title: Cathepsin G, a leukocyte protease, activates coagulation factor VIII.
abstract: Neutrophils and monocytes express cathepsin G and can also bind to activated platelets, thus they can be localized to the site of active coagulation. Previous studies have suggested that cathepsin G inactivated coagulation factor VIII (FVIII) and was thus anticoagulant. But other studies have indicated procoagulant functions for cathepsin G in activation of coagulation factor V or activation of platelets among other possible mechanisms. Therefore, it remains unclear if cathepsin G is anticoagulant or procoagulant. We investigated the effects of human neutrophil cathepsin G on FVIII/VIIIa. Cathepsin G activates FVIII to a partially active form while having only a minor inactivating effect on thrombin-activated FVIIIa. This inactivation is mostly due to decreased stability of FVIIIa since a disulfide bond that prevents A2 subunit dissociation from FVIIIa prevents any loss of activity due to cathepsin G proteolysis. FVIII that has been cleaved by cathepsin G can still be activated by thrombin if A2 subunit dissociation is prevented. Cathepsin G cleavages of FVIII are limited to a few specific sites that are mostly located near known activating and inactivating cleavage sites. Cathepsin G cleavage sites near to thrombin cleavage sites likely contribute to the partial activation of FVIII. Therefore, it is possible that cathepsin G from neutrophils and monocytes may provide some pro-coagulant effect by activating FVIII.
authors.affiliation: Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, California 92037, USA. agale@scripps.edu
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Gale
authors.forename: Diana
authors.initials: D
authors.lastname: Rozenshteyn
mesh_terms: D001777:Blood Coagulation; D056649:Cathepsin G; D002403:Cathepsins / Q000378:metabolism*; D004220:Disulfides / Q000378:metabolism; D005169:Factor VIII / Q000235:genetics / Q000378:metabolism*; D015944:Factor VIIIa / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D009154:Mutation; D009504:Neutrophils / Q000201:enzymology*; D010314:Partial Thromboplastin Time; D011994:Recombinant Proteins / Q000378:metabolism; D012697:Serine Endopeptidases / Q000378:metabolism*; D013917:Thrombin / Q000378:metabolism
chemical_list: D004220:Disulfides; D011994:Recombinant Proteins; D015944:Factor VIIIa; C078147:F8 protein, human; D005169:Factor VIII; D002403:Cathepsins; D012697:Serine Endopeptidases; C534094:CTSG protein, human; D056649:Cathepsin G; D013917:Thrombin