Premium
Increased transport of pteridines compensates for mutations in the high affinity folate transporter and contributes to methotrexate resistance in the protozoan parasite Leishmania tarentolae
Author(s) -
Kündig Christoph,
Haimeur Anass,
Légaré Danielle,
Papadopoulou Barbara,
Ouellette Marc
Publication year - 1999
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/18.9.2342
Subject(s) - biology , parasite hosting , transporter , biochemistry , kinetoplastida , leishmania , genetics , gene , immunology , protozoal disease , world wide web , computer science , malaria
Functional cloning led to the isolation of a novel methotrexate (MTX) resistance gene in the protozoan parasite Leishmania . The gene corresponds to orfG , an open reading frame (ORF) of the LD1/CD1 genomic locus that is frequently amplified in several Leishmania stocks. A functional ORF G–green fluorescence protein fusion was localized to the plasma membrane. Transport studies indicated that ORF G is a high affinity biopterin transporter. ORF G also transports folic acid, with a lower affinity, but does not transport the drug analog MTX. Disruption of both alleles of orfG led to a mutant strain that became hypersensitive to MTX and had no measurable biopterin transport. Leishmania tarentolae MTX‐resistant cells without their high affinity folate transporters have a rearranged orfG gene and increased orfG RNA levels. Overexpression of orfG leads to increased biopterin uptake and, in folate‐rich medium, to increased folate uptake. MTX‐resistant cells compensate for mutations in their high affinity folate/MTX transporter by overexpressing ORF G, which increases the uptake of pterins and selectively increases the uptake of folic acid, but not MTX.