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Vacuolar sequential exocytosis of large dense‐core vesicles in adrenal medulla
Author(s) -
Kishimoto Takuya,
Kimura Ryoichi,
Liu TingTing,
Nemoto Tomomi,
Takahashi Noriko,
Kasai Haruo
Publication year - 2006
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1038/sj.emboj.7600983
Subject(s) - exocytosis , vesicle , secretory vesicle , vesicle fusion , biology , microbiology and biotechnology , lipid bilayer fusion , cytoplasm , adrenal medulla , snap25 , biophysics , membrane , biochemistry , synaptic vesicle , catecholamine , neuroscience
Individual exocytic events in intact adrenal medulla were visualized by two‐photon extracellular polar‐tracer imaging. Exocytosis of chromaffin vesicles often occurred in a sequential manner, involving first vesicles located at the cell periphery and then those present deeper within the cytoplasm. Sequential exocytosis occurred preferentially at regions of the plasma membrane facing the intercellular space. The compound vesicles swelled to more than five times their original volume and formed vacuolar exocytic lumens as a result of expansion of intravesicular gels and their confinement within the lumen by the fusion pore and the narrow intercellular space. Such luminal swelling greatly promoted sequential exocytosis. The SNARE protein SNAP25 rapidly migrated from the plasma membrane to the membrane of fused vesicles. These data indicate that vesicles present deeper within the cytoplasm can be fusion ready like those at the cell periphery, and that swelling of exocytic lumens promotes assembly of the fusion machinery. We suggest the existence of two molecular configurations for fusion‐ready states in Ca 2+ ‐dependent exocytosis.