title: The multidrug transporter MATE1 sequesters OCs within an intracellular compartment that has no influence on OC secretion in renal proximal tubules.
abstract: Secretion of organic cations (OCs) across renal proximal tubules (RPTs) involves basolateral OC transporter (OCT)2-mediated uptake from the blood followed by apical multidrug and toxin extruder (MATE)1/2-mediated efflux into the tubule filtrate. Whereas OCT2 supports electrogenic OC uniport, MATE is an OC/H(+) exchanger. As assessed by epifluorescence microscopy, cultured Chinese hamster ovary (CHO) cells that stably expressed human MATE1 accumulated the fluorescent OC N,N,N-trimethyl-2-[methyl(7-nitrobenzo[c][l,2,5]oxadiazol-4-yl)amino]ethanaminium (NBD-MTMA) in the cytoplasm and in a smaller, punctate compartment; accumulation in human OCT2-expressing cells was largely restricted to the cytoplasm. A second intracellular compartment was also evident in the multicompartmental kinetics of efflux of the prototypic OC [(3)H]1-methyl-4-phenylpyridinium (MPP) from MATE1-expressing CHO cells. Punctate accumulation of NBD-MTMA was markedly reduced by coexposure of MATE1-expressing cells with 5 μM bafilomycin (BAF), an inhibitor of V-type H(+)-ATPase, and accumulation of [(3)H]MPP and [(3)H]NBD-MTMA was reduced by >30% by coexposure with 5 μM BAF. BAF had no effect on the initial rate of MATE1-mediated uptake of NBD-MTMA, suggesting that the influence of BAF was a secondary effect involving inhibition of V-type H(+)-ATPase. The accumulation of [(3)H]MPP by isolated single nonperfused rabbit RPTs was also reduced >30% by coexposure to 5 μM BAF, suggesting that the native expression in RPTs of MATE protein within endosomes can increase steady-state OC accumulation. However, the rate of [(3)H]MPP secretion by isolated single perfused rabbit RPTs was not affected by 5 μM BAF, suggesting that vesicles loaded with OCs(+) are not likely to recycle into the apical plasma membrane at a rate sufficient to provide a parallel pathway for OC secretion.
authors.affiliation: Department of Physiology, College of Medicine, University of Arizona, Tucson, Arizona.
authors.forename: L J
authors.initials: LJ
authors.lastname: Martínez-Guerrero
authors.affiliation: Department of Physiology, College of Medicine, University of Arizona, Tucson, Arizona.
authors.forename: K K
authors.initials: KK
authors.lastname: Evans
authors.affiliation: Department of Physiology, College of Medicine, University of Arizona, Tucson, Arizona.
authors.forename: W H
authors.initials: WH
authors.lastname: Dantzler
authors.affiliation: Department of Physiology, College of Medicine, University of Arizona, Tucson, Arizona shwright@email.arizona.edu.
authors.forename: S H
authors.initials: SH
authors.lastname: Wright
mesh_terms: D015655:1-Methyl-4-phenylpyridinium / Q000378:metabolism; D009327:4-Chloro-7-nitrobenzofurazan / Q000031:analogs & derivatives / Q000378:metabolism; D000818:Animals; D016466:CHO Cells; D003412:Cricetulus; D011992:Endosomes / Q000378:metabolism; D005456:Fluorescent Dyes / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008856:Microscopy, Fluorescence; D027701:Organic Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D000075102:Organic Cation Transporter 2; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D011817:Rabbits; D065667:Renal Elimination; D065608:Renal Reabsorption; D014162:Transfection; D025262:Vacuolar Proton-Translocating ATPases / Q000378:metabolism
chemical_list: D005456:Fluorescent Dyes; C583572:N,N,N-trimethyl-2-(methyl(7-nitrobenzo(c)(l,2,5)oxadiazol-4-yl)amino)ethanaminium; D027701:Organic Cation Transport Proteins; D000075102:Organic Cation Transporter 2; D000644:Quaternary Ammonium Compounds; C491013:SLC22A2 protein, human; C521869:SLC47A1 protein, human; D025262:Vacuolar Proton-Translocating ATPases; D009327:4-Chloro-7-nitrobenzofurazan; D015655:1-Methyl-4-phenylpyridinium
keywords: multidrug and toxin extruder 1; organic cation secretion; proximal tubule; transport