Recombinant expression of the Ca(2+)-sensitive aspartate/glutamate carrier increases mitochondrial ATP production in agonist-stimulated Chinese hamster ovary cells.
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.
Lasorsa
Francesco Massimo
FM
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.
Pinton
Paolo
P
Palmieri
Luigi
L
Fiermonte
Giuseppe
G
Rizzuto
Rosario
R
Palmieri
Ferdinando
F
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
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