Glutamate utilization couples oxidative stress defense and the tricarboxylic acid cycle in Francisella phagosomal escape

• Published in: PLoS pathogens Vol. 10; no. 1; p. e1003893
• Main Authors: Ramond, Elodie, Gesbert, Gael, Rigard, Mélanie, Dairou, Julien, Dupuis, Marion, Dubail, Iharilalao, Meibom, Karin, Henry, Thomas, Barel, Monique, Charbit, Alain
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 01.01.2014; Public Library of Science (PLoS)
• Subjects: Amino Acid Transport System X-AG - genetics; Amino Acid Transport System X-AG - metabolism; Animals; Bacteria; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Bacteriology; Biology; Carboxylic acids; Cell Line; Citric Acid Cycle; Couples; Defense mechanisms; Enzymes; Experiments; Female; Francisella tularensis - genetics; Francisella tularensis - metabolism; Francisella tularensis - pathogenicity; Genomes; Glutamate; Glutamic Acid - genetics; Glutamic Acid - metabolism; Gram-positive bacteria; Health aspects; Immunology; Innate immunity; Life Sciences; Macrophages - metabolism; Macrophages - microbiology; Macrophages - pathology; Membrane Proteins - genetics; Membrane Proteins - metabolism; Mice; Mice, Inbred BALB C; Microbiological research; Microbiology and Parasitology; Mutation; NADPH Oxidases - genetics; NADPH Oxidases - metabolism; Oxidative stress; Phagosomes - genetics; Phagosomes - metabolism; Phagosomes - microbiology; Phagosomes - pathology; Proteobacteria; Tularemia - genetics; Tularemia - metabolism; France
• ISSN: 1553-7374; 1553-7366; 1553-7374
• DOI: 10.1371/journal.ppat.1003893

Intracellular bacterial pathogens have developed a variety of strategies to avoid degradation by the host innate immune defense mechanisms triggered upon phagocytocis. Upon infection of mammalian host cells, the intracellular pathogen Francisella replicates exclusively in the cytosolic compartment. Hence, its ability to escape rapidly from the phagosomal compartment is critical for its pathogenicity. Here, we show for the first time that a glutamate transporter of Francisella (here designated GadC) is critical for oxidative stress defense in the phagosome, thus impairing intra-macrophage multiplication and virulence in the mouse model. The gadC mutant failed to efficiently neutralize the production of reactive oxygen species. Remarkably, virulence of the gadC mutant was partially restored in mice defective in NADPH oxidase activity. The data presented highlight links between glutamate uptake, oxidative stress defense, the tricarboxylic acid cycle and phagosomal escape. This is the first report establishing the role of an amino acid transporter in the early stage of the Francisella intracellular lifecycle.