On the Cooperativity of Microtubule Motors during Cargo Transport and Directional Filament Sliding

Abstract

The stepping behavior of single microtubule-based motor proteins has been studied in great detail. However, in cells, these motors often do not work alone but rather function in groups when they transport cellular cargo or slide microtubules against each other. Until now, the cooperative interactions between motors in such groups are poorly understood. We will report on in vitro experiments specifically designed to study the activity of coupled motors. With respect to cargo transport by rigidly-coupled kinesin-1 motors, we investigated (i) the step-size distribution of small groups of motors, (ii) the motility behavior in the presence of obstacles, and (iii) the tug-of-war between antagonistically acting force generators. With respect to the activity of diffusively-coupled kinesin-14 motors during cell division, we studied (i) the directional sliding of microtubules, (ii) the adaptive braking by passive crosslinkers, and (iii) the generation of torsional motion. All observed behaviors result from the collaborative action of multiple motors - none of the described properties is found in the activity of single motors.