Activating adapter involved in cargo sorting from early/recycling endosomes. Regulates retrieval of proteins from endosomes to the trans-Golgi network through interaction with the dynein-dynactin complex (PubMed:36282215). Dual effector of RAB4B and RAB14, mediates a cooperative interaction allowing endosomal tethering and fusion (PubMed:20534812). Binds phospholipid vesicles containing phosphatidylinositol 3-phosphate and participates in early endosomal trafficking (PubMed:14617813). In oocytes, self-assembles to form a protein matrix which hold together endolysosomes, autophagosomes and proteasomes and generate non-membrane-bound compartments called endo- lysosomal vesicular assemblies (ELVAs). In immature oocytes, ELVAs sequester ubiquitinated protein aggregates and degrade them upon oocyte maturation (By similarity). {ECO:0000250|UniProtKB:Q8BIJ7, ECO:0000269|PubMed:14617813, ECO:0000269|PubMed:20534812, ECO:0000269|PubMed:36282215}. This is the function of RUFY1 (RUN and FYVE domain containing 1, Ensembl gene identifier ENSG00000176783).