The multidrug transporter MATE1 sequesters OCs within an intracellular compartment that has no influence on OC secretion in renal proximal tubules

Am J Physiol Renal Physiol. 2016 Jan 1;310(1):F57-67. doi: 10.1152/ajprenal.00318.2015. Epub 2015 Nov 4.

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.

Keywords: multidrug and toxin extruder 1; organic cation secretion; proximal tubule; transport.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • 1-Methyl-4-phenylpyridinium / metabolism
  • 4-Chloro-7-nitrobenzofurazan / analogs & derivatives
  • 4-Chloro-7-nitrobenzofurazan / metabolism
  • Animals
  • CHO Cells
  • Cricetulus
  • Endosomes / metabolism
  • Fluorescent Dyes / metabolism
  • Kidney Tubules, Proximal / metabolism*
  • Kinetics
  • Male
  • Microscopy, Fluorescence
  • Organic Cation Transport Proteins / genetics
  • Organic Cation Transport Proteins / metabolism*
  • Organic Cation Transporter 2
  • Quaternary Ammonium Compounds / metabolism
  • Rabbits
  • Renal Elimination*
  • Renal Reabsorption*
  • Transfection
  • Vacuolar Proton-Translocating ATPases / metabolism

Substances

  • Fluorescent Dyes
  • N,N,N-trimethyl-2-(methyl(7-nitrobenzo(c)(l,2,5)oxadiazol-4-yl)amino)ethanaminium
  • Organic Cation Transport Proteins
  • Organic Cation Transporter 2
  • Quaternary Ammonium Compounds
  • SLC22A2 protein, human
  • SLC47A1 protein, human
  • Vacuolar Proton-Translocating ATPases
  • 4-Chloro-7-nitrobenzofurazan
  • 1-Methyl-4-phenylpyridinium