title: Mechanisms of arsenical and diamidine uptake and resistance in Trypanosoma brucei.
abstract: Sleeping sickness, caused by Trypanosoma brucei spp., has become resurgent in sub-Saharan Africa. Moreover, there is an alarming increase in treatment failures with melarsoprol, the principal agent used against late-stage sleeping sickness. In T. brucei, the uptake of melarsoprol as well as diamidines is thought to be mediated by the P2 aminopurine transporter, and loss of P2 function has been implicated in resistance to these agents. The trypanosomal gene TbAT1 has been found to encode a P2-type transporter when expressed in yeast. Here we investigate the role of TbAT1 in drug uptake and drug resistance in T. brucei by genetic knockout of TbAT1. Tbat1-null trypanosomes were deficient in P2-type adenosine transport and lacked adenosine-sensitive transport of pentamidine and melaminophenyl arsenicals. However, the null mutants were only slightly resistant to melaminophenyl arsenicals and pentamidine, while resistance to other diamidines such as diminazene was more pronounced. Nevertheless, the reduction in drug sensitivity might be of clinical significance, since mice infected with tbat1-null trypanosomes could not be cured with 2 mg of melarsoprol/kg of body weight for four consecutive days, whereas mice infected with the parental line were all cured by using this protocol. Two additional pentamidine transporters, HAPT1 and LAPT1, were still present in the null mutant, and evidence is presented that HAPT1 may be responsible for the residual uptake of melaminophenyl arsenicals. High-level arsenical resistance therefore appears to involve the loss of more than one transporter.
authors.affiliation: Institute of Cell Biology, CH-3012 Bern, Switzerland.
authors.forename: Enock
authors.initials: E
authors.lastname: Matovu
authors.forename: Mhairi L
authors.initials: ML
authors.lastname: Stewart
authors.forename: Federico
authors.initials: F
authors.lastname: Geiser
authors.forename: Reto
authors.initials: R
authors.lastname: Brun
authors.forename: Pascal
authors.initials: P
authors.lastname: Mäser
authors.forename: Lynsey J M
authors.initials: LJ
authors.lastname: Wallace
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Burchmore
authors.forename: John C K
authors.initials: JC
authors.lastname: Enyaru
authors.forename: Michael P
authors.initials: MP
authors.lastname: Barrett
authors.forename: Ronald
authors.initials: R
authors.lastname: Kaminsky
authors.forename: Thomas
authors.initials: T
authors.lastname: Seebeck
authors.forename: Harry P
authors.initials: HP
authors.lastname: de Koning
mesh_terms: D000225:Adenine / Q000494:pharmacology; D000241:Adenosine / Q000493:pharmacokinetics / Q000494:pharmacology; D000818:Animals; D001152:Arsenicals / Q000493:pharmacokinetics* / Q000494:pharmacology; D001550:Benzamidines / Q000494:pharmacology; D016923:Cell Death / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D004133:Diminazene / Q000494:pharmacology; D004351:Drug Resistance / Q000235:genetics; D005260:Female; D020868:Gene Silencing; D019271:Hypoxanthine / Q000494:pharmacology; D020128:Inhibitory Concentration 50; D007288:Inosine / Q000494:pharmacology; D008549:Melarsoprol / Q000494:pharmacology; D051379:Mice; D009154:Mutation; D033703:Nucleoside Transport Proteins / Q000235:genetics / Q000502:physiology*; D010419:Pentamidine / Q000493:pharmacokinetics* / Q000494:pharmacology; D013266:Stilbamidines / Q000494:pharmacology; D014346:Trypanosoma brucei brucei / Q000187:drug effects / Q000378:metabolism*
chemical_list: D001152:Arsenicals; D001550:Benzamidines; D033703:Nucleoside Transport Proteins; C486446:P2 transporter, Trypanosoma brucei; D013266:Stilbamidines; C029341:oxophenylarsine; D019271:Hypoxanthine; C044719:melarsen oxide; D007288:Inosine; D010419:Pentamidine; C062789:melaminylthioarsenate; C005555:propamidine; D000225:Adenine; D000241:Adenosine; C042560:stilbamidine; D004133:Diminazene; D008549:Melarsoprol