Single Molecule Imaging In Live Cells Reveals Selection Of Microtubule Tracks By Kinesin Motors

Abstract

Long-distance transport of vesicular and protein cargoes in cells requires microtubules and their associated molecular motors. The basic mechanistic principles of tubulin polymerization and motor motility have been discovered from in vitro studies. The challenge is to translate the mechanics of these individual parts into the workings of ensembles of molecules inside cells. By imaging single kinesin motors in live cells, we reveal new properties about the interactions of motors and microtubules. We show that single Kinesin-1 motors move preferentially on a subset of microtubules available in COS cells. Preferential motility does not occur on dynamic microtubules marked by end binding protein 3 (EB3), which decorates the plus tips of growing microtubules. Rather, retrospective immunofluorescence staining demonstrates that single Kinesin-1 motors utilize stable microtubules marked by specific post-translational modifications. Preferential motility on stable microtubules is not a general property of kinesin motors as neither the kinesin-2 family member KIF17 nor the kinesin-3 family member KIF1A moved on a subset of microtubules. Selective transport enables Kinesin-1 to carry vesicles containing the marker protein vesicular stomatitis virus (VSV)-G along stable microtubules in COS cells whereas KIF17 transport of vesicles containing the voltage-activated potassium channel Kv1.5 occurs along both stable and dynamic microtubules in HL-1 atrial myocytes. These results support the hypothesis that a tubulin code of post-translational modifications can direct kinesin transport events in cells.