title: Calcium-regulation of mitochondrial respiration maintains ATP homeostasis and requires ARALAR/AGC1-malate aspartate shuttle in intact cortical neurons.
abstract: Neuronal respiration is controlled by ATP demand and Ca2+ but the roles played by each are unknown, as any Ca2+ signal also impacts on ATP demand. Ca2+ can control mitochondrial function through Ca2+-regulated mitochondrial carriers, the aspartate-glutamate and ATP-Mg/Pi carriers, ARALAR/AGC1 and SCaMC-3, respectively, or in the matrix after Ca2+ transport through the Ca2+ uniporter. We have studied the role of Ca2+ signaling in the regulation of mitochondrial respiration in intact mouse cortical neurons in basal conditions and in response to increased workload caused by increases in [Na+]cyt (veratridine, high-K+ depolarization) and/or [Ca2+]cyt (carbachol). Respiration in nonstimulated neurons on 2.5-5 mm glucose depends on ARALAR-malate aspartate shuttle (MAS), with a 46% drop in aralar KO neurons. All stimulation conditions induced increased OCR (oxygen consumption rate) in the presence of Ca2+, which was prevented by BAPTA-AM loading (to preserve the workload), or in Ca2+-free medium (which also lowers cell workload). SCaMC-3 limits respiration only in response to high workloads and robust Ca2+ signals. In every condition tested Ca2+ activation of ARALAR-MAS was required to fully stimulate coupled respiration by promoting pyruvate entry into mitochondria. In aralar KO neurons, respiration was stimulated by veratridine, but not by KCl or carbachol, indicating that the Ca2+ uniporter pathway played a role in the first, but not in the second condition, even though KCl caused an increase in [Ca2+]mit. The results suggest a requirement for ARALAR-MAS in priming pyruvate entry in mitochondria as a step needed to activate respiration by Ca2+ in response to moderate workloads.
authors.affiliation: Departament of Molecular Biology, Centre for Molecular Biology Severo Ochoa UAM-CSIC, Autonomous University of Madrid, Madrid, Spain.
authors.forename: Irene
authors.initials: I
authors.lastname: Llorente-Folch
authors.forename: Carlos B
authors.initials: CB
authors.lastname: Rueda
authors.forename: Ignacio
authors.initials: I
authors.lastname: Amigo
authors.forename: Araceli
authors.initials: A
authors.lastname: del Arco
authors.forename: Takeyori
authors.initials: T
authors.lastname: Saheki
authors.forename: Beatriz
authors.initials: B
authors.lastname: Pardo
authors.forename: Jorgina
authors.initials: J
authors.lastname: Satrústegui
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D002217:Carbachol / Q000494:pharmacology; D019069:Cell Respiration / Q000187:drug effects / Q000235:genetics*; D002540:Cerebral Cortex / Q000166:cytology; D005947:Glucose / Q000378:metabolism; D006706:Homeostasis; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008928:Mitochondria / Q000378:metabolism*; D000226:Mitochondrial ADP, ATP Translocases / Q000378:metabolism; D033681:Mitochondrial Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism; D009474:Neurons / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D011189:Potassium Chloride / Q000494:pharmacology; D011773:Pyruvates / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D014701:Veratridine / Q000494:pharmacology
chemical_list: D033681:Mitochondrial Membrane Transport Proteins; D011773:Pyruvates; C535088:Slc25a41 protein, mouse; D011189:Potassium Chloride; D014701:Veratridine; D000255:Adenosine Triphosphate; D002217:Carbachol; D000226:Mitochondrial ADP, ATP Translocases; D012964:Sodium; D005947:Glucose; D010100:Oxygen; D002118:Calcium