Conditional Deletion of the Glutamate Transporter GLT-1 Reveals That Astrocytic GLT-1 Protects against Fatal Epilepsy While Neuronal GLT-1 Contributes Significantly to Glutamate Uptake into Synaptosomes

作者：Geraldine T. Petr, Yan Sun, Natalie M. Frederick, Yun Zhou, Sameer C. Dhamne, Mustafa Qadir Hameed, Clive Jude Miranda, Edward A. Bedoya, Kathryn D. Fischer, Wencke Armsen, Jianlin Wang, Niels Christian Danbolt, Alexander Rotenberg, Chiye J. Aoki, Paul A. Rosenberg · 发表于：Journal of Neuroscience · 年份：2015 · DOI：10.1523/jneurosci.4255-14.2015 · 被引用次数：311 · 研究领域：Neuroscience and Neuropharmacology Research、Epilepsy research and treatment、Ion channel regulation and function

GLT-1 (EAAT2; slc1a2) is the major glutamate transporter in the brain, and is predominantly expressed in astrocytes, but at lower levels also in excitatory terminals. We generated a conditional GLT-1 knock-out mouse to uncover cell-type-specific functional roles of GLT-1. Inactivation of the GLT-1 gene was achieved in either neurons or astrocytes by expression of synapsin-Cre or inducible human GFAP-CreERT2. Elimination of GLT-1 from astrocytes resulted in loss of ∼80% of GLT-1 protein and of glutamate uptake activity that could be solubilized and reconstituted in liposomes. This loss was accompanied by excess mortality, lower body weight, and seizures suggesting that astrocytic GLT-1 is of major importance. However, there was only a small (15%) reduction that did not reach significance of glutamate uptake into crude forebrain synaptosomes. In contrast, when GLT-1 was deleted in neurons, both the GLT-1 protein and glutamate uptake activity that could be solubilized and reconstituted in liposomes were virtually unaffected. These mice showed normal survival, weight gain, and no seizures. However, the synaptosomal glutamate uptake capacity (Vmax) was reduced significantly (40%). In conclusion, astrocytic GLT-1 performs critical functions required for normal weight gain, resistance to epilepsy, and survival. However, the contribution of astrocytic GLT-1 to glutamate uptake into synaptosomes is less than expected, and the contribution of neuronal GLT-1 to synaptosomal glutamate up...