Ca2+-Independent and Voltage-Dependent Exocytosis in mouse chromaffin cells.

JOSÉ MOYA-DÍAZ; LUCAS BAYONÉS; MAURICIO MONTENEGRO; ANA MARÍA CÁRDENAS; HENNER KOCH; ATSUSHI DOI; FERNANDO D. MARENGO

ACTA PHYSIOLOGICA

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2020 vol. 228

1748-1708

Aim: It is widely accepted that the exocytosis of synaptic and secretory vesicles is triggered by Ca2+ entry through voltage-dependent Ca2+ channels. However, there is evidence of an alternative mode of exocytosis induced by membrane depolarization but lacking Ca2+ current and intracellular Ca2+ increase. In this work we investigated if such a mechanism contributes to secretory vesicle exocytosis in mouse chromaffin cells.Methods: Exocytosis was evaluated by patch-clamp membrane capacitance measurements, carbon fiber amperometry and TIRF. Cytosolic Ca2+ was estimated using epifluorescence microscopy and fluo-8 (salt form). Results: Cells stimulated by brief depolatizations in absence of extracellular Ca+2 show moderate but consistent exocytosis, even in presence of high cytosolic BAPTA concentration and pharmacologic inhibition of Ca+2 release from intracellular stores. This exocytosis is tightly dependent on membrane potential, is inhibited by neurotoxin Bont-B (cleaves the v-SNARE synaptobrevin), is very fast (saturates with time constant