The function of RAB11B (RAB11B, member RAS oncogene family, ENSG00000185236) is as follows. 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 set of downstream effectors directly responsible for vesicle formation, movement, tethering and fusion (PubMed:14627637, PubMed:19029296, PubMed:19244346, PubMed:20717956, PubMed:21248079, PubMed:22129970, PubMed:26032412). RAB11B plays a role in endocytic recycling, regulating apical recycling of several transmembrane proteins including cystic fibrosis transmembrane conductance regulator/CFTR, epithelial sodium channel/ENaC, potassium voltage-gated channel, and voltage-dependent L-type calcium channel. May also regulate constitutive and regulated secretion, like insulin granule exocytosis. Required for melanosome transport and release from melanocytes. Also regulates V-ATPase intracellular transport in response to extracellular acidosis (PubMed:14627637, PubMed:19029296, PubMed:19244346, PubMed:20717956, PubMed:21248079, PubMed:22129970). Promotes Rabin8/RAB3IP preciliary vesicular trafficking to mother centriole by forming a ciliary targeting complex containing Rab11, ASAP1, Rabin8/RAB3IP, RAB11FIP3 and ARF4, thereby regulating ciliogenesis initiation (PubMed:25673879). On the contrary, upon LPAR1 receptor signaling pathway activation, interaction with phosphorylated WDR44 prevents Rab11-RAB3IP-RAB11FIP3 complex formation and cilia growth (PubMed:31204173). Also interacts with RABL3 to promote ciliary vesicle formation (PubMed:36052645). {ECO:0000269|PubMed:14627637, ECO:0000269|PubMed:19029296, ECO:0000269|PubMed:19244346, ECO:0000269|PubMed:20717956, ECO:0000269|PubMed:21248079, ECO:0000269|PubMed:22129970, ECO:0000269|PubMed:25673879, ECO:0000269|PubMed:26032412, ECO:0000269|PubMed:31204173, ECO:0000269|PubMed:36052645}.