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Membrane localization and pH-dependent transport of a newly cloned organic cation transporter (PMAT) in kidney cells.
- Source :
-
American journal of physiology. Renal physiology [Am J Physiol Renal Physiol] 2007 Feb; Vol. 292 (2), pp. F682-90. Date of Electronic Publication: 2006 Oct 03. - Publication Year :
- 2007
-
Abstract
- Plasma membrane monoamine transporter (PMAT) is a novel membrane transporter recently cloned and characterized in our laboratory. We previously demonstrated that PMAT functions as a polyspecific organic cation transporter and efficiently transports many organic cations such as monoamine neurotransmitters and 1-methyl-4-phenylpyridinium (MPP(+)). In this study, we explored the role of PMAT in the renal handling of organic cations. Using a polyclonal antibody generated toward the NH(2)-terminal 66 amino acid residues of human PMAT, we showed that the PMAT protein (approximately 55 kDa) is expressed in the human kidney and is primarily targeted to the apical membranes when expressed in polarized Madin-Darby canine kidney (MDCK) cells. Using MDCK cells stably expressing human PMAT, we showed that PMAT-mediated MPP(+) uptake is strongly dependent on extracellular pH. Lowering extracellular pH from 7.4 to 6.6 greatly stimulated PMAT-mediated MPP(+) uptake, whereas elevating extracellular pH to 8.2 abolished transporter activity. Kinetic analysis revealed that the apparent V(max) at pH 6.6 is about fourfold higher than that at pH 7.4, whereas the apparent K(m) values were not statistically different at these two conditions. Under acidic conditions (pH 6.6), the proton ionophore, carbonyl cyanide p-trifluormethoxyphenylhydrazone, drastically reduced PMAT-mediated MPP(+) uptake, suggesting that the stimulatory effect of proton may be due to transporter coupling with a proton gradient. Taken together, our data suggest that PMAT is expressed on the apical membranes of renal epithelial cells and may use luminal proton gradient to drive organic cation reabsorption in the kidney.
- Subjects :
- 1-Methyl-4-phenylpyridinium metabolism
Adenosine pharmacology
Animals
Antibody Formation
Cells, Cultured
Cladribine pharmacology
Dogs
Equilibrative Nucleoside Transport Proteins
Histamine metabolism
Humans
Kidney cytology
Nerve Tissue Proteins immunology
Organic Cation Transport Proteins immunology
Tubercidin analogs & derivatives
Tubercidin pharmacology
Cell Membrane chemistry
Kidney chemistry
Nerve Tissue Proteins metabolism
Organic Cation Transport Proteins metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 1931-857X
- Volume :
- 292
- Issue :
- 2
- Database :
- MEDLINE
- Journal :
- American journal of physiology. Renal physiology
- Publication Type :
- Academic Journal
- Accession number :
- 17018840
- Full Text :
- https://doi.org/10.1152/ajprenal.00302.2006