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Streptococcus pyogenes protein F promotes invasion of HeLa cells
Nobuhiko Okada1, Lchiro Tatsuno1, Emanuel Hanski2
1Department of Bacteriology, Institute of Medical Science, University of Tokyo, Tokyo 1 08, Japan.
Abstract:
Although the Gram-positive bacterium Streptococcus pyogenes (group A streptococcus) has been considered an extracellular pathogen which adheres to human mucosal epithelium, the streptococcus possesses invasive capacity for cultured human epithelial cells. This study provides genetic and functional evidence supporting the conclusion that protein F is capable of mediating entry of S. pyogenes into HeLa cells. Using Tn916 insertion mutagenesis or an isogenic S. pyogenes strain with a defined mutation in the gene encoding protein F (prtF), it was observed that the invasive capacity was affected by the levels of surface-exposed protein F, but not by those of M protein. In addition, heterologous expression of protein F on Enterococcus faecalis conferred upon the bacteria an efficient invasive phenotype. Several assays demonstrated that both the fibronectin-binding domains of protein F, UR and RD2, were involved in host-cell invasion. In addition, coinfection experiments of HeLa cells with S. pyogenes and an Escherichia coli K-12 strain expressing an afimbrial adhesin AFA-I showed that the uptake of S. pyogenes did not permit internalization of the E. coli cells.
Insights
Streptococcus pyogenes invades human cells via protein F. This study demonstrates protein F
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Cell Biology
Background:
- Streptococcus pyogenes (group A streptococcus) is primarily an extracellular pathogen adhering to mucosal epithelium.
- However, S. pyogenes exhibits invasive capabilities into host cells.
Purpose of the Study:
- To investigate the role of protein F in the invasion of human epithelial cells by Streptococcus pyogenes.
- To determine if protein F mediates bacterial entry into host cells.
Main Methods:
- Genetic manipulation of Streptococcus pyogenes using Tn916 insertion mutagenesis and targeted gene mutation of prtF.
- Heterologous expression of protein F in Enterococcus faecalis.
- Functional assays to assess bacterial invasion and fibronectin-binding domains.
Main Results:
- Invasive capacity of S. pyogenes correlated with surface-exposed protein F levels, not M protein.
- Heterologous expression of protein F in E. faecalis resulted in an invasive phenotype.
- Specific fibronectin-binding domains (UR and RD2) of protein F were implicated in host-cell invasion.
Conclusions:
- Protein F is a key mediator of Streptococcus pyogenes invasion into human epithelial cells.
- The fibronectin-binding domains of protein F are crucial for this invasive mechanism.