The Choline-binding Protein PspC of Streptococcus pneumoniae Interacts with the C-terminal Heparin-binding Domain of Vitronectin

Abstract

Background: Adhesins are essential for pneumococcal colonization and pathogenesis. Results: PspC, identified as a vitronectin-binding protein, interacts with the C-terminal heparin-binding domain of vitronectin, and when bound to PspC, it retains complement inhibitory function. Conclusion: PspC is an adhesin for vitronectin, and the PspC-vitronectin interaction inhibits immune attack. Significance: The PspC-vitronectin interaction provides new insights into pneumococcal adhesion and complement inhibition.

Pneumococcal Adhesins PavB and PspC Are Important for the Interplay with Human Thrombospondin-1

“…Nevertheless, a sterical blocking of PspC binding through heparin cannot be excluded. Notably, a heparin-dependent inhibition of PspC binding to human Vn was recently demonstrated (31), further supporting the idea of the involvement of heparin binding domains in the interactions of PspC and PavB with hTSP-1 and Vn.…”

“…Heterologous Expression and Purification of Recombinant Proteins-N-terminally His 6 -tagged PavB and PspC proteins used in this study have been described earlier (11,31,40,48). Using Ni 2ϩ affinity chromatography, His 6 -tagged proteins were purified from E. coli BL21 cell lysates after induction of protein expression (at A 600 ϭ 0.8) with 1 mM IPTG at 30°C for 3 h. After using either 1-ml HisTrap TM FF crude columns (GE Healthcare) and Äkta TM purifier system (GE Healthcare) or a prepacked Protino nickel column kit (Macherey-Nagel), proteins were dialyzed (12-14-kDa molecular weight cut off) against PBS (pH 7.4) at 4°C overnight.…”

“…The most promising candidates were pneumococcal surface protein C (PspC) and pneumococcal adherence and virulence factor B (PavB). Both proteins possess repeating structures and were previously shown to bind various human extracellular/matricellular matrix proteins such as fibronectin or Vn (11,31), thereby mediating pneumococcal colonization and invasion of host cells (11,(32)(33)(34)(35)(36).…”

“…PspC binds to the secretory component of the human polymeric immunoglobulin receptor (pIgR) and the 67 kDa-laminin receptor, which leads to an internalization of pneumococci into host cells. Furthermore, PspC sequesters Factor H, Vn and the C4B-binding protein (C4BP), contributing to pneumococcal immune evasion (31,(37)(38)(39)(40)(41).…”

Repeating Structures of the Major Staphylococcal Autolysin Are Essential for the Interaction with Human Thrombospondin 1 and Vitronectin

“…However, Eap also exhibits repeating sequences that are involved in binding to hTSP-1, Vn, and other extracellular matrix proteins (13). Similarly, pneumococcal proteins composed of repetitive sequences, such as the PspC and PavB proteins, interact via their repeats with Vn and fibronectin, respectively (27,66).…”