Identification of the multidrug-resistance protein (MRP) as the glutathione-S-conjugate export pump of erythrocytes.
The identification of the multidrug resistance protein (MRP) as a conjugate export pump in several cell types suggested its involvement in the long-known glutathione-S-conjugate transport across erythrocyte membranes. We investigated the ATP-dependent transport of glutathione S-conjugates in human erythrocyte and erythroleukemia cell membrane vesicles using the endogenous conjugate leukotriene C4 (LTC4), known to be a high-affinity substrate for MRP, in addition to S-(2,4-dinitrophenyl)glutathione. The kinetic parameters, including the Km value for LTC4 of 118 +/- 5 nM and the inhibition constants for transport of both substrates for the quinoline-based inhibitor MK 571, were similar to those obtained for transport mediated by recombinant MRP. Direct photoaffinity labeling of human erythrocyte membranes with [3H]LTC4 revealed a major binding protein of about 190 kDa which was immunoprecipitated by an anti-MRP serum. The radiolabeling of this protein was specifically suppressed by the transport inhibitor MK 571. Several additional anti-MRP sera detected the protein of about 190 kDa in human erythrocyte and erythroleukemia cell membranes. These data identify for the first time the glutathione-S-conjugate transporting protein in erythrocyte membranes.
Division of Tumor Biochemistry, Deutsches Krebsforschungszentrum, Heidelberg, Germany.
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L
Pulaski
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Jedlitschky
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I
Leier
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U
Buchholz
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D
Keppler
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000097:blood*; D000255:Adenosine Triphosphate / Q000097:blood; D000345:Affinity Labels; D001693:Biological Transport, Active; D002352:Carrier Proteins / Q000097:blood; D004910:Erythrocyte Membrane / Q000378:metabolism; D004912:Erythrocytes / Q000378:metabolism*; D005978:Glutathione / Q000097:blood*; D006801:Humans; D066298:In Vitro Techniques; D004915:Leukemia, Erythroblastic, Acute / Q000097:blood; D017997:Leukotriene C4 / Q000097:blood; D014407:Tumor Cells, Cultured
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000345:Affinity Labels; D002352:Carrier Proteins; D017997:Leukotriene C4; D000255:Adenosine Triphosphate; D005978:Glutathione