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The role of DNA mismatch repair in generating genetic diversity and drug resistance in malaria parasites.

ABSTRACT: Although the mechanisms by which malaria parasites develop resistance to drugs are unclear, current knowledge suggests a main mechanism of resistance is the alteration of target enzymes by point mutation. In other organisms, defects in DNA mismatch repair have been linked to increased mutation rates and drug resistance. We have identified an unusual complement of mismatch repair genes in the Plasmodium genome. An initial functional test of two of these genes (PfMSH2-1 and PfMSH2-2) using a dominant mutator assay showed an elevation in mutation frequency with the PfMSH2-2 homolog, indirectly demonstrating a role for this gene in mismatch repair. We successfully disrupted PbMSH2-2 in the Plasmodium berghei laboratory isolate NK65, and showed that this gene is not essential for parasite growth in either the asexual (rodent) or sexual (mosquito) stages of the lifecycle. Although we observed some differences in levels of drug resistance between wild type and mutant parasites, no uniform trend emerged and preliminary evidence does not support a strong link between PbMSH2-2 disruption and dramatically increased drug resistance. We found microsatellite polymorphism in the PbMSH2-2 disrupted parasites in less than 40 life cycles post-transfection, but not in PbMap2K disrupted controls or mosquito-passaged wild type parasites, which suggests a possible role for PbMSH2-2 in preventing microsatellite slippage, similar to MSH2 in other organisms. Our studies suggest that Plasmodium species may have evolved a unique variation on the highly conserved system of DNA repair compared to the mismatch repair systems in other eukaryotes.

SUBMITTER: Bethke L

PROVIDER: S-EPMC3683857 | biostudies-literature | 2007 Sep

REPOSITORIES: biostudies-literature

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The role of DNA mismatch repair in generating genetic diversity and drug resistance in malaria parasites.

Bethke Lara L Thomas Susan S Walker Kerone K Lakhia Ronak R Rangarajan Radha R Wirth Dyann D

Molecular and biochemical parasitology 20070513 1

Although the mechanisms by which malaria parasites develop resistance to drugs are unclear, current knowledge suggests a main mechanism of resistance is the alteration of target enzymes by point mutation. In other organisms, defects in DNA mismatch repair have been linked to increased mutation rates and drug resistance. We have identified an unusual complement of mismatch repair genes in the Plasmodium genome. An initial functional test of two of these genes (PfMSH2-1 and PfMSH2-2) using a domin ...[more]

PMID: 17583362

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Project description:In the malaria parasite Plasmodium falciparum, synthesis of isoprenoids from glycolytic intermediates is essential for survival. The antimalarial fosmidomycin (FSM) inhibits isoprenoid synthesis. In P. falciparum, we identified a loss-of-function mutation in HAD2 (P. falciparum 3D7_1226300 [PF3D7_1226300]) as necessary for FSM resistance. Enzymatic characterization revealed that HAD2, a member of the haloacid dehalogenase-like hydrolase (HAD) superfamily, is a phosphatase. Harnessing a growth defect in resistant parasites, we selected for suppression of HAD2-mediated FSM resistance and uncovered hypomorphic suppressor mutations in the locus encoding the glycolytic enzyme phosphofructokinase 9 (PFK9). Metabolic profiling demonstrated that FSM resistance is achieved via increased steady-state levels of methylerythritol phosphate (MEP) pathway and glycolytic intermediates and confirmed reduced PFK9 function in the suppressed strains. We identified HAD2 as a novel regulator of malaria parasite metabolism and drug sensitivity and uncovered PFK9 as a novel site of genetic metabolic plasticity in the parasite. Our report informs the biological functions of an evolutionarily conserved family of metabolic regulators and reveals a previously undescribed strategy by which malaria parasites adapt to cellular metabolic dysregulation.IMPORTANCE Unique and essential aspects of parasite metabolism are excellent targets for development of new antimalarials. An improved understanding of parasite metabolism and drug resistance mechanisms is urgently needed. The antibiotic fosmidomycin targets the synthesis of essential isoprenoid compounds from glucose and is a candidate for antimalarial development. Our report identifies a novel mechanism of drug resistance and further describes a family of metabolic regulators in the parasite. Using a novel forward genetic approach, we also uncovered mutations that suppress drug resistance in the glycolytic enzyme PFK9. Thus, we identify an unexpected genetic mechanism of adaptation to metabolic insult that influences parasite fitness and tolerance of antimalarials.

Dataset Information

The role of DNA mismatch repair in generating genetic diversity and drug resistance in malaria parasites.

Publications

The role of DNA mismatch repair in generating genetic diversity and drug resistance in malaria parasites.

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