14 pN. The findings suggest the FLNC dimerization interface provides sufficient mechanical stability that enables force-dependent structural changes in rod-2 domains for signaling protein binding and maintains structural integrity of the rod-1 domains.
细丝蛋白 C（FLNC）是一种存在于肌肉细胞中的大型二聚体肌动蛋白结合蛋白，在细胞骨架和膜受体与细胞骨架之间的力传递中发挥着关键作用。它通过与信号蛋白的力依赖性相互作用，执行关键的机械传感和下游机械转导功能。FLNC 中的突变与肌肉和心脏疾病有关。FLNC 中力承载元件的机械响应尚未确定。本研究使用磁镊研究了 FLNC 结构域及其二聚化界面的机械响应。结果表明，在 rod-1 段中的 N 端结构域具有很高的稳定性，但在几皮牛顿（pN）的力作用下，rod-2 结构域发生了显著变化。由 R24 结构域形成的二聚化界面在 pN 力下具有数秒到数十秒的寿命，而在大于 14 pN 的力下，它会在 1 秒内解离。研究结果表明，FLNC 二聚化界面提供了足够的机械稳定性，使 rod-2 结构域能够发生力依赖性的结构变化，从而与信号蛋白结合，并保持 rod-1 结构域的结构完整性。
