A general protein O-glycosylation machinery conserved in Burkholderia species improves bacterial fitness and elicits glycan immunogenicity in humans
Authors:
- Fathy Mohamed, Yasmine
- Scott, Nichollas E.
- Molinaro, Antonio
- Creuzenet, Carole
- Ortega, Ximena
- Lertmemongkolchai, Ganjana
- Tunney, Michael M.
- Green, Heather
- Jones, Andrew M.
- DeShazer, David
- Currie, Bart J.
- Foster, Leonard J.
- Ingram, Rebecca
- De Castro, Cristina
- Valvano, Miguel A.
Details:
Journal of Biological Chemistry, Volume 294, Issue 36, 2019-09-06
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The Burkholderia genus encompasses many Gram-negative bacteria living in the rhizosphere. Some Burkholderia species can cause life-threatening human infections, highlighting the need for clinical interventions targeting specific lipopolysaccharide proteins. Burkholderia cenocepacia O-linked protein glycosylation has been reported, but the chemical structure of the O-glycan and the machinery required for its biosynthesis are unknown and could reveal potential therapeutic targets. Here, using bioinformatics approaches, gene-knockout mutants, purified recombinant proteins, LC-MS–based analyses of O-glycans, and NMR-based structural analyses, we identified a B. cenocepacia O-glycosylation (ogc) gene cluster necessary for synthesis, assembly, and membrane translocation of a lipid-linked O-glycan, as well as its structure, which consists of a β-Gal-(1,3)–α-GalNAc-(1,3)–β-GalNAc trisaccharide. We demonstrate that the ogc cluster is conserved in the Burkholderia genus, and we confirm the production of glycoproteins with similar glycans in the Burkholderia species: B. thailandensis, B. gladioli, and B. pseudomallei. Furthermore, we show that absence of protein O-glycosylation severely affects bacterial fitness and accelerates bacterial clearance in a Galleria mellonella larva infection model. Finally, our experiments revealed that patients infected with B. cenocepacia, Burkholderia multivorans, B. pseudomallei, or Burkholderia mallei develop O-glycan–specific antibodies. Together, these results highlight the importance of general protein O-glycosylation in the biology of the Burkholderia genus and its potential as a target for inhibition or immunotherapy approaches to control Burkholderia infections.