title: Physical and functional interaction of NCX1 and EAAC1 transporters leading to glutamate-enhanced ATP production in brain mitochondria.
abstract: Glutamate is emerging as a major factor stimulating energy production in CNS. Brain mitochondria can utilize this neurotransmitter as respiratory substrate and specific transporters are required to mediate the glutamate entry into the mitochondrial matrix. Glutamate transporters of the Excitatory Amino Acid Transporters (EAATs) family have been previously well characterized on the cell surface of neuronal and glial cells, representing the primary players for glutamate uptake in mammalian brain. Here, by using western blot, confocal microscopy and immunoelectron microscopy, we report for the first time that the Excitatory Amino Acid Carrier 1 (EAAC1), an EAATs member, is expressed in neuronal and glial mitochondria where it participates in glutamate-stimulated ATP production, evaluated by a luciferase-luciferin system. Mitochondrial metabolic response is counteracted when different EAATs pharmacological blockers or selective EAAC1 antisense oligonucleotides were used. Since EAATs are Na(+)-dependent proteins, this raised the possibility that other transporters regulating ion gradients across mitochondrial membrane were required for glutamate response. We describe colocalization, mutual activity dependency, physical interaction between EAAC1 and the sodium/calcium exchanger 1 (NCX1) both in neuronal and glial mitochondria, and that NCX1 is an essential modulator of this glutamate transporter. Only NCX1 activity is crucial for such glutamate-stimulated ATP synthesis, as demonstrated by pharmacological blockade and selective knock-down with antisense oligonucleotides. The EAAC1/NCX1-dependent mitochondrial response to glutamate may be a general and alternative mechanism whereby this neurotransmitter sustains ATP production, since we have documented such metabolic response also in mitochondria isolated from heart. The data reported here disclose a new physiological role for mitochondrial NCX1 as the key player in glutamate-induced energy production.
authors.affiliation: Department of Biomedical Sciences and Public Health, University Politecnica delle Marche, Ancona, Italy.
authors.forename: Simona
authors.initials: S
authors.lastname: Magi
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Lariccia
authors.forename: Pasqualina
authors.initials: P
authors.lastname: Castaldo
authors.forename: Sara
authors.initials: S
authors.lastname: Arcangeli
authors.forename: Annamaria Assunta
authors.initials: AA
authors.lastname: Nasti
authors.forename: Antonio
authors.initials: A
authors.lastname: Giordano
authors.forename: Salvatore
authors.initials: S
authors.lastname: Amoroso
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000378:metabolism*; D050580:Excitatory Amino Acid Transporter 3 / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism*; D006801:Humans; D007477:Ions; D008293:Malates / Q000737:chemistry; D018613:Microscopy, Confocal / Q000379:methods; D016253:Microscopy, Immunoelectron / Q000379:methods; D008928:Mitochondria / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism; D018384:Oxidative Stress; D016716:PC12 Cells; D019289:Pyruvic Acid / Q000737:chemistry; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000378:metabolism; D019831:Sodium-Calcium Exchanger / Q000378:metabolism*; D013552:Swine
chemical_list: D050580:Excitatory Amino Acid Transporter 3; D007477:Ions; D008293:Malates; C493400:SLC1A1 protein, human; C493398:Slc1a1 protein, rat; D019831:Sodium-Calcium Exchanger; C110374:sodium-calcium exchanger 1; D018698:Glutamic Acid; C030298:malic acid; D019289:Pyruvic Acid; D000255:Adenosine Triphosphate; D012964:Sodium