Molecular cloning, functional characterization and genomic organization offour alternatively spliced isoforms of the human organic cation transporter 1 (hOCT1/SLC22A1)

In this study we report the cloning of four human OCT1 (hOCT1/SLC22A1) isof orms: a long form, hOCT1G/L554, and three shorter forms (hOCT1G/L506, hOCT1 G483 and hOCT1G353). All four variants could be identified in the human gli oma cell line SK-MG-1, whereas only two isoforms (hOCT1G/L554 and hOCT1G/L5 06) were found in human liver cDNA. The llOCT1G/L554 represents the full le ngth hOCT1 since the sequence of this clone is more than 99% identical to p reviously cloned hOCT1 cDNAs. Elucidation of the gene structure of human OC T1 demonstrated that the other isolated isoforms are alternatively spliced variants. The hOCT1 gene consists of 7 exons and 6 introns. When stably exp ressed in human embryonic kidney (HEK293) cells, only the full length hOCT1 cDNA mediated decynium-22 (D22)-sensitive uptake of tritiated 1-methyl-4-p henylpgridinium ([H-3]-MPP+).