Active Restructuring of Actin-Microtubule Composites by Kinesin and Myosin

The cytoskeleton is a dynamic network of proteins, including semiflexible actin filaments, rigid microtubules, crosslinking proteins, and myosin and kinesin motors, that enable key processes in the cell such as growth, movement, and cell division. While active actomyosin and kinesin-microtubule systems have been extensively studied in recent years, how interactions between actin and microtubules impact cytoskeletal restructuring by myosin and kinesin remains poorly understood. Here, we investigate the active dynamics and restructuring of actin-microtubule composites driven by kinesin motors and myosin II minifilaments. We combine spatial image autocorrelation and particle image velocimetry to characterize time-varying network structure and velocity flow fields during motor activity. We find that myosin activity causes network contraction into microscale foci whereas kinesin motors induce large-scale flow and bundling. Crosslinking of actin or microtubules tunes the flow rate and the resulting network structure. These findings provide insight into how the different components of the cytoskeleton work in concert to enable diverse cellular processes and structures, and advance their use as a tunable active matter system.