Streptococcus pneumoniae binds collagens and C1q via the SSURE repeats of the PfbB adhesin

• Published in: Molecular microbiology Vol. 117; no. 6; pp. 1479 - 1492
• Main Authors: De Gaetano, Giuseppe Valerio, Coppolino, Francesco, Lentini, Germana, Famà, Agata, Cullotta, Chiara, Raffaele, Ivana, Motta, Chiara, Teti, Giuseppe, Speziale, Pietro, Pietrocola, Giampiero, Beninati, Concetta
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01-06-2022; John Wiley and Sons Inc
• Subjects: Adhesins; Adhesion; Antibodies; Cell walls; Clonal deletion; Collagen; Complement component C1q; Endothelial cells; Epithelial cells; Epithelium; Fibronectin; Gene deletion; Infections; Molecular modelling; Pathogenesis; Protein B; Proteins; Streptococcus infections; Streptococcus pneumoniae
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1111/mmi.14920

The binding of Streptococcus pneumoniae to collagen is likely an important step in the pathogenesis of pneumococcal infections, but little is known of the underlying molecular mechanisms. Streptococcal surface repeats (SSURE) are highly conserved protein domains present in cell wall adhesins from different Streptococcus species. We find here that SSURE repeats of the pneumococcal adhesin plasminogen and fibronectin binding protein B (PfbB) bind to various types of collagen. Moreover, deletion of the pfbB gene resulted in a significant impairment of the ability of encapsulated or unencapsulated pneumococci to bind collagen. Notably, a PfbB SSURE domain is also bound to the complement component C1q that bears a collagen‐like domain and promotes adherence of pneumococci to host cells by acting as a bridge between bacteria and epithelial cells. Accordingly, deletion of PfbB or pre‐treatment with anti‐SSURE antibodies markedly decreased pneumococcal binding to C1q as well as C1q‐dependent adherence to epithelial and endothelial cells. Further data indicated that C1q promotes pneumococcal adherence by binding to integrin α2β1. In conclusion, our results indicate that the SSURE domains of the PfbB protein promote interactions of pneumococci with various types of collagen and with C1q. These repeats may be useful targets in strategies to control S. pneumoniae infections.
We show here that the SSURE domains of the bacterial cell wall adhesin PfbB contribute to the ability of pneumococci to bind various types of collagens and C1q, a complement component. We also show that C1q acts as a bridge between PfbB SSURE domains and the α2β1 integrin thereby promoting adherence to, and invasion of, endothelial and epithelial cells. Targeting SSURE domains may be advantageous in alternative strategies to control pneumococcal infections.