Resistance to Pentamidine in Leishmania mexicana Involves Exclusion of the Drug from the Mitochondrion

Abstract

The uptake of [3 H]pentamidine into wild-type and drug-resistant strains of Leishmania mexicana was compared. Uptake was carrier mediated. Pentamidine-resistant parasites showed cross-resistance to other toxic diamidine derivatives. A substantial decrease in accumulation of the drug accompanied the resistance phenotype, although the apparent affinity for pentamidine by its carrier was not altered when initial uptake velocity was measured. The apparent V max , however, was reduced. An efflux of pentamidine could be measured in both wild-type and resistant cells. Only a relatively small proportion of the total accumulated pentamidine was available for efflux in wild-type cells, while in resistant cells the majority of loaded pentamidine was available for release. Pharmacological reagents which diminish the mitochondrial membrane potential reduced pentamidine uptake in wild-type parasites, and the mitochondrial membrane potential was shown to be reduced in resistant cells. A fluorescent analogue of pentamidine, 4,6-diamidino-2-phenylindole, accumulated in the kinetoplast of wild-type but not resistant parasites. These data together indicate that diamidine drugs accumulate in the Leishmania mitochondrion and that the development of the resistance phenotype is accompanied by lack of mitochondrial accumulation of the drug and its exclusion from the parasites.

Functional genetic identification of PRP1, an ABC transporter superfamily member conferring pentamidine resistance in Leishmania major

“…Our data raise the possibility that PRP1 encodes a transporter involved in the decrease of mitochondrial PEN uptake observed by these authors. Consistent with this possibility, reversion of PEN resistant by VER was also observed in the PEN r L. mexicana cells [4]. PRP1 also conferred cross-resistance to SbCl 3 (Table 2), as seen previously for PGPA of L. major to Sb(III) tartrate, SbCl 3 , and SbO 3 [9].…”

“…The properties of this transporter suggest that it may be related to ones implicated in L. mexicana in PEN r mutants [4]. Future studies will address this possibility, and the role of PRP1 in Leishmania metabolism.…”

“…Significantly, Basselin et al showed that PEN uptake in L. mexicana was not mediated by nucleoside transporters but by a carrier that recognizes diamidines with high affinity [4]. These authors showed that the mitochondrion may be the main target of PEN action in Leishmania, as resistance involved decreased mitochondrial PEN accumulation in resistant parasites [4].…”

“…resistance (PEN r ) in some resistant lines involves decreased drug accumulation in this organelle [4]. Gene amplification has been frequently observed in Leishmania following stepwise selection [5][6][7].…”

Identification and Characterization of a Polyamine Permease from the Protozoan Parasite Leishmania major

“…These data parallel results with intact Leishmania in which polyamine transport is potently inhibited by pentamidine yet pentamidine uptake is not affected by excess polyamines (20,38). Although pentamidine transport has not been meticulously investigated in Leishmania (21,38), at least three biochemically distinct pentamidine transporters have been identified in T. brucei (39).…”