title: Apicoplast isoprenoid precursor synthesis and the molecular basis of fosmidomycin resistance in Toxoplasma gondii.
abstract: Apicomplexa are important pathogens that include the causative agents of malaria, toxoplasmosis, and cryptosporidiosis. Apicomplexan parasites contain a relict chloroplast, the apicoplast. The apicoplast is indispensable and an attractive drug target. The apicoplast is home to a 1-deoxy-D-xylulose-5-phosphate (DOXP) pathway for the synthesis of isoprenoid precursors. This pathway is believed to be the most conserved function of the apicoplast, and fosmidomycin, a specific inhibitor of the pathway, is an effective antimalarial. Surprisingly, fosmidomycin has no effect on most other apicomplexans. Using Toxoplasma gondii, we establish that the pathway is essential in parasites that are highly fosmidomycin resistant. We define the molecular basis of resistance and susceptibility, experimentally testing various host and parasite contributions in T. gondii and Plasmodium. We demonstrate that in T. gondii the parasite plasma membrane is a critical barrier to drug uptake. In strong support of this hypothesis, we engineer de novo drug-sensitive T. gondii parasites by heterologous expression of a bacterial transporter protein. Mice infected with these transgenic parasites can now be cured from a lethal challenge with fosmidomycin. We propose that the varied extent of metabolite exchange between host and parasite is a crucial determinator of drug susceptibility and a predictor of future resistance.
authors.affiliation: Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA.
authors.forename: Sethu C
authors.initials: SC
authors.lastname: Nair
authors.forename: Carrie F
authors.initials: CF
authors.lastname: Brooks
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Goodman
authors.forename: Angelika
authors.initials: A
authors.lastname: Sturm
authors.forename: Angelika
authors.initials: A
authors.lastname: Strurm
authors.forename: Geoffrey I
authors.initials: GI
authors.lastname: McFadden
authors.forename: Sandeep
authors.initials: S
authors.lastname: Sundriyal
authors.forename: Justin L
authors.initials: JL
authors.lastname: Anglin
authors.forename: Yongcheng
authors.initials: Y
authors.lastname: Song
authors.forename: Silvia N J
authors.initials: SN
authors.lastname: Moreno
authors.forename: Boris
authors.initials: B
authors.lastname: Striepen
mesh_terms: D019747:Aldose-Ketose Isomerases / Q000235:genetics / Q000378:metabolism; D000818:Animals; D030801:Animals, Genetically Modified; D000981:Antiprotozoal Agents / Q000494:pharmacology; D002463:Cell Membrane Permeability; D004351:Drug Resistance / Q000502:physiology; D005578:Fosfomycin / Q000031:analogs & derivatives* / Q000494:pharmacology; D006790:Host-Parasite Interactions / Q000187:drug effects; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D053858:Metabolic Networks and Pathways; D051379:Mice; D008954:Models, Biological; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism; D015388:Organelles / Q000378:metabolism; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D010428:Pentosephosphates / Q000378:metabolism; D010962:Plasmodium berghei / Q000187:drug effects / Q000378:metabolism / Q000472:pathogenicity; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013729:Terpenes / Q000378:metabolism*; D014122:Toxoplasma / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity
chemical_list: C109460:1-deoxylulose 5-phosphate; D000981:Antiprotozoal Agents; C488962:GlpT protein, E coli; D026901:Membrane Transport Proteins; D009097:Multienzyme Complexes; D010428:Pentosephosphates; D011994:Recombinant Proteins; D013729:Terpenes; D005578:Fosfomycin; C024640:fosmidomycin; D010088:Oxidoreductases; C114231:1-deoxy-D-xylulose 5-phosphate reductoisomerase; D019747:Aldose-Ketose Isomerases