STAGES OF REGULATED EXOCYTOSIS

Despite its unique features of spatial organization, Ca2+ regulation a nd speed, neurotransmitter secretion is a paradigm for studies of memb rane fusion because it shares homologous proteins and common mechanism s with constitutive exocytosis in all eukaryotic cells. Recent advance s have expanded knowledge of the number of gene products required for neurosecretion, and a current major challenge is to determine their me chanisms of action and the stages at which they function in the multis tep exocytic pathway. This review discusses progress in this direction from in vivo and in vitro studies that have characterized roles for s pecific proteins in post-docking steps proximal to membrane fusion.