Streptococcal inhibitor of complement-mediated lysis (SIC): an anti-inflammatory virulence determinant.
Since the late 1980s, a worldwide increase of severe Streptococcus pyogenes infections has been associated with strains of the M1 serotype, strains which all secrete the streptococcal inhibitor of complement-mediated lysis (SIC). Previous work has shown that SIC blocks complement-mediated haemolysis, inhibits the activity of antibacterial peptides and has affinity for the human plasma proteins clusterin and histidine-rich glycoprotein; the latter is a member of the cystatin protein family. The present work demonstrates that SIC binds to cystatin C, high-molecular-mass kininogen (HK) and low-molecular-mass kininogen, which are additional members of this protein family. The binding sites in HK are located in the cystatin-like domain D3 and the endothelial cell-binding domain D5. Immobilization of HK to cellular structures plays a central role in activation of the human contact system. SIC was found to inhibit the binding of HK to endothelial cells, and to reduce contact activation as measured by prolonged blood clotting time and impaired release of bradykinin. These results suggest that SIC modifies host defence systems, which may contribute to the virulence of S. pyogenes strains of the M1 serotype.
Åkesson
Per
P
Department of Clinical Sciences, Division of Infection Medicine, Lund University, BMC, B14, SE-22184 Lund, Sweden.
Herwald
Heiko
H
Department of Clinical Sciences, Division of Infection Medicine, Lund University, BMC, B14, SE-22184 Lund, Sweden.
Rasmussen
Magnus
M
Department of Clinical Sciences, Division of Infection Medicine, Lund University, BMC, B14, SE-22184 Lund, Sweden.
HÅkansson
Katarina
K
Department of Laboratory Medicine, Division of Clinical Chemistry and Pharmacology, Lund University, University Hospital, SE-22185 Lund, Sweden.
Abrahamson
Magnus
M
Department of Laboratory Medicine, Division of Clinical Chemistry and Pharmacology, Lund University, University Hospital, SE-22185 Lund, Sweden.
Hasan
Ahmed A K
AAK
Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA.
Schmaier
Alvin H
AH
Department of Medicine, Division of Hematology and Oncology, Case Western Reserve University, Cleveland, OH, USA.
Müller-Esterl
Werner
W
Institute for Biochemistry II, University of Frankfurt, Frankfurt, Germany.
Björck
Lars
L
Department of Clinical Sciences, Division of Infection Medicine, Lund University, BMC, B14, SE-22184 Lund, Sweden.
D001426:Bacterial Proteins / Q000235:genetics / Q000276:immunology*; D003165:Complement System Proteins; D055316:Cystatin C / Q000276:immunology; D054884:Host-Pathogen Interactions; D006801:Humans; D019679:Kininogen, High-Molecular-Weight / Q000276:immunology; D011485:Protein Binding; D013290:Streptococcal Infections / Q000276:immunology / Q000382:microbiology*; D013297:Streptococcus pyogenes / Q000235:genetics / Q000276:immunology* / Q000472:pathogenicity*; D014774:Virulence
D001426:Bacterial Proteins; D055316:Cystatin C; D019679:Kininogen, High-Molecular-Weight; C097739:SIC protein, Streptococcus; D003165:Complement System Proteins