title: Deletion of glutamate dehydrogenase 1 (Glud1) in the central nervous system affects glutamate handling without altering synaptic transmission.
abstract: Glutamate dehydrogenase (GDH), encoded by GLUD1, participates in the breakdown and synthesis of glutamate, the main excitatory neurotransmitter. In the CNS, besides its primary signaling function, glutamate is also at the crossroad of metabolic and neurotransmitter pathways. Importance of brain GDH was questioned here by generation of CNS-specific GDH-null mice (CnsGlud1(-/-)); which were viable, fertile and without apparent behavioral problems. GDH immunoreactivity as well as enzymatic activity were absent in Cns-Glud1(-/-) brains. Immunohistochemical analyses on brain sections revealed that the pyramidal cells of control animals were positive for GDH, whereas the labeling was absent in hippocampal sections of Cns-Glud1(-/-) mice. Electrophysiological recordings showed that deletion of GDH within the CNS did not alter synaptic transmission in standard conditions. Cns-Glud1(-/-) mice exhibited deficient oxidative catabolism of glutamate in astrocytes, showing that GDH is required for Krebs cycle pathway. As revealed by NMR studies, brain glutamate levels remained unchanged, whereas glutamine levels were increased. This pattern was favored by up-regulation of astrocyte-type glutamate and glutamine transporters and of glutamine synthetase. Present data show that the lack of GDH in the CNS modifies the metabolic handling of glutamate without altering synaptic transmission.
authors.affiliation: Department of Cell Physiology and Metabolism, University of Geneva Medical Centre, Geneva, Switzerland.
authors.forename: Francesca
authors.initials: F
authors.lastname: Frigerio
authors.forename: Melis
authors.initials: M
authors.lastname: Karaca
authors.forename: Mathias
authors.initials: M
authors.lastname: De Roo
authors.forename: Vladimír
authors.initials: V
authors.lastname: Mlynárik
authors.forename: Dorte M
authors.initials: DM
authors.lastname: Skytt
authors.forename: Stefania
authors.initials: S
authors.lastname: Carobbio
authors.forename: Kamilla
authors.initials: K
authors.lastname: Pajęcka
authors.forename: Helle S
authors.initials: HS
authors.lastname: Waagepetersen
authors.forename: Rolf
authors.initials: R
authors.lastname: Gruetter
authors.forename: Dominique
authors.initials: D
authors.lastname: Muller
authors.forename: Pierre
authors.initials: P
authors.lastname: Maechler
mesh_terms: D000818:Animals; D001921:Brain / Q000201:enzymology* / Q000473:pathology / Q000502:physiology; D002478:Cells, Cultured; D005260:Female; D017353:Gene Deletion; D005969:Glutamate Dehydrogenase; D018698:Glutamic Acid / Q000378:metabolism*; D005973:Glutamine / Q000378:metabolism; D008297:Male; D051379:Mice; D057507:Mice, 129 Strain; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009434:Neural Pathways / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D009924:Organ Culture Techniques; D017470:Receptors, Glutamate / Q000172:deficiency* / Q000235:genetics* / Q000502:physiology; D009435:Synaptic Transmission / Q000235:genetics* / Q000502:physiology
chemical_list: D017470:Receptors, Glutamate; D005973:Glutamine; D018698:Glutamic Acid; C570817:GluD1 protein, mouse; D005969:Glutamate Dehydrogenase