Axon-terminals expressing EAAT2 (GLT-1; Slc1a2) are common in the forebrain and not limited to the hippocampus

被引:46
作者
Zhou, Yun [1 ]
Hassel, Bjornar [2 ]
Eid, Tore [1 ,3 ]
Danbolt, Niels Christian [1 ]
机构
[1] Univ Oslo, Inst Basic Med Sci, Dept Mol Med, Neurotransporter Grp, N-0317 Oslo, Norway
[2] Univ Oslo, Oslo Univ Hosp, Dept Complex Neurol & Neurohabilitat, Oslo, Norway
[3] Yale Sch Med, Dept Lab Med, New Haven, CT 06520 USA
关键词
Synaptosomes; Glutamate metabolism; Glutamate uptake; Excitatory amino acid transporter 2; Syn1-cre; Presynaptic; GLIAL GLUTAMATE TRANSPORTERS; IN-SITU HYBRIDIZATION; RAT-BRAIN; AUTORADIOGRAPHIC LOCALIZATION; DIFFERENTIAL DISTRIBUTION; CONDITIONAL DELETION; CEREBRAL-CORTEX; D-ASPARTATE; NEURONS; PROTEIN;
D O I
10.1016/j.neuint.2018.03.006
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The excitatory amino acid transporter type 2 (EAAT2) represents the major mechanism for removal of extracellular glutamate. In the hippocampus, there is some EAAT2 in axon-terminals, whereas most of the protein is found in astroglia. The functional importance of the neuronal EAAT2 is unknown, and it is debated whether EAAT2-expressing nerve terminals are present in other parts of the brain. Here we selectively deleted the EAAT2 gene in neurons (by crossing EAAT2-flox mice with synapsin 1-Cre mice in the C5766 background). To reduce interference from astroglial EAAT2, we measured glutamate accumulation in crude tissue homogenates. EAAT2 proteins levels were measured by immunoblotting. Although synapsin 1-Cre mediated gene deletion only reduced the forebrain tissue content of EAAT2 protein to 95.5 +/- 3.4% of wild-type (littermate) controls, the glutamate accumulation in homogenates of neocortex, hippocampus, striatum and thalamus were nevertheless diminished to, respectively, 54 +/- 4, 46 +/- 3, 46 +/- 2 and 65 +/- 7% of controls (average +/- SEM, n = 3 pairs of littermates). GABA uptake was unaffected. After injection of U-C-13-glucose, lack of neuronal EAAT2 resulted in higher C-13-labeling of glutamine and GABA in the hippocampus suggesting that neuronal EAAT2 is partly short-circuiting the glutamate-glutamine cycle in wild-type mice. Crossing synapsin 1-Cre mice with Ai9 reporter mice revealed that Cre-mediated excision occurred efficiently in hippocampus CA3, but less efficiently in other regions and hardly at all in the cerebellum. Conclusions: (1) EAAT2 is expressed in nerve terminals in multiple brain regions. (2) The uptake catalyzed by neuronal EAAT2 plays a role in glutamate metabolism, at least in the hippocampus. (3) Synapsin 1-Cre does not delete floxed genes in all neurons, and the contribution of neuronal EAAT2 is therefore likely to be larger than revealed in the present study. (C) 2018 Elsevier Ltd. All rights reserved.
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页码:101 / 113
页数:13
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