Binding of albumin promotes bacterial survival at the epithelial surface.

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Albumin (HSA) is the dominating protein in human plasma. Many bacterial species, especially streptococci, express surface proteins that bind HSA with high specificity and affinity, but the biological consequences of these protein-protein interactions are poorly understood. Group G streptococci (GGS), carrying the HSA-binding protein G, colonize the skin and the mucosa of the upper respiratory tract, mostly without causing disease. In case of bacterial invasion, pro-inflammatory cytokines are released that activate the epithelium to produce antibacterial peptides, in particular the chemokine MIG/CXCL9. In addition, the inflammation causes capillary leakage and extravasation of HSA and other plasma proteins; environmental changes at the epithelial surface to which the bacteria need to respond. In this study, we find that GGS adsorb HSA from both saliva and plasma via binding to protein G, and that HSA bound to protein G binds and inactivates the antibacterial MIG/CXCL9 peptide. Another surface protein of GGS, FOG, was found to mediate adherence of the bacteria to pharyngeal epithelial cells through interaction with glycosaminoglycans. This adherence was not affected by the activation of the epithelium with a combination of IFN-γ and TNF-α, leading to the production of MIG/CXCL9. However, at the activated epithelial surface, adherent GGS were protected against killing by MIG/CXCL9 through protein G dependent HSA-coating. The findings identify a previously unknown bacterial survival strategy that help to explain the evolution of HSA-binding proteins among bacterial species of the normal human microbiota.


Enheter & grupper

Ämnesklassifikation (UKÄ) – OBLIGATORISK

  • Lungmedicin och allergi
  • Infektionsmedicin
Sidor (från-till)2469-2476
TidskriftJournal of Biological Chemistry
StatusPublished - 2011
Peer review utfördJa


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