Document Detail

Human coagulation factor V is activated to the functional cofactor by elastase and cathepsin G expressed at the monocyte surface.
MedLine Citation:
PMID:  7836408     Owner:  NLM     Status:  MEDLINE    
The ability of intact peripheral blood monocytes to modulate factor V procoagulant activity was studied using electrophoretic and autoradiographic techniques coupled to functional assessment of cofactor activity. Incubation of plasma concentrations of factor V with monocytes (5 x 10(6)/ml) resulted in the time-dependent cleavage of the 330-kDa protein. Activation occurred via several high molecular mass intermediates (> or = 200 kDa) to yield peptides of 150, 140, 120, 94, 91, 82, and 80 kDa, which paralleled the expression of cofactor activity. The cleavage pattern observed differed from that obtained with either thrombin or factor Xa as an activator. The incubation time required to achieve full cofactor activity was dependent on the monocyte donor and ranged from 10 min to 1 h and was consistently slightly lower than that obtained with thrombin-activated factor Va. Cofactor activity was not diminished by additional incubation. The cofactor activity generated bound to the monocyte such that a competent prothrombinase complex was formed at the monocyte membrane surface. Furthermore, within 5 min of factor V addition to monocytes, near maximal cofactor activity (approximately 70%) was bound and expressed on the monocyte membrane. The proteolytic activity toward factor V was associated primarily with the monocyte membrane, as little proteolytic activity was released into the cell-free supernatant. Proteolytic activity was inhibited by diisopropyl fluorophosphate and phenylmethanesulfonyl fluoride. However, the inhibitor profile obtained with alpha 1-antiproteinase inhibitor, alpha 1-antichymotrypsin, and alpha 2-macroglobulin suggested membrane-bound forms of elastase and cathepsin G were mediating, in large part, the proteolysis observed. These data were confirmed using purified preparations of both proteases and a specific anti-human leukocyte elastase antibody. Thus, expression of these proteases at the monocyte surface may contribute to thrombin generation at extravascular tissue sites by catalyzing the activation of the essential cofactor, factor Va, which binds to the monocyte surface and supports the factor Xa-catalyzed activation of prothrombin.
D H Allen; P B Tracy
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  270     ISSN:  0021-9258     ISO Abbreviation:  J. Biol. Chem.     Publication Date:  1995 Jan 
Date Detail:
Created Date:  1995-02-24     Completed Date:  1995-02-24     Revised Date:  2009-11-19    
Medline Journal Info:
Nlm Unique ID:  2985121R     Medline TA:  J Biol Chem     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1408-15     Citation Subset:  IM    
Department of Biochemistry, University of Vermont College of Medicine, Burlington 05405.
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MeSH Terms
Cathepsin G
Cathepsins / metabolism*
Cell Membrane / enzymology
Factor V / metabolism*
Leukocyte Elastase
Monocytes / enzymology*
Pancreatic Elastase / metabolism*
Serine Endopeptidases
Grant Support
Reg. No./Substance:
9001-24-5/Factor V; EC 3.4.-/Cathepsins; EC 3.4.21.-/Serine Endopeptidases; EC protein, human; EC G; EC Elastase; EC Elastase

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