MASP-1 of the complement system promotes clotting via prothrombin activation.
Mannan-binding lectin-associated serine protease-1 (MASP-1), a protein of the complement lectin pathway, resembles thrombin in terms of structural features and substrate specificity, and it has been shown to activate coagulation factors. Here we studied the effects of MASP-1 on clot formation in whole blood (WB) and platelet-poor plasma (PPP) by thrombelastography and further elucidated the underlying mechanism. Cleavage of prothrombin by MASP-1 was investigated by SDS-PAGE and N-terminal sequencing of cleavage products. Addition of MASP-1 or thrombin to WB and PPP shortened the clotting time and clot formation time significantly compared to recalcified-only samples. The combination of MASP-1 and thrombin had additive effects. In a purified system, MASP-1 was able to induce clotting only in presence of prothrombin. Analysis of MASP-1-digested prothrombin confirmed that MASP-1 cleaves prothrombin at three cleavage sites. In conclusion, we have shown that MASP-1 is able to induce and promote clot formation measured in a global setting using the technique of thrombelastography. We further confirmed that MASP-1-induced clotting is dependent on prothrombin. Finally, we have demonstrated that MASP-1 cleaves prothrombin and identified its cleavage sites, suggesting that MASP-1 gives rise to an alternative active form of thrombin by cleaving at the cleavage site R393.
University Clinic of Haematology, Haemostasis Research Laboratory, University Hospital Bern, 3010 Bern, Switzerland; Department of Clinical Research, University of Bern, Bern, Switzerland.
Lorenz
L
Jenny
Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar tudósok krt 2, H-1113 Budapest, Hungary.
József
J
Dobó
Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar tudósok krt 2, H-1113 Budapest, Hungary.
Péter
P
Gál
University Clinic of Haematology, Haemostasis Research Laboratory, University Hospital Bern, 3010 Bern, Switzerland; Department of Clinical Research, University of Bern, Bern, Switzerland. Electronic address: verena.schroeder@insel.ch.
Verena
V
Schroeder
D001777:Blood Coagulation; D004789:Enzyme Activation / Q000276:immunology; D005260:Female; D006801:Humans; D008297:Male; D050606:Mannose-Binding Protein-Associated Serine Proteases / Q000737:chemistry* / Q000276:immunology; D059748:Proteolysis; D011516:Prothrombin / Q000737:chemistry* / Q000276:immunology; D013916:Thrombelastography
D011516:Prothrombin; C084067:MASP1 protein, human; D050606:Mannose-Binding Protein-Associated Serine Proteases
Coagulation; Complement system; MASP-1; Mannan-binding lectin-associated serine protease; Prothrombin; Thrombelastography