title: The intracellular parasite Toxoplasma gondii depends on the synthesis of long-chain and very long-chain unsaturated fatty acids not supplied by the host cell.
abstract: Apicomplexa are parasitic protozoa that cause important human diseases including malaria, cryptosporidiosis and toxoplasmosis. The replication of these parasites within their target host cell is dependent on both salvage as well as de novo synthesis of fatty acids. In Toxoplasma gondii, fatty acid synthesis via the apicoplast-localized FASII is essential for pathogenesis, while the role of two other fatty acid biosynthetic complexes remains unclear. Here, we demonstrate that the ER-localized fatty acid elongation (ELO) complexes are essential for parasite growth. Conditional knockdown of the nonredundant hydroxyacyl-CoA dehydratase and enoyl-CoA reductase enzymes in the ELO pathway severely repressed intracellular parasite growth. (13) C-glucose and (13) C-acetate labeling and comprehensive lipidomic analyses of these mutants showed a selective defect in synthesis of unsaturated long and very long-chain fatty acids (LCFAs and VLCFAs) and depletion of phosphatidylinositol and phosphatidylethanolamine species containing unsaturated LCFAs and VLCFAs. This requirement for ELO pathway was bypassed by supplementing the media with specific fatty acids, indicating active but inefficient import of host fatty acids. Our experiments highlight a gap between the fatty acid needs of the parasite and availability of specific fatty acids in the host cell that the parasite has to close using a dedicated synthesis and modification pathway.
authors.affiliation: Department of Cellular Biology, University of Georgia, Athens, GA, USA.
authors.forename: Srinivasan
authors.initials: S
authors.lastname: Ramakrishnan
authors.affiliation: Center for Tropical & Emerging Global, University of Georgia, Athens, GA, USA.
authors.forename: Melissa D
authors.initials: MD
authors.lastname: Docampo
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Melbourne, Melbourne, Vic., Australia.
authors.forename: James I
authors.initials: JI
authors.lastname: MacRae
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Melbourne, Melbourne, Vic., Australia.
authors.forename: Julie E
authors.initials: JE
authors.lastname: Ralton
authors.affiliation: Metabolomics Australia, Bio21 Institute of Molecular Science and Biotechnology, University of Melbourne, Melbourne, Vic., Australia.
authors.forename: Thusitha
authors.initials: T
authors.lastname: Rupasinghe
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Melbourne, Melbourne, Vic., Australia.
authors.forename: Malcolm J
authors.initials: MJ
authors.lastname: McConville
authors.affiliation: Department of Cellular Biology, University of Georgia, Athens, GA, USA.|Center for Tropical & Emerging Global, University of Georgia, Athens, GA, USA.
authors.forename: Boris
authors.initials: B
authors.lastname: Striepen
mesh_terms: D000818:Animals; D044943:Fatty Acid Desaturases / Q000235:genetics / Q000378:metabolism; D054889:Fatty Acid Synthase, Type II / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000096:biosynthesis*; D055785:Gene Knockdown Techniques; D006790:Host-Parasite Interactions; D006801:Humans; D009097:Multienzyme Complexes / Q000378:metabolism; D009154:Mutation; D014122:Toxoplasma / Q000201:enzymology / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*
chemical_list: D005231:Fatty Acids, Unsaturated; D009097:Multienzyme Complexes; D044943:Fatty Acid Desaturases; D054889:Fatty Acid Synthase, Type II
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