title: TheTrypanosoma brucei TbHrg protein is a heme transporter involved in the regulation of stage-specific morphological transitions.
abstract: The human parasiteTrypanosoma bruceidoes not synthesize hemede novoand instead relies entirely on heme supplied by its vertebrate host or its insect vector, the tsetse fly. In the host bloodstreamT. bruceiscavenges heme via haptoglobin-hemoglobin (HpHb) receptor-mediated endocytosis occurring in the flagellar pocket. However, in the procyclic developmental stage, in whichT. bruceiis confined to the tsetse fly midgut, this receptor is apparently not expressed, suggesting thatT. bruceitakes up heme by a different, unknown route. To define this alternative route, we functionally characterized heme transporterTbHrg in the procyclic stage. RNAi-induced down-regulation ofTbHrg in heme-limited culture conditions resulted in slower proliferation, decreased cellular heme, and marked changes in cellular morphology so that the cells resemble mesocyclic trypomastigotes. Nevertheless, theTbHrg KO developed normally in the tsetse flies at rates comparable with wild-type cells.T. bruceicells overexpressingTbHrg displayed up-regulation of the early procyclin GPEET and down-regulation of the late procyclin EP1, two proteins coating theT. bruceisurface in the procyclic stage. Light microscopy of immunostainedTbHrg indicated localization to the flagellar membrane, and scanning electron microscopy revealed more intenseTbHrg accumulation toward the flagellar pocket. Based on these findings, we postulate thatT. bruceisenses heme levels via the flagellarTbHrg protein. Heme deprivation in the tsetse fly anterior midgut might represent an environmental stimulus involved in the transformation of this important human parasite, possibly through metabolic remodeling.
authors.affiliation: From the Institute of Parasitology, Biology Center, Czech Academy of Sciences, 37005 České Budějovice (Budweis), Czech Republic.
authors.forename: Eva
authors.initials: E
authors.lastname: Horáková
authors.affiliation: From the Institute of Parasitology, Biology Center, Czech Academy of Sciences, 37005 České Budějovice (Budweis), Czech Republic.
authors.forename: Piya
authors.initials: P
authors.lastname: Changmai
authors.affiliation: From the Institute of Parasitology, Biology Center, Czech Academy of Sciences, 37005 České Budějovice (Budweis), Czech Republic.|Faculty of Sciences, University of South Bohemia, 37005 České Budějovice (Budweis), Czech Republic.
authors.forename: Marie
authors.initials: M
authors.lastname: Vancová
authors.affiliation: Faculty of Sciences, University of South Bohemia, 37005 České Budějovice (Budweis), Czech Republic.|Institute of Microbiology, Czech Academy of Sciences, 37981 Třeboň, Czech Republic.
authors.forename: Roman
authors.initials: R
authors.lastname: Sobotka
authors.affiliation: Department of Biomedical Sciences, Unit of Veterinary Protozoology, Institute of Tropical Medicine, B2000 Antwerp, Belgium.
authors.forename: Jan
authors.initials: J
authors.lastname: Van Den Abbeele
authors.affiliation: Institut de Biologie et de Médecine Moléculaires, Université Libre de Bruxelles, B6041 Gosselies, Belgium, and.
authors.forename: Benoit
authors.initials: B
authors.lastname: Vanhollebeke
authors.affiliation: From the Institute of Parasitology, Biology Center, Czech Academy of Sciences, 37005 České Budějovice (Budweis), Czech Republic, jula@paru.cas.cz.|Faculty of Sciences, University of South Bohemia, 37005 České Budějovice (Budweis), Czech Republic.|Canadian Institute for Advanced Research, Toronto, Ontario M5G 1Z8, Canada.
authors.forename: Julius
authors.initials: J
authors.lastname: Lukeš
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport; D049109:Cell Proliferation; D015536:Down-Regulation; D005407:Flagella / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D006418:Heme / Q000378:metabolism*; D008018:Life Cycle Stages; D026901:Membrane Transport Proteins / Q000378:metabolism*; D008855:Microscopy, Electron, Scanning; D015800:Protozoan Proteins / Q000378:metabolism*; D034622:RNA Interference; D060888:Real-Time Polymerase Chain Reaction; D011956:Receptors, Cell Surface / Q000378:metabolism; D019076:Transgenes; D014346:Trypanosoma brucei brucei / Q000378:metabolism*; D014370:Tsetse Flies / Q000469:parasitology*
chemical_list: D026901:Membrane Transport Proteins; D015800:Protozoan Proteins; D011956:Receptors, Cell Surface; C027079:hemoglobin-haptoglobin receptor; D006418:Heme
keywords: differentiation; flagellum; heme; import; parasite; procyclin; transporter; trypanosome