The small GTPases Rab are key regulators of intracellular membrane trafficking, from the formation of transport vesicles to their fusion with membranes (PubMed:20163571, PubMed:21808068). 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:18448665, PubMed:20163571, PubMed:21808068). RAB33B acts, in coordination with RAB6A, to regulate intra-Golgi retrograde trafficking (PubMed:20163571). Participates in autophagosome formation by recruiting the ATG12-ATG5-ATG16L1 complex to phagophores, probably in a nucleotide-independent manner (PubMed:18448665, PubMed:32960676). {ECO:0000269|PubMed:18448665, ECO:0000269|PubMed:20163571, ECO:0000269|PubMed:21808068, ECO:0000269|PubMed:32960676}. This is the function of ENSG00000172007 (RAB33B, RAB33B, member RAS oncogene family).