TY - JOUR
T1 - Conditional Knockout of GLT-1 in Neurons Leads to Alterations in Aspartate Homeostasis and Synaptic Mitochondrial Metabolism in Striatum and Hippocampus
AU - McNair, Laura F.
AU - Andersen, Jens V.
AU - Nissen, Jakob D.
AU - Sun, Yan
AU - Fischer, Kathryn D.
AU - Hodgson, Nathaniel W.
AU - Du, Muzi
AU - Aoki, Chiye J.
AU - Waagepetersen, Helle S.
AU - Rosenberg, Paul A.
AU - Aldana, Blanca I.
N1 - Funding Information:
This work was supported, in part, by a grant from Aase og Ejnar Danielsens Fond, and National Institute of Health grants NS066019, MH104318, MH105846, EY13079, and HD018655. NMR equipment used in this work was purchased via Grant #10?085264 from The Danish Research Council for Independent Research | Nature and Universe, ?Apotekerfonden af 1991?, and the Danish Agency for Science, Technology and Innovation via the National Research Infrastructure funds. Laura F. McNair acknowledges the Department of Drug Design and Pharmacology (University of Copenhagen, Denmark) for granting of a PhD scholarship. Blanca Aldana is subsidized by a Grant from the Ministry of Science, Technology and Innovation (SECITI) of Mexico. Jens Andersen kindly thanks the Scholarship of Peter & Emma Thomsens for personal financial support. We thank Heidi Nielsen, Michaela C. Hohnholt, Nils Nyberg and Ursula Sonnewald for helpful assistance in the laboratory and data analysis.
Funding Information:
This work was supported, in part, by a grant from Aase og Ejnar Danielsens Fond, and National Institute of Health grants NS066019, MH104318, MH105846, EY13079, and HD018655. NMR equipment used in this work was purchased via Grant #10–085264 from The Danish Research Council for Independent Research | Nature and Universe, ‘Apotekerfonden af 1991′, and the Danish Agency for Science, Technology and Innovation via the National Research Infrastructure funds. Laura F. McNair acknowledges the Department of Drug Design and Pharmacology (University of Copenhagen, Denmark) for granting of a PhD scholarship. Blanca Aldana is subsidized by a Grant from the Ministry of Science, Technology and Innovation (SECITI) of Mexico. Jens Andersen kindly thanks the Scholarship of Peter & Emma Thomsens for personal financial support. We thank Heidi Nielsen, Michaela C. Hohnholt, Nils Nyberg and Ursula Sonnewald for helpful assistance in the laboratory and data analysis.
Publisher Copyright:
© 2020, Springer Science+Business Media, LLC, part of Springer Nature.
PY - 2020/6/1
Y1 - 2020/6/1
N2 - Expression of the glutamate transporter GLT-1 in neurons has been shown to be important for synaptic mitochondrial function in the cerebral cortex. Here we determined whether neuronal GLT-1 plays a similar role in the hippocampus and striatum, using conditional GLT-1 knockout mice in which GLT-1 was inactivated in neurons by expression of synapsin-Cre (synGLT-1 KO). Ex vivo 13C-labelling using [1,2-13C]acetate, representing astrocytic metabolism, yielded increased [4,5-13C]glutamate levels, suggesting increased astrocyte-neuron glutamine transfer, in the striatum but not in the hippocampus of the synGLT-1 KO. Moreover, aspartate concentrations were reduced − 38% compared to controls in the hippocampus and the striatum of the synGLT-1 KO. Mitochondria isolated from the hippocampus of synGLT-1 KO mice exhibited a lower oxygen consumption rate in the presence of oligomycin A, indicative of a decreased proton leak across the mitochondrial membrane, whereas the ATP production rate was unchanged. Electron microscopy revealed reduced mitochondrial inter-cristae distance within excitatory synaptic terminals in the hippocampus and striatum of the synGLT-1 KO. Finally, dilution of 13C-labelling originating from [U-13C]glucose, caused by metabolism of unlabelled glutamate, was reduced in hippocampal synGLT-1 KO synaptosomes, suggesting that neuronal GLT-1 provides glutamate for synaptic tricarboxylic acid cycle metabolism. Collectively, these data demonstrate an important role of neuronal expression of GLT-1 in synaptic mitochondrial metabolism in the forebrain.
AB - Expression of the glutamate transporter GLT-1 in neurons has been shown to be important for synaptic mitochondrial function in the cerebral cortex. Here we determined whether neuronal GLT-1 plays a similar role in the hippocampus and striatum, using conditional GLT-1 knockout mice in which GLT-1 was inactivated in neurons by expression of synapsin-Cre (synGLT-1 KO). Ex vivo 13C-labelling using [1,2-13C]acetate, representing astrocytic metabolism, yielded increased [4,5-13C]glutamate levels, suggesting increased astrocyte-neuron glutamine transfer, in the striatum but not in the hippocampus of the synGLT-1 KO. Moreover, aspartate concentrations were reduced − 38% compared to controls in the hippocampus and the striatum of the synGLT-1 KO. Mitochondria isolated from the hippocampus of synGLT-1 KO mice exhibited a lower oxygen consumption rate in the presence of oligomycin A, indicative of a decreased proton leak across the mitochondrial membrane, whereas the ATP production rate was unchanged. Electron microscopy revealed reduced mitochondrial inter-cristae distance within excitatory synaptic terminals in the hippocampus and striatum of the synGLT-1 KO. Finally, dilution of 13C-labelling originating from [U-13C]glucose, caused by metabolism of unlabelled glutamate, was reduced in hippocampal synGLT-1 KO synaptosomes, suggesting that neuronal GLT-1 provides glutamate for synaptic tricarboxylic acid cycle metabolism. Collectively, these data demonstrate an important role of neuronal expression of GLT-1 in synaptic mitochondrial metabolism in the forebrain.
KW - Brain energy metabolism
KW - Forebrain
KW - Glutamate
KW - Glutamine
KW - TCA cycle
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UR - http://www.scopus.com/inward/citedby.url?scp=85081212735&partnerID=8YFLogxK
U2 - 10.1007/s11064-020-03000-7
DO - 10.1007/s11064-020-03000-7
M3 - Article
C2 - 32144526
AN - SCOPUS:85081212735
SN - 0364-3190
VL - 45
SP - 1420
EP - 1437
JO - Neurochemical Research
JF - Neurochemical Research
IS - 6
ER -