Impact of cell-sized confinement on particle transport within a motor-driven cytoskeletal network.

Abstract

Intracellular transport of small particles and macromolecules is affected by the degree of crowding, confinement, and motor-driven activity within the cell. In vitro studies have examined how transport dynamics depend on each of these factors. But studies have primarily focused on these factors in isolation. Previously, we showed how crowding and confinement synergistically couple to slow the diffusion of DNA molecules. Here, we explore the combined effects of crowding by a composite network of actin and microtubule filaments, activity driven by molecular motors, and confinement by a lipid membrane to cell-sized volumes. We quantify transport of tracer particles within this tunable in vitro environment using differential dynamic microscopy (DDM) and single particle tracking. We simultaneously measure the dynamics and spatial organization of the composite network to link transport dynamics to network properties. To what degree tracers exhibit subdiffusive motion due to caging within the network mesh or superdiffusive motion due to motor activity depends on network composition, motor concentration, and confinement size.