title: Cutting edge: complement-activating complex of ficolin and mannose-binding lectin-associated serine protease.
abstract: Both ficolins and mannose-binding lectin (MBL) are lectins characterized by the presence of collagen-like and carbohydrate-binding domains in a subunit, although their carbohydrate-binding moieties are quite different. A fibrinogen-like domain is in ficolins, and a carbohydrate recognition domain is in MBL. On binding to pathogens, human MBL activates the complement system via the lectin pathway in association with two types of MBL-associated serine proteases (MASP), MASP-1 and MASP-2 and its truncated form, small MBL-associated protein (sMAP, also called MAp19). We report here that ficolin/P35, a human serum ficolin, was found to copurify with MASPs and sMAP. MASPs that were complexed with ficolin/P35 exhibited proteolytic activities against complement components C4, C2, and C3. The ficolin/P35-MASPs-sMAP complex that was bound to Salmonella typhimurium activated complement. These findings indicate that ficolin/P35 is a second collagenous lectin capable of activating the lectin pathway and thus plays a role in innate immunity.
authors.affiliation: Department of Biochemistry, Fukushima Medical University School of Medicine, Fukushima, Japan. mmatsu@fmu.ac.jp
authors.forename: M
authors.initials: M
authors.lastname: Matsushita
authors.forename: Y
authors.initials: Y
authors.lastname: Endo
authors.forename: T
authors.initials: T
authors.lastname: Fujita
mesh_terms: D001704:Biopolymers / Q000097:blood / Q000276:immunology / Q000302:isolation & purification; D002352:Carrier Proteins / Q000097:blood / Q000276:immunology* / Q000302:isolation & purification; D037222:Collectins; D003167:Complement Activation / Q000276:immunology*; D015922:Complement C1q / Q000276:immunology / Q000378:metabolism; D003176:Complement C3 / Q000276:immunology / Q000378:metabolism; D004789:Enzyme Activation / Q000276:immunology; D006801:Humans; D037102:Lectins / Q000276:immunology*; D050606:Mannose-Binding Protein-Associated Serine Proteases; D011233:Precipitin Tests; D012697:Serine Endopeptidases / Q000097:blood / Q000276:immunology* / Q000302:isolation & purification; D000097604:Ficolins
chemical_list: D001704:Biopolymers; D002352:Carrier Proteins; D037222:Collectins; D015922:Complement C1q; D003176:Complement C3; D037102:Lectins; D050606:Mannose-Binding Protein-Associated Serine Proteases; D012697:Serine Endopeptidases; D000097604:Ficolins