Multivalent actin-binding proteins augment the variety of morphologies in actomyosin networks

We study the role of multivalent actin-binding proteins in remodeling actomyosin networks, using a numerical model of semiflexible filaments. We find that the valency of actin-binding proteins greatly affects the organization of actomyosin networks. The rich variety of emergent architectures and morphologies inspired us to develop order parameters based on network theory, to quantitatively characterize the self-assembled organization in the simulated network. First, actin-binding proteins with a valency greater than two promote filament bundles and large filament clusters to a much greater extent than bivalent multilinkers. Second, active myosin-like motor proteins promote rich phases of actomyosin, as characterized by network theory. Lastly, we find that both high content of multilinkers and active motors are necessary to the reduction of node degree correlation in the network of filaments. Our work provides a framework to describe the dendritic structures of actomyosin networks mediated by ABP with the ability of binding multiple filaments, such as Ca2+/Calmodulin-dependent Kinase II (CaMKII). We expect this work to motivate future directions to embrace network theory as a tool to analyze experiments as well as to establish a quantitative understanding of the role of dendritic spine growth in synaptic plasticity.