title: Acetate produced in the mitochondrion is the essential precursor for lipid biosynthesis in procyclic trypanosomes.
abstract: Acetyl-CoA produced in mitochondria from carbohydrate or amino acid catabolism needs to reach the cytosol to initiate de novo synthesis of fatty acids. All eukaryotes analyzed so far use a citrate/malate shuttle to transfer acetyl group equivalents from the mitochondrial matrix to the cytosol. Here we investigate how this acetyl group transfer occurs in the procyclic life cycle stage of Trypanosoma brucei, a protozoan parasite responsible of human sleeping sickness and economically important livestock diseases. Deletion of the potential citrate lyase gene, a critical cytosolic enzyme of the citrate/malate shuttle, has no effect on de novo biosynthesis of fatty acids from (14)C-labeled glucose, indicating that another route is used for acetyl group transfer. Because acetate is produced from acetyl-CoA in the mitochondrion of this parasite, we considered genes encoding cytosolic enzymes producing acetyl-CoA from acetate. We identified an acetyl-CoA synthetase gene encoding a cytosolic enzyme (AceCS), which is essential for cell viability. Repression of AceCS by inducible RNAi results in a 20-fold reduction of (14)C-incorporation from radiolabeled glucose or acetate into de novo synthesized fatty acids. Thus, we demonstrate that the essential cytosolic enzyme AceCS of T. brucei is responsible for activation of acetate into acetyl-CoA to feed de novo biosynthesis of lipids. To date, Trypanosoma is the only known eukaryotic organism that uses acetate instead of citrate to transfer acetyl groups over the mitochondrial membrane for cytosolic lipid synthesis.
authors.affiliation: Laboratoire de Microbiologie Cellulaire et Moléculaire et Pathogénicité, Unité Mixte de Recherche 5234 Centre National de la Recherche Scientifique, Université Victor Segalen Bordeaux 2, 146 rue Léo Saignat, 33076 Bordeaux cedex, France.
authors.forename: Loïc
authors.initials: L
authors.lastname: Rivière
authors.forename: Patrick
authors.initials: P
authors.lastname: Moreau
authors.forename: Stefan
authors.initials: S
authors.lastname: Allmann
authors.forename: Matthias
authors.initials: M
authors.lastname: Hahn
authors.forename: Marc
authors.initials: M
authors.lastname: Biran
authors.forename: Nicolas
authors.initials: N
authors.lastname: Plazolles
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Franconi
authors.forename: Michael
authors.initials: M
authors.lastname: Boshart
authors.forename: Frédéric
authors.initials: F
authors.lastname: Bringaud
mesh_terms: D000106:Acetate-CoA Ligase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology; D000085:Acetates / Q000378:metabolism*; D000105:Acetyl Coenzyme A / Q000378:metabolism; D000818:Animals; D019343:Citric Acid / Q000378:metabolism; D008055:Lipids / Q000096:biosynthesis*; D008293:Malates / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000235:genetics / Q000502:physiology; D007652:Oxo-Acid-Lyases / Q000235:genetics / Q000502:physiology; D034622:RNA Interference; D014346:Trypanosoma brucei brucei / Q000378:metabolism*
chemical_list: D000085:Acetates; D008055:Lipids; D008293:Malates; D009097:Multienzyme Complexes; D019343:Citric Acid; D000105:Acetyl Coenzyme A; C030298:malic acid; D007652:Oxo-Acid-Lyases; C019909:citrate (pro-3S)-lyase; D000106:Acetate-CoA Ligase