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 use auxin-mediated degradation to deplete UNC-116 protein at different developmental stages and monitor the effects on cargo transport and locomotion. UNC-116 is substantially degraded within 1 hour of auxin treatment, by which time bidirectional dense core vesicle (DCV) motility is affected. After 4 hours, dynein-driven DCV movement is lost and only limited plus-end-directed DCV motility remains, likely driven by kinesin-3 (UNC-104). DCV movement recovers substantially after rescue from auxin for 24 hours. There is a time-lag between loss of protein and effects on locomotion, as crawling and swimming/thrashing is unaffected until 6-14 hours on auxin. By 18-24 hours, animals are as uncoordinated as the unc-116(rh24sb79) mutant. Notably, degradation of UNC-116 in neurons alone inhibits crawling and swimming, revealing the importance of neuronal kinesin-1 for locomotion. Overall, by bypassing early developmental UNC-116 functions, we reveal that UNC-116 is essential for bidirectional DCV transport and crucial for locomotion.