title: Selective inhibition of the lectin pathway of complement with phage display selected peptides against mannose-binding lectin-associated serine protease (MASP)-1 and -2: significant contribution of MASP-1 to lectin pathway activation.
abstract: The complement system, an essential part of the innate immune system, can be activated through three distinct routes: the classical, the alternative, and the lectin pathways. The contribution of individual activation pathways to different biological processes can be assessed by using pathway-selective inhibitors. In this paper, we report lectin pathway-specific short peptide inhibitors developed by phage display against mannose-binding lectin-associated serine proteases (MASPs), MASP-1 and MASP-2. On the basis of the selected peptide sequences, two 14-mer peptides, designated as sunflower MASP inhibitor (SFMI)-1 and SFMI-2, were produced and characterized. SFMI-1 inhibits both MASP-1 and MASP-2 with a K(I) of 65 and 1030 nM, respectively, whereas SFMI-2 inhibits only MASP-2 with a K(I) of 180 nM. Both peptides block the lectin pathway activation completely while leaving the classical and the alternative routes intact and fully functional, demonstrating that of all complement proteases only MASP-1 and/or MASP-2 are inhibited by these peptides. In a C4 deposition inhibitor assay using preactivated MASP-2, SFMI-2 is 10-fold more effective than SFMI-1 in accordance with the fact that SFMI-2 is a more potent inhibitor of MASP-2. Surprisingly, however, out of the two peptides, SFMI-1 is much more effective in preventing C3 and C4 deposition when normal human serum containing zymogen MASPs is used. This suggests that MASP-1 has a crucial role in the initiation steps of lectin pathway activation most probably by activating MASP-2. Because the lectin pathway has been implicated in several life-threatening pathological states, these inhibitors should be considered as lead compounds toward developing lectin pathway blocking therapeutics.
authors.affiliation: Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, Budapest, Hungary.
authors.forename: Andrea
authors.initials: A
authors.lastname: Kocsis
authors.forename: Katalin A
authors.initials: KA
authors.lastname: Kékesi
authors.forename: Róbert
authors.initials: R
authors.lastname: Szász
authors.forename: Barbara M
authors.initials: BM
authors.lastname: Végh
authors.forename: Júlia
authors.initials: J
authors.lastname: Balczer
authors.forename: József
authors.initials: J
authors.lastname: Dobó
authors.forename: Péter
authors.initials: P
authors.lastname: Závodszky
authors.forename: Péter
authors.initials: P
authors.lastname: Gál
authors.forename: Gábor
authors.initials: G
authors.lastname: Pál
mesh_terms: D000595:Amino Acid Sequence; D002851:Chromatography, High Pressure Liquid; D037582:Complement Pathway, Mannose-Binding Lectin / Q000502:physiology*; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology*; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D050606:Mannose-Binding Protein-Associated Serine Proteases / Q000378:metabolism*; D008969:Molecular Sequence Data; D019151:Peptide Library; D016133:Polymerase Chain Reaction; D011480:Protease Inhibitors / Q000494:pharmacology*
chemical_list: D019151:Peptide Library; D011480:Protease Inhibitors; C084067:MASP1 protein, human; C105296:MASP2 protein, human; D050606:Mannose-Binding Protein-Associated Serine Proteases