BPS2026 – The role of catch bonds in actomyosin networks

The actin cytoskeleton is an intracellular structure playing a central role in cell mechanics, consisting of actin filaments interconnected by actin cross-linking proteins (ACPs). Dozens of ACPs with different affinities for actin filaments have been identified. While most of them had been understood as slip bonds showing a higher unbinding rate with greater forces, recent studies have shown some of the ACPs behave as catch bonds showing a lower unbinding rate with an increase in forces at low force levels. Our previous studies demonstrated that ACPs exhibiting the catch bond behavior enhance the strength of passive actin networks without myosin motors. In this study, we employed an agent-based computational model to probe how the catch-bond nature of ACPs regulates force generation and transmission in actomyosin networks. We found that the catch-bond ACPs were redistributed toward high-tension regions, enabling more effective contractile force generation and long-range force propagation compared to those in networks with slip-bond ACPs. Furthermore, we examined how the force pattern induced by myosin motors differs between networks with the two types of ACPs, by varying the properties of myosin thick filaments. It was found that networks containing fewer, longer thick filaments exhibited larger differences in force generation and transmission between networks cross-linked by the catch-bond ACPs and the slip-bond ACPs. These results reveal the role of ACPs with the catch-bond nature in actomyosin networks. Further, our findings provide mechanistic insight into how actomyosin assemblies maintain robustness under dynamic loading.