title: A genetically hard-wired metabolic transcriptome in Plasmodium falciparum fails to mount protective responses to lethal antifolates.
abstract: 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.
authors.affiliation: Department of Chemistry and Global Health, University of Washington, Seattle, Washington, United States of America.
authors.forename: Karthikeyan
authors.initials: K
authors.lastname: Ganesan
authors.forename: Napawan
authors.initials: N
authors.lastname: Ponmee
authors.forename: Lei
authors.initials: L
authors.lastname: Jiang
authors.forename: Joseph W
authors.initials: JW
authors.lastname: Fowble
authors.forename: John
authors.initials: J
authors.lastname: White
authors.forename: Sumalee
authors.initials: S
authors.lastname: Kamchonwongpaisan
authors.forename: Yongyuth
authors.initials: Y
authors.lastname: Yuthavong
authors.forename: Prapon
authors.initials: P
authors.lastname: Wilairat
authors.forename: Pradipsinh K
authors.initials: PK
authors.lastname: Rathod
mesh_terms: D000818:Animals; D000962:Antimalarials / Q000494:pharmacology; D004351:Drug Resistance / Q000235:genetics*; D004912:Erythrocytes / Q000469:parasitology; D005492:Folic Acid / Q000096:biosynthesis; D005493:Folic Acid Antagonists / Q000494:pharmacology*; D020869:Gene Expression Profiling; D023281:Genomics; D006801:Humans; D053858:Metabolic Networks and Pathways / Q000235:genetics*; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors; D010963:Plasmodium falciparum / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D011743:Pyrimidines / Q000096:biosynthesis; D016053:RNA, Protozoan / Q000032:analysis; D013762:Tetrahydrofolate Dehydrogenase; D013940:Thymidylate Synthase / Q000037:antagonists & inhibitors; D014158:Transcription, Genetic
chemical_list: D000962:Antimalarials; D005493:Folic Acid Antagonists; D009097:Multienzyme Complexes; D011743:Pyrimidines; D016053:RNA, Protozoan; C056930:thymidylate synthase-dihydrofolate reductase; D005492:Folic Acid; D013762:Tetrahydrofolate Dehydrogenase; D013940:Thymidylate Synthase; C030986:pyrimidine