title: The amplified H circle of methotrexate-resistant leishmania tarentolae contains a novel P-glycoprotein gene.
abstract: Acquired resistance to methotrexate in Leishmania species is often associated with the amplification of H circles, 68 kb duplex DNA circles containing a 30 kb inverted repeat. We report here that the H circle of Leishmania tarentolae contains an open reading frame, ltpgpA, that has the attributes of P-glycoproteins (large plasma membrane proteins known to extrude lipophilic drugs from mammalian cells). Although amplification of H circles is associated with proportionally increased levels of a 5.5 kb transcript of the ltpgpA gene, such methotrexate resistant mutants are not cross-resistant to any of the drugs extruded by mammalian multi-drug resistant cells. In Leishmania, ltpgpA is part of a gene family containing at least two other members. Sequences homologous to one of the nucleotide binding sites of ltpgpA are conserved in other kinetoplastida.
authors.affiliation: Division of Molecular Biology, Netherlands Cancer Institute, Amsterdam.
authors.forename: M
authors.initials: M
authors.lastname: Ouellette
authors.forename: F
authors.initials: F
authors.lastname: Fase-Fowler
authors.forename: P
authors.initials: P
authors.lastname: Borst
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018528:ATP-Binding Cassette Transporters / Q000235:genetics*; D000465:Algorithms; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D004351:Drug Resistance / Q000235:genetics*; D005784:Gene Amplification; D005796:Genes; D006801:Humans; D007891:Leishmania / Q000187:drug effects / Q000235:genetics*; D008562:Membrane Glycoproteins / Q000235:genetics*; D008727:Methotrexate / Q000494:pharmacology*; D008969:Molecular Sequence Data; D011487:Protein Conformation; D015800:Protozoan Proteins; D015183:Restriction Mapping; D012689:Sequence Homology, Nucleic Acid
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018528:ATP-Binding Cassette Transporters; D008562:Membrane Glycoproteins; C106891:PgpA protein, Leishmania; D015800:Protozoan Proteins; D008727:Methotrexate