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

Elodie Ramond; Gael Gesbert; Mélanie Rigard; Julien Dairou; Marion Dupuis; Iharilalao Dubail; Karin Meibom; Thomas Henry; Monique Barel; Alain Charbit

doi:10.1371/journal.ppat.1003893

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

PLoS Pathog. 2014 Jan;10(1):e1003893. doi: 10.1371/journal.ppat.1003893. Epub 2014 Jan 16.

Authors

Affiliations

¹ Université Paris Descartes, Sorbonne Paris Cité, Bâtiment Leriche, Paris, France ; INSERM, U1002, Unité de Pathogénie des Infections Systémiques, Paris, France.
² Centre international de recherche en infectiologie, Université de Lyon, Lyon, France ; Bacterial Pathogenesis and Innate Immunity Laboratory, INSERM U851 "Immunity, Infection and Vaccination", Lyon, France.
³ Platform "Bioprofiler" Université Paris Diderot, Paris, France.

Abstract

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.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Amino Acid Transport System X-AG / genetics
Amino Acid Transport System X-AG / metabolism
Animals
Bacterial Proteins / genetics
Bacterial Proteins / metabolism
Cell Line
Citric Acid Cycle*
Female
Francisella tularensis / genetics
Francisella tularensis / metabolism*
Francisella tularensis / pathogenicity
Glutamic Acid / genetics
Glutamic Acid / metabolism*
Macrophages / metabolism
Macrophages / microbiology*
Macrophages / pathology
Membrane Proteins / genetics
Membrane Proteins / metabolism
Mice
Mice, Inbred BALB C
Mutation
NADPH Oxidases / genetics
NADPH Oxidases / metabolism
Phagosomes / genetics
Phagosomes / metabolism*
Phagosomes / microbiology
Phagosomes / pathology
Tularemia / genetics
Tularemia / metabolism*

Substances

Amino Acid Transport System X-AG
Bacterial Proteins
GadC protein, bacteria
Membrane Proteins
Glutamic Acid
NADPH Oxidases

Grants and funding

These studies were supported by INSERM, CNRS and Université Paris Descartes Paris Cité Sorbonne. Elodie Ramond was funded by a fellowship from the “Région Ile de France” and Gael Gesbert by a fellowship from the “Délégation Générale à l'Armement” (DGA). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.