Actin–Fascin Bundle Formation Under Pressure

Abstract

Studies of the dependence of fascin:actin bundle formation on thermodynamic properties are important for understanding cell processes such as migration and differentiation. We report a novel approach utilizing an expanded equilibrium polymerization Flory–Huggins type model to model fascin:actin bundle formation under thermodynamic pressure. A free energy expression that considers both polymer solution physics and both the deactivation of fascin and propagation of fascin:actin bundles was derived for this system. Using this free energy expression, we report the composition’s dependency on pressure while varying: fascin to actin molar ratios [1,3, and 6], initial F-actin concentration [9.52 × 10−9–5.7 × 10−8 mM], specific volume, and K deact. Bundle formation was shown to increase as a function of pressure and to be limited by F-actin. Furthermore, our model was able to quantitatively predict an optimal size parameter for the deactivated fascin molecule (s F = 4645) and for the deactivation equilibrium constant (K deact = 2.66 × 108). These results present a novel approach to study fascin cross-linking of actin bundles and provide avenues for future experiments to develop a more comprehensive understanding of cell–matrix interactions.