JIP3 regulates bi-directional organelle transport in neurons through its interaction with dynein and kinesin-1

The conserved MAP kinase and motor scaffold JIP3 prevents excess lysosome accumulation in axons of vertebrates and invertebrates. Whether and how JIP39s interaction with dynein and kinesin-1 contributes to this critical organelle clearance function is unclear. Using purified recombinant human proteins, we show that dynein light intermediate chain (DLIC) binds to the N-terminal RH1 domain of JIP3, its paralog JIP4, and the lysosomal adaptor RILP. A point mutation in a hydrophobic pocket of the RH1 domain, previously shown to abrogate RILPL2 binding to myosin Va, abrogates the binding of JIP3/4 and RILP to DLIC without perturbing the interaction between the JIP3 RH1 domain and kinesin heavy chain. Characterization of this separation-of-function mutation in Caenorhabditis elegans shows that JIP3-bound dynein is required for organelle clearance in the anterior process of touch receptor neurons. Unlike JIP3 null mutants, JIP3 that cannot bind DLIC causes prominent accumulation of endo-lysosomal organelles at the neurite tip, which is rescued by a disease-associated point mutation in JIP39s leucine zipper that abrogates kinesin light chain binding. These results highlight that RH1 domains are interaction hubs for cytoskeletal motors and suggest that JIP3-bound dynein and kinesin-1 participate in bi-directional organelle transport.