Deletion of neuronal GLT-1 in mice reveals its role in synaptic glutamate homeostasis and mitochondrial function

TY - JOUR

T1 - Deletion of neuronal GLT-1 in mice reveals its role in synaptic glutamate homeostasis and mitochondrial function

AU - McNair, Laura F.

AU - Andersen, Jens V.

AU - Aldana, Blanca I.

AU - Hohnholt, Michaela C.

AU - Nissen, Jakob D.

AU - Sun, Yan

AU - Fischer, Kathryn D.

AU - Sonnewald, Ursula

AU - Nyberg, Nils

AU - Webster, Sophie C

AU - Kapur, Kush

AU - Rimmele, Theresa S

AU - Barone, Ilaria

AU - Hawks-Mayer, Hannah

AU - Lipton, Jonathan O

AU - Hodgson, Nathaniel W

AU - Aoki, Chiye J

AU - Rosenberg, Paul A

AU - Waagepetersen, Helle S

N1 - Copyright © 2019 the authors.

PY - 2019/6/19

Y1 - 2019/6/19

N2 - The glutamate transporter GLT-1 is highly expressed in astrocytes but also in neurons, primarily in axon terminals. We generated a conditional neuronal GLT-1KOusing synapsin 1-Cre (synGLT-1 KO) to elucidate the metabolic functions of GLT-1 expressed in neurons, here focusing on the cerebral cortex. Both synaptosomal uptake studies and electron microscopic immunocytochemistry demonstrated knockdown of GLT-1 in the cerebral cortex in the synGLT-1 KO mice. Aspartate content was significantly reduced in cerebral cortical extracts as well as synaptosomes from cerebral cortex of synGLT-1 KO compared with control littermates. 13C-Labeling of tricarboxylic acid cycle intermediates originating from metabolism of [U-13C]-glutamate was significantly reduced in synGLT-1KOsynaptosomes. The decreased aspartate content was due to diminished entry of glutamate into the tricarboxylic acid cycle. Pyruvate recycling, a pathway necessary for full glutamate oxidation, was also decreased. ATP production was significantly increased, despite unaltered oxygen consumption, in isolated mitochondria from the synGLT-1 KO. The density of mitochondria in axon terminals and perisynaptic astrocytes was increased in the synGLT-1 KO. Intramitochondrial cristae density of synGLT-1 KO mice was increased, suggesting increased mitochondrial efficiency, perhaps in compensation for reduced access to glutamate. SynGLT-1KOsynaptosomes exhibited an elevated oxygen consumption rate when stimulated with veratridine, despite a lower baseline oxygen consumption rate in the presence of glucose. GLT-1 expressed in neurons appears to be required to provide glutamate to synaptic mitochondria and is linked to neuronal energy metabolism and mitochondrial function.

AB - The glutamate transporter GLT-1 is highly expressed in astrocytes but also in neurons, primarily in axon terminals. We generated a conditional neuronal GLT-1KOusing synapsin 1-Cre (synGLT-1 KO) to elucidate the metabolic functions of GLT-1 expressed in neurons, here focusing on the cerebral cortex. Both synaptosomal uptake studies and electron microscopic immunocytochemistry demonstrated knockdown of GLT-1 in the cerebral cortex in the synGLT-1 KO mice. Aspartate content was significantly reduced in cerebral cortical extracts as well as synaptosomes from cerebral cortex of synGLT-1 KO compared with control littermates. 13C-Labeling of tricarboxylic acid cycle intermediates originating from metabolism of [U-13C]-glutamate was significantly reduced in synGLT-1KOsynaptosomes. The decreased aspartate content was due to diminished entry of glutamate into the tricarboxylic acid cycle. Pyruvate recycling, a pathway necessary for full glutamate oxidation, was also decreased. ATP production was significantly increased, despite unaltered oxygen consumption, in isolated mitochondria from the synGLT-1 KO. The density of mitochondria in axon terminals and perisynaptic astrocytes was increased in the synGLT-1 KO. Intramitochondrial cristae density of synGLT-1 KO mice was increased, suggesting increased mitochondrial efficiency, perhaps in compensation for reduced access to glutamate. SynGLT-1KOsynaptosomes exhibited an elevated oxygen consumption rate when stimulated with veratridine, despite a lower baseline oxygen consumption rate in the presence of glucose. GLT-1 expressed in neurons appears to be required to provide glutamate to synaptic mitochondria and is linked to neuronal energy metabolism and mitochondrial function.

U2 - 10.1523/jneurosci.0894-18.2019

DO - 10.1523/jneurosci.0894-18.2019

M3 - Journal article

C2 - 30926746

SN - 0270-6474

VL - 39

SP - 4847

EP - 4863

JO - The Journal of neuroscience : the official journal of the Society for Neuroscience

JF - The Journal of neuroscience : the official journal of the Society for Neuroscience

IS - 25

ER -