title: Characterization of the human MATE2 proton-coupled polyspecific organic cation exporter.
abstract: Human multidrug and toxic compound extrusion 2 (hMATE2) is a kidney-specific isoform of hMATE1, an exporter of toxic organic cations (OCs) of exogenous and endogenous origins at the final excretion step in the kidneys and liver (Otsuka et al., 2005), and contains a splicing variant, MATE2K, that has an exon of hMATE2 deleted (Masuda et al., 2006). In the present study, we characterized the degree of expression and the transport properties of hMATE2. Quantitative PCR analysis with probes specific for hMATE2 indicated the presence of hMATE2 mRNA in the kidneys, which corresponded to 39% of total mRNA encoding both hMATE2 and hMATE2K. hMATE2-specific antibodies immunostained the renal urinary tubules. Upon expression in HEK293 cells, hMATE2 was localized in intracellular vesicular structures, and thus transport activity of tetraethylammonium (TEA), a typical substrate for MATE transporters, by the cells was not detected. The hMATE2 protein was purified and reconstituted into liposomes. An artificially imposed pH gradient (ΔpH) across the proteoliposomal membrane drove the uptake of TEA. Dissipation of ΔpH by ammonium sulfate effectively inhibited the TEA uptake, while that of the membrane potential by valinomycin had little effect. The profiles of cis-inhibition of TEA transport by hMATE2 and hMATE2K are similar to each other. Thus, both hMATE2 and hMATE2K equally operate in the human kidneys to extrude OCs into the urine.
authors.affiliation: Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan.
authors.forename: Toshinori
authors.initials: T
authors.lastname: Komatsu
authors.forename: Miki
authors.initials: M
authors.lastname: Hiasa
authors.forename: Takaaki
authors.initials: T
authors.lastname: Miyaji
authors.forename: Takuji
authors.initials: T
authors.lastname: Kanamoto
authors.forename: Takuya
authors.initials: T
authors.lastname: Matsumoto
authors.forename: Masato
authors.initials: M
authors.lastname: Otsuka
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Moriyama
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Omote
mesh_terms: D000906:Antibodies / Q000378:metabolism; D001711:Biotransformation; D002460:Cell Line; D022162:Cytoplasmic Vesicles / Q000378:metabolism; D006801:Humans; D007668:Kidney / Q000378:metabolism* / Q000473:pathology; D008081:Liposomes / Q000378:metabolism; D009928:Organ Specificity; D027701:Organic Cation Transport Proteins / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism*; D009930:Organic Chemicals / Q000493:pharmacokinetics*; D019154:Protein Splicing; D021381:Protein Transport; D013379:Substrate Specificity; D019789:Tetraethylammonium / Q000378:metabolism; D019076:Transgenes / Q000235:genetics
chemical_list: D000906:Antibodies; D008081:Liposomes; D027701:Organic Cation Transport Proteins; D009930:Organic Chemicals; C521869:SLC47A1 protein, human; C521870:SLC47A2 protein, human; D019789:Tetraethylammonium