title: MASP-3 and its association with distinct complexes of the mannan-binding lectin complement activation pathway.
abstract: The mannan-binding lectin (MBL) pathway of complement activation is part of the innate immune defense. The binding of MBL to microbial carbohydrates activates the MBL-associated serine proteases (MASPs), which recruit the complement factors, C4 and C2, to generate the C3 convertase or directly activate C3. We present a phylogenetically highly conserved member of the MBL complex, MASP-3, which is generated through alternative splicing of the MASP-1/3 gene. The designation of MASP-3 as a protease is based on homology to known MASPs. Different MBL oligomers were found to have distinct MASP composition and biological activities. MASP-1, MAp19, and direct C3-cleaving activity are associated with smaller oligomers whereas MASP-3 is found together with MASP-2 on larger oligomers. MASP-3 downregulate the C4 and C2 cleaving activity of MASP-2.
authors.affiliation: Department of Medical Microbiology and Immunology, University of Aarhus, DK 8000, Aarhus, Denmark.
authors.forename: M R
authors.initials: MR
authors.lastname: Dahl
authors.forename: S
authors.initials: S
authors.lastname: Thiel
authors.forename: M
authors.initials: M
authors.lastname: Matsushita
authors.forename: T
authors.initials: T
authors.lastname: Fujita
authors.forename: A C
authors.initials: AC
authors.lastname: Willis
authors.forename: T
authors.initials: T
authors.lastname: Christensen
authors.forename: T
authors.initials: T
authors.lastname: Vorup-Jensen
authors.forename: J C
authors.initials: JC
authors.lastname: Jensenius
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000378:metabolism*; D003001:Cloning, Molecular; D037222:Collectins; D003167:Complement Activation; D006801:Humans; D050606:Mannose-Binding Protein-Associated Serine Proteases; D008969:Molecular Sequence Data; D012697:Serine Endopeptidases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
chemical_list: D002352:Carrier Proteins; D037222:Collectins; D050606:Mannose-Binding Protein-Associated Serine Proteases; D012697:Serine Endopeptidases