The P-glycoprotein-related gene family in Leishmania

P-glycoprotein gene amplification has been described in several drug-resistant parasitic protozoa. The first P-glycoprotein related gene described in Leishmania was ltpgpA, a gene frequently amplified in arsenite resistant Leishmania. Hybridization experiments indicated that ltpgpA was part of a gene family. In addition to ltpgpA, four novel genes were cloned that are present in two loci: ltpgpB and ltpgpC tandemly linked to ltpgpA on a 800-kb chromosome; and ltpgpD and ltpgpE closely linked on a chromosome ranging from 950 kb to 1400 kb, depending on the Leishmania species. Another P-glycoprotein gene, homologous to the more recently described ldmdr1, was linked to ltpgpD and ltpgpE. Nucleotide sequencing of ltpgpB and ltpgpE revealed that the Leishmania P-glycoprotein-related genes have diverged considerably from the main branch of P-glycoproteins and are more homologous to the recently described multidrug resistance-associated protein found in multidrug-resistant human lung cancer cell lines. Cross-resistance studies and gene transfection experiments indicated that under the conditions tested only ltpgpA and ldmdr1 are involved in resistance to arsenite and antimonials or hydrophobic drugs such as vinblastine respectively.