Strength and stability of active ligand-receptor bonds: a microtubule attached to a wall by molecular motor tethers

TL;DR

This study models the complex dynamics of microtubule attachment to cell cortex via motor proteins, revealing how force influences bond stability and lifetime, with implications for understanding cellular mechanics.

Contribution

It introduces a stochastic kinetic model capturing the interplay of polymerization, motor activity, and force-dependent unbinding in microtubule attachments.

Findings

Attachment behaves as a catch-bond or slip-bond depending on parameters.

Force affects the lifetime and stability of the microtubule-cortex connection.

Analytical approximations align with simulation results.

Abstract

We develop a stochastic kinetic model of a pre-formed attachment of a mictrotuble (MT) with a cell cortex, in which the MT is tethered to the cell by a group of active motor proteins. Such an attachment is a particularly unique case of ligand-receptor bonds: The MT ligand changes its length (and thus binding sites) with time by polymerization-depolymerization kinetics, while multiple motor receptors tend to walk actively along the MT length. These processes, combined with force-mediated unbinding of the motors, result in an elaborate behavior of the MT connection to the cell cortex. We present results for the strength and lifetime of the system through the well-established force-clamp and force-ramp protocols when external tension is applied to the MT. The simulation results reveal that the MT-cell attachment behaves as a catch-bond or slip-bond depending on system parameters. We provide analytical approximations of the lifetime and discuss implications of our results on in-vitro experiments.