The small GTPases Rab are key regulators of intracellular membrane trafficking, from the formation of transport vesicles to their fusion with membranes. Rabs cycle between an inactive GDP-bound form and an active GTP-bound form that is able to recruit to membranes different sets of downstream effectors directly responsible for vesicle formation, movement, tethering and fusion (PubMed:16086013, PubMed:17562788). Involved in early endocytic trafficking (PubMed:16086013, PubMed:17562788). Required for EEA1 recruitment to early endosomes (PubMed:16086013, PubMed:17562788). Required for EGF and transferrin endocytosis and trafficking through early endosomes (PubMed:16086013, PubMed:17562788). {ECO:0000269|PubMed:16086013, ECO:0000269|PubMed:17562788}. This is the function of Ensembl gene identifier ENSG00000111540 (RAB5B, RAB5B, member RAS oncogene family).