Lateral diffusion of receptor-ligand bonds in membrane adhesion zones: Effect of thermal membrane roughness

TL;DR

This study models how thermal membrane fluctuations, along with bond size, slow down the lateral diffusion of receptor-ligand bonds in cell adhesion zones, highlighting the significant impact of membrane shape fluctuations.

Contribution

It introduces a model incorporating thermal membrane roughness to explain the reduced diffusion of receptor-ligand bonds, extending previous assumptions focused solely on bond size.

Findings

Membrane fluctuations reduce bond diffusion constant by nearly a factor of 2.

Thermal shape fluctuations significantly influence receptor-ligand mobility.

Bond size alone does not account for the observed diffusion slowdown.

Abstract

The adhesion of cells is mediated by membrane receptors that bind to complementary ligands in apposing cell membranes. It is generally assumed that the lateral diffusion of mobile receptor-ligand bonds in membrane-membrane adhesion zones is slower than the diffusion of unbound receptors and ligands. We find that this slowing down is not only caused by the larger size of the bound receptor-ligand complexes, but also by thermal fluctuations of the membrane shape. We model two adhering membranes as elastic sheets pinned together by receptor-ligand bonds and study the diffusion of the bonds using Monte Carlo simulations. In our model, the fluctuations reduce the bond diffusion constant in planar membranes by a factor close to 2 in the biologically relevant regime of small bond concentrations.