title: Ca2+ hot spots on the mitochondrial surface are generated by Ca2+ mobilization from stores, but not by activation of store-operated Ca2+ channels.
abstract: Although it is widely accepted that mitochondria in living cells can efficiently uptake Ca(2+) during stimulation because of their vicinity to microdomains of high [Ca(2+)], the direct proof of Ca(2+) hot spots' existence is still lacking. Thanks to a GFP-based Ca(2+) probe localized on the cytosolic surface of the outer mitochondrial membrane, we demonstrate that, upon Ca(2+) mobilization, the [Ca(2+)] in small regions of the mitochondrial surface reaches levels 5- to 10-fold higher than in the bulk cytosol. We also show that the [Ca(2+)] to which mitochondria are exposed during capacitative Ca(2+) influx is similar between near plasma membrane mitochondria and organelles deeply located in the cytoplasm, whereas it is 2- to 3-fold higher in subplasma membrane mitochondria upon activation of voltage-gated Ca(2+) channels. These results demonstrate that mitochondria are exposed to Ca(2+) hot spots close to the ER but are excluded from the regions where capacitative Ca(2+) influx occurs.
authors.affiliation: Department of Biomedical Sciences, University of Padova, Padova, Italy.
authors.forename: Marta
authors.initials: M
authors.lastname: Giacomello
authors.forename: Ilaria
authors.initials: I
authors.lastname: Drago
authors.forename: Mario
authors.initials: M
authors.lastname: Bortolozzi
authors.forename: Michele
authors.initials: M
authors.lastname: Scorzeto
authors.forename: Alessio
authors.initials: A
authors.lastname: Gianelle
authors.forename: Paola
authors.initials: P
authors.lastname: Pizzo
authors.forename: Tullio
authors.initials: T
authors.lastname: Pozzan
mesh_terms: D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology*; D002412:Cations / Q000378:metabolism*; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007150:Immunohistochemistry; D007700:Kinetics; D021962:Membrane Microdomains / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism; D010911:Pituitary Neoplasms / Q000473:pathology; D014162:Transfection
chemical_list: D015220:Calcium Channels; D002412:Cations; D049452:Green Fluorescent Proteins; D002118:Calcium