Cell Cytoskeleton Dynamics: Mechano-Sensing Properties

Abstract

`The actin cytoskeleton network is the dominant structure of eukaryotic cells. It is highly
dynamic and plays a central role in a wide range of mechanical and biological functions.
Cytoskeleton is composed mainly of actin filaments (F-actin) resulting from the self-assembly
of monomeric actin (G-actin) and cross-linked by actin cross-linking proteins (ACPs) whose
nature and concentration determine the morphological and rheological properties of the
network. These actin filaments are reversibly coupled to membrane proteins (critical to the
response of cells to external stress) and in conjunction with motor proteins from the myosin
family, are able to generate contractile force during cell migration. Knowledge of actin
cytoskeleton and its rheological properties is therefore indispensable for understanding the
underlying mechanics and various biological processes of cells. Here, we present a 3-D
Brownian dynamics (BD) computational model in which actin monomers polymerize and
become cross-linked by two types of ACPs, forming either parallel filament bundles or
orthogonal networks. Also, the active and dynamic behaviour of motors is included. In this
simulation, actin monomers, filaments, ACPs, and motors experience thermal motion and
interact with each other with binding probabilities and defined potentials. Displacements are
governed by the Langevin equation, and positions of all elements are updated using the Euler
integration scheme.
In this first part of the work, the mechano-sensing properties of active networks are investigated
by evaluating stress and strain rate in response to different substrate stiffness.