Identification of the flagellin glycosylation system in Burkholderia cenocepacia and the contribution of glycosylated flagellin to evasion of human innate immune responses.
Burkholderia cenocepacia is an opportunistic pathogen threatening patients with cystic fibrosis. Flagella are required for biofilm formation, as well as adhesion to and invasion of epithelial cells. Recognition of flagellin via the Toll-like receptor 5 (TLR5) contributes to exacerbate B. cenocepacia-induced lung epithelial inflammatory responses. In this study, we report that B. cenocepacia flagellin is glycosylated on at least 10 different sites with a single sugar, 4,6-dideoxy-4-(3-hydroxybutanoylamino)-D-glucose. We have identified key genes that are required for flagellin glycosylation, including a predicted glycosyltransferase gene that is linked to the flagellin biosynthesis cluster and a putative acetyltransferase gene located within the O-antigen lipopolysaccharide cluster. Another O-antigen cluster gene, rmlB, which is required for flagellin glycan and O-antigen biosynthesis, was essential for bacterial viability, uncovering a novel target against Burkholderia infections. Using glycosylated and nonglycosylated purified flagellin and a cell reporter system to assess TLR5-mediated responses, we also show that the presence of glycan in flagellin significantly impairs the inflammatory response of epithelial cells. We therefore suggest that flagellin glycosylation reduces recognition of flagellin by host TLR5, providing an evasive strategy to infecting bacteria.
From the Centre for Infection and Immunity, School of Medicine, Dentistry and Biomedical Sciences, Queen's University, Belfast BT9 7AE, Ireland, United Kingdom.
Anna
A
Hanuszkiewicz
the Don Rix Protein Identification Facility, Department of Biochemistry, University of Western Ontario, London, Ontario N6A 5C1, Canada.
Paula
P
Pittock
the Institute of Immunology, Department of Biology, National University of Ireland at Maynooth, Maynooth, County Kildare, Ireland.
Fiachra
F
Humphries
the Bioanalytical Chemistry, Research Centre Borstel, 23845 Borstel, Germany.
Hermann
H
Moll
the Department of Microbiology and Immunology, University of Western Ontario, London, Ontario N6A 5C1, Canada, and.
Amanda Roa
AR
Rosales
the Dipartimento di Scienze Chimiche, Università di Napoli, Federico II, 80134 Naples, Italy.
Antonio
A
Molinaro
From the Centre for Infection and Immunity, School of Medicine, Dentistry and Biomedical Sciences, Queen's University, Belfast BT9 7AE, Ireland, United Kingdom, the Institute of Immunology, Department of Biology, National University of Ireland at Maynooth, Maynooth, County Kildare, Ireland.
Paul N
PN
Moynagh
the Don Rix Protein Identification Facility, Department of Biochemistry, University of Western Ontario, London, Ontario N6A 5C1, Canada.
Gilles A
GA
Lajoie
From the Centre for Infection and Immunity, School of Medicine, Dentistry and Biomedical Sciences, Queen's University, Belfast BT9 7AE, Ireland, United Kingdom, the Department of Microbiology and Immunology, University of Western Ontario, London, Ontario N6A 5C1, Canada, and m.valvano@qub.ac.uk.
Miguel A
MA
Valvano
D000595:Amino Acid Sequence; D018441:Biofilms / Q000254:growth & development; D057508:Burkholderia cenocepacia / Q000235:genetics / Q000276:immunology* / Q000378:metabolism* / Q000502:physiology; D002460:Cell Line; D004847:Epithelial Cells / Q000276:immunology / Q000382:microbiology; D005408:Flagellin / Q000737:chemistry / Q000235:genetics / Q000276:immunology* / Q000378:metabolism*; D005947:Glucose / Q000737:chemistry / Q000378:metabolism; D006031:Glycosylation; D006801:Humans; D007113:Immunity, Innate; D008969:Molecular Sequence Data; D009068:Movement; D051198:Toll-Like Receptor 5 / Q000378:metabolism
D051198:Toll-Like Receptor 5; D005408:Flagellin; D005947:Glucose
Bacteria; Carbohydrate Glycoprotein; Glycoprotein Biosynthesis; Lipopolysaccharide (LPS); Toll-like Receptor (TLR)