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Transfection studies to explore essential folate metabolism and antifolate drug synergy in the human malaria parasite Plasmodium falciparum.
- Source :
-
Molecular microbiology [Mol Microbiol] 2004 Mar; Vol. 51 (5), pp. 1425-38. - Publication Year :
- 2004
-
Abstract
- Folate metabolism in Plasmodium falciparum is the target of important antimalarial agents. The biosynthetic pathway converts GTP to polyglutamated derivatives of tetrahydrofolate (THF), essential cofactors for DNA synthesis. Tetrahydrofolate can also be acquired by salvage mechanisms. Using a transfection system adapted to studying this pathway, we investigated modulation of dihydropteroate synthase (DHPS) activity on parasite phenotypes. Dihydropteroate synthase incorporates p-aminobenzoate (pABA) into dihydropteroate, the precursor of dihydrofolate. We were unable to obtain viable parasites where the dhps gene had been truncated. However, parasites where the protein was full-length but mutated at two key residues and having < 10% of normal activity were viable in folate-supplemented medium. Metabolic labelling showed that these parasites could still convert pABA to polyglutamated folates, albeit at a very low level, but they could not survive on pABA supplementation alone. This degree of disablement in DHPS also abolished the synergy of the antifolate combination pyrimethamine/sulfadoxine. These data indicate that DHPS activity above a low but critical level is essential regardless of the availability of salvageable folate and formally prove the role of this enzyme in antifolate drug synergy and folate biosynthesis in vivo. However, we found no evidence of a significant role for DHPS in folate salvage. Moreover, when biosynthesis was compromised by the absence of a fully functional DHPS, the parasite was able to compensate by increasing flux through the salvage pathway.
- Subjects :
- Animals
Antimalarials metabolism
Antimalarials pharmacology
Drug Synergism
Erythrocytes parasitology
Folic Acid chemistry
Folic Acid Antagonists metabolism
Humans
Plasmids
Plasmodium falciparum drug effects
Plasmodium falciparum genetics
Pyrimethamine metabolism
Sulfadoxine metabolism
Dihydropteroate Synthase metabolism
Drug Resistance
Folic Acid metabolism
Folic Acid Antagonists pharmacology
Plasmodium falciparum metabolism
Transfection
Subjects
Details
- Language :
- English
- ISSN :
- 0950-382X
- Volume :
- 51
- Issue :
- 5
- Database :
- MEDLINE
- Journal :
- Molecular microbiology
- Publication Type :
- Academic Journal
- Accession number :
- 14982635
- Full Text :
- https://doi.org/10.1111/j.1365-2958.2003.03915.x