title: Calcium-dependent trapping of mitochondria near plasma membrane in stimulated astrocytes.
abstract: Growing evidence suggests that astrocytes are the active partners of neurons in many brain functions. Astrocytic mitochondria are highly motile organelles which regulate the temporal and spatial patterns of Ca( 2+ ) dynamics, in addition to being a major source of ATP and reactive oxygen species. Previous studies have shown that mitochondria translocate to endoplasmic reticulum during Ca( 2+ ) release from internal stores, but whether a similar spatial interaction between mitochondria and plasma membrane occurs is not known. Using total internal reflection fluorescence (TIRF) microscopy we show that a fraction of mitochondria became trapped near the plasma membrane of cultured hippocampal astrocytes during exposure to the transmitters glutamate or ATP, resulting in net translocation of the mitochondria to the plasma membrane. This translocation was dependent on the intracellular Ca( 2+ ) rise because it was blocked by pre-incubation with BAPTA AM and mimicked by application of the Ca( 2+ ) ionophore ionomycin. Transmembrane Ca( 2+ ) influx induced by raising external Ca( 2+ ) also caused mitochondrial trapping, which occurred more rapidly than that produced by glutamate or ATP. In astrocytes treated with the microtubule-disrupting agent nocodazole, intracellular Ca( 2+ ) rises failed to induce trapping of mitochondria near plasma membrane, suggesting a role for microtubules in this phenomenon. Our data reveal the Ca( 2+ )-dependent trapping of mitochondria near the plasma membrane as a novel form of mitochondrial regulation, which is likely to control the perimembrane Ca( 2+ ) dynamics and regulate signaling by mitochondria-derived reactive oxygen species.
authors.affiliation: Neuroscience Center, University of Helsinki, P.O. Box 56, (Viikinkaari 4), FIN-00014, Helsinki, Finland.
authors.forename: Julia
authors.initials: J
authors.lastname: Kolikova
authors.forename: Ramil
authors.initials: R
authors.lastname: Afzalov
authors.forename: Asiya
authors.initials: A
authors.lastname: Giniatullina
authors.forename: Alexander
authors.initials: A
authors.lastname: Surin
authors.forename: Rashid
authors.initials: R
authors.lastname: Giniatullin
authors.forename: Leonard
authors.initials: L
authors.lastname: Khiroug
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D001253:Astrocytes / Q000166:cytology / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D002614:Chelating Agents / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D018698:Glutamic Acid / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D015739:Nocodazole / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology
chemical_list: D000970:Antineoplastic Agents; D002614:Chelating Agents; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D018698:Glutamic Acid; D004533:Egtazic Acid; D000255:Adenosine Triphosphate; D015739:Nocodazole; D002118:Calcium