title: Interaction of tomato lectin with ABC transporter in cancer cells: glycosylation confers functional conformation of P-gp.
abstract: Phospho-glycoprotein (P-gp) is a polytopic plasma membrane protein whose overexpression causes multidrug resistance (MDR) responsible for the failure of cancer chemotherapy. P-gp 170 is a member of the ATP-binding cassette (ABC) transporter superfamily and has two potentially interesting regions for drugs interfering with its efflux function, namely the oligosaccharides on the first extracellular loop with unknown function and the two intracellular ATP-binding regions providing the energy for drug efflux function. The polylactoseamine oligosaccharides on the first loop can specifically bind the tomato lectin (TL). The P-gp efflux activities of TL-pre-treated MDR resistant cells were measured in the presence of structurally unrelated resistance modifiers such as phenothiazines, terpenoids and carotenoids. The inhibition of efflux activity was measured via the increased rhodamine uptake by mouse lymphoma cells transfected in human MDR1 gene and in human brain capillary endothelial cells. The tested resistance modifiers inhibit the function of ABC transporter resulting in increased R123 accumulation in MDR1 expressing cells. TL prevented the inhibitory action of phenothiazine and verapamil on brain capillary endothelial and MDR1-lymphoma cells, presumably due to the stabilization of the functional active conformation of P-gp. Our results indicate that the polylactosamine chains of P-gp are part of the functionally active protein conformation.
authors.affiliation: Department of Medical Microbiology and Immunbiology, Faculty of Medicine, University of Szeged, Dom ter 10, H-6720 Szeged, Hungary. molnarj@comser.szote.u-szeged.hu
authors.forename: Joseph
authors.initials: J
authors.lastname: Molnár
authors.forename: Meltem Demirel
authors.initials: MD
authors.lastname: Kars
authors.forename: Ufuk
authors.initials: U
authors.lastname: Gündüz
authors.forename: Helga
authors.initials: H
authors.lastname: Engi
authors.forename: Udo
authors.initials: U
authors.lastname: Schumacher
authors.forename: Els J
authors.initials: EJ
authors.lastname: Van Damme
authors.forename: Willy J
authors.initials: WJ
authors.lastname: Peumans
authors.forename: Josef
authors.initials: J
authors.lastname: Makovitzky
authors.forename: Nóra
authors.initials: N
authors.lastname: Gyémánt
authors.forename: Péter
authors.initials: P
authors.lastname: Molnár
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000737:chemistry* / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects*; D002460:Cell Line; D045744:Cell Line, Tumor; D018492:Dopamine Antagonists / Q000493:pharmacokinetics / Q000494:pharmacology; D018432:Drug Resistance, Multiple / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D019084:Fluorescent Antibody Technique, Indirect; D005456:Fluorescent Dyes / Q000493:pharmacokinetics / Q000494:pharmacology; D006031:Glycosylation / Q000187:drug effects*; D006634:Histamine H1 Antagonists / Q000493:pharmacokinetics / Q000494:pharmacology; D006801:Humans; D051379:Mice; D008968:Molecular Conformation; D010640:Phenothiazines / Q000493:pharmacokinetics / Q000494:pharmacology; D037121:Plant Lectins / Q000494:pharmacology*; D011398:Promethazine / Q000493:pharmacokinetics / Q000494:pharmacology; D012235:Rhodamines / Q000493:pharmacokinetics / Q000494:pharmacology; D014268:Trifluoperazine / Q000493:pharmacokinetics / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018492:Dopamine Antagonists; D005456:Fluorescent Dyes; D006634:Histamine H1 Antagonists; D010640:Phenothiazines; D037121:Plant Lectins; D012235:Rhodamines; C034981:tomato lectin; D014268:Trifluoperazine; D011398:Promethazine