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  • Title: Ephrin-A3 reverse signaling regulates hippocampal neuronal damage and astrocytic glutamate transport after transient global ischemia.
    Author: Yang J, Luo X, Huang X, Ning Q, Xie M, Wang W.
    Journal: J Neurochem; 2014 Nov; 131(3):383-94. PubMed ID: 25040798.
    Abstract:
    Increasing evidence indicates that the Eph receptors and their ephrin ligands are involved in the regulation of interactions between neurons and astrocytes. Moreover, astrocytic ephrin-A3 reverse signaling mediated by EphA4 receptors is necessary for controlling the abundance of glial glutamate transporters. However, the role of ephrin-A3 reverse signaling in astrocytic function and neuronal death under ischemic conditions remains unclear. In the present study, we found that the EphA4 receptor and its ephrin-A3 ligand, which were distributed in neurons and astrocytes, respectively, in the hippocampus showed a coincident up-regulation of protein expression in the early stage of ischemia. Application of clustered EphA4 decreased the expressions of astrocytic glutamate transporters together with astrocytic glutamate uptake capacity through activating ephrin-A3 reverse signaling. In consequence, neuronal loss was aggravated in the CA1 region of the hippocampus accompanied by impaired hippocampus-dependent spatial memory when clustered EphA4 treatment was administered prior to transient global ischemia. These findings indicate that EphA4-mediated ephrin-A3 reverse signaling is a crucial mechanism for astrocytes to control glial glutamate transporters and prevent glutamate excitotoxicity under pathological conditions. Astrocytic ephrin-A3 reverse signaling mediated by EphA4 receptor is necessary for controlling the abundance of glial glutamate transporters under physiological conditions. However, the role of ephrin-A3 reverse signaling in astrocytic function and neuronal death under ischemic conditions remains unclear. We found EphA4-mediated ephrin-A3 reverse signaling to be a crucial mechanism for astrocytes to control glial glutamate transporters and protect hippocampal neurons from glutamate excitotoxicity under ischemic conditions, this cascade representing a potential therapeutic target for stroke.
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