Multiple genetic mechanisms lead to loss of functional TbAT1 expression in drug-resistant trypanosomes.
The P2 aminopurine transporter, encoded by TbAT1 in African trypanosomes in the Trypanosoma brucei group, carries melaminophenyl arsenical and diamidine drugs into these parasites. Loss of this transporter contributes to drug resistance. We identified the genomic location of TbAT1 to be in the subtelomeric region of chromosome 5 and determined the status of the TbAT1 gene in two trypanosome lines selected for resistance to the melaminophenyl arsenical, melarsamine hydrochloride (Cymelarsan), and in a Trypanosoma equiperdum clone selected for resistance to the diamidine, diminazene aceturate. In the Trypanosoma brucei gambiense STIB 386 melarsamine hydrochloride-resistant line, TbAT1 is deleted, while in the Trypanosoma brucei brucei STIB 247 melarsamine hydrochloride-resistant and T. equiperdum diminazene-resistant lines, TbAT1 is present, but expression at the RNA level is no longer detectable. Further characterization of TbAT1 in T. equiperdum revealed that a loss of heterozygosity at the TbAT1 locus accompanied loss of expression and that P2-mediated uptake of [(3)H]diminazene is lost in drug-resistant T. equiperdum. Adenine-inhibitable adenosine uptake is still detectable in a DeltaTbat1 T. b. brucei mutant, although at a greatly reduced capacity compared to that of the wild type, indicating that an additional adenine-inhibitable adenosine permease, distinct from P2, is present in these cells.
Stewart
Mhairi L
ML
Division of Infection & Immunity, Faculty of Biomedical and Life Sciences, Glasgow Biomedical Research Centre, University of Glasgow, Glasgow G12 8TA, United Kingdom.
Burchmore
Richard J S
RJ
Clucas
Caroline
C
Hertz-Fowler
Christiane
C
Brooks
Karen
K
Tait
A
A
Macleod
A
A
Turner
C Michael R
CM
De Koning
Harry P
HP
Wong
Pui Ee
PE
Barrett
Michael P
MP
D020413:3' Untranslated Regions; D016054:DNA, Protozoan / Q000378:metabolism; D004133:Diminazene / Q000031:analogs & derivatives / Q000494:pharmacology; D004351:Drug Resistance / Q000235:genetics; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism; D016366:Open Reading Frames; D015800:Protozoan Proteins / Q000235:genetics* / Q000378:metabolism; D014344:Trypanocidal Agents / Q000494:pharmacology*; D014346:Trypanosoma brucei brucei / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism
D020413:3' Untranslated Regions; D016054:DNA, Protozoan; D026901:Membrane Transport Proteins; D015800:Protozoan Proteins; D014344:Trypanocidal Agents; C003915:diminazene aceturate; D004133:Diminazene