Restructuring in Active Cytoskeletal Composites: A Coarse-Grained Simulation Study

Cytoskeletal filaments such as F-actin and microtubules organize into dynamic networks and bundles through the cooperative action of associating crosslinking and motor proteins, which generate both passive connections and active stresses essential for cellular structure and motility. In vitro, these interactions give rise to active cytoskeletal composites (ACCs) that display rich equilibrium and nonequilibrium morphologies and serve as model systems for adaptive soft materials. We present coarse-grained Brownian dynamics simulations capturing ACC restructuring driven by motor- and passive-crosslinker-mediated connections; we also include filament elasticity, steric repulsion, and viscous and thermal forces from the surrounding medium. The simulations reveal dynamic formation of bundles, asters, and interconnected networks whose morphology depends on the concentrations and affinities of crosslinking and motor proteins. We further introduce micron-scale probe particles that respond to local stresses or external fields, providing a simulation analogue of microrheology. This mesoscopic approach captures key features of cytoskeletal remodeling and informs the design of synthetic active materials.