title: Substrate specificity of MATE1 and MATE2-K, human multidrug and toxin extrusions/H(+)-organic cation antiporters.
abstract: The substrate specificities of human (h) multidrug and toxin extrusion (MATE) 1 and hMATE2-K were examined to find functional differences between these two transporters by the transfection of the cDNA of hMATE1 and hMATE2-K into HEK293 cells. Western blotting revealed specific signals for hMATE1 and hMATE2-K consistent with a size of 50 and 40kDa, respectively, in the transfectants as well as human renal brush-border membranes under reducing conditions. In the presence of oppositely directed H(+)-gradient, the transport activities of various compounds such as tetraethylammonium, 1-methyl-4-phenylpyridinium, cimetidine, metformin, creatinine, guanidine, procainamide, and topotecan were stimulated in hMATE1- and hMATE2-K-expressing cells. In addition to cationic compounds, anionic estrone sulfate, acyclovir, and ganciclovir were also recognized as substrates of these transporters. Kinetic analyses demonstrated the Michaelis-Menten constants for the hMATE1-mediated transport of tetraethylammonium, 1-methyl-4-phenylpyridinium, cimetidine, metformin, guanidine, procainamide, topotecan, estrone sulfate, acycrovir, and ganciclovir to be (in mM) 0.38, 0.10, 0.17, 0.78, 2.10, 1.23, 0.07, 0.47, 2.64, and 5.12, respectively. Those for hMATE2-K were 0.76, 0.11, 0.12, 1.98, 4.20, 1.58, 0.06, 0.85, 4.32, and 4.28, respectively. Although their affinity for hMATE1 and hMATE2-K was similar, the zwitterionic cephalexin and cephradine were revealed to be specific substrates of hMATE1, but not of hMATE2-K. Levofloxacin and ciprofloxacin were not transported, but were demonstrated to be potent inhibitors of these transporters. These results suggest that hMATE1 and hMATE2-K function together as a detoxication system, by mediating the tubular secretion of intracellular ionic compounds across the brush-border membranes of the kidney.
authors.affiliation: Department of Pharmacy, Kyoto University Hospital, Sakyo-ku, Kyoto 606-8507, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Tanihara
authors.forename: Satohiro
authors.initials: S
authors.lastname: Masuda
authors.forename: Tomoko
authors.initials: T
authors.lastname: Sato
authors.forename: Toshiya
authors.initials: T
authors.lastname: Katsura
authors.forename: Osamu
authors.initials: O
authors.lastname: Ogawa
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Inui
mesh_terms: D002478:Cells, Cultured; D002506:Cephalexin / Q000378:metabolism; D006801:Humans; D007668:Kidney / Q000378:metabolism*; D027701:Organic Cation Transport Proteins / Q000502:physiology*; D011522:Protons; D013379:Substrate Specificity; D013757:Tetraethylammonium Compounds / Q000378:metabolism; D014118:Toxins, Biological / Q000378:metabolism*
chemical_list: D027701:Organic Cation Transport Proteins; D011522:Protons; C521869:SLC47A1 protein, human; C521870:SLC47A2 protein, human; D013757:Tetraethylammonium Compounds; D014118:Toxins, Biological; D002506:Cephalexin