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.Comment: 14 pages, 13 figure
