A genetically hard-wired metabolic transcriptome in Plasmodium falciparum fails to mount protective responses to lethal antifolates

• Published in: PLoS pathogens 2008-11, Vol.4 (11), p.e1000214-e1000214
• Main Authors: Ganesan, Karthikeyan, Ponmee, Napawan, Jiang, Lei, Fowble, Joseph W, White, John, Kamchonwongpaisan, Sumalee, Yuthavong, Yongyuth, Wilairat, Prapon, Rathod, Pradipsinh K
• Format: Article
• Language: English
• Subjects: Animals; Antimalarials - pharmacology; Biochemistry/Drug Discovery; Biochemistry/Small Molecule Chemistry; Biochemistry/Transcription and Translation; Cell Biology/Gene Expression; Cell Biology/Microbial Growth and Development; Drug Resistance - genetics; Erythrocytes - parasitology; Escherichia coli; Evolutionary Biology/Microbial Evolution and Genomics; Folic Acid - biosynthesis; Folic Acid Antagonists - pharmacology; Gene Expression Profiling; Genetics and Genomics/Functional Genomics; Genetics and Genomics/Microbial Evolution and Genomics; Genomics; Humans; Infectious Diseases/Antimicrobials and Drug Resistance; Infectious Diseases/Neglected Tropical Diseases; Malaria; Medical research; Metabolic Networks and Pathways - genetics; Microbiology/Microbial Evolution and Genomics; Microbiology/Parasitology; Multienzyme Complexes - antagonists & inhibitors; Parasites; Pharmacology; Plasmodium falciparum; Plasmodium falciparum - drug effects; Plasmodium falciparum - genetics; Plasmodium falciparum - metabolism; Proteins; Pyrimidines - biosynthesis; RNA, Protozoan - analysis; Tetrahydrofolate Dehydrogenase; Thymidylate Synthase - antagonists & inhibitors; Transcription, Genetic
• ISSN: 1553-7374; 1553-7366; 1553-7374
• DOI: 10.1371/journal.ppat.1000214

Genome sequences of Plasmodium falciparum allow for global analysis of drug responses to antimalarial agents. It was of interest to learn how DNA microarrays may be used to study drug action in malaria parasites. In one large, tightly controlled study involving 123 microarray hybridizations between cDNA from isogenic drug-sensitive and drug-resistant parasites, a lethal antifolate (WR99210) failed to over-produce RNA for the genetically proven principal target, dihydrofolate reductase-thymidylate synthase (DHFR-TS). This transcriptional rigidity carried over to metabolically related RNA encoding folate and pyrimidine biosynthesis, as well as to the rest of the parasite genome. No genes were reproducibly up-regulated by more than 2-fold until 24 h after initial drug exposure, even though clonal viability decreased by 50% within 6 h. We predicted and showed that while the parasites do not mount protective transcriptional responses to antifolates in real time, P. falciparum cells transfected with human DHFR gene, and adapted to long-term WR99210 exposure, adjusted the hard-wired transcriptome itself to thrive in the presence of the drug. A system-wide incapacity for changing RNA levels in response to specific metabolic perturbations may contribute to selective vulnerabilities of Plasmodium falciparum to lethal antimetabolites. In addition, such regulation affects how DNA microarrays are used to understand the mode of action of antimetabolites.