RESEARCH ARTICLE
Heparin Alters Viral Serpin, Serp-1, Anti-Thrombolytic Activity to Anti-Thrombotic Activity
Xing Li1, Heather Schneider1, Andrew Peters1, Colin Macaulay1, Elaine King1, Yunming Sun1, 2, Liying Liu2, 3, Erbin Dai2, 3, Jennifer A Davids3, Grant McFadden2, 3, Alexandra Lucas*, 2, 3
Article Information
Identifiers and Pagination:
Year: 2008Volume: 2
First Page: 6
Last Page: 15
Publisher ID: TOBIOCJ-2-6
DOI: 10.2174/1874091X00802010006
Article History:
Received Date: 28/11/2007Revision Received Date: 8/1/2008
Acceptance Date: 17/1/2008
Electronic publication date: 6/2/2008
Collection year: 2008

Abstract
Serine protease inhibitors (serpins) regulate coagulation and inflammation. Heparin, a glycosaminoglycan, is an important cofactor for modulation of the inhibitory function of mammalian serpins. The secreted myxoma viral serpin, Serp-1 exerts profound anti-inflammatory activity in a wide range of animal models. Serp-1 anti-inflammatory and anti-atherogenic activity is dependent upon inhibition of the uPA / uPA receptor thrombolytic complex. We demonstrate here that heparin binds to Serp-1 and enhances Serp-1 inhibition of thrombin, a human pro-thrombotic serine protease, in vitro, altering inhibitory activity to a more predominant anti-thrombotic activity. Heparin also facilitates the simultaneous thrombin-mediated cleavage of Serp-1 and prevents formation of a serpin-typical SDS-resistant complex, implying mutual neutralization of Serp-1 and thrombin. In a cell-based assay, heparin facilitates Serp-1 reversal of cellular activation by stabilizing cellular membrane fluidity in thrombin-activated monocytes. In conclusion, heparin and other GAGs serve as cofactors enhancing Serp-1 regulation of local thrombotic and inflammatory pathways