Regulation of the Glial Na+-Dependent Glutamate Transporters by Cyclic AMP Analogs and Neurons

• DOI: 10.1124/mol.53.3.355
• Publication Date: 2018-01-08T20:29:50Z
• Authors: Brian D. Schlag; Joanna R. Vondrasek; Muhammad Munir; Avtandil Kalandadze; Olga A. Zelenaia; Jeffrey D. Rothstein; Michael B. Robinson
• Keywords: Neuroglia; Glutamate aspartate transporter

Sodium-dependent transport into astrocytes is critical for maintaining the extracellular concentrations of glutamate below toxic levels in central nervous system. In this study, expression glial transporters GLT-1 and GLAST was studied primary cultures derived from cortical tissue. astrocytes, protein were approximately one half those observed tissue, but present at very low compared with Maintenance these medium supplemented dibutyryl-cAMP (dbcAMP) caused a dramatic change cell morphology, increased mRNA ≈5-fold, ≈2-fold, ≥8–20-fold. These increases accompanied by 2-fold <i>V</i>_max and<i>K</i>_<i>m</i> values Na⁺-dependentl-[³H]glutamate activity. Although sensitive to inhibition dihydrokainate heterologous systems, no sensitivity astrocyte that expressed GLT-1. Biotinylation membrane-impermeant reagent, separation biotinylated/cell surface proteins, subsequent Western blotting demonstrated both surface. Coculturing neurons also induced GLT-1, which colocalized specific marker, fibrillary acidic protein. Neurons small increase Several studies performed examine mechanism regulate transporters. Three different kinase A (PKA) antagonists did not block effect on protein, addition dbcAMP mixed cause further. This suggests do activation PKA through convergent pathways. As cocultures blocked antagonists, unlike ≈2-fold. separated semipermeable membrane indicating mediated diffusible molecule. Treatment high either<i>N</i>-methyl-d-aspartate or killed neurons, decrease, increase. suggest are regulated independently molecule secreted induces astrocytes.