A Syd and RUFY dynein adaptor complex mediates axonal circulation of dense core vesicles

Neuropeptide-containing dense core vesicles (DCVs) generated in neuronal somata are circulated in axons to supply distal release sites, depending on kinesin-1, kinesin-3, and dynein, but how the motors are recruited remains unclear. Here we use proximity proteomics in the living Drosophila nervous system to identify the protein complex responsible for recruitment of kinesin-1 and dynein on DCVs. We find that the dynein and kinesin-1 adaptor Sunday driver (Syd/dJIP3/4) interact with the DCV-located GTPase Rab2 and also bind the Arl8 effector RUFY. Disrupting Rab2, Syd, RUFY, the Arl8 activator BORC, or dynein impedes retrograde DCV flux and induces axonal accumulation of immobile DCVs. Our data suggest that dynein is recruited and activated by a Syd/RUFY complex anchored to DCVs by Rab2 and Arl8. Rab2 loss but not disruption of Syd, RUFY, or dynein causes missorting of DCV membrane proteins into vesicle aggregates in motor neuron somata, suggesting that Rab2 employs separate effectors in DCV biogenesis and motility.