A model of sliding and stalling in microtubule bundles

Microtubules, motor proteins, and crosslinkers self-assemble a variety of cytoskeletal networks within the cell. Minimal systems of two antiparallel microtubules, kinesin-4 motors, and PRC1 crosslinkers reconstitute controlled sliding and stalling, leading to stable antiparallel overlaps like those seen in the mitotic spindle. Experiments show that the final overlap length and initial sliding velocity are both linearly proportional to the two microtubules’ initial overlap length. However, the mechanisms behind this length-sensing are not fully understood. We develop a model to show how crosslinker-motor interactions produce these regulated microtubule overlaps. We observe sliding even when motors exert no direct forces on neighboring microtubules due to purely steric interactions. Direct binding interactions between crosslinkers and motors can significantly increase the lifetime of the final overlap.