Document Detail

Microbe-specific C3b deposition in the horseshoe crab complement system in a C2/factor B-dependent or -independent manner.
MedLine Citation:
PMID:  22611464     Owner:  NLM     Status:  MEDLINE    
Complement C3 plays an essential role in the opsonization of pathogens in the mammalian complement system, whereas the molecular mechanism underlying C3 activation in invertebrates remains unknown. To understand the molecular mechanism of C3b deposition on microbes, we characterized two types of C2/factor B homologs (designated TtC2/Bf-1 and TtC2/Bf-2) identified from the horseshoe crab Tachypleus tridentatus. Although the domain architectures of TtC2/Bf-1 and TtC2/Bf-2 were identical to those of mammalian homologs, they contained five-repeated and seven-repeated complement control protein domains at their N-terminal regions, respectively. TtC2/Bf-1 and TtC2/Bf-2 were synthesized and glycosylated in hemocytes and secreted to hemolymph plasma, which existed in a complex with C3 (TtC3), and their activation by microbes was absolutely Mg(2+)-dependent. Flow cytometric analysis revealed that TtC3b deposition was Mg(2+)-dependent on Gram-positive bacteria or fungi, but not on Gram-negative bacteria. Moreover, this analysis demonstrated that Ca(2+)-dependent lectins (C-reactive protein-1 and tachylectin-5A) were required for TtC3b deposition on Gram-positive bacteria, and that a Ca(2+)-independent lectin (Tachypleus plasma lectin-1) was definitely indispensable for TtC3b deposition on fungi. In contrast, a horseshoe crab lipopolysaccharide-sensitive protease factor C was necessary and sufficient to deposit TtC3b on Gram-negative bacteria. We conclude that plasma lectins and factor C play key roles in microbe-specific TtC3b deposition in a C2/factor B-dependent or -independent manner.
Keisuke Tagawa; Toyoki Yoshihara; Toshio Shibata; Kazuki Kitazaki; Yuichi Endo; Teizo Fujita; Takumi Koshiba; Shun-ichiro Kawabata
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2012-05-07
Journal Detail:
Title:  PloS one     Volume:  7     ISSN:  1932-6203     ISO Abbreviation:  PLoS ONE     Publication Date:  2012  
Date Detail:
Created Date:  2012-05-21     Completed Date:  2012-09-17     Revised Date:  2013-06-24    
Medline Journal Info:
Nlm Unique ID:  101285081     Medline TA:  PLoS One     Country:  United States    
Other Details:
Languages:  eng     Pagination:  e36783     Citation Subset:  IM    
Graduate School of Systems Life Sciences, Kyushu University, Fukuoka, Japan.
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MeSH Terms
Cloning, Molecular
Complement Activation / immunology
Complement C2 / genetics,  immunology*,  metabolism
Complement C3b / immunology*,  metabolism
Complement Factor B / genetics,  immunology*,  metabolism
DNA, Complementary
Forkhead Transcription Factors / immunology,  metabolism
Fungi / immunology
Gram-Positive Bacteria / immunology
Horseshoe Crabs / immunology*,  microbiology
Magnesium / metabolism
Models, Biological
Protein Binding / immunology
Protein Structure, Tertiary
Reg. No./Substance:
0/Complement C2; 0/DNA, Complementary; 0/Forkhead Transcription Factors; 7439-95-4/Magnesium; 80295-43-8/Complement C3b; EC Factor B

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