Relations between intracellular Ca2+ stores and store-operated Ca2+ entry in primary cultured human glioblastoma cells.
1. In primary cultured human glioblastoma cells extracellular application of ATP triggered elevation in cytoplasmic calcium concentration ([Ca2+]i) mediated entirely by generation of inositol 1,4,5-trisphosphate (InsP3)-dependent Ca2+ release from endoplasmic reticulum Ca2+ stores followed by the activation of store-operated Ca2+ entry into the cells. 2. Sensitivity of P2Y purinoceptors to extracellular ATP was regulated by extracellular Ca2+: in Ca2+-free extracellular solution the threshold concentration of ATP that induced an increase in [Ca2+]i was reduced by one order of magnitude. 3. Activation of Ca2+ release and store-operated Ca2+ entry was dissociated: low concentrations of ATP induced substantial Ca2+ release without activation of Ca2+ entry; activation of the latter required higher ATP concentrations. 4. Mitochondria participated in buffering Ca2+ loads that resulted from store-operated Ca2+ influx; in contrast Ca2+ released from intracellular stores was not accumulated by the mitochondrial depot. 5. We conclude that ATP-induced Ca2+ responses are governed by several pathways with different sensitivities to the agonist. This enables cells to respond either with pure Ca2+ release from intracellular stores (at low ATP concentrations) or (at high ATP concentrations) the response is amplified by plasmalemmal Ca2+ influx. Store-operated Ca2+ entry increases mitochondrial Ca2+ content providing a link between cellular activation and mitochondrial function.
Hartmann
J
J
Max-Delbruck-Centre for Molecular Medicine, Robert-Rossle-Strasse 10, 13122 Berlin Buch, Germany.jh@nero.glia.mdc-berlin.de
Verkhratsky
A
A
D000255:Adenosine Triphosphate / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D005110:Extracellular Space / Q000378:metabolism; D005909:Glioblastoma / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism; D009994:Osmolar Concentration; D011983:Receptors, Purinergic / Q000378:metabolism / Q000502:physiology; D014407:Tumor Cells, Cultured / Q000187:drug effects
D011983:Receptors, Purinergic; D000255:Adenosine Triphosphate; D002118:Calcium