Binding of Efb from Staphylococcus aureus to Fibrinogen Blocks Neutrophil Adherence

Center for Infectious and Inflammatory Disease, Institute of Bioscience and Technology, Texas A&M Health Science Center, Houston, Texas 77030, USA.
Journal of Biological Chemistry (Impact Factor: 4.57). 03/2011; 286(11):9865-74. DOI: 10.1074/jbc.M110.199687
Source: PubMed

ABSTRACT In addition to its pivotal role in hemostasis, fibrinogen (Fg) and provisional fibrin matrices play important roles in inflammation and regulate innate immune responses by interacting with leukocytes. Efb (the extracellular fibrinogen-binding protein) is a secreted Staphylococcus aureus protein that engages host Fg and complement C3. However, the molecular details underlying the Efb-Fg interaction and the biological relevance of this interaction have not been determined. In the present study, we characterize the interaction of Efb with Fg. We demonstrate that the Fg binding activity is located within the intrinsically disordered N-terminal half of Efb (Efb-N) and that the D fragment of Fg is the region that mediates Efb-N binding. More detailed studies of the Efb-N-Fg interactions using ELISA and surface plasmon resonance analyses revealed that Efb-N exhibits a much higher affinity for Fg than typically observed with Fg-binding MSCRAMMs (microbial surface components recognizing adhesive matrix molecules), and data obtained from ELISA analyses using truncated Efb-N constructs demonstrate that Efb-N contains two binding sites located within residues 30-67 and 68-98, respectively. Efb-N inhibits neutrophil adhesion to immobilized Fg by binding to Fg and blocking the interaction of the protein with the leukocyte integrin receptor, α(M)β(2). A motif in the Fg γ chain previously shown to be central to the α(M)β(2) interaction was shown to be functionally distinguishable from the Efb-N binding site, suggesting that the Fg-Efb interaction indirectly impedes Fg engagement by α(M)β(2). Taken together, these studies provide insights into how Efb interacts with Fg and suggest that Efb may support bacterial virulence at least in part by impeding Fg-driven leukocyte adhesion events.

Download full-text


Available from: Xiaowen Liang, Sep 29, 2015
31 Reads
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Staphylocoagulase and von Willebrand binding protein (VWbp) bind to prothrombin to form the staphylothrombin complex that converts fibrinogen into fibrin. To study the role of staphylothrombin and its inhibition by dabigatran on Staphylococcus aureus virulence. We studied the effect of staphylothrombin inhibition on bacterial attachment to polystyrene surfaces, leukocyte activation and bactericidal activity for S. aureus ATCC 25923, S. aureus Newman, and staphylocoagulase- and VWbp-negative S. aureus Newman mutants in the presence or absence of prothrombin and fibrinogen. We measured the abscess size after subcutaneous (s.c.) injection of S. aureus ATCC 25923 and S. aureus Newman, as well as an S. aureus Newman mutant strain lacking staphylocoagulase and VWbp, in mice treated with either dabigatran or placebo. Staphylothrombin-mediated fibrin increased the association of S. aureus to polystyrene surfaces and reduced the bactericidal activity of leukocytes. The absence or inhibition of staphylothrombin decreased the bacterial association, enhanced leukocyte activation and reduced bacterial survival in vitro. Abscess size was smaller in mice treated with dabigatran or infected with a coagulase-negative mutant. Inhibition or the absence of staphylothrombin reduced S. aureus virulence in in vitro and in vivo models.
    Journal of Thrombosis and Haemostasis 12/2011; 9(12):2436-46. DOI:10.1111/j.1538-7836.2011.04529.x · 5.72 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Staphylococcus aureus is a leading human pathogen that causes a large variety of diseases. In vitro studies have shown that S. aureus secretes several small proteins that block specific elements of the host innate immune system, but their role in bacterial pathogenicity is unknown. For instance, the extracellular complement-binding protein (Ecb) impairs complement activation by binding to the C3d domain of C3. Its homolog, the extracellular fibrinogen-binding protein (Efb), is known to block both complement activation and neutrophil adhesion to fibrinogen. Here, we show that targeted inactivation of the genes encoding Ecb and Efb strongly attenuates S. aureus virulence in a murine infection model: mice experienced significantly higher mortality rates upon intravenous infection with wild-type bacteria (79%) than with an isogenic ΔEcbΔEfb mutant (21%). In addition, Ecb and Efb are both required for staphylococcal persistence in host tissues and abscess formation in the kidneys (27% for wild-type vs. 7% for the ΔEcbΔEfb mutant). During staphylococcal pneumonia, Ecb and Efb together promote bacterial survival in the lungs (p = 0.03) and block neutrophil influx into the lungs. Thus, Ecb and Efb are essential to S. aureus virulence in vivo and could be attractive targets in future vaccine development efforts.
    Journal of Innate Immunity 02/2012; 4(3):301-11. DOI:10.1159/000334604 · 4.35 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Knowledge of the immunological correlates of Staphylococcus aureus and Streptococcus pneumoniae colonization is required for the search for future protein vaccines. We evaluated natural antibody levels against pneumococcal and staphylococcal proteins in relation to previous bacterial colonization with both pathogens. In a randomized controlled trial, nasopharyngeal samples were obtained from children at 1.5, 6, 12, 18, and 24 months and cultured for S. aureus and S. pneumoniae. Approximately 50% of the children were PCV7 vaccinated. Serum IgG against 18 pneumococcal and 40 staphylococcal proteins was semiquantified by Luminex technology from 111 12 month olds and 158 24 month olds. Previous culture-proven S. aureus colonization was associated with higher IgG levels against 6/40 staphylococcal proteins (ClfB, ClfA, Efb, CHIPS, LukD, and LukF [P ≤ 0.001]) compared to noncarriers. Previous pneumococcal colonization was associated with increased IgG levels against 12/18 pneumococcal proteins compared to noncarriers (P ≤ 0.003). Increasing age was associated with higher levels of antibodies to most pneumococcal proteins and lower levels of antibodies to over half the staphylococcal proteins, reflecting natural colonization dynamics. Anti-S. pneumoniae and anti-S. aureus protein antibodies at the age of 12 months were not negatively correlated with subsequent colonization with the homologous species in the following year and did not differ between PCV7-vaccinated and nonvaccinated children. Colonization with S. aureus and S. pneumoniae induces serum IgG against many proteins, predominantly proteins with immune-modulating functions, irrespective of PCV7 vaccination. None of them appeared to be protective against new acquisition with both pathogens, possibly due to the polymorphic nature of those proteins in the circulating bacterial population.
    Infection and immunity 03/2012; 80(6):2186-93. DOI:10.1128/IAI.00037-12 · 3.73 Impact Factor
Show more