Evolving roles and dynamics for catch and slip bonds during adhesion cluster maturation

TL;DR

This study uses numerical simulations to explore how the combination of slip and catch bonds in focal adhesions enhances their mechanical stability and mechanosensory functions, revealing load-dependent integrin behaviors.

Contribution

It demonstrates how mixed slip and catch bonds improve focal adhesion stability and load response, a novel insight into adhesion cluster dynamics.

Findings

Mixing slip and catch bonds enhances mechanical integrity.

Load-dependent integrin diffusivity affects adhesion behavior.

Catch bonds alone lack low-force stability.

Abstract

Focal adhesions are the loci of cellular adhesion to the extracellular matrix. At these sites, various integrins forge connections between the intracellular cytoskeleton and the outside world: large patches of multiple types of integrins together grip hold of collagen, fibronectin and other extracellular matrix components. The mixture of integrins composing the FA will, in general, contain both slip bond integrins and catch bond integrins---bonds whose lifetime increases with applied load and bonds for whom it decreases when forced. Prior work suggests that catch bonds are essential for proper FA stability and mechanosensory functionality. In the present work, we investigate, numerically, the interplay between the two distinct types of bonds and ask how the presence, in the same FA cluster, of slip bonds augments the behavior of the catch bonds. We show, that mixing the two components m low-force mechanical integrity, lacking in purely catch systems, while preserving the potential to strengthen the FA bond by force as well as the mechanosensory qualities of the catch bonds. We investigate the spatial distribution in mixed-integrin FA's and show that the differential response to loading leads, via an excluded volume interaction, to a dependence of the individual integrin diffusivities on the applied load, an effect that has been reported in experiments.