Identification and characterization of novel polymorphisms in the basal promoter of the human transporter, MATE1

Abstract

Human multidrug and toxin extrusion member 1, MATE1 (SLC47A1), plays an important role in the renal and biliary excretion of endogenous and exogenous organic cations including many therapeutic drugs. In this study, we characterized the transcriptional effects of five polymorphic variants and six common haplotypes in the basal promoter region of MATE1 that were identified in 272 DNA samples from ethnically diverse U.S. populations. We measured luciferase activities of the six common promoter haplotypes of MATE1 using in vitro and in vivo reporter assays. Haplotypes that contain the most common variant (mean allele frequency in four ethnics: 0.322), g.−66T>C, showed a significant decrease in reporter activities compared to the reference. Two transcription factors, AP-1 and AP-2rep, were predicted to bind to the promoter in the region of g.−66T>C. Results from electrophoretic mobility shift assays showed that the g.−66T allele, exhibited greater binding to AP-1 than the g.−66C allele. AP-2rep inhibited the binding of AP-1 to the MATE1 basal promoter region, and the effect was considerably greater for the g.−66T>C. These data suggest that the reduced transcriptional activity of g.−66T>C results from a reduction in the binding potency of the transcriptional activator, AP-1, and an enhanced binding potency of the repressor, AP-2rep to the MATE1 basal promoter region. Consistent with the reporter assays, MATE1 mRNA expression levels were significantly lower in kidney samples from individuals who were homozygous or heterozygous for g.−66T>C in comparison to samples from individuals who were homozygous for the g.−66T allele. Our study suggests that the rate of transcription of MATE1 is regulated by AP-1 and AP-2rep and that a common promoter variant, g.−66T>C may affect the expression level of MATE1 in human kidney, and ultimately result in variation in drug disposition and response.

SLC47A1 gene rs2289669 G>A variants enhance the glucose-lowering effect of metformin via delaying its excretion in Chinese type 2 diabetes patients

“…The mutations G64D and V480M caused the expression abolition in membranes, resulting in a complete loss of function. Moreover, polymorphisms in the promoter and 5 0 UTR region of MATE1 were reported to decrease transcriptional activity with respective allelic frequency of 3.7% and 23.1-44.5% [23,28]. The SNP rs2289669 is located in the 10th intron of the SLC47A1, and this SNP does not code for an amino acid change.…”

“…Previous study suggested that metformin was a substrate for MATE1 and MATE1 protein mediated transcellular transport of metformin in vitro [21,22]. Meanwhile, novel polymorphisms in MATE1 were reported to affect the expression level and transport function of MATE1 in human kidney, ultimately resulting in variation in metformin disposition and response [23,24]. The oral absorption, hepatic uptake and renal excretion were considered to be key determinants of the glucose lowering response to metformin [25].…”

The Effect of Famotidine, a MATE1-Selective Inhibitor, on the Pharmacokinetics and Pharmacodynamics of Metformin

“…Likewise, a common mutation in the promoter region of the MATE1 gene (T>C, SNP rs2252281) is associated with improved response to metformin in T2DM patients (greater A1C reduction) as well as in healthy volunteers (greater glucose-lowering effect)[22]. Functional studies demonstrate that the T>C mutation in the promoter region of the MATE1 gene alters the binding affinity for MATE1 transcription factors (i.e., activator AP-1 and repressor AP-2rep), which reduces MATE1 mRNA expression levels in in vitro assays [26]. Although an effect of genetic variants in MATE1 on human pharmacokinetics has not been observed, these studies suggest that MATE1 plays an important role in the distribution of metformin to target tissues as well as in the glycemic response to metformin.…”

The Hydrodynamic Tail Vein Assay as a Tool for the Study of Liver Promoters and Enhancers

“…In addition, the reference sequence of the assayed promoter is typically used as a baseline to compare the promoter activity of nucleotide variants [19]. …”