title: Overexpression of the putative thiol conjugate transporter TbMRPA causes melarsoprol resistance in Trypanosoma brucei.
abstract: Melaminophenyl arsenical drugs are a mainstay of chemotherapy against late-stage African sleeping sickness, but drug resistance is increasingly prevalent. We describe here the characterization of two genes encoding putative metal-thiol conjugate transporters from Trypanosoma brucei. The two proteins, TbMRPA and TbMRPE, were each overexpressed in trypanosomes, with or without co-expression of two key enzymes in trypanothione biosynthesis, ornithine decarboxylase and gamma-glutamyl-cysteine synthetase. Overexpression of gamma-glutamyl-cysteine synthetase resulted in a twofold increase in cellular trypanothione, whereas overexpression of ornithine decarboxylase had no effect on the trypanothione level. The overexpression of TbMRPA resulted in a 10-fold increase in the IC50 of melarsoprol. The overexpression of the trypanothione biosynthetic enzymes alone gave two- to fourfold melarsoprol resistance, but did not enhance resistance caused by MRPA. Overexpression of TbMRPE had little effect on susceptibility to melarsoprol but did give two- to threefold resistance to suramin.
authors.affiliation: ZMBH, Im Neuenheimer Feld 282, D-69120 Heidelberg, Germany.
authors.forename: Sanjay K
authors.initials: SK
authors.lastname: Shahi
authors.forename: R Luise
authors.initials: RL
authors.lastname: Krauth-Siegel
authors.forename: Christine E
authors.initials: CE
authors.lastname: Clayton
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D004351:Drug Resistance; D005721:Glutamate-Cysteine Ligase / Q000378:metabolism; D005978:Glutathione / Q000031:analogs & derivatives* / Q000378:metabolism; D008549:Melarsoprol / Q000494:pharmacology*; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D009955:Ornithine Decarboxylase / Q000378:metabolism; D021261:Parasitic Sensitivity Tests; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D013095:Spermidine / Q000031:analogs & derivatives* / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000378:metabolism; D014344:Trypanocidal Agents / Q000494:pharmacology*; D014346:Trypanosoma brucei brucei / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism
chemical_list: D018528:ATP-Binding Cassette Transporters; D002352:Carrier Proteins; C461386:MRPA protein, Trypanosoma brucei; C461387:MRPE protein, Trypanosoma brucei; D026901:Membrane Transport Proteins; D015800:Protozoan Proteins; D013438:Sulfhydryl Compounds; D014344:Trypanocidal Agents; C044809:trypanothione; D009955:Ornithine Decarboxylase; D005721:Glutamate-Cysteine Ligase; D005978:Glutathione; D013095:Spermidine; D008549:Melarsoprol