Thromb Haemost 1992; 67(02): 226-232
DOI: 10.1055/s-0038-1648417
Original Articles
Schattauer GmbH Stuttgart

Thrombomodulin Is a Cofactor for Thrombin Degradation of Recombinant Single-Chain Urokinase Plasminogen Activator "In Vitro" and in a Perfused Rabbit Heart Model

Antonio Molinari
The Haemostasis Unit, Cardiovascular Line, IRCCS Maggiore Hospital and University of Milano, Italy
,
Carla Giorgetti
The Haemostasis Unit, Cardiovascular Line, IRCCS Maggiore Hospital and University of Milano, Italy
,
Jacqueline Lansen
The Haemostasis Unit, Cardiovascular Line, IRCCS Maggiore Hospital and University of Milano, Italy
,
Fabrizio Vaghi
The Haemostasis Unit, Cardiovascular Line, IRCCS Maggiore Hospital and University of Milano, Italy
,
Gaetano Orsini
*   Biotechnology Department, R & D, Farmitalia Carlo Erba, Erbamont Group, IRCCS Maggiore Hospital and University of Milano, Italy
,
Elena Maria Faioni
**   Angelo Bianchi Bonomi, Haemophilia and Thrombosis Center and Institute of Internal Medicine, IRCCS Maggiore Hospital and University of Milano, Italy
,
Pier Mannuccio Mannucci
**   Angelo Bianchi Bonomi, Haemophilia and Thrombosis Center and Institute of Internal Medicine, IRCCS Maggiore Hospital and University of Milano, Italy
› Author Affiliations
Further Information

Publication History

Received 13 March 1991

Accepted after revision 21 August 1991

Publication Date:
02 July 2018 (online)

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Summary

Thrombin cleaves single-chain urokinase-type plasminogen activator (scu-PA) to a two-chain derivative (tcu-PA) fibrinolyti-cally inactive. This reaction was accelerated in vitro by purified rabbit lung thrombomodulin in equimolar complex with thrombin. Polyclonal antibodies to rabbit thrombomodulin prevented this effect.

We also observed that heparin and other sulfated polysaccharides had an accelerating effect on thrombin cleavage of recombinant scu-PA. Their effect was concentration-dependent and then reversed at high levels. The effect of heparin and heparan sulfate was independent and synergic with respect to thrombomodulin. All observations except the effect of heparin, could be confirmed in a Langendorff isolated rabbit heart model. From competition experiments carried out with scu-PA derivatives and mutants, we postulate that the amino-terminal sequence of rscu-PA, containing the epidermal growth factor (EGF)-like and the kringle domains is involved in the cofactor effect of thrombomodulin on scu-PA inactivation by thrombin. We conclude that a regulatory mechanism of scu-PA inactivation is present at the cell surface.