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Directed Protein Packaging within Outer Membrane Vesicles from Escherichia coli: Design, Production and Purification
Published on: November 16, 2016
Contribution of the outer membrane protein OmpW in Escherichia coli to complement resistance from binding to factor H
Weiyan Li1, Liangyou Wen1, Chuchu Li1
1School of Life Sciences, Zhejiang Sci-Tech University, Hangzhou 310018, China.
Abstract:
The serum complement system is essential for innate immune defense against invading pathogenic bacteria. Some of the 8-stranded β-barrel outer membrane proteins confer bacterial resistance to the innate host immunity. We have previously demonstrated that OmpW, also an 8-stranded β-barrel protein that was identified a decade ago, protects bacteria against host phagocytosis. In this study, we investigated the complement resistance of OmpW. Our results indicate that the upregulation of OmpW is associated with increased survival when bacteria are exposed to normal human sera (NHS). Mutant bacteria lacking OmpW in NHS exhibited significantly lower survival rates in comparison to wild-type and ompW complemented bacteria. Furthermore, the bacterial survival significantly decreased in NHS that was supplemented with EGTA-Mg(2+) compared to that in NHS supplemented with EDTA. These results suggest that OmpW confer resistance to alternative complement pathway-mediated killing. Moreover, the binding of OmpW to factor H, a major inhibitor of alternative pathway, was found, indicating that OmpW recruitment of factor H is a mechanism for bacterial evasion of complement attack.
Insights
The bacterial outer membrane protein OmpW enhances survival against the host immune system by resisting complement-mediated killing. OmpW achieves this by binding to factor H, a key regulator of the alternative complement pathway.
Area of Science:
- Immunology
- Microbiology
- Bacterial Pathogenesis
Background:
- The serum complement system is crucial for innate immunity against bacterial infections.
- Outer membrane proteins (OMPs) with an 8-stranded β-barrel structure can confer bacterial resistance to host immunity.
- OmpW, an OMP, was previously shown to protect bacteria from phagocytosis.
Purpose of the Study:
- To investigate the role of OmpW in bacterial resistance to serum complement.
- To determine the specific complement pathway(s) involved in OmpW-mediated resistance.
- To elucidate the mechanism by which OmpW confers complement resistance.
Main Methods:
- Exposure of wild-type, OmpW-deficient mutant, and complemented bacteria to normal human sera (NHS).
- Assessment of bacterial survival rates in NHS with different complement pathway inhibitors (EGTA-Mg(2+) and EDTA).
- Investigation of OmpW binding to complement factor H.
Main Results:
- Upregulation of OmpW correlated with increased bacterial survival in NHS.
- OmpW-deficient mutants showed significantly reduced survival in NHS compared to wild-type.
- Bacterial survival was significantly lower in NHS supplemented with EGTA-Mg(2+) (alternative pathway inhibited) compared to EDTA (alternative and classical pathways inhibited).
- OmpW was found to bind to complement factor H.
Conclusions:
- OmpW confers resistance to killing mediated by the alternative complement pathway.
- OmpW promotes bacterial evasion of complement attack through the recruitment of factor H.
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