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Effect of Vibrio-Derived Extracellular Protease vEP-45 on the Blood Complement System
So Hyun Kwon1, Jung Eun Park1,2, Yeong Hee Cho1,2
1Department of Biomedical Science, College of Natural Sciences and Public Health and Safety, Chosun University, Gwangju 61452, Korea.
Abstract:
Vibrio vulnificus is a pathogenic bacterium that can causes wound infections and fetal septicemia. We have reported that V. vulnificus ATCC29307 produces an extracellular zinc-metalloprotease (named vEP-45). Our previous results showed that vEP-45 can convert prothrombin to active thrombin and also activate the plasma kallikrein/kinin system. In this study, the effect of vEP-45 on the activation of the complement system was examined. We found that vEP-45 could proteolytically convert the key complement precursor molecules, including C3, C4, and C5, to their corresponding active forms (e.g., C3a, C3b, C4a, C4b, and C5a) in vitro cleavage assays. C5b production from C5 cleavage mediated by vEP-45 was not observed, whereas the level of C5a was increased in a dose-dependent manner compared to that of the non-treated control. The cleavage of the complement proteins in human plasma by vEP-45 was also confirmed via Western blotting. Furthermore, vEP-45 could convert C3 and C5 to active C3a and C5a as a proinflammatory mediator, while no cleavage of C4 was observed. These results suggest that vEP-45 can activate the complement system involved in innate immunity through an alternative pathway.
Insights
Vibrio vulnificus protease vEP-45 activates the complement system by cleaving C3 and C5. This protease generates pro-inflammatory mediators, suggesting a role in innate immunity via the alternative pathway.
Area of Science:
- Microbiology
- Immunology
- Biochemistry
Background:
- Vibrio vulnificus is a pathogen causing severe infections.
- V. vulnificus ATCC29307 produces an extracellular zinc-metalloprotease, vEP-45.
- Previous studies showed vEP-45 activates thrombin and the kallikrein/kinin system.
Purpose of the Study:
- To investigate the effect of vEP-45 on the complement system activation.
- To determine if vEP-45 cleaves complement precursor molecules.
- To understand the role of vEP-45 in innate immunity.
Main Methods:
- In vitro cleavage assays using purified complement proteins (C3, C4, C5).
- Western blotting to confirm complement protein cleavage in human plasma.
- Dose-dependent analysis of C5a production.
Main Results:
- vEP-45 proteolytically cleaved C3, C4, and C5 into active forms (C3a, C3b, C4a, C4b, C5a).
- vEP-45 increased C5a levels in a dose-dependent manner, but C5b production was not observed.
- Cleavage of C3 and C5 was confirmed in human plasma, generating pro-inflammatory C3a and C5a; C4 cleavage was not observed.
Conclusions:
- vEP-45 activates the complement system, specifically C3 and C5.
- vEP-45 generates pro-inflammatory mediators (C3a, C5a), suggesting a role in innate immunity.
- The activation appears to occur through the alternative complement pathway.
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