The novel fibrinogen-binding protein FbsB promotes Streptococcus agalactiae invasion into epithelial cells.
Streptococcus agalactiae is a major cause of bacterial sepsis and meningitis in human newborns. The interaction of S. agalactiae with host proteins and the entry into host cells thereby represent important virulence traits of these bacteria. The present report describes the identification of the fbsB gene, encoding a novel fibrinogen-binding protein that plays a crucial role in the invasion of S. agalactiae into human cells. In Western blots and enzyme-linked immunosorbent assay (ELISA) experiments, the FbsB protein was demonstrated to interact with soluble and immobilized fibrinogen. Binding studies showed the N-terminal 388 residues of FbsB and the Aalpha-subunit of human fibrinogen to recognize each other. By reverse transcription (RT)-PCR, the fbsB gene was shown to be cotranscribed with the gbs0851 gene in S. agalactiae. Deletion of the fbsB gene in the genome of S. agalactiae did not influence the binding of the bacteria to fibrinogen, suggesting that FbsB does not participate in the attachment of S. agalactiae to fibrinogen. In tissue culture experiments, however, the fbsB deletion mutant was severely impaired in its invasion into lung epithelial cells. Bacterial invasion could be reestablished by introducing the fbsB gene on a shuttle plasmid into the fbsB deletion mutant. Furthermore, treatment of lung epithelial cells with FbsB fusion protein blocked S. agalactiae invasion of epithelial cells in a dose-dependent fashion. These results suggest an important role of the FbsB protein in the overall process of host cell entry by S. agalactiae.
Gutekunst
Heike
H
Department of Microbiology and Biotechnology, University of Ulm, D-89069 Ulm, Germany.
Eikmanns
Bernhard J
BJ
Reinscheid
Dieter J
DJ
D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000378:metabolism*; D001665:Binding Sites; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D002460:Cell Line; D004847:Epithelial Cells / Q000382:microbiology*; D005340:Fibrinogen / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D017353:Gene Deletion; D006801:Humans; D007231:Infant, Newborn; D008168:Lung / Q000166:cytology / Q000382:microbiology*; D008969:Molecular Sequence Data; D013292:Streptococcus agalactiae / Q000472:pathogenicity* / Q000502:physiology; D014774:Virulence
D001426:Bacterial Proteins; D002352:Carrier Proteins; C487204:FbsB protein, Streptococcus agalactiae; D005340:Fibrinogen