Deletion of glutamate dehydrogenase 1 (Glud1) in the central nervous system affects glutamate handling without altering synaptic transmission

TY - JOUR

T1 - Deletion of glutamate dehydrogenase 1 (Glud1) in the central nervous system affects glutamate handling without altering synaptic transmission

AU - Frigerio, Francesca

AU - Karaca, Melis

AU - De Roo, Mathias

AU - Mlynárik, Vladimír

AU - Skytt, Dorte M

AU - Carobbio, Stefania

AU - Pajęcka, Kamilla

AU - Waagepetersen, Helle S.

AU - Gruetter, Rolf

AU - Muller, Dominique

AU - Maechler, Pierre

N1 - © 2012 The Authors Journal of Neurochemistry © 2012 International Society for Neurochemistry.

PY - 2012/11

Y1 - 2012/11

N2 - 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. We investigated the role of GDH in synaptic transmission and in the maintenance of glutamate-glutamine balance. Our data show that the lack of Glud1 in mouse brain inhibits GDH activity, modifies glutamate handling, decreases glutamate catabolism and increases glutamine levels; without affecting synaptic transmission. This study reports the first mouse model with brain-specific ablation of GDH, named Cns-Glud1-/-.

AB - 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. We investigated the role of GDH in synaptic transmission and in the maintenance of glutamate-glutamine balance. Our data show that the lack of Glud1 in mouse brain inhibits GDH activity, modifies glutamate handling, decreases glutamate catabolism and increases glutamine levels; without affecting synaptic transmission. This study reports the first mouse model with brain-specific ablation of GDH, named Cns-Glud1-/-.

KW - Animals

KW - Brain

KW - Cells, Cultured

KW - Female

KW - Gene Deletion

KW - Glutamic Acid

KW - Glutamine

KW - Male

KW - Mice

KW - Mice, 129 Strain

KW - Mice, Inbred C57BL

KW - Mice, Knockout

KW - Mice, Transgenic

KW - Neural Pathways

KW - Organ Culture Techniques

KW - Receptors, Glutamate

KW - Synaptic Transmission

U2 - 10.1111/j.1471-4159.2012.07933.x

DO - 10.1111/j.1471-4159.2012.07933.x

M3 - Journal article

C2 - 22924626

SN - 0022-3042

VL - 123

SP - 342

EP - 348

JO - Journal of Neurochemistry

JF - Journal of Neurochemistry

IS - 3

ER -