title: TFPI inhibits lectin pathway of complement activation by direct interaction with MASP-2.
abstract: The lectin pathway (LP) of complement has a protective function against invading pathogens. Recent studies have also shown that the LP plays an important role in ischemia/reperfusion (I/R)-injury. MBL-associated serine protease (MASP)-2 appears to be crucial in this process. The serpin C1-inhibitor is the major inhibitor of MASP-2. In addition, aprotinin, a Kunitz-type inhibitor, was shown to inhibit MASP-2 activity in vitro. In this study we investigated whether the Kunitz-type inhibitor tissue factor pathway inhibitor (TFPI) is also able to inhibit MASP-2. Ex vivo LP was induced and detected by C4-deposition on mannan-coated plates. The MASP-2 activity was measured in a fluid-phase chromogenic assay. rTFPI in the absence or presence of specific monoclonal antibodies was used to investigate which TFPI-domains contribute to MASP-2 inhibition. Here, we identify TFPI as a novel selective inhibitor of MASP-2, without affecting MASP-1 or the classical pathway proteases C1s and C1r. Kunitz-2 domain of TFPI is required for the inhibition of MASP-2. Considering the role of MASP-2 in complement-mediated I/R-injury, the inhibition of this protease by TFPI could be an interesting therapeutic approach to limit the tissue damage in conditions such as cerebral stroke, myocardial infarction or solid organ transplantation.
authors.affiliation: Department of Immunopathology, Sanquin Research and Landsteiner Laboratory AMC, University of Amsterdam, Amsterdam, the Netherlands; Emma Children's Hospital, Academic Medical Center (AMC), University of Amsterdam, Amsterdam, the Netherlands; Department of Blood Cell Research, Sanquin Research and Landsteiner Laboratory AMC, University of Amsterdam, Amsterdam, the Netherlands.
authors.forename: Mischa P
authors.initials: MP
authors.lastname: Keizer
authors.forename: Richard B
authors.initials: RB
authors.lastname: Pouw
authors.forename: Angela M
authors.initials: AM
authors.lastname: Kamp
authors.forename: Sanne
authors.initials: S
authors.lastname: Patiwael
authors.forename: Gerben
authors.initials: G
authors.lastname: Marsman
authors.forename: Margreet H
authors.initials: MH
authors.lastname: Hart
authors.forename: Sacha
authors.initials: S
authors.lastname: Zeerleder
authors.forename: Taco W
authors.initials: TW
authors.lastname: Kuijpers
authors.forename: Diana
authors.initials: D
authors.lastname: Wouters
mesh_terms: D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000276:immunology; D002863:Chromogenic Compounds; D015923:Complement C1r / Q000737:chemistry / Q000276:immunology; D003173:Complement C1s / Q000737:chemistry / Q000276:immunology; D003181:Complement C4 / Q000737:chemistry / Q000276:immunology*; D037582:Complement Pathway, Mannose-Binding Lectin; D006801:Humans; D007118:Immunoassay; D008074:Lipoproteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D050606:Mannose-Binding Protein-Associated Serine Proteases / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000276:immunology; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D015842:Serine Proteinase Inhibitors / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D012996:Solutions
chemical_list: D000911:Antibodies, Monoclonal; D002863:Chromogenic Compounds; D003181:Complement C4; D008074:Lipoproteins; D011994:Recombinant Proteins; D015842:Serine Proteinase Inhibitors; D012996:Solutions; C051928:lipoprotein-associated coagulation inhibitor; C084067:MASP1 protein, human; C105296:MASP2 protein, human; D050606:Mannose-Binding Protein-Associated Serine Proteases; D015923:Complement C1r; D003173:Complement C1s
keywords: Complement inhibition; Complement-coagulation crosstalk; MASP-2; TFPI