Research ReportAmino-terminal isoforms of the human glycine transporter GlyT1 exhibit similar pharmacology

Alternative promoter usage and mRNA precursor splicing produce three amino-terminal isoforms of the human glycine transporter type 1 (GlyT1). To enable discovery of pharmacological tools that might distinguish them, each of these isoforms was stably expressed in CHO-K1 cells and clonal isolates were generated by limiting dilution. Glycine uptake assays were validated for two lines for each isoform, one low and one high expressor. The data show a modest trend for lower potency against higher expressing lines. IC50 values for reference GlyT1 inhibitors ALX-5407 (Allelix), (S)-13h (Merck), and SSR504734 (Sanofi-Synthelabo) were similar across isoforms. The greatest variation was observed for ALX-5407, and its IC50 values across isoforms were still within one log unit of each other. Antipsychotics previously shown to be weak inhibitors of GlyT1 likewise had similar potency against all three isoforms. The cell lines validated here are tools for discovering inhibitors that might distinguish among GlyT1 isoforms.

Research Highlights► Three amino-terminal isoforms of GlyT1 are each expressed in clonal cell lines. ► Inhibitor potency depends modestly on transporter expression level. ► Amino-terminal isoforms of GlyT1 exhibit similar pharmacology.