title: P-glycoprotein overexpression in methotrexate-resistant Leishmania tropica.
abstract: A methotrexate (MTX)-resistant Leishmania tropica line develops a stable drug-resistant phenotype in which the resistance mechanism is associated with a significant reduction in MTX accumulation. After a 2 hr exposure to [3H]MTX, a L. tropica line resistant to 1000 microM of MTX did not accumulate more than 3% of the amount of drug incorporated by wild-type cells. The same resistant cell line was found to be cross-resistant to several unrelated drugs. The monoclonal antibody C219, directed against the cytoplasmic domain of mammalian P-glycoproteins, recognized a putative P-glycoprotein of 240 kDa overexpressed in the resistant line. Also, this resistant line showed the overexpression of the putative homolog of the ltpgpE gene, as determined by northern blot analysis using gene-specific probes for the P-glycoprotein genes of Leishmania tarentolae. This overexpression was not correlated with a proportional increase in the copy number of the gene, but Southern blot analysis suggested that the ltpgpE homolog was overexpressed as a consequence of gene rearrangement. This would be considered as an epiphenomenon that probably does not arise from the same MTX-resistant mechanism.
authors.affiliation: Instituto de Parasitología y Biomedicina Lopez-Neyra, Consejo Superior de Investigaciones Científicas, Granada, Spain.
authors.forename: F
authors.initials: F
authors.lastname: Gamarro
authors.forename: M J
authors.initials: MJ
authors.lastname: Chiquero
authors.forename: M V
authors.initials: MV
authors.lastname: Amador
authors.forename: D
authors.initials: D
authors.lastname: Légaré
authors.forename: M
authors.initials: M
authors.lastname: Ouellette
authors.forename: S
authors.initials: S
authors.lastname: Castanys
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D004351:Drug Resistance / Q000235:genetics; D015870:Gene Expression; D007895:Leishmania tropica / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008727:Methotrexate / Q000494:pharmacology*; D010641:Phenotype
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D008727:Methotrexate