Multimotor cargo navigation in microtubule networks with various mesh sizes.

The kinesin superfamily of motor proteins is a major driver of anterograde transport of vesicles and organelles within eukaryotic cells via microtubules. Numerous studies have elucidated the step size, velocities, forces, and navigation ability of kinesins both in reconstituted systems and in live cells. Outside of cells, the kinesin-based transport is physically regulated and can be controlled by obstacles or defects in the path or the interaction between several motors on the same cargo. To explore the physical control parameters on kinesin-driven transport, we created increasingly dense microtubule networks in vitro to test how kinesin cargoes made from quantum dots with one to 10 kinesin motors attached are able to navigate the network. We find that many motors on the quantum dot increase the distance walked by a factor of 2, association time increased by a factor of 4 to 5, and the average speed by a factor of 2. We quantified the tortuosity and the trajectory persistence length and found the persistence length increased by a factor of 5 to 8 when multiple motors are on the cargo. We also find that these transport parameters depend linearly on the mesh size of the dense network for cargoes with multiple motors. Thus, both motor number and network density are physical aspects that regulate where cargoes traverse in space and time.