Mechanical stress induced by the polymerisation of an active gel near a surface

TL;DR

This paper models how actin polymerization and flow generate mechanical stresses on cell membranes, analyzing conditions for membrane instability through analytical and numerical methods.

Contribution

It introduces a hydrodynamic model of active gel polymerization near membranes, revealing how actin dynamics influence membrane stress and stability.

Findings

Analytical solutions map stress as functions of key parameters.

Identifies conditions for membrane linear instability due to actin polymerization.

Finite element methods complement analytical results in complex regimes.

Abstract

Actin flow in the cortical cytoskeleton underneath the cell membrane generates mechanical stresses that shape the cell surface. We study this mechanism using a hydrodynamic model of a compressible active gel polymerizing at the membrane and undergoing turnover. We determine how actin flow, density relaxation and friction of actin with the membrane generate stress on a corrugated membrane at the linear order in deformation. Analytical solutions in limiting regimes, combined with finite element methods in the general case, provide a map of normal and tangential stresses as functions of compressibility, interfacial friction and actin turnover, and determine the conditions under which actin polymerization can render the membrane linearly unstable. The non-linear regime is also briefly discussed.