title: Uncouplers of mitochondrial oxidative phosphorylation are not substrates of the erythrocyte glutathione-S-conjugate pump.
abstract: Uncouplers of mitochondrial oxidative phosphorylation, dinitrophenol (DNP) and carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP), were found to stimulate Mg(2+)-ATPase activity of human erythrocyte membranes in a manner competitive with respect to 2,4-dinitrophenyl-S-glutathione (DNP-SG) which suggested that these compounds may also be substrates of the glutathione-S-conjugate pump. We confirm that the stimulation of erythrocyte membrane ATPase activity by DNP and by another uncoupler, carbonyl cyanide m-chlorophenylhydrazone (CCCP), is competitive with respect to DNP-SG. However, we found no evidence for active transport of DNP and CCCP out of erythrocytes and demonstrate that they inhibit the low-affinity component of DNP-SG transport noncompetitively while stimulating the high-affinity DNP-SG transport (mediated by multidrug resistance-associated protein, MRP1). Implications of these findings may indicate the electrogenic nature of MRP1-mediated transport of glutathione-S conjugates and stimulation of aminophospholipid translocase (flippase) rather than the glutathione-S-conjugate pump by the uncouplers.
authors.affiliation: Department of Molecular Biophysics, University of Lódź, Poland. asokal@biol.uni.lodz.pl
authors.forename: A
authors.initials: A
authors.lastname: Sokal
authors.forename: G
authors.initials: G
authors.lastname: Bartosz
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism*; D004912:Erythrocytes / Q000378:metabolism* / Q000648:ultrastructure; D005978:Glutathione / Q000031:analogs & derivatives* / Q000378:metabolism; D006801:Humans; D008928:Mitochondria / Q000378:metabolism*; D010085:Oxidative Phosphorylation
chemical_list: D018528:ATP-Binding Cassette Transporters; C030190:S-(2,4-dinitrophenyl)glutathione; D000251:Adenosine Triphosphatases; D005978:Glutathione