Metabolite-mediated reversal of motor hyperactivity restores ciliary function

Hyperactive missense mutations can produce phenotypes that are difficult to predict from sequence alone. Here, we dissect such a discrepancy in Caenorhabditis elegans, where the kinesin mutant osm-3(A340V) shortens sensory cilia despite exhibiting elevated in vitro motility. A forward genetic screen identified osm-7, a hypodermal secreted protein, whose loss restored ciliary architecture by elevating intracellular glycerol over 100-fold. Glycerol supplementation alone recapitulated this rescue, re-establishing intraflagellar transport in neurons and modulating OSM-3(A340V) motility in vitro. Molecular dynamics simulations suggest that A340V restricts neck-helix relaxation, a defect reversed by glycerol-induced conformational tuning. Our study indicates that impairment of neck-helix flexibility leads to kinesin hyperactivity in vitro and motility defects in vivo, and that metabolite-mediated conformational tuning represents a mechanism for reversing such motor defects. A hyperactive kinesin mutation that shortens cilia is rescued by glycerol, which restores motor coordination and ciliary transport through conformational tuning, revealing a mechanism for correcting hyperactivity defects.