In a groundbreaking study published in Nature, researchers have unveiled the intricate interplay between myosin-generated forces and the structural remodeling of filamentous actin (F-actin), illuminating the mechanosensitive recognition by actin-binding proteins (ABPs) such as α-catenin. This investigation harnesses advanced cryo-electron microscopy (cryo-EM) to dissect the asymmetric binding patterns and conformational dynamics governing the α-catenin ABD–F-actin interface under physiological force conditions. The findings not only reveal a novel mechanistic basis for force-induced cytoskeletal adaptation but also underscore the cooperative molecular architecture enabling force sensing in cellular contexts.
Actin filaments are fundamental components of the cytoskeleton, orchestrating myriad cellular functions through dynamic interactions with various ABPs. Myosin motors generate mechanical forces that regulate these interactions, modulating processes like cell motility, adhesion, and morphogenesis. Previous research hinted at force-dependent engagement of ABPs, yet the structural underpinnings remained elusive. To probe this, the team focused on the isolated actin-binding domain (ABD) of αE-catenin, a protein whose binding affinity to F-actin is modulated by mechanical forces exerted by myosin.
Employing a dual motor cryo-EM experimental setup with sub-saturating α-catenin concentrations, the researchers captured a series of conformational states at approximately 10.4-Å resolution. Intriguingly, the reconstruction showcased asymmetric decoration patterns, where α-catenin preferentially bound to one actin strand before switching at the filament’s crossover point. This asymmetric binding starkly contrasts with prior observations under saturating, force-free conditions that revealed symmetric decoration, indicating a force-specific recognition mechanism.
To delve deeper, the team applied advanced three-dimensional variability analysis (3DVA) to probe the dynamic relationship between α-catenin binding and F-actin structural rearrangements. By rigid-body docking of high-resolution α-catenin ABD–F-actin structures (PDB 6UPV) into each frame of the 3DVA trajectory, they quantified α-catenin occupancy as a proxy for binding strength and monitored filament curvature. This approach unveiled two distinct filament curvature states, only one of which correlated with high α-catenin occupancy, linking curvature modulation to protein binding affinity.
Further scrutiny of the helical parameters revealed a unique force-dependent conformational landscape. While low α-catenin intensity states mirrored the canonical supercoil of unbound F-actin, the high occupancy states exhibited pronounced rises in the filament rise parameter, coupled with suppressed twist deviations. This elongation and twist stabilization imply that α-catenin selectively binds to and stabilizes F-actin conformations favored under mechanical strain, suggesting an active remodeling role in force transduction.
Focusing on particles corresponding to high α-catenin occupancy facilitated a refined 12.3-Å reconstruction, which elucidated inter-ABD contacts mediated by the α-catenin C-terminal extension. This segment, encompassing residues 865–871, appears pivotal in cooperative binding, mediating longitudinal ABD interactions that reinforce the force-sensitive engagement. Notably, binding intensity displayed a clear preference for filament regions exhibiting extended helical rise, anchoring α-catenin’s mechanosensitive specificity to distinct lattice conformations.
The structural remodeling was further characterized through molecular dynamics flexible fitting (MDFF) simulations, which highlighted conformational shifts in actin subdomains. Subdomain 2 emerged as a flexible nexus, undergoing repositioning at both bound and unbound filament sites under mechanical excitation. This widespread subdomain 2 rearrangement indicates an allosteric modulation by α-catenin binding, propagating structural changes beyond direct contact points and facilitating lattice plasticity critical for force accommodation.
High α-catenin occupancy sites demonstrated a characteristic displacement of subdomain 2 away from the filament core. This unique conformational state differs from both canonical and supercoiled F-actin and is accompanied by reduced compaction of subdomains 1 and 4, likely relieving steric strain induced by mechanical forces. These rearrangements underscore α-catenin’s role in not only detecting but also actively modulating actin filament architecture in response to mechanical cues.
The cooperative inter-ABD interactions, stabilized by the C-terminal extension, appear essential for sustaining these force-modulated lattice transitions. This molecular synergy enables α-catenin to act as a mechanosensitive sensor and effector, translating actomyosin-generated forces into structural and functional outcomes within the cytoskeleton. Such insights enrich our understanding of force transmission pathways underpinning cell adhesion and mechanotransduction processes.
Crucially, this study bridges a pivotal knowledge gap by linking the geometry of α-catenin engagement to specific conformational states of F-actin caused by myosin-generated forces. It reveals that mechanosensation is not merely a biochemical affinity change but involves a dynamic remodeling of actin filaments, orchestrated by ABPs to fine-tune cellular mechanics. This paradigm shift could have broad implications for interpreting cytoskeletal behavior in development, disease, and tissue engineering.
Moreover, the asymmetric binding pattern characterized here may underpin directional cellular responses to mechanical stimuli, influencing how cells interpret spatial cues through cytoskeletal rearrangements. By delineating the molecular choreography of force-dependent protein recognition, this research lays the groundwork for future endeavors aiming to manipulate cytoskeletal mechanics therapeutically or in biomimetic systems.
The integration of cutting-edge cryo-EM structural analyses with state-of-the-art computational modeling embodies a powerful approach to unravel the complexities of cytoskeletal mechanobiology. This multidisciplinary methodology paves the way for deciphering other force-sensitive interactions within the cell, offering a molecular blueprint for the mechanosensitive functions of a diverse array of ABPs.
In sum, Carl et al. have provided a compelling and detailed portrait of how myosin forces elicit structural remodeling in F-actin, enabling α-catenin to detect and reciprocally modulate filament architecture. Their discovery underscores the sophistication of cellular force sensing and responsiveness, marking a significant advance in the field of cytoskeletal dynamics and mechanotransduction.
Subject of Research: Mechanosensitive interactions between myosin forces, F-actin remodeling, and α-catenin binding dynamics.
Article Title: Myosin forces remodel F-actin for mechanosensitive protein recognition.
Article References:
Carl, A.G., Reynolds, M.J., Sun, X. et al. Myosin forces remodel F-actin for mechanosensitive protein recognition. Nature (2026). https://doi.org/10.1038/s41586-026-10398-7
Image Credits: AI Generated
DOI: https://doi.org/10.1038/s41586-026-10398-7
Keywords: F-actin, α-catenin, mechanotransduction, myosin forces, cryo-electron microscopy, cytoskeleton, actin-binding proteins, molecular dynamics flexible fitting, filament remodeling, mechanosensitive binding
