title: Escherichia coli Pyruvate Dehydrogenase Complex Is an Important Component of CXCL10-Mediated Antimicrobial Activity.
abstract: Chemokines are best recognized for their role within the innate immune system as chemotactic cytokines, signaling and recruiting host immune cells to sites of infection. Certain chemokines, such as CXCL10, have been found to play an additional role in innate immunity, mediating CXCR3-independent killing of a diverse array of pathogenic microorganisms. While this is still not clearly understood, elucidating the mechanisms underlying chemokine-mediated antimicrobial activity may facilitate the development of novel therapeutic strategies effective against antibiotic-resistant Gram-negative pathogens. Here, we show that CXCL10 exerts antibacterial effects on clinical and laboratory strains of Escherichia coli and report that disruption of pyruvate dehydrogenase complex (PDHc), which converts pyruvate to acetyl coenzyme A, enables E. coli to resist these antimicrobial effects. Through generation and screening of a transposon mutant library, we identified two mutants with increased resistance to CXCL10, both with unique disruptions of the gene encoding the E1 subunit of PDHc, aceE. Resistance to CXCL10 also occurred following deletion of either aceF or lpdA, genes that encode the remaining two subunits of PDHc. Although PDHc resides within the bacterial cytosol, electron microscopy revealed localization of immunogold-labeled CXCL10 to the bacterial cell surface in both the E. coli parent and aceE deletion mutant strains. Taken together, our findings suggest that while CXCL10 interacts with an as-yet-unidentified component on the cell surface, PDHc is an important mediator of killing by CXCL10. To our knowledge, this is the first description of PDHc as a key bacterial component involved in the antibacterial effect of a chemokine.
authors.affiliation: Department of Medicine, Division of Infectious Diseases and International Health, University of Virginia, Charlottesville, Virginia, USA.
authors.forename: Kirsten M
authors.initials: KM
authors.lastname: Schutte
authors.affiliation: Department of Medicine, Division of Infectious Diseases and International Health, University of Virginia, Charlottesville, Virginia, USA.
authors.forename: Debra J
authors.initials: DJ
authors.lastname: Fisher
authors.affiliation: Department of Medicine, Division of Pulmonary and Critical Care Medicine, University of Virginia, Charlottesville, Virginia, USA.
authors.forename: Marie D
authors.initials: MD
authors.lastname: Burdick
authors.affiliation: Department of Medicine, Division of Pulmonary and Critical Care Medicine, University of Virginia, Charlottesville, Virginia, USA.
authors.forename: Borna
authors.initials: B
authors.lastname: Mehrad
authors.affiliation: Department of Medicine, Division of Infectious Diseases and International Health, University of Virginia, Charlottesville, Virginia, USA.
authors.forename: Amy J
authors.initials: AJ
authors.lastname: Mathers
authors.affiliation: Department of Medicine, Division of Infectious Diseases and International Health, University of Virginia, Charlottesville, Virginia, USA.
authors.forename: Barbara J
authors.initials: BJ
authors.lastname: Mann
authors.affiliation: Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia, USA.
authors.forename: Robert K
authors.initials: RK
authors.lastname: Nakamoto
authors.affiliation: Department of Medicine, Division of Infectious Diseases and International Health, University of Virginia, Charlottesville, Virginia, USA mah3x@virginia.edu.
authors.forename: Molly A
authors.initials: MA
authors.lastname: Hughes
mesh_terms: D000900:Anti-Bacterial Agents / Q000378:metabolism*; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism*; D001665:Binding Sites; D054357:Chemokine CXCL10 / Q000378:metabolism*; D008058:Dihydrolipoamide Dehydrogenase / Q000235:genetics; D051047:Dihydrolipoyllysine-Residue Acetyltransferase / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D004926:Escherichia coli; D055786:Gene Knockout Techniques; D006801:Humans; D007113:Immunity, Innate / Q000276:immunology*; D011485:Protein Binding; D030481:Pyruvate Dehydrogenase (Lipoamide) / Q000235:genetics / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; D054357:Chemokine CXCL10; D030481:Pyruvate Dehydrogenase (Lipoamide); D008058:Dihydrolipoamide Dehydrogenase; D051047:Dihydrolipoyllysine-Residue Acetyltransferase