CHARACTERIZATION OF GLYCINE RELEASE MEDIATED BY GLYCINE TRANSPORTER-1STABLY EXPRESSED IN HEK-293 CELLS

We constructed a cell line which stably expresses glycine transporter 1 (GlyT1) proteins. The cell line showed significant [C-14]glycine upt ake and could keep steep glycine concentration gradient between intrac ellular and extracellular space (in > out). Using this cell line, we i nvestigated glycine release mediated by this transporter. The [C-14]gl ycine release was enhanced by extracellular glycine and sarcosine, a s elective inhibitor of the transporter, in a dose-dependent manner. In addition, the replacement of extracellular Na+ with Li+ or extracellul ar Cl- with acetate(-) markedly increased the release. Furthermore, we investigated the effects of extracellular Ca2+ and K+. The removal of these ions also showed enhancement of the release. These results sugg est that glycine transporter 1 protein, which might be involved in the NMDA receptor neurotransmission, can release glycine into the extrace llular space in the vicinity of synapses, and that the release might b e influenced by the extracellular substrate concentration and ion comp osition in the synaptic cleft. (C) 1997 Elsevier Science B.V.