Curvature instability of an active gel growing on a wavy membrane

TL;DR

This paper presents a theoretical model showing how curvature-sensitive actin nucleators can destabilize a membrane, leading to spontaneous protrusions, unlike uniform actin polymerization which stabilizes the membrane.

Contribution

It introduces a coupled model of membrane mechanics and actin dynamics that explains how curvature-sensitive proteins induce membrane instability.

Findings

Curvature-sensitive actin nucleators can cause membrane instability.

Uniform actin polymerization stabilizes membrane deformation.

Spontaneous membrane protrusions can arise from actin-membrane interactions.

Abstract

Cell shape changes are largely controlled by the actin cytoskeleton, a dynamic filament network beneath the plasma membrane. Several cell types can form extended free-standing protrusions not supported by an extracellular substrate or matrix, and regulated by proteins that modulate cytoskeletal dynamics in a way sensitive to the curvature of the cell membrane. We develop a theoretical model for the mechanics of a free-standing viscous actin network growing on a corrugated membrane. The model couples the dynamics of the viscous active gel with membrane deformation and the recruitment of curvature-sensitive actin nucleators. We show that an actin layer polymerising uniformly on the membrane always exerts a stabilising effect that reduces membrane deformation. However, curvature-sensitive actin nucleator proteins can render the membrane linearly unstable, depending on the interplay between membrane and actin dynamics, giving rise to spontaneous membrane deformation which could initiate extended free-standing cellular protrusion.