title: Ca2+-H+ antiport activity in synaptic vesicles isolated from sheep brain cortex.
abstract: Synaptic vesicles isolated from sheep brain cortex exhibit an ATP-dependent Ca2+ accumulation that is inhibited by the protonophore uncoupler carbonyl cyanide m-chorophenylhydrazone (CCCP) and completely released by the Ca2+ ionophore ionomycin. This transport activity was sensitive to the V-type ATPase inhibitor, bafilomycin, but not to the P-type ATPase inhibitor, vanadate. We also observed that the proton gradient, established across the synaptic vesicle membranes in the presence of ATP, is partially dissipated by the addition of Ca2+ (100-860 microM) in correlation to an increase of ATP hydrolysis by the H+-pumping ATPase. In contrast, the activity of the H+-ATPase, measured under uncoupling conditions (presence of CCCP), appears to be unaltered by the calcium ion. The Ca2+-induced H+ release visualized by fluorescence quenching of acridine orange correlates well with the Ca2+ uptake determined isotopically. These results indicate that synaptic vesicles accumulate Ca2+, via a low affinity Ca2+-H+ antiport system energized by the protonmotive force originated from the H+-pumping ATPase activity.
authors.affiliation: Departamento de Biologia, Universidade de Aveiro, Portugal. pgoncalves@bio.ua.pt
authors.forename: P P
authors.initials: PP
authors.lastname: Gonçalves
authors.forename: S M
authors.initials: SM
authors.lastname: Meireles
authors.forename: C
authors.initials: C
authors.lastname: Gravato
authors.forename: M G
authors.initials: MG
authors.lastname: Vale
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D017920:Antiporters / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002118:Calcium / Q000494:pharmacology; D002135:Calcium-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D027682:Cation Transport Proteins; D002540:Cerebral Cortex / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D018942:Macrolides; D009419:Nerve Tissue Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors; D012756:Sheep; D013572:Synaptic Vesicles / Q000378:metabolism*; D014475:Uncoupling Agents / Q000494:pharmacology; D014638:Vanadates / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D017920:Antiporters; D002135:Calcium-Binding Proteins; D027682:Cation Transport Proteins; D004791:Enzyme Inhibitors; D007476:Ionophores; D018942:Macrolides; D009419:Nerve Tissue Proteins; D014475:Uncoupling Agents; C027614:calcium-hydrogen antiporters; D014638:Vanadates; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D015759:Ionomycin; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases; D002118:Calcium