Dynein catch bond as a mediator of codependent bidirectional cellular transport
Intracellular bidirectional transport of cargo on microtubule filaments is achieved by the collective action of oppositely directed dynein and kinesin motors. Experiments have found that in certain cases, inhibiting the activity of one type of motor results in an overall decline in the motility of the cellular cargo in both directions. This counter-intuitive observation, referred to as {\em paradox of codependence} is inconsistent with the existing paradigm of a mechanistic tug-of-war between oppositely directed motors. Unlike kinesin, dynein motors exhibit catchbonding, wherein the unbinding rates of these motors decrease with increasing force on them. Incorporating this catchbonding behavior of dynein in a theoretical model, we show that the functional divergence of the two motors species manifests itself as an internal regulatory mechanism, and leads to codependent transport behaviour in biologically relevant regimes. Using analytical methods and stochastic simulations, we analyse the processivity characteristics and probability distribution of run times and pause times of transported cellular cargoes. We show that catchbonding can drastically alter the transport characteristics and also provide a plausible resolution of the paradox of codependence.