title: Chemical rescue of malaria parasites lacking an apicoplast defines organelle function in blood-stage Plasmodium falciparum.
abstract: Plasmodium spp parasites harbor an unusual plastid organelle called the apicoplast. Due to its prokaryotic origin and essential function, the apicoplast is a key target for development of new anti-malarials. Over 500 proteins are predicted to localize to this organelle and several prokaryotic biochemical pathways have been annotated, yet the essential role of the apicoplast during human infection remains a mystery. Previous work showed that treatment with fosmidomycin, an inhibitor of non-mevalonate isoprenoid precursor biosynthesis in the apicoplast, inhibits the growth of blood-stage P. falciparum. Herein, we demonstrate that fosmidomycin inhibition can be chemically rescued by supplementation with isopentenyl pyrophosphate (IPP), the pathway product. Surprisingly, IPP supplementation also completely reverses death following treatment with antibiotics that cause loss of the apicoplast. We show that antibiotic-treated parasites rescued with IPP over multiple cycles specifically lose their apicoplast genome and fail to process or localize organelle proteins, rendering them functionally apicoplast-minus. Despite the loss of this essential organelle, these apicoplast-minus auxotrophs can be grown indefinitely in asexual blood stage culture but are entirely dependent on exogenous IPP for survival. These findings indicate that isoprenoid precursor biosynthesis is the only essential function of the apicoplast during blood-stage growth. Moreover, apicoplast-minus P. falciparum strains will be a powerful tool for further investigation of apicoplast biology as well as drug and vaccine development.
authors.affiliation: Department of Pathology, Stanford Medical School, Stanford, California, United States of America. ellenyeh@stanford.edu
authors.forename: Ellen
authors.initials: E
authors.lastname: Yeh
authors.forename: Joseph L
authors.initials: JL
authors.lastname: DeRisi
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D016923:Cell Death / Q000187:drug effects; D002736:Chloroplasts / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D005578:Fosfomycin / Q000031:analogs & derivatives / Q000494:pharmacology; D018503:Genome, Protozoan / Q000235:genetics; D045782:Hemiterpenes / Q000494:pharmacology*; D006801:Humans; D008018:Life Cycle Stages / Q000187:drug effects*; D008288:Malaria / Q000469:parasitology*; D008954:Models, Biological; D009943:Organophosphorus Compounds / Q000494:pharmacology*; D010271:Parasites / Q000166:cytology / Q000187:drug effects / Q000235:genetics / Q000254:growth & development*; D010963:Plasmodium falciparum / Q000166:cytology / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development*; D021381:Protein Transport / Q000187:drug effects; D015800:Protozoan Proteins / Q000378:metabolism; D013729:Terpenes / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D045782:Hemiterpenes; D009943:Organophosphorus Compounds; D015800:Protozoan Proteins; D013729:Terpenes; D005578:Fosfomycin; C004809:isopentenyl pyrophosphate; C024640:fosmidomycin