Human kinesin-5 KIF11 drives the helical motion of anti-parallel and parallel microtubules around each other

Abstract

During mitosis, motor proteins and microtubule-associated protein organize the spindle apparatus by cross-linking and sliding microtubules. Kinesin-5 plays a vital role in spindle formation and maintenance, potentially inducing twist in the spindle fibers. The off-axis power stroke of kinesin-5 could generate this twist, but its implications in microtubule organization remain unclear. Here, we investigate 3D microtubule-microtubule sliding mediated by the human kinesin-5, KIF11, and found that the motor caused right-handed rotation of anti-parallel microtubules around each other. The effective sidestepping probability of KIF11 increased with reduced ATP concentration, indicating that forward and sideways stepping of the motor are not strictly coupled. Further, the microtubule-microtubule distance (motor extension) during sliding decreased with increasing sliding velocity. Intriguingly, parallel microtubules cross-linked by KIF11 orbit without forward motion, with nearly full extension. Altering the length of the neck linker increased the forward velocity and pitch of microtubules in anti-parallel overlaps. Taken together, we suggest that helical motion and orbiting of microtubules, driven by KIF11, enable flexible and context-dependent filament organization, as well as torque regulation within the mitotic spindle.

Torques within and outside the human spindle balance twist at anaphase

“…The torques produced by kinesins that crosslink and slide microtubule pairs are sufficiently strong to twist and coil two microtubules around each other (Mitra et al, 2020). The plus-end-directed yeast kinesin-8 Kip3 (Bormuth et al, 2012;Mitra et al, 2018) and Caenorhabditis elegans kinesin-6 ZEN-4 (Maruyama et al, 2021) both have a left-handed stepping bias, as does the kinesin-5 Eg5 (Yajima et al, 2008), although this motor's directional preference has recently been called into question (Meißner et al, 2023). By contrast, the minus-end-directed kinesin-14 Ncd (Mitra et al, 2020;Nitzsche et al, 2016;Walker et al, 1990) has a right-handed stepping bias, and the minus-end-directed cytoplasmic dynein also has a weak righthanded bias (Can et al, 2014;Elshenawy et al, 2019).…”