Tuning the depolymerization and restructuring of actin networks via thymosin and cofilin*

Actin is a key component of the cytoskeleton responsible for vital functions ranging from motility to structural support of cells. This multifunctionality is due, in large part, to the dynamic polymerization of actin monomers into semiflexible filaments, the depolymerization of filaments into monomers, and the changing lengths of filaments. Polymerization drives cell migration, while depolymerization and turnover mediate cell growth and restructuring. Thymosin-β4 and cofilin are two key actin-binding proteins that promote depolymerization by sequestering actin monomers or severing filaments, respectively.  Here, we incorporate thymosin and cofilin into entangled actin networks and visualize the subsequent in situ depolymerization and restructuring via confocal microscopy. We use fourier image analysis techniques to characterize the time-varying dynamics and restructuring of the networks and map their dependence on the concentrations of actin, cofilin and thymosin. Our results not only shed light on cellular processes that rely on actin polymerization and depolymerization, but also may inspire the engineering of non-equilibrium materials that leverage depolymerization as a route to dynamically transition from gel-like to fluid-like states.