title: Essential role of aralar in the transduction of small Ca2+ signals to neuronal mitochondria.
abstract: Aralar, the neuronal Ca(2+)-binding mitochondrial aspartate-glutamate carrier, has Ca(2+) binding domains facing the extramitochondrial space and functions in the malate-aspartate NADH shuttle (MAS). Here we showed that MAS activity in brain mitochondria is stimulated by extramitochondrial Ca(2+) with an S(0.5) of 324 nM. By employing primary neuronal cultures from control and aralar-deficient mice and NAD(P)H imaging with two-photon excitation microscopy, we showed that lactate utilization involves a substantial transfer of NAD(P)H to mitochondria in control but not aralar-deficient neurons, in agreement with the lack of MAS activity associated with aralar deficiency. The increase in mitochondrial NAD(P)H was greatly potentiated by large [Ca(2+)](i) signals both in control and aralar-deficient neurons, showing that these large signals activate the Ca(2+) uniporter and mitochondrial dehydrogenases but not MAS activity. On the other hand, small [Ca(2+)](i) signals potentiate the increase in mitochondrial NAD(P)H only in control but not in aralar-deficient neurons. We concluded that neuronal MAS activity is selectively activated by small Ca(2+) signals that fall below the activation range of the Ca(2+) uniporter and plays an essential role in mitochondrial Ca(2+) signaling.
authors.affiliation: Departamento de Biología Molecular, Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid, Spain.
authors.forename: Beatriz
authors.initials: B
authors.lastname: Pardo
authors.forename: Laura
authors.initials: L
authors.lastname: Contreras
authors.forename: Antonio
authors.initials: A
authors.lastname: Serrano
authors.forename: Milagros
authors.initials: M
authors.lastname: Ramos
authors.forename: Keiko
authors.initials: K
authors.lastname: Kobayashi
authors.forename: Mikio
authors.initials: M
authors.lastname: Iijima
authors.forename: Takeyori
authors.initials: T
authors.lastname: Saheki
authors.forename: Jorgina
authors.initials: J
authors.lastname: Satrústegui
mesh_terms: D000483:Alleles; D000818:Animals; D001921:Brain / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005838:Genotype; D007773:Lactates / Q000737:chemistry; D008297:Male; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D008853:Microscopy; D008928:Mitochondria / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins; D024101:Mitochondrial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008954:Models, Biological; D018482:Muscle, Skeletal / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D009474:Neurons / Q000378:metabolism*; D017785:Photons; D016133:Polymerase Chain Reaction; D011773:Pyruvates / Q000737:chemistry / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction; D013997:Time Factors
chemical_list: D007773:Lactates; D026901:Membrane Transport Proteins; D033681:Mitochondrial Membrane Transport Proteins; D024101:Mitochondrial Proteins; D011773:Pyruvates; C491956:Slc25a12 protein, mouse; C491957:Slc25a12 protein, rat; D009249:NADP; D004247:DNA; D002118:Calcium