Actin dynamics and the elasticity of cytoskeletal networks

Abstract

Abstract. The structural integrity of a cell depends on its cytoskeleton, which includes an actin network. This network is transient and depends upon the continual polymerization and depolymerization of actin. The degradation of an actin network, and a corresponding reduction in cell stiffness, can indicate the presence of disease. Numerical simulations will be invaluable for understanding the physics of these systems and the correlation between actin dynamics and elasticity. Here we develop a model that is capable of generating actin network structures. In particular, we develop a model of actin dynamics which considers the polymerization, depolymerization, nucleation, severing, and capping of actin filaments. The structures obtained are then fed directly into a mechanical model. This allows us to qualitatively assess the effects of changing various parameters associated with actin dynamics on the elasticity of the material.

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

“…The F-actin filaments are also continuously undergoing polym- erization and depolymerization, leading to an active network structure [15,[22][23][24]. These cross-linkers and the degree of crosslinking also lead to strain stiffening behavior exhibited by the F-actin [13,25]. Microtubules, the second major component of the cytoskeleton network, exhibit hollow cylindrical shapes composed of monomers α and β-tubulin with persistent lengths of 6 mm [13,15].…”

“…They, along with the F-actin, act as the tension-bearing components under deformation and have a rope-like structure consisting of different proteins [12][13]25]. They are more stable compared to F-actin and microtubules and can withstand higher stresses and strains before rupture [25].…”

“…Microtubules, the second major component of the cytoskeleton network, exhibit hollow cylindrical shapes composed of monomers α and β-tubulin with persistent lengths of 6 mm [13,15]. They have higher bending stiffness, are more active in nature than actin filaments, and continuously undergo polymerization and depolymerization [25,26]. The microtubules are known to be the compressive load-bearing component of the network as balanced against the tensed actin and intermediate filaments [27].…”

Energy distribution in disordered elastic networks

“…The first one considers struts as simple strings [21], while in the second the bending stiffness of the struts is also taken into account [2, 8,10,11,[22][23][24][25][26][27]. In both groups it can be distinguished between affine and nonaffine regimes depending on whether the deformation is ideally homogeneous or not, respectively [3,4,8].…”

“…The cytoskeleton is composed of macromolecules (actin filaments, intermediate filaments, and microtubules) forming a disordered network of semifiexible polymers [1] due to both the bending and longitudinal stiffness of the filaments. Many authors have investigated the properties of the cytoskeleton by means of micromechanical models [2][3][4][5][6][7][8][9][10][11]. These are expected to be useful for the understanding, for instance, of mechanotransduction, tissue development, or anomalous behavior of ill cells in comparison with healthy ones [12][13][14].…”