title: Identification and functional characterization of novel nonsynonymous variants in the human multidrug and toxin extrusion 2-K.
abstract: This study was performed to identify genetic polymorphisms in multidrug and toxin extrusion 2-K (MATE2-K, SLC47A2), a proton/organic cation antiporter that plays a role in the transport of organic cations across the apical membrane in kidney epithelial cells into the urine, and to demonstrate their effects on MATE2-K functions in vitro. Four of the thirty single nucleotide polymorphisms (SNPs) we identified in three ethnic groups (Caucasian, African American, and Japanese) were novel [308C>G (P103R), c.487-8C>T, 818A>G (Y273C), and c.1018+14T>C]. The transport activities of the prototypical substrates, tetraethylammonium and metformin, for four nonsynonymous SNPs (P103R, P162L, G211V, and Y273C) were significantly different from those of the wild-type. In particular, transport activity was higher in P103R than in the wild-type, which is the first time elevated transport activity was demonstrated due to these coding SNPs. Kinetic analysis revealed that P103R had a higher Vmax value, whereas Y273C had a lower value than that in the wild-type. Cell surface protein expression levels were higher for P103R than for the wild-type, whereas Y273C expression was decreased. Immunofluorescence analysis revealed that the P103R protein was localized to the plasma membrane, whereas Y273C showed cytoplasmic localization. Therefore, the difference in transport activities between P103R and Y273C variants was suggested to be responsible for the different protein expression levels observed at the plasma membrane. Four nonsynonymous SNPs in this study showed relatively low allelic frequencies (0.5 to 2.1%), but these were associated with markedly reduced or increased MATE2-K function.
authors.affiliation: Department of Clinical Pharmacokinetics, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Kenta
authors.initials: K
authors.lastname: Nishimura
authors.affiliation: Department of Clinical Pharmacokinetics, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Ide
authors.affiliation: Department of Clinical Pharmacokinetics, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Hirota
authors.affiliation: Department of Clinical Pharmacokinetics, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Kana
authors.initials: K
authors.lastname: Kawazu
authors.affiliation: Department of Clinical Pharmacokinetics, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Sho
authors.initials: S
authors.lastname: Kodama
authors.affiliation: Department of Clinical Pharmacokinetics, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Takesue
authors.affiliation: Department of Clinical Pharmacokinetics, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan ieiri-ttr@umin.ac.jp.
authors.forename: Ichiro
authors.initials: I
authors.lastname: Ieiri
mesh_terms: D000483:Alleles; D002460:Cell Line; D002462:Cell Membrane / Q000235:genetics; D005787:Gene Frequency / Q000235:genetics; D005838:Genotype; D057809:HEK293 Cells; D006801:Humans; D007700:Kinetics; D027701:Organic Cation Transport Proteins / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide / Q000235:genetics*
chemical_list: D027701:Organic Cation Transport Proteins; C521870:SLC47A2 protein, human