The function of ENSG00000155961 (RAB39B, RAB39B, member RAS oncogene family) 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 sets of downstream effectors directly responsible for vesicle formation, movement, tethering and fusion (PubMed:27103069). RAB39B is involved in autophagy and may function in autophagosome formation (PubMed:27103069, PubMed:37821429). Binds downstream effector PICK1 to ensure selectively GRIA2 exit from the endoplasmic reticulum to the Golgi and to regulate AMPAR composition at the post-synapses and thus synaptic transmission (By similarity). May regulate the homeostasis of SNCA/alpha-synuclein (By similarity). {ECO:0000250|UniProtKB:Q8BHC1, ECO:0000269|PubMed:27103069, ECO:0000269|PubMed:37821429}.