Cargo Trapping on 1D Microtubule Arrays: An Effective Landscape for Active Transport

Cytoskeletal networks are crucial for vesicular transport and distribution in highly extended neuronal projections. In proximal mammalian dendrites, short microtubules are distributed in parallel, unpolarized arrays, an arrangement thought to enable broad scattering of processively moving cargos.

Through mean-field and agent-based simulations, we show that unidirectional cargos moving along one-dimensional microtubule arrays are highly likely to cluster around traps that emerge from convergently aligned microtubules.The locations and depths of traps are determined by the kinetic parameters of transport and the spatial organization of the microtubules. A spatiotemporal propagator for cargos that switch between diffusive and processive motion is leveraged to develop an effective field theory in the rapid-switching regime, defining the transition rates between neighboring traps. Despite the active nature of this transport system, we show that the cargo dynamics can be mapped to motion along an effective energy landscape, closely connecting transition rates and the steady-state cargo distribution.

Our results shed light on the interplay between microtubule architecture and intracellular cargo distribution. Furthermore, we highlight how a disordered active transport system can be mapped to an effectively equilibrium behavior on a one-dimensional landscape.