Active and Passive Transport of Cargo in a Corrugated Channel: A Lattice Model Study

TL;DR

This study models motor-driven cargo transport in confined cellular environments, revealing how confinement influences transport efficiency depending on binding kinetics and velocity, with implications for understanding intracellular cargo movement.

Contribution

It introduces a minimal two-state lattice model combining active and passive transport, incorporating entropic barriers and confinement effects, validated through simulations and analytical methods.

Findings

Confinement reduces effective diffusivity and velocity generally.

Enhanced binding rates can increase average cargo velocity.

Transport properties depend critically on binding kinetics and bound velocity.

Abstract

Inside cells, cargos such as vesicles and organelles are transported by molecular motors to their correct locations via active motion on cytoskeletal tracks and passive, Brownian diffusion. During the transportation of cargos, motor-cargo complexes (MCC) navigate the confining and crowded environment of the cytoskeletal network and other macromolecules. Motivated by this, we study a minimal two-state model of motor-driven cargo transport in confinement and predict transport properties that can be tested in experiments. We assume that the motion of the MCC is directly affected by the entropic barrier due to confinement if it is in the passive, unbound state, but not in the active, bound state where it moves with a constant bound velocity. We construct a lattice model based on a Fokker Planck description of the two-state system, study it using a kinetic Monte Carlo method and compare our numerical results with analytical expressions for a mean field limit. We find that the effect of confinement strongly depends on the bound velocity and the binding kinetics of the MCC. Confinement effectively reduces the effective diffusivity and average velocity, except when it results in an enhanced average binding rate and thereby leads to a larger average velocity than when unconfined.