title: High calcium concentrations shift the mode of exocytosis to the kiss-and-run mechanism.
abstract: Exocytosis, the fusion of secretory vesicles with the plasma membrane to allow release of the contents of the vesicles into the extracellular environment, and endocytosis, the internalization of these vesicles to allow another round of secretion, are coupled. It is, however, uncertain whether exocytosis and endocytosis are tightly coupled, such that secretory vesicles fuse only transiently with the plasma membrane before being internalized (the 'kiss-and-run' mechanism), or whether endocytosis occurs by an independent process following complete incorporation of the secretory vesicle into the plasma membrane. Here we investigate the fate of single secretory vesicles after fusion with the plasma membrane by measuring capacitance changes and transmitter release in rat chromaffin cells using the cell-attached patch-amperometry technique. We show that raised concentrations of extracellular calcium ions shift the preferred mode of exocytosis to the kiss-and-run mechanism in a calcium-concentration-dependent manner. We propose that, during secretion of neurotransmitters at synapses, the mode of exocytosis is modulated by calcium to attain optimal conditions for coupled exocytosis and endocytosis according to synaptic activity.
authors.affiliation: Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Alés
authors.forename: L
authors.initials: L
authors.lastname: Tabares
authors.forename: J M
authors.initials: JM
authors.lastname: Poyato
authors.forename: V
authors.initials: V
authors.lastname: Valero
authors.forename: M
authors.initials: M
authors.lastname: Lindau
authors.forename: G
authors.initials: G
authors.lastname: Alvarez de Toledo
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002395:Catecholamines / Q000378:metabolism; D002462:Cell Membrane / Q000502:physiology*; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000502:physiology*; D003594:Cytoplasmic Granules / Q000502:physiology*; D005089:Exocytosis / Q000502:physiology*; D008561:Membrane Fusion / Q000502:physiology; D008564:Membrane Potentials / Q000502:physiology; D008954:Models, Biological; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D013569:Synapses / Q000502:physiology
chemical_list: D002395:Catecholamines; D002118:Calcium