title: ATP: The crucial component of secretory vesicles.
abstract: The colligative properties of ATP and catecholamines demonstrated in vitro are thought to be responsible for the extraordinary accumulation of solutes inside chromaffin cell secretory vesicles, although this has yet to be demonstrated in living cells. Because functional cells cannot be deprived of ATP, we have knocked down the expression of the vesicular nucleotide carrier, the VNUT, to show that a reduction in vesicular ATP is accompanied by a drastic fall in the quantal release of catecholamines. This phenomenon is particularly evident in newly synthesized vesicles, which we show are the first to be released. Surprisingly, we find that inhibiting VNUT expression also reduces the frequency of exocytosis, whereas the overexpression of VNUT drastically increases the quantal size of exocytotic events. To our knowledge, our data provide the first demonstration that ATP, in addition to serving as an energy source and purinergic transmitter, is an essential element in the concentration of catecholamines in secretory vesicles. In this way, cells can use ATP to accumulate neurotransmitters and other secreted substances at high concentrations, supporting quantal transmission.
authors.affiliation: Unidad de Farmacología, Facultad de Medicina, Universidad de la Laguna, Tenerife 38320, Spain;
authors.forename: Judith
authors.initials: J
authors.lastname: Estévez-Herrera
authors.affiliation: Unidad de Farmacología, Facultad de Medicina, Universidad de la Laguna, Tenerife 38320, Spain;
authors.forename: Natalia
authors.initials: N
authors.lastname: Domínguez
authors.affiliation: Unidad de Farmacología, Facultad de Medicina, Universidad de la Laguna, Tenerife 38320, Spain; Instituto Universitario de Bio-Orgánica 'Antonio González', Universidad de la Laguna, Tenerife 38320, Spain.
authors.forename: Marta R
authors.initials: MR
authors.lastname: Pardo
authors.affiliation: Unidad de Farmacología, Facultad de Medicina, Universidad de la Laguna, Tenerife 38320, Spain;
authors.forename: Ayoze
authors.initials: A
authors.lastname: González-Santana
authors.affiliation: Unidad de Farmacología, Facultad de Medicina, Universidad de la Laguna, Tenerife 38320, Spain;
authors.forename: Edward W
authors.initials: EW
authors.lastname: Westhead
authors.affiliation: Unidad de Farmacología, Facultad de Medicina, Universidad de la Laguna, Tenerife 38320, Spain; Instituto Universitario de Bio-Orgánica 'Antonio González', Universidad de la Laguna, Tenerife 38320, Spain rborges@ull.es.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Borges
authors.affiliation: Unidad de Farmacología, Facultad de Medicina, Universidad de la Laguna, Tenerife 38320, Spain;
authors.forename: José David
authors.initials: JD
authors.lastname: Machado
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002395:Catecholamines / Q000378:metabolism*; D002417:Cattle; D019439:Chromaffin Cells; D005089:Exocytosis; D033704:Nucleotide Transport Proteins / Q000378:metabolism*; D022142:Secretory Vesicles / Q000378:metabolism*
chemical_list: D002395:Catecholamines; D033704:Nucleotide Transport Proteins; D000255:Adenosine Triphosphate
keywords: VNUT; exocytosis; purines; quantum size; secretory vesicles