The recombinant GABA transporter GAT1 is downregulated upon activation of protein kinase C

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Abstract
Treatment of human embryonic kidney 293 cells expressing the rat γ‐aminobutyric acid (GABA) transporter 1 (GAT1) with the protein kinase C (PKC) activator phorbol 12‐myristate 13‐acetate (PMA) was found to decrease the velocity of specific [3H]GABA uptake. This downregulation varied with extracellular GABA concentration and was blocked by the PKC inhibitors 1‐(5‐isoquinolinylsulphonyl)‐2‐methylpiperazine (H7) and staurosporine. An about 50% reduction of uptake velocity by PMA treatment was observed at GABA concentrations > 1 μM, whereas only a minor effect was seen at low substrate concentrations. These data indicate that GAT1 activity is downregulated by PKC activation.