How cargo driven by kinesin motors can pass efficiently through tau islands on microtubules

Kinesin-1 is a biological molecular motor that can step processively on microtubules toward the plus end to transport cargo in cells. On microtubules tau proteins can assembly into static cohesive envelopes that are also called islands. Upon reaching the tau island boundary, the kinesin-1 motor dissociates rapidly. An interesting but unclear issue is how the cargo can be transported efficiently by kinesin-1 motors to the plus end in the presence of tau islands. Here, the force dependencies of the dynamics of the single kinesin-1 motor in the absence and presence of tau islands are determined theoretically, with which the dynamics of the cargo transport by two kinesin-1 motors connecting to the cargo is studied. The strategy adopted by the kinesin-1 motors to make the cargo pass efficiently through the tau island is explored. Similarly, the cargo transport by two kinesin-3 motors is also studied, showing that the cargo can pass much more efficiently through the tau island. For comparison, the dynamics of the kinesin-1 motor with a large-sized stationary obstacle on the front tubulin is also studied. The theoretical results explain well the conflicting published experimental data showing that after encountering a small-sized obstacle or tau island the kinesin-1 motor can dissociate rapidly whereas after encountering a large-sized obstacle the kinesin-1 motor can pause for a long time.