title: Activation of the lectin complement pathway by H-ficolin (Hakata antigen).
abstract: Ficolins are a group of proteins which consist of a collagen-like domain and a fibrinogen-like domain. In human serum, there are two types of ficolins named L-ficolin/P35 and H-ficolin (Hakata Ag), both of which have lectin activity. We recently demonstrated that L-ficolin/P35 is associated with mannose-binding lectin (MBL)-associated serine proteases (MASP) 1 and 2 and small MBL-associated protein (sMAP), and that the complex activates the lectin pathway. In this study, we report the characterization of H-ficolin in terms of its ability to activate complement. Western blotting analysis showed the presence of MASP-1, MASP-2, MASP-3, and sMAP in H-ficolin preparations isolated from Cohn Fraction III. The MASPs in the preparations had proteolytic activities against C4, C2, and C3 in the fluid phase. When H-ficolin preparations were bound to anti-H-ficolin Ab which had been coated on ELISA plates, they activated C4, although no C4 activation was noted when anti-MBL and anti-L-ficolin/P35 were used. H-ficolin binds to PSA, a polysaccharide produced by Aerococcus viridans. C4 was activated by H-ficolin preparations bound to PSA which had been coated on ELISA plates. These results indicate that H-ficolin is a second ficolin which is associated with MASPs and sMAP, and which activates the lectin pathway.
authors.affiliation: Department of Biochemistry, Fukushima Medical University School of Medicine, Fukushima, Japan. mmatsu@fmu.ac.jp
authors.forename: Misao
authors.initials: M
authors.lastname: Matsushita
authors.forename: Mikio
authors.initials: M
authors.lastname: Kuraya
authors.forename: Naotaka
authors.initials: N
authors.lastname: Hamasaki
authors.forename: Mitsushi
authors.initials: M
authors.lastname: Tsujimura
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Shiraki
authors.forename: Teizo
authors.initials: T
authors.lastname: Fujita
mesh_terms: D000911:Antibodies, Monoclonal / Q000378:metabolism; D001422:Bacterial Adhesion / Q000276:immunology; D001666:Binding Sites, Antibody; D002352:Carrier Proteins / Q000378:metabolism; D037222:Collectins; D003166:Complement Activating Enzymes / Q000302:isolation & purification / Q000378:metabolism / Q000502:physiology; D003167:Complement Activation / Q000276:immunology*; D006023:Glycoproteins / Q000276:immunology / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D037102:Lectins / Q000378:metabolism*; D050606:Mannose-Binding Protein-Associated Serine Proteases; D011135:Polysaccharides, Bacterial / Q000378:metabolism; D011485:Protein Binding / Q000276:immunology; D012697:Serine Endopeptidases / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism / Q000502:physiology; D013289:Streptococcaceae / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D002352:Carrier Proteins; D037222:Collectins; C109662:FCN3 protein, human; D006023:Glycoproteins; D037102:Lectins; D011135:Polysaccharides, Bacterial; D003166:Complement Activating Enzymes; C105296:MASP2 protein, human; D050606:Mannose-Binding Protein-Associated Serine Proteases; D012697:Serine Endopeptidases