The kinases male germ cell-associated kinase and cell cycle-related kinase regulate kinesin-2 motility in Caenorhabditis elegans neuronal cilia

Kinesin-2 motors power anterograde intraflagellar transport (IFT), a highly ordered process that assembles and maintains cilia. However, it remains elusive how kinesin-2 motors are regulated in vivo. Here, we performed forward genetic screens to isolate suppressors that rescue the ciliary defects of OSM-3-kinesin (homolog of mammalian homodimeric kinesin-2 KIF17) mutants in Caenorhabditis elegans. We identified the C. elegansdyf-5 and dyf-18, which encode the homologs of mammalian male germ cell-associated kinase and cell cycle-related kinase, respectively. Using time-lapse fluorescence microscopy, we show that DYF-5 and DYF-18 are IFT cargo molecules and are enriched at the distal segments of sensory cilia. Mutations of dyf-5 and dyf-18 generate elongated cilia and ectopic localization of the heterotrimeric kinesin-2 (kinesin-II) at the ciliary distal segments. Genetic analyses reveal that dyf-5 and dyf-18 are important for stabilizing the interaction between IFT particles and OSM-3-kinesin. Our data suggest that DYF-5 and DYF-18 act in the same pathway to promote handover between kinesin-II and OSM-3 in sensory cilia.