title: Recombinant expression of the Ca(2+)-sensitive aspartate/glutamate carrier increases mitochondrial ATP production in agonist-stimulated Chinese hamster ovary cells.
abstract: The Ca(2+)-sensitive dehydrogenases of the mitochondrial matrix are, so far, the only known effectors to allow Ca2+ signals to couple the activation of plasma membrane receptors to the stimulation of aerobic metabolism. In this study, we demonstrate a novel mechanism, based on Ca(2+)-sensitive metabolite carriers of the inner membrane. We expressed in Chinese hamster ovary cells aralar1 and citrin, aspartate/glutamate exchangers that have Ca(2+)-binding sites in their sequence, and measured mitochondrial Ca2+ and ATP levels as well as cytosolic Ca2+ concentration with targeted recombinant probes. The increase in mitochondrial ATP levels caused by cell stimulation with Ca(2+)-mobilizing agonists was markedly larger in cells expressing aralar and citrin (but not truncated mutants lacking the Ca(2+)-binding site) than in control cells. Conversely, the cytosolic and the mitochondrial Ca2+ signals were the same in control cells and cells expressing the different aralar1 and citrin variants, thus ruling out an indirect effect through the Ca(2+)-sensitive dehydrogenases. Together, these data show that the decoding of Ca2+ signals in mitochondria depends on the coordinate activity of mitochondrial enzymes and carriers, which may thus represent useful pharmacological targets in this process of major pathophysiological interest.
authors.affiliation: Department of Pharmaco-Biology, Laboratory of Biochemistry and Molecular Biology, University of Bari and CNR Institute of Biomembranes and Bioenergetics, Via Orabona 4, 70125 Bari, Italy.
authors.forename: Francesco Massimo
authors.initials: FM
authors.lastname: Lasorsa
authors.forename: Paolo
authors.initials: P
authors.lastname: Pinton
authors.forename: Luigi
authors.initials: L
authors.lastname: Palmieri
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Fiermonte
authors.forename: Rosario
authors.initials: R
authors.lastname: Rizzuto
authors.forename: Ferdinando
authors.initials: F
authors.lastname: Palmieri
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000331:Aequorin / Q000494:pharmacology; D000818:Animals; D001224:Aspartic Acid / Q000737:chemistry*; D001665:Binding Sites; D015153:Blotting, Western; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D006224:Cricetinae; D003600:Cytosol / Q000378:metabolism; D018698:Glutamic Acid / Q000737:chemistry*; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D008163:Luminescent Measurements; D026901:Membrane Transport Proteins / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins; D024101:Mitochondrial Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D027361:Organic Anion Transporters / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D014162:Transfection
chemical_list: D002135:Calcium-Binding Proteins; D026901:Membrane Transport Proteins; D033681:Mitochondrial Membrane Transport Proteins; D024101:Mitochondrial Proteins; D027361:Organic Anion Transporters; D011994:Recombinant Proteins; C114606:SLC25A12 protein, human; C008822:citrin; D001224:Aspartic Acid; D018698:Glutamic Acid; D000331:Aequorin; D000255:Adenosine Triphosphate; D008156:Luciferases; D010100:Oxygen; D002118:Calcium