title: Novel sterol metabolic network of Trypanosoma brucei procyclic and bloodstream forms.
abstract: Trypanosoma brucei is the protozoan parasite that causes African trypanosomiasis, a neglected disease of people and animals. Co-metabolite analysis, labelling studies using [methyl-2H3]-methionine and substrate/product specificities of the cloned 24-SMT (sterol C24-methyltransferase) and 14-SDM (sterol C14demethylase) from T. brucei afforded an uncommon sterol metabolic network that proceeds from lanosterol and 31-norlanosterol to ETO [ergosta-5,7,25(27)-trien-3β-ol], 24-DTO [dimethyl ergosta-5,7,25(27)-trienol] and ergosterol [ergosta-5,7,22(23)-trienol]. To assess the possible carbon sources of ergosterol biosynthesis, specifically 13C-labelled specimens of lanosterol, acetate, leucine and glucose were administered to T. brucei and the 13C distributions found were in accord with the operation of the acetate-mevalonate pathway, with leucine as an alternative precursor, to ergostenols in either the insect or bloodstream form. In searching for metabolic signatures of procyclic cells, we observed that the 13C-labelling treatments induce fluctuations between the acetyl-CoA (mitochondrial) and sterol (cytosolic) synthetic pathways detected by the progressive increase in 13C-ergosterol production (control<[2-(13)C]leucine<[2-(13)C]acetate<[1-(13)C]glucose) and corresponding depletion of cholesta-5,7,24-trienol. We conclude that anabolic fluxes originating in mitochondrial metabolism constitute a flexible part of sterol synthesis that is further fluctuated in the cytosol, yielding distinct sterol profiles in relation to cell demands on growth.
authors.affiliation: Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409, USA. wdavid.nes@ttu.edu
authors.forename: Craigen R
authors.initials: CR
authors.lastname: Nes
authors.forename: Ujjal K
authors.initials: UK
authors.lastname: Singha
authors.forename: Jialin
authors.initials: J
authors.lastname: Liu
authors.forename: Kulothungan
authors.initials: K
authors.lastname: Ganapathy
authors.forename: Fernando
authors.initials: F
authors.lastname: Villalta
authors.forename: Michael R
authors.initials: MR
authors.lastname: Waterman
authors.forename: Galina I
authors.initials: GI
authors.lastname: Lepesheva
authors.forename: Minu
authors.initials: M
authors.lastname: Chaudhuri
authors.forename: W David
authors.initials: WD
authors.lastname: Nes
mesh_terms: D004926:Escherichia coli; D055442:Metabolome; D008780:Methyltransferases / Q000096:biosynthesis / Q000737:chemistry; D015800:Protozoan Proteins / Q000096:biosynthesis / Q000737:chemistry; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry; D058886:Sterol 14-Demethylase / Q000096:biosynthesis / Q000737:chemistry; D013261:Sterols / Q000096:biosynthesis* / Q000737:chemistry / Q000378:metabolism; D014346:Trypanosoma brucei brucei / Q000378:metabolism / Q000502:physiology*
chemical_list: D015800:Protozoan Proteins; D011994:Recombinant Proteins; D013261:Sterols; D058886:Sterol 14-Demethylase; D008780:Methyltransferases