title: Trypanosoma brucei Bloodstream Forms Depend upon Uptake of myo-Inositol for Golgi Complex Phosphatidylinositol Synthesis and Normal Cell Growth.
abstract: myo-Inositol is a building block for all inositol-containing phospholipids in eukaryotes. It can be synthesized de novo from glucose-6-phosphate in the cytosol and endoplasmic reticulum. Alternatively, it can be taken up from the environment via Na(+)- or H(+)-linked myo-inositol transporters. While Na(+)-coupled myo-inositol transporters are found exclusively in the plasma membrane, H(+)-linked myo-inositol transporters are detected in intracellular organelles. In Trypanosoma brucei, the causative agent of human African sleeping sickness, myo-inositol metabolism is compartmentalized. De novo-synthesized myo-inositol is used for glycosylphosphatidylinositol production in the endoplasmic reticulum, whereas the myo-inositol taken up from the environment is used for bulk phosphatidylinositol synthesis in the Golgi complex. We now provide evidence that the Golgi complex-localized T. brucei H(+)-linked myo-inositol transporter (TbHMIT) is essential in bloodstream-form T. brucei. Downregulation of TbHMIT expression by RNA interference blocked phosphatidylinositol production and inhibited growth of parasites in culture. Characterization of the transporter in a heterologous expression system demonstrated a remarkable selectivity of TbHMIT for myo-inositol. It tolerates only a single modification on the inositol ring, such as the removal of a hydroxyl group or the inversion of stereochemistry at a single hydroxyl group relative to myo-inositol.
authors.affiliation: Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland.
authors.forename: Amaia
authors.initials: A
authors.lastname: González-Salgado
authors.affiliation: Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Steinmann
authors.affiliation: Biomedical Sciences Research Complex, University of St Andrews, North Haugh, St. Andrews, Fife, United Kingdom.
authors.forename: Louise L
authors.initials: LL
authors.lastname: Major
authors.affiliation: Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland.
authors.forename: Erwin
authors.initials: E
authors.lastname: Sigel
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern, Bern, Switzerland.
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Reymond
authors.affiliation: Biomedical Sciences Research Complex, University of St Andrews, North Haugh, St. Andrews, Fife, United Kingdom tks1@st-andrews.ac.uk peter.buetikofer@ibmm.unibe.ch.
authors.forename: Terry K
authors.initials: TK
authors.lastname: Smith
authors.affiliation: Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland tks1@st-andrews.ac.uk peter.buetikofer@ibmm.unibe.ch.
authors.forename: Peter
authors.initials: P
authors.lastname: Bütikofer
mesh_terms: D000818:Animals; D006056:Golgi Apparatus / Q000378:metabolism*; D007294:Inositol / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000096:biosynthesis; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D027981:Symporters / Q000235:genetics / Q000378:metabolism*; D014346:Trypanosoma brucei brucei / Q000254:growth & development / Q000378:metabolism*; D014981:Xenopus
chemical_list: D010716:Phosphatidylinositols; D015800:Protozoan Proteins; D027981:Symporters; D007294:Inositol