Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore.
Department of Physics, Xiamen University, Xiamen 361000, China.
Proc Natl Acad Sci U S A. 2024 Sep 10;121(37):e2400654121. doi: 10.1073/pnas.2400654121. Epub 2024 Sep 5.
The HMP-2/HMP-1 complex, akin to the mammalian [Formula: see text]-catenin-[Formula: see text]-catenin complex, serves as a critical mechanosensor at cell-cell adherens junctions, transducing tension between HMR-1 (also known as cadherin in mammals) and the actin cytoskeleton. Essential for embryonic development and tissue integrity in , this complex experiences tension from both internal actomyosin contractility and external mechanical microenvironmental perturbations. While offering a valuable evolutionary comparison to its mammalian counterpart, the impact of tension on the mechanical stability of HMP-1 and HMP-2/HMP-1 interactions remains unexplored. In this study, we directly quantified the mechanical stability of full-length HMP-1 and its force-bearing modulation domains (M1-M3), as well as the HMP-2/HMP-1 interface. Notably, the M1 domain in HMP-1 exhibits significantly higher mechanical stability than its mammalian analog, attributable to interdomain interactions with M2-M3. Introducing salt bridge mutations in the M3 domain weakens the mechanical stability of the M1 domain. Moreover, the intermolecular HMP-2/HMP-1 interface surpasses its mammalian counterpart in mechanical stability, enabling it to support the mechanical activation of the autoinhibited M1 domain for mechanotransduction. Additionally, the phosphomimetic mutation Y69E in HMP-2 weakens the mechanical stability of the HMP-2/HMP-1 interface, compromising the force-transmission molecular linkage and its associated mechanosensing functions. Collectively, these findings provide mechanobiological insights into the HMP-2/HMP-1 complex, highlighting the impact of salt bridges on mechanical stability in [Formula: see text]-catenin and demonstrating the evolutionary conservation of the mechanical switch mechanism activating the HMP-1 modulation domain for protein binding at the single-molecule level.
HMP-2/HMP-1 复合物类似于哺乳动物的 [Formula: see text]-连环蛋白-[Formula: see text]-连环蛋白复合物，作为细胞间黏附连接的关键机械感受器，将 HMR-1（在哺乳动物中也称为钙粘蛋白）与肌动蛋白细胞骨架之间的张力转导。该复合物对于胚胎发育和组织完整性至关重要，它会受到来自内部肌球蛋白收缩和外部机械微环境扰动的张力。虽然它为与哺乳动物对应物的进化比较提供了有价值的参考，但张力对 HMP-1 和 HMP-2/HMP-1 相互作用的机械稳定性的影响仍未得到探索。在这项研究中，我们直接量化了全长 HMP-1 及其承重调节域（M1-M3）以及 HMP-2/HMP-1 界面的机械稳定性。值得注意的是，HMP-1 中的 M1 结构域的机械稳定性明显高于其哺乳动物类似物，这归因于与 M2-M3 之间的结构域相互作用。在 M3 结构域中引入盐桥突变会削弱 M1 结构域的机械稳定性。此外，HMP-2/HMP-1 界面的机械稳定性超过其哺乳动物对应物，使其能够支持机械激活自动抑制的 M1 结构域进行机械转导。此外，HMP-2 中的磷酸模拟突变 Y69E 削弱了 HMP-2/HMP-1 界面的机械稳定性，破坏了力传递分子连接及其相关的机械传感功能。总的来说，这些发现为 HMP-2/HMP-1 复合物提供了机械生物学见解，强调了盐桥对 [Formula: see text]-连环蛋白机械稳定性的影响，并展示了机械开关机制在激活 HMP-1 调节域以在单分子水平上进行蛋白结合方面的进化保守性。
