Streptococcal collagen-like surface protein 1 promotes adhesion to the respiratory epithelial cell

Abstract

BackgroundCollagen-like surface proteins Scl1 and Scl2 on Streptococcus pyogenes contain contiguous Gly-X-X triplet amino acid motifs, the characteristic structure of human collagen. Although the potential role of Scl1 in adhesion has been studied, the conclusions may be affected by the use of different S. pyogenes strains and their carriages of various adhesins. To explore the bona fide nature of Scl1 in adherence to human epithelial cells without the potential interference of other streptococcal surface factors, we constructed a scl1 isogenic mutant from the Scl2-defective S. pyogenes strain and a Scl1-expressed Escherichia coli.ResultsLoss of Scl1 in a Scl2-defective S. pyogenes strain dramatically decreased the adhesion of bacteria to HEp-2 human epithelial cells. Expression of Scl1 on the surface of the heterologous bacteria E. coli significantly increased adhesion to HEp-2. The increase in adhesion was nullified when Scl1-expressed E. coli was pre-incubated with proteases or antibodies against recombinant Scl1 (rScl1) protein. Treatment of HEp-2 cells with rScl protein or pronase drastically reduced the binding capability of Scl1-expressed E. coli. These findings suggest that the adhesion is mediated through Scl1 on bacterial surface and protein receptor(s) on epithelial cells. Further blocking of potential integrins revealed significant contributions of α2 and β1 integrins in Scl1-mediated binding to epithelial cells.ConclusionsTogether, these results underscore the importance of Scl1 in the virulence of S. pyogenes and implicate Scl1 as an adhesin during pathogenesis of streptococcal infection.

AhrC and Eep Are Biofilm Infection-Associated Virulence Factors in Enterococcus faecalis

“…The genes deleted in these strains may have functions in infection or biofilm formation that are redundant with other genetic determinants, such that their phenotypes are masked in the assays used here. This precise type of effect has been reported with streptococcal adhesins (50,51).…”

Role for Streptococcal Collagen-Like Protein 1 in M1T1 Group A Streptococcus Resistance to Neutrophil Extracellular Traps

“…S1 in the supplemental material). Furthermore, the role of Scl-1 in immune resistance is likely due to the N-terminal domain of M1 serotype Scl-1, as the collagen-like domain appears to chiefly play a role in bacterial adhesion to host cells (19,20). Sequence analysis of the N-terminal domain of M1 Scl-1 did not reveal significant homology to other proteins of known function (data not shown).…”

“…Scl-1 is an LP(X)TG motif protein anchored to the GAS cell wall, and in studies utilizing recombinant protein, Scl-1 has been shown to interact with extracellular matrix proteins and host cells (15,(18)(19)(20). We first tested whether Scl-1 contributed to M1T1 GAS virulence using a mouse model of localized subcutaneous infection.…”

“…Scl-1 encodes a surface protein bearing a collagen-like domain that is conserved among GAS strains and a hypervariable N-terminal domain (14,15). In other, less virulent GAS serotype strains, Scl-1 has been shown to participate in biofilm formation (16,17), attachment to extracellular matrix proteins (18), and attachment to lung epithelial cells (15,19,20) but not pharyngeal cells (14). Studies using recombinant Scl-1 have shown that the protein, via its serotype-hypervariable N terminus, can bind a variety of host proteins, including serum lipoproteins (21,22), integrins (23,24), the complement inhibitors FH and FH-related protein 1 (25,26), and the thrombin-activatable fibrinolysis inhibitor (27).…”

Growth Phase-Dependent Modulation of Rgg Binding Specificity in Streptococcus pyogenes

“…Rgg bound to noncoding DNA upstream of genes encoding the antiphagocytic M protein (20,21,56), SOF (57), SfbX49 (30), and streptococcal collagen-like surface protein B (SclB) (19). Each gene product is localized to the cell surface and covalently attached to peptidoglycan, and each is thought to contribute to virulence (19,20,21,29,47,57). Previous analyses showed that Rgg represses the expression of each of the genes (26), suggesting that the protein directly represses their expression.…”