title: Cutting edge: members of the Staphylococcus aureus extracellular fibrinogen-binding protein family inhibit the interaction of C3d with complement receptor 2.
abstract: Staphylococcus aureus expresses a highly diversified arsenal of immune evasion proteins, many of which target the complement system. The extracellular fibrinogen-binding protein (Efb) and the Efb homologous protein (Ehp) have previously been demonstrated to bind to C3 and inhibit complement activation and amplification. In this study we present the first evidence that Efb and Ehp are also capable of inhibiting the interaction of C3d with complement receptor 2 (CR2), which plays an important role in B cell activation and maturation. The C-terminal domain of Efb efficiently blocked this interaction both in surface plasmon resonance-based competition studies and cellular assays and prevented the CR2-mediated stimulation of B cells. Furthermore, analyses of the available structural data were consistent with a molecular mechanism that reflects both steric and electrostatic effects on the C3d-CR2 interaction. Our study therefore suggests that S. aureus may disrupt both the innate and adaptive immune responses with a single protein module.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Ricklin
authors.forename: Salome K
authors.initials: SK
authors.lastname: Ricklin-Lichtsteiner
authors.forename: Maciej M
authors.initials: MM
authors.lastname: Markiewski
authors.forename: Brian V
authors.initials: BV
authors.lastname: Geisbrecht
authors.forename: John D
authors.initials: JD
authors.lastname: Lambris
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism; D001426:Bacterial Proteins / Q000276:immunology* / Q000378:metabolism; D002460:Cell Line; D003167:Complement Activation / Q000276:immunology; D015933:Complement C3d / Q000276:immunology* / Q000378:metabolism; D003169:Complement Inactivator Proteins / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D007113:Immunity, Innate; D008213:Lymphocyte Activation / Q000276:immunology; D051379:Mice; D011485:Protein Binding / Q000276:immunology; D017434:Protein Structure, Tertiary; D017464:Receptors, Complement 3d / Q000276:immunology* / Q000378:metabolism; D013211:Staphylococcus aureus / Q000276:immunology* / Q000378:metabolism; D055672:Static Electricity; D013329:Structure-Activity Relationship; D020349:Surface Plasmon Resonance
chemical_list: D001426:Bacterial Proteins; D003169:Complement Inactivator Proteins; C114014:Efb protein, Staphylococcus aureus; C524396:Ehp protein, Staphylococcus aureus; D017464:Receptors, Complement 3d; D015933:Complement C3d