Plasminogen- and fibronectin-binding protein B is involved in the adherence of Streptococcus pneumoniae to human epithelial cells.
Streptococcus pneumoniae is a major cause of morbidity and mortality worldwide. The ability of this bacterium to adhere to epithelial cells is considered as an essential early step in colonization and infection. By screening a whole genome phage display library with sera from infected patients, we previously identified three antigenic fragments matching open reading frame spr0075 of the strain R6 genome. This locus encodes for an approximately 120-kDa protein, herein referred to as plasminogen- and fibronectin-binding protein B (PfbB), which displays an LPXTG cell wall anchoring motif and six repetitive domains. In this study, by using isogenic pfbB-deleted mutants of the encapsulated D39 and of the unencapsulated DP1004 type 2 pneumococcal strains, we show that PfbB is involved in S. pneumoniae adherence to various epithelial respiratory tract cell lines. Our data suggest that PfbB directly mediates bacterial adhesion, because fluorescent beads coated with the recombinant PfbB sp17 fragment (encompassing one of the six repetitive domains and the C-terminal region) efficiently bound to epithelial cells. Mutants lacking PfbB bound to fibronectin and plasminogen considerably less efficiently than wild type bacteria, whereas sp17-coated beads specifically bound to both of these substrates. Taken together, our data suggest that, by directly interacting with fibronectin, PfbB significantly increases the ability of S. pneumoniae to adhere to human epithelial cells.
Papasergi
Salvatore
S
Elie Metchnikoff Department, Università di Messina, Messina I-98125, Italy.
Garibaldi
Manuela
M
Tuscano
Giovanna
G
Signorino
Giacomo
G
Ricci
Susanna
S
Peppoloni
Samuele
S
Pernice
Ida
I
Lo Passo
Carla
C
Teti
Giuseppe
G
Felici
Franco
F
Beninati
Concetta
C
D018829:Adhesins, Bacterial / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001422:Bacterial Adhesion / Q000502:physiology*; D001426:Bacterial Proteins / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D004847:Epithelial Cells / Q000166:cytology / Q000382:microbiology*; D005353:Fibronectins / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008863:Microspheres; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D010958:Plasminogen / Q000378:metabolism*; D011008:Pneumococcal Infections / Q000378:metabolism; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013296:Streptococcus pneumoniae / Q000378:metabolism*
D018829:Adhesins, Bacterial; D001426:Bacterial Proteins; D002352:Carrier Proteins; D005353:Fibronectins; C548982:PfbB protein, Streptococcus pneumoniae; D011993:Recombinant Fusion Proteins; D010958:Plasminogen