RAB3B, Member RAS Oncogene Family (RAB3B)

The mammalian RAB proteins show striking similarities to the S. cerevisiae YPT1 and SEC4 proteins, Ras-related GTP-binding proteins involved in the regulation of secretion.RAB3B protein shares 78% identity with RAB3A.

After endocytosis, the PIGR-dIgA complex traverses several endosomal compartments and is exocytosed at the apical plasma membrane Rab3b localized to vesicular structures containing Pigr in canine kidney cells and that GTP-bound Rab3b interacted directly with the cytoplasmic domain of Pigr. Binding of dIgA to Pigr dissociated Rab3b, but a constitutively active Rab3b mutant maintained its interaction with Pigr in dIgA-treated cells. Furthermore, GTP-locked Rab3b inhibited dIgA-stimulated transcytosis.