Decreased function of genetic variants, Pro283Leu and Arg287Gly, in human organic cation transporter hOCT1.

We have evaluated the functional consequences of genetic variations in human organic cation transporter hOCT1 (SLC22A1). Three coding single nucleotide polymorphisms (cSNPs) resulted in the amino acid changes Pro283Leu, Arg287Gly and Pro341Leu were assessed. Uptake experiments with transient expression system using HEK293 cells revealed that the variants Pro283Leu and Arg287Gly had completely diminished transport activity. The other variant Pro341Leu had a significantly, but not completely, decreased transport activity. Western blot analysis showed that the expression levels of all three variant proteins in the crude membranes of HEK293 cells were comparable to those of wild type hOCT1. Moreover, the expression of variant proteins at the plasma membrane was confirmed by indirect immunofluorescence, indicating that these SNPs did not affect the membrane localization of hOCT1. Present results suggest that the amino acid residues Pro283 and Arg287 have a substantial role in substrate recognition of hOCT1.