Auxin-inducible degradation of UNC-116 in C. elegans inhibits bidirectional dense core vesicle transport and worm locomotion on different timescales

The microtubule motor kinesin-1 is vital in neurons, with mutations being associated with neurological diseases. Deletion of the Caenorhabditis elegans kinesin-1 gene unc-116 is lethal, and viable mutants are uncoordinated. Here, we perform auxin-mediated degradation of the UNC-116 protein and monitor effects on worm locomotion and dense core vesicle (DCV) transport. UNC-116 is degraded within 1-3 hours of auxin treatment. Impaired swimming/thrashing and crawling are detected after 6-14 hours, depending on organismal age, and degradation of UNC-116 in neurons alone disrupts locomotion. Effects on DCV transport are observed sooner, with 4 hours of degradation strongly inhibiting both anterograde and retrograde movement. This motility recovers when worms are transferred to auxin-free plates for 24 hours, even though protein level recovery is incomplete. Rescue from a 10-hour auxin treatment completely restores crawling speed, but although swimming is initially unaffected, it becomes strongly inhibited during the rescue period, suggesting that UNC-116 has distinct roles in these locomotive gaits. Overall, by bypassing early developmental UNC-116 functions, we reveal that UNC-116 is essential for bidirectional DCV transport and crucial for worm locomotion.