Tunable Intracellular Transport on Converging Microtubule Morphologies with Professor Oleg Kogan from Queens College, CUNY

Cargo inside cells is transported by molecular motors that move ballistically on cytoskeleton, interspersed with diffusive episodes when motor-cargo complexes detach from the cytoskeleton.  A common type of cytoskeletal morphology involves multiple converging microtubules with their minus ends collected at the microtubule organizing center (MTOC) in the interior of the cell.  This arrangement enables MTOC to serve as a trap, enabling accumulation of cargo.  The general principles governing dynamics and tunability of transport, as well as the trapping ability of MTOC is not fully understood.  To address this, we develop a one-dimensional model that includes advective transport towards an attractor (such as the MTOC), and diffusive transport that allows particles to reach absorbing boundaries (such as cellular membranes).  We show that in some parameter regimes, the mean first passage time (MFPT) to reach the boundaries can experience a dramatic growth in magnitude – transitioning from a low to high MFPT regime over a window of cargo attachment-detachment rates that is close to in vivo values.  We also find that when the attractor is placed asymmetrically, increasing the attachment or detachment rate can result lowering of the MFPT – thus producing in optimal dispersal away from the MTOC.  Finally, we describe a regime of rare events where the MFPT scales exponentially with advective velocity towards the attractor and the escape location becomes exponentially sensitive to the attractor positioning.   Overall, we identify parameter regimes in which the MTOC serves to sequester cargo, and regimes in which it allows for easy dispersal of cargo throughout the cell.