title: Binding properties of monoclonal antibodies recognizing external epitopes of the human MDR1 P-glycoprotein.
abstract: Monoclonal antibodies (MAbs) recognizing external epitopes of the human MDR1 P-glycoprotein have been used both for the detection of multidrug-resistant cells and as specific inhibitors of P-glycoprotein-mediated multidrug resistance. Using a panel of recently developed transfected or transgenic cell lines containing variants of the human MDR1 and MDR3 P-glycoproteins, we have compared the specificity and binding properties of the previously isolated MAbs MRK16, HYB-241, UIC2 and 4E3, and of the newly isolated MAb 7G4. The removal of 1, 2 or all 3 of the N-glycosylation sites present in the first extracellular loop of MDR1 P-glycoprotein did not significantly affect the binding of these MAbs. In contrast, 20 amino acid deletion in the first extracellular loop of MDR1 P-glycoprotein completely abolished binding of UIC2, whereas the binding of all other MAbs was hardly affected. None of the MAbs tested bound detectably to cell lines containing a high level of the human MDR3 P-glycoprotein. The differences in the binding specificity between UIC2 and the other tested antibodies parallel the reported functional differences in the ability of these antibodies to inhibit P-glycoprotein-mediated drug efflux.
authors.affiliation: Division of Molecular Biology, The Netherlands Cancer Institute, Amsterdam.
authors.forename: A H
authors.initials: AH
authors.lastname: Schinkel
authors.forename: R J
authors.initials: RJ
authors.lastname: Arceci
authors.forename: J J
authors.initials: JJ
authors.lastname: Smit
authors.forename: E
authors.initials: E
authors.lastname: Wagenaar
authors.forename: F
authors.initials: F
authors.lastname: Baas
authors.forename: M
authors.initials: M
authors.lastname: Dollé
authors.forename: T
authors.initials: T
authors.lastname: Tsuruo
authors.forename: E B
authors.initials: EB
authors.lastname: Mechetner
authors.forename: I B
authors.initials: IB
authors.lastname: Roninson
authors.forename: P
authors.initials: P
authors.lastname: Borst
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D002352:Carrier Proteins / Q000032:analysis / Q000276:immunology / Q000378:metabolism*; D002462:Cell Membrane / Q000276:immunology / Q000378:metabolism; D004351:Drug Resistance; D005347:Fibroblasts / Q000378:metabolism; D005434:Flow Cytometry; D006031:Glycosylation; D006801:Humans; D008545:Melanoma / Q000235:genetics / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000032:analysis / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000911:Antibodies, Monoclonal; D002352:Carrier Proteins; D008562:Membrane Glycoproteins