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Membrane-associated mucins protect epithelial cell surfaces against pathogenic threats by serving as nonproductive decoys that capture infectious agents and clear them from the cell surface and by erecting a physical barrier that restricts their access to target receptors on host cells. However, the mechanisms through which mucins function are still poorly defined because of a limited repertoire of tools available for tailoring their structure and composition in living cells with molecular precision. Using synthetic glycopolymer mimetics of mucins, we modeled the mucosal glycocalyx on red blood cells (RBCs) and evaluated its influence on lectin (SNA) and virus (H1N1) adhesion to endogenous sialic acid receptors. The glycocalyx inhibited the rate of SNA and H1N1 adhesion in a size- and density-dependent manner, consistent with the current view of mucins as providing a protective shield against pathogens. Counterintuitively, increasing the density of the mucin mimetics enhanced the retention of bound lectins and viruses. Careful characterization of SNA behavior at the RBC surface using a range of biophysical and imaging techniques revealed lectin-induced crowding and reorganization of the glycocalyx with concomitant enhancement in lectin clustering, presumably through the formation of a more extensive glycan receptor patch at the cell membrane. Our findings indicate that glycan-targeting pathogens may exploit the biophysical and biomechanical properties of mucins to overcome the mucosal glycocalyx barrier.
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Flagellin is essential for initial attachment to mucosal surfaces by Clostridioides difficile
ABSTRACT Mucins are glycoproteins which can be found in host cell membranes and as a gelatinous surface formed from secreted mucins. Mucosal surfaces in mammals form a barrier to invasive microbes, particularly bacteria, but are a point of attachment for others.Clostridioides difficileis an anaerobic bacterium, which colonizes the mammalian gastrointestinal (GI) tract and is a common cause of acute GI inflammation leading to a variety of negative outcomes. AlthoughC. difficiletoxicity stems from secreted toxins, colonization is a prerequisite forC. difficiledisease. WhileC. difficileis known to associate with the mucous layer and underlying epithelium, the mechanisms underlying these interactions that facilitate colonization are less well understood. To understand the molecular mechanisms by whichC. difficileinteracts with mucins, we usedex vivomucosal surfaces to test the ability ofC. difficileto bind to mucins from different mammalian tissues. We found significant differences inC. difficileadhesion based upon the source of mucins, with highest levels of binding observed to mucins purified from the human colonic adenocarcinoma line LS174T and lowest levels of binding to porcine gastric mucin. We also observed defects in adhesion by mutants deficient in flagella but not type IV pili. These results imply that interactions between host mucins andC. difficileflagella facilitate the initial host attachment ofC. difficileto host cells and secreted mucus. IMPORTANCEClostridioides difficileis one of the leading causes of hospital-acquired infections worldwide and presents challenges in treatment due to recurrent gastrointestinal disease after treatment with antimicrobials. The mechanisms by whichC. difficilecolonizes the gut represent a key gap in knowledge, including its association with host cells and mucosa. Our results show the importance of flagellin for specific adhesion to mucosal hydrogels and can help to explain prior observations of adhesive defects in flagellin and pilin mutants.
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- PAR ID:
- 10496191
- Editor(s):
- Atack, John M.
- Publisher / Repository:
- Microbiology Spectrum
- Date Published:
- Journal Name:
- Microbiology Spectrum
- Volume:
- 11
- Issue:
- 6
- ISSN:
- 2165-0497
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1128/spectrum.02120-23
