Using a form-finding model to analyze the effect of actin bundles on the stiffness of a cytoskeleton network

Abstract

Networks of actin filaments and bundles are ubiquitous in cellular cytoskeletons, but the elasticity of the network is not well understood. In this paper, a computational model based on form-finding analysis is proposed to investigate the stiffness of cytoskeleton networks consisting of actin filaments and bundles. The model shows that networks with parallel bundles aligned in the stretching direction are stiffer than those with randomly distributed bundles. The results provide a mechanical explanation for the experimental observation that cells primarily create parallel rather than disordered bundles during cell adhesion and cell motion. The effect of filament undulations on network stiffness is explored briefly. The results show that undulations can soften the network by increasing the bending-dominated deformations in filaments and bundles. Finally, we find that the effect of the relative density of bundles depends on their orientation. Increasing the density of randomly distributed bundles has no effect on the stiffness of cells, but softens the cytoskeleton network. In contrast, the stiffness of networks of parallel bundles first increases, then reduces as the relative density of bundles increases. The stiffest network is a mixture of actin filaments and bundles.

Dissociation Mechanisms of G-actin Subunits Govern Deformation Response of Actin Filament

“…Actin filament bundles and networks are cytoskeletal high-order structures that consist of actin filaments binding with various actin-binding proteins. Hence, their deformation response mostly depends on the size, orientation, and arrangement of the constituents . However, since these fibrous structures mainly consist of actin filaments, their response to the applied force is strongly influenced by F-actin mechanics.…”

“…Hence, their deformation response mostly depends on the size, orientation, and arrangement of the constituents. 67 However, since these fibrous structures mainly consist of actin filaments, their response to the applied force is strongly influenced by F-actin mechanics. Therefore, the deformation mechanics of single actin filament presented here is crucial to understand their high-order/bulk structural behavior.…”

Modeling and simulation of biopolymer networks: Classification of the cytoskeleton models according to multiple scales

“…A recent study, which proposed a form-finding model (a 2D model was used earlier [107]), found that cells create parallel rather than disordered bundles of actin filaments during cell motion and cell adhesion. The parallel bundles align in the stretched direction, increasing the stiffness of the cell [108].…”