Thromb Haemost 2014; 111(01): 29-40
DOI: 10.1160/TH13-04-0340
Blood Coagulation, Fibrinolysis and Cellular Haemostasis
Schattauer GmbH

Three monoclonal antibodies against the serpin protease nexin-1 prevent protease translocation

Tina M. Kousted
1   Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
,
Karsten Skjoedt
2   Department of Cancer and Inflammation, University of Southern Denmark, Odense, Denmark
,
Steen V. Petersen
3   Department of Biomedicine, Aarhus University, Aarhus, Denmark
,
Claus Koch
2   Department of Cancer and Inflammation, University of Southern Denmark, Odense, Denmark
,
Lars Vitved
2   Department of Cancer and Inflammation, University of Southern Denmark, Odense, Denmark
,
Maja Sochalska
1   Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
,
Céline Lacroix
1   Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
,
Lisbeth M. Andersen
1   Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
,
Troels Wind
1   Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
,
Peter A. Andreasen
1   Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
,
Jan K. Jensen
1   Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
› Author Affiliations
Financial support: This study was supported by the Alfred Nielsen’s Foundation; The Cancer Research Foundation of 1989; the Danish Cancer Society; Danish National Research Foundation (26–331–6); The Faculty of Science and Technology, Aarhus University; The Research Council for Production and Technology (09–072885); The Lundbeck Foundation.
Further Information

Publication History

Received: 26 April 2013

Accepted after major revision: 24 August 2013

Publication Date:
21 November 2017 (online)

Summary

Protease nexin-1 (PN-1) belongs to the serpin family and is an inhibitor of thrombin, plasmin, urokinase-type plasminogen activator, and matriptase. Recent studies have suggested PN-1 to play important roles in vascular-, neuro-, and tumour-biology. The serpin inhibitory mechanism consists of the serpin presenting its so-called reactive centre loop as a substrate to its target protease, resulting in a covalent complex with the inactivated enzyme. Previously, three mechanisms have been proposed for the inactivation of serpins by monoclonal antibodies: steric blockage of protease recognition, conversion to an inactive conformation or induction of serpin substrate behaviour. Until now, no inhibitory antibodies against PN-1 have been thoroughly characterised. Here we report the development of three monoclonal antibodies binding specifically and with high affinity to human PN-1. The antibodies all abolish the protease inhibitory activity of PN-1. In the presence of the antibodies, PN-1 does not form a complex with its target proteases, but is recovered in a reactive centre cleaved form. Using site-directed mutagenesis, we mapped the three overlapping epitopes to an area spanning the gap between the loop connecting α-helix F with β-strand 3A and the loop connecting α-helix A with β-strand 1B. We conclude that antibody binding causes a direct blockage of the final critical step of protease translocation, resulting in abortive inhibition and premature release of reactive centre cleaved PN-1. These new antibodies will provide a powerful tool to study the in vivo role of PN-1’s protease inhibitory activity.

 
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