The FbaB-type fibronectin-binding protein of Streptococcus pyogenes promotes specific invasion into endothelial cells

Area of Science:

• Microbiology
• Cell Biology
• Infectious Diseases

Background:

• Invasive serotype M3 Streptococcus pyogenes frequently cause invasive streptococcal disease.
• These bacteria can rapidly and efficiently invade primary human endothelial cells (EC).

Purpose of the Study:

• To identify the specific mechanism and protein responsible for Streptococcus pyogenes M3 invasion of endothelial cells.
• To characterize the role of the fibronectin-binding protein FbaB in this invasive process.

Main Methods:

• Utilized heterologous gene expression and allelic replacement techniques.
• Investigated the uptake mechanism and cellular pathway of FbaB-mediated invasion.
• Confirmed FbaB's essentiality and sufficiency for endothelial cell invasion.

Main Results:

• Identified FbaB, a fibronectin-binding protein of M3 S. pyogenes, as a potent endothelial cell (EC) invasin.
• Demonstrated that FbaB is essential and sufficient to induce EC invasion through a Rac1-dependent, phagocytosis-like mechanism.
• Showed that FbaB-mediated uptake follows the classical endocytic pathway, leading to lysosomal degradation.

Conclusions:

• FbaB acts as a novel streptococcal invasin with specific tropism for endothelial cells.
• FbaB initiates an invasion process that likely contributes to the deep tissue tropism and vascular spread of invasive S. pyogenes.