Microtuble Pair Separation under Kinesin Driving with PRC1 Crosslinker Resistance

The regulation of a passive crosslinking protein in mitotic spindle formation, PRC1, has been previously studied experimentally (Alfieri, Gaska, Forth, Current Biology 2021) via an in vitro gliding assay configuration, with microtubule sliding motion driven by surface-bound kinesin-1. In that work, PRC1 was found to resist microtubule separation by antiparallel pairs via two distinct modes. To explore the possible mechanisms behind these observations, we developed a computational model based on th CyLaKS framework (Fiorenza, Steckhahn, Betterton, European Physical Journal E, 2021), with parameter fits capable of reproducing both resistive modes seen in experiments. In the simulations, we found that the mode with greater slowing of microtubule separation was associated with a substantially smaller separation (20 nm) between the crosslinked microtubules than the mode with slighter slowing (30 nm). The closer separation allows the PRC1 to be more aligned with the microtubules, leading to more than a two-fold increase in the longitudinal force against the microtubule sliding and reduced hopping by PRC1 heads. The microtubule dynamics in the computational simulations were represented by a novel mean field reduction of a stochastic model for the driving by the kinesin molecules under load from the PRC1 force.