AMPA receptor protein expression and function in astrocytes cultured from hippocampus

Abstract

Glutamate receptors guide the proliferation, migration, and differentiation of glial cells. Here, we characterize AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid) and NMDA receptor protein expression and function and mRNA expression in hippocampal glial cultures. By immunocytochemistry, GluR2 (the subunit that limits the Ca(2+) permeability of AMPA receptors) exhibited prominent labeling in hippocampal glial cultures. Double-labeling of GluR2 with GFAP and with A2B5 revealed GluR2 subunit expression on type-1 and type-2 astrocyte lineage cells. GluR1 subunit expression was more prominent in type-1 than in type-2 astrocytes. To characterize functional properties of glutamate receptors expressed in cultured hippocampal astrocytes, we performed whole-cell patch clamp recording. Application of L-glutamate, AMPA, and kainate, but not NMDA, to small, rounded cells (morphologically identified as type-2 astrocytes) elicited inward currents which were blocked by the AMPA/kainate antagonist 6-cyano-7-nitroquinoxaline-2, 3-dione (CNQX). Cyclothiazide potentiated AMPA- and kainate-elicited currents, indicative of AMPA-preferring receptors. Current voltage analysis indicated that type-2 astrocyte AMPA receptors were electrically linear, indicative of GluR2-containing, Ca(2+)-impermeable AMPA receptors. By Northern blot analysis, GluR1 mRNA was highest in astrocyte cultures from cerebellum and hippocampus and moderate in astrocyte cultures from neocortex and striatum. GluR3 mRNA was detectable in astrocyte cultures from cerebellum and neocortex. GluR2 and NR1 mRNA expression were not detected in astrocytes cultured from any brain region examined. In situ hybridization studies showed wide expression of GluR1 mRNA in cultured astrocytes; GluR2 and GluR3 mRNAs were near background levels. Thus, cultured type-2 astrocytes express functional AMPA receptors in a cell-specific and region-specific manner, consistent with their role in neuronal-glial communication.

Remodeling of α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid receptor subunit composition in hippocampal neurons after global ischemia

“…Second, Westerns do not distinguish between neuronal and nonneuronal cell protein. Cultured hippocampal astrocytes exhibit intense GluR1 and weak GluR2 immunolabeling (44). Although GluR2 immunolabeling is strongest in cell somata and proximal dendrites of neurons, labeling of distal dendrites and astrocytes in a larger volume might contribute significantly.…”

AMPA Receptor-Dependent H2O2 Generation in Striatal Medium Spiny Neurons But Not Dopamine Axons: One Source of a Retrograde Signal That Can Inhibit Dopamine Release

“…Of course, contributions from the remaining 5-10% of striatal neurons could also occur as most of these express AMPAR subunits (Deng et al 2007). Striatal glia might contribute, as well, with the caveat that although cultured striatal astrocytes express AMPAR protein (Fan et al 1999), there are no reports of functional consequences of AMPAR activation in these cells in striatum.…”

Neurotoxicity of Domoic Acid in Cerebellar Granule Neurons in a Genetic Model of Glutathione Deficiency

“…at ASPET Journals on May 11, 2018 molpharm.aspetjournals.org sponses to KA have been reported, possibly mediated by AMPA receptors (Telgkamp et al, 1996;Fan et al, 1999). Furthermore, whether NMDA receptors exist in astrocytes is also controversial (Ziak et al, 1998;Seifert and Steinhauser, 2001).…”