Rab3A, Rab3B, Rab3C, and Rab3D constitute a family of GTP-binding proteins that are
implicated in regulated exocytosis. Various localizations and distinct functions have been
proposed for different and occasionally even for the same Rab3 protein. This is exemplified
by studies demonstrating that deletion of Rab3A in knock-out mice results in dysregulation of
the final stages of exocytosis, whereas overexpression of Rab3A in neuroendocrine cells
causes nearly complete inhibition of Ca 2+-triggered exocytosis. We have now examined …