Purpose: Organic cation transporters 1-3 (OCT1-3; Slc22a1-3) mediate the membrane transport of organic cations in the kidney. We previously reported that rat (r)OCT2 expression in the kidney was regulated by testosterone. In this study, we examined the transcriptional mechanisms underlying the testosterone-dependent regulation of rOCT2 expression.
Methods: Approximately 3000-bp fragments of the rOCT1-3 promoter region were isolated, and promoter activities were measured in the renal epithelial cell line LLC-PK1 with the coexpression of rat androgen receptor.
Results: Among reporter constructs tested, only rOCT2 promoter activity was stimulated by testosterone. This stimulation was suppressed by nilutamide, an antiandrogen drug. Reporter assays using deletion constructs and mutational constructs of putative androgen response elements (ARE) in the rOCT2 promoter region suggested that two AREs, located at approximately -3000 and -1300, respectively, play an important role in the induction by testosterone.
Conclusions: Testosterone induces the expression of rOCT2, but not of rOCT1 and rOCT3, via the AR-mediated transcriptional pathway. This is the first study to address the transcriptional mechanisms of testosterone-dependent gene regulation of the Slc22 family.