Collagen-Binding Proteins in Streptococcus mutans Pathogenicity

Collagen-binding proteins expressed by Streptococcus mutans, notably Cnm and Cbm, are large cell-surface adhesins that recognise and bind host collagenous tissues. In the oral environment, these proteins enhance bacterial attachment to dentine and pulp fibroblasts, promoting aggressive caries and facilitating invasion during endodontic infections. Upon entry into the bloodstream, collagen-binding strains adhere to exposed vascular collagen and engage endothelial receptors, triggering host signalling pathways that contribute to infective endocarditis. In extra-oral sites, such as the liver in the context of a high-fat diet, Cnm-mediated adhesion to hepatocytes exacerbates non-alcoholic steatohepatitis. Structural and regulatory studies have delineated the modular domains responsible for collagen recognition and identified two-component systems that control CBP expression. These insights underscore the global significance of collagen-binding proteins in both local and systemic manifestations of S. mutans infection and highlight potential targets for anti-adhesive therapies.

Research from Nature Portfolio

Recent studies have uncovered the molecular mechanism by which Cnm promotes endothelial invasion in infective endocarditis. In a serum-supplemented model, Cnm-positive S. mutans strains were shown to interact with type IV collagen and fibrinogen, leading to upregulation of endothelial small G protein regulators and enhanced bacterial uptake. Disruption of this pathway significantly reduced cardiac tissue colonisation and damage. In a complementary high-fat diet mouse model, the combined action of Cnm and a 190-kDa surface antigen was found to mediate adhesion to hepatocytes in the presence of unsaturated fatty acids, aggravating liver inflammation and steatohepatitis. Mutants lacking Cnm or the partner antigen failed to induce these pathological changes, highlighting the central role of collagen-binding adhesins in systemic disease beyond the oral cavity.

Collagen-Binding Proteins in Streptococcus mutans Pathogenicity publication trend

The graph below shows the total number of articles in collagen-binding proteins in streptococcus mutans pathogenicity across all publications each year (not limited to Nature Index journals).

Technical terms

Collagen-Binding Protein (CBP): A microbial surface adhesin that recognises and binds the triple-helical structure of host collagens.

Cnm/Cbm: Specific CBP variants in S. mutans; Cnm is linked to endothelial and hepatic invasion, Cbm to collagenous tissue binding in the oral cavity.

Adhesin: A bacterial protein that mediates attachment to host cells or extracellular matrix components.

Endocarditis: Inflammation of the cardiac endothelium, often initiated by bacterial adhesion to heart valves.

Extracellular Matrix (ECM): The complex network of proteins, including collagens, that provides structural support and signalling cues in tissues.

References

1. Collagen Binding Proteins of Gram-Positive Pathogens. Frontiers in Microbiology (2021).
2. Contributions of Streptococcus mutans Cnm and PA antigens to aggravation of non-alcoholic steatohepatitis in mice. Scientific Reports (2016).
3. Contribution of the Collagen-Binding Proteins of Streptococcus mutans to Bacterial Colonization of Inflamed Dental Pulp. PLOS ONE (2016).
4. Potential involvement of Streptococcus mutans possessing collagen binding protein Cnm in infective endocarditis. Scientific Reports (2020).
5. The Enterococcus faecalis MSCRAMM ACE Binds Its Ligand by the Collagen Hug Model*. Journal of Biological Chemistry (2007).