8 research outputs found
Structure of the Tyrosine-sulfated C5a Receptor N Terminus in Complex with Chemotaxis Inhibitory Protein of Staphylococcus aureus*Sâ
Complement component C5a is a potent pro-inflammatory agent inducing
chemotaxis of leukocytes toward sites of infection and injury. C5a mediates
its effects via its G protein-coupled C5a receptor (C5aR). Although under
normal conditions highly beneficial, excessive levels of C5a can be
deleterious to the host and have been related to numerous inflammatory
diseases. A natural inhibitor of the C5aR is chemotaxis inhibitory protein of
Staphylococcus aureus (CHIPS). CHIPS is a 121-residue protein
excreted by S. aureus. It binds the N terminus of the C5aR (residues
1-35) with nanomolar affinity and thereby potently inhibits C5a-mediated
responses in human leukocytes. Therefore, CHIPS provides a starting point for
the development of new anti-inflammatory agents. Two O-sulfated
tyrosine residues located at positions 11 and 14 within the C5aR N terminus
play a critical role in recognition of C5a, but their role in CHIPS binding
has not been established so far. By isothermal titration calorimetry, using
synthetic Tyr-11- and Tyr-14-sulfated and non-sulfated C5aR N-terminal
peptides, we demonstrate that the sulfate groups are essential for tight
binding between the C5aR and CHIPS. In addition, the NMR structure of the
complex of CHIPS and a sulfated C5aR N-terminal peptide reveals the precise
binding motif as well as the distinct roles of sulfated tyrosine residues sY11
and sY14. These results provide a molecular framework for the design of novel
CHIPS-based C5aR inhibitors
The TLR2 Antagonist Staphylococcal Superantigen-Like Protein 3 Acts as a Virulence Factor to Promote Bacterial Pathogenicity in vivo
Toll-like receptor (TLR) signaling is important in the initiation of immune responses and subsequent instigation of adaptive immunity. TLR2 recognizes bacterial lipoproteins and plays a central role in the host defense against bacterial infections, including those caused by Staphylococcus aureus. Many studies have demonstrated the importance of TLR2 in murine S. aureus infection. S. aureus evades TLR2 activation by secreting two proteins, staphylococcal superantigen-like protein 3 (SSL3) and 4 (SSL4). In this study, we demonstrate that antibodies against SSL3 and SSL4 are found in healthy individuals, indicating that humans are exposed to these proteins during S. aureus colonization or infection. To investigate the TLR2-antagonistic properties of SSL3 and SSL4, we compared the infection with wild-type and SSL3/4 knockout S. aureus strains in an intravenous murine infection model. Direct evaluation of the contribution of SSL3/4 to infection pathogenesis was hindered by the fact that the SSLs were not expressed in the murine system. To circumvent this limitation, an SSL3-overproducing strain (pLukM-SSL3) was generated, resulting in constitutive expression of SSL3. pLukM-SSL3 exhibited increased virulence compared to the parental strain in a murine model that was found to be TLR2 dependent. Altogether, these data indicate that SSL3 contributes to S. aureus virulence in vivo
The TLR2 Antagonist Staphylococcal Superantigen-Like Protein 3 Acts as a Virulence Factor to Promote Bacterial Pathogenicity in vivo
LukMFâČ is the major secreted leukocidin of bovine Staphylococcus aureus and is produced in vivo during bovine mastitis
Staphylococcus aureus is a major human and animal pathogen and a common cause of mastitis in cattle. S. aureus secretes several leukocidins that target bovine neutrophils, crucial effector cells in the defence against bacterial pathogens. In this study, we investigated the role of staphylococcal leukocidins in the pathogenesis of bovine S. aureus disease. We show that LukAB, in contrast to the Îł-hemolysins, LukED, and LukMFâČ, was unable to kill bovine neutrophils, and identified CXCR2 as a bovine receptor for HlgAB and LukED. Furthermore, we assessed functional leukocidin secretion by bovine mastitis isolates and observed that, although leukocidin production was strain dependent, LukMFâČ was most abundantly secreted and the major toxin killing bovine neutrophils. To determine the role of LukMFâČ in bovine mastitis, cattle were challenged with high (S1444) or intermediate (S1449, S1463) LukMFâČ-producing isolates. Only animals infected with S1444 developed severe clinical symptoms. Importantly, LukM was produced in vivo during the course of infection and levels in milk were associated with the severity of mastitis. Altogether, these findings underline the importance of LukMFâČ as a virulence factor and support the development of therapeutic approaches targeting LukMFâČ to control S. aureus mastitis in cattle.</p