Organization and Dynamics of Crosslinked Actin Networks under Confinement

The actin cytoskeleton is vital for intracellular transport in plant cells, where it remains challenging to understand how its organization is impacted by the interplay between physical confinement and the crosslinking of semiflexible actin filaments. We employ coarse-grained computer simulations to study the dynamics and organization of semiflexible actin filaments as we vary as the system shape, the number and type of crosslinking proteins, and the length of filaments. A variety of structures emerge, including isolated clusters of filaments, highly connected filament bundles, and networks of interconnected bundles with loops. We explore various measures of dynamics of network formation and find, with sufficiently large numbers of crosslinkers, a fast initial response followed by slower relaxation at longer times. Crosslinker properties impact the initial network response and subsequent relaxation. We characterize the bending energy of individual filaments and find, in some cases, highly unfavorable filament configurations that are difficult to relax. Finally, we examine organelle transport by molecular motors and the resulting impact on network organization.