ARL8 effector that promotes the coupling of endolysosomes to dynein-dynactin for retrograde transport along microtubules. Acts by binding both GTP-bound ARL8 and dynein-dynactin. In nonneuronal cells, promotes concentration of endolysosomes in the juxtanuclear area. In hippocampal neurons, drives retrograde transport of endolysosomes from the axon to the soma (PubMed:35314674). Plays a role in the generation of neuronal polarity formation and axon growth (By similarity). Implicated in the formation of a single axon by developing neurons (By similarity). May inhibit the formation of additional axons by inhibition of PI3K in minor neuronal processes (By similarity). Plays a role in the formation of F-actin-enriched protrusive structures at the cell periphery (PubMed:25766321). Plays a role in cytoskeletal organization by regulating the subcellular localization of FSCN1 and DBN1 at axonal growth cones (By similarity). {ECO:0000250|UniProtKB:Q5FVJ0, ECO:0000250|UniProtKB:Q9D394, ECO:0000269|PubMed:25766321, ECO:0000269|PubMed:35314674}. This is the function of ENSG00000018189 (RUFY3, RUN and FYVE domain containing 3).