The Burkholderia cenocepacia peptidoglycan-associated lipoprotein is involved in epithelial cell attachment and elicitation of inflammation

Cell Microbiol. 2017 May;19(5). doi: 10.1111/cmi.12691. Epub 2016 Nov 25.

Abstract

The Burkholderia cepacia complex (Bcc) is a group of Gram-negative opportunistic pathogens causing infections in people with cystic fibrosis (CF). Bcc is highly antibiotic resistant, making conventional antibiotic treatment problematic. The identification of novel targets for anti-virulence therapies should improve therapeutic options for infected CF patients. We previously identified that the peptidoglycan-associated lipoprotein (Pal) was immunogenic in Bcc infected CF patients; however, its role in Bcc pathogenesis is unknown. The virulence of a pal deletion mutant (Δpal) in Galleria mellonella was 88-fold reduced (p < .001) compared to wild type. The lipopolysaccharide profiles of wild type and Δpal were identical, indicating no involvement of Pal in O-antigen transport. However, Δpal was more susceptible to polymyxin B. Structural elucidation by X-ray crystallography and calorimetry demonstrated that Pal binds peptidoglycan fragments. Δpal showed a 1.5-fold reduced stimulation of IL-8 in CF epithelial cells relative to wild type (p < .001), demonstrating that Pal is a significant driver of inflammation. The Δpal mutant had reduced binding to CFBE41o- cells, but adhesion of Pal-expressing recombinant E. coli to CFBE41o- cells was enhanced compared to wild-type E. coli (p < .0001), confirming that Pal plays a direct role in host cell attachment. Overall, Bcc Pal mediates host cell attachment and stimulation of cytokine secretion, contributing to Bcc pathogenesis.

Keywords: cystic fibrosis; host cell attachment; inflammation; pathogen-associated molecular patterns; peptidoglycan-associated lipoprotein.

MeSH terms

  • Animals
  • Bacterial Adhesion
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / physiology
  • Binding Sites
  • Burkholderia Infections / immunology*
  • Burkholderia Infections / microbiology
  • Burkholderia cenocepacia / immunology*
  • Burkholderia cenocepacia / pathogenicity
  • Cell Adhesion
  • Cells, Cultured
  • Crystallography, X-Ray
  • Cystic Fibrosis / microbiology
  • Cytokines / metabolism
  • Drug Resistance, Bacterial
  • Epithelial Cells / microbiology
  • Epithelial Cells / physiology*
  • Escherichia coli
  • Humans
  • Larva / microbiology
  • Lipopolysaccharides / physiology
  • Lipoproteins / chemistry*
  • Lipoproteins / physiology
  • Models, Molecular
  • Moths
  • Peptidoglycan / chemistry
  • Polymyxins / pharmacology
  • Protein Binding
  • Protein Domains

Substances

  • Bacterial Proteins
  • Cytokines
  • Lipopolysaccharides
  • Lipoproteins
  • Peptidoglycan
  • Polymyxins