Motility states in bidirectional cargo transport

TL;DR

This paper investigates whether bidirectional cargo transport in cells results from stochastic motor activity or requires coordination, by extending a mean-field model to explicitly include motor positions and interactions.

Contribution

It introduces a non-mean field model accounting for individual motor positions and examines motor-motor activation, clarifying conditions under which high motility states occur.

Findings

High motility states disappear in the non-mean field model.

Strong motor-motor activation can recover mean-field results.

High number of motors and activation are key for coordinated transport.

Abstract

Intracellular cargos which are transported by molecular motors move stochastically along cytoskeleton filaments. In particular for bidirectionally transported cargos it is an open question whether the characteristics of their motion can result from pure stochastic fluctuations or whether some coordination of the motors is needed. The results of a mean-field model of cargo-motors dynamics, which was proposed by M\"uller et al.[1] suggest the existence of high motility states which would result from a stochastic tug-of-war. Here we analyze a non-mean field extension of their model, that takes explicitly the position of each motor into account. We find that high motility states then disappear. We consider also a mutual motor-motor activation, as an explicit mechanism of motor coordination. We show that the results of the mean-field model are recovered only in case of a strong motor-motor activation in the limit of a high number of motors.