title: Enhanced exocytotic-like insertion of Orai1 into the plasma membrane upon intracellular Ca2+ store depletion.
abstract: Ca+ release-activated Ca2+ (CRAC) channels are activated when free Ca2+ concentration in the intracellular stores is substantially reduced and mediate sustained Ca2+ entry. Recent studies have identified Orai1 as a CRAC channel subunit. Here we demonstrate that passive Ca2+ store depletion using the inhibitor of the sarcoendoplasmic reticulum Ca2+-ATPase, thapsigargin (TG), enhances the surface expression of Orai1, a process that depends on rises in cytosolic free Ca2+ concentration, as demonstrated in cells loaded with dimethyl BAPTA, an intracellular Ca2+ chelator that prevented TG-evoked cytosolic free Ca2+ concentration elevation. Similar results were observed with a low concentration of carbachol. Cleavage of the soluble N-ethylmaleimide-sensitive-factor attachment protein receptor, synaptosomal-assiciated protein-25 (SNAP-25), with botulinum neurotoxin A impaired TG-induced increase in the surface expression of Orai1. In addition, SNAP-25 cleaving by botulinum neurotoxin A reduces the maintenance but not the initial stages of store-operated Ca2+ entry. In aggregate, these findings demonstrate that store depletion enhances Orai1 plasma membrane expression in an exocytotic manner that involves SNAP-25, a process that contributes to store-dependent Ca2+ entry.
authors.affiliation: National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA.
authors.forename: Geoffrey E
authors.initials: GE
authors.lastname: Woodard
authors.forename: Ginés M
authors.initials: GM
authors.lastname: Salido
authors.forename: Juan A
authors.initials: JA
authors.lastname: Rosado
mesh_terms: D019274:Botulinum Toxins, Type A / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D002614:Chelating Agents / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005089:Exocytosis / Q000187:drug effects; D006367:HeLa Cells; D006801:Humans; D000071740:ORAI1 Protein; D021381:Protein Transport; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism; D050825:Synaptosomal-Associated Protein 25 / Q000378:metabolism; D019284:Thapsigargin / Q000494:pharmacology; D013997:Time Factors; D015854:Up-Regulation
chemical_list: D015220:Calcium Channels; D002614:Chelating Agents; D004791:Enzyme Inhibitors; D000071740:ORAI1 Protein; C510746:ORAI1 protein, human; D050825:Synaptosomal-Associated Protein 25; D004533:Egtazic Acid; D019284:Thapsigargin; D002217:Carbachol; D019274:Botulinum Toxins, Type A; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium