Synergistic cofactor function of factor V and protein S to activated protein C in the inactivation of the factor VIIIa - factor IXa complex -- species specific interactions of components of the protein C anticoagulant system.
Human factor V has been shown not only to be a precursor to procoagulant factor Va but also to express anticoagulant properties. Thus, factor V was recently found to potentiate the effect of protein S as cofactor to activated protein C (APC) in the inactivation of the factor VIIIa-factor IXa complex. The purpose of this study was to determine whether the APC-cofactor function of factor V was also expressed in the bovine protein C system and to elucidate the molecular background for the species specificity of APC. For this purpose, the effects of protein S and factor V on APC-mediated inactivation of factor VIIIa were studied using purified APC, protein S and factor V of human and bovine origin. The factor VIIIa investigated here was part of a Xase complex (i.e. factor IXa, factor VIIIa, phospholipid and calcium) and the APC-mediated inhibition of factor VIIIa was monitored by the ability of the Xase complex to activate factor X. Synergistic APC-cofactor function of factor V and protein S was demonstrated in the bovine system. The effect of bovine APC was potentiated by bovine protein S but not by human protein S, whereas both human or bovine protein S stimulated the function of human APC. Factor V did not express species specificity in its APC-cofactor activity even though bovine factor V was more potent than its human counterpart. Recombinant human/bovine protein S chimeras were used to demonstrate that the thrombin sensitive region and first epidermal growth factor-like module of protein S determine the species specificity of the APC-protein S interaction. In conclusion, both human and bovine factor V were found to express APC-cofactor activity which depends on the presence of protein S. The species specificity of APC was shown to be caused by the interaction between APC and protein S.
Shen
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Department of Clinical Chemistry, Lund University, University Hospital, Malmö, Sweden.
He
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Dahlbäck
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D000818:Animals; D001665:Binding Sites; D001777:Blood Coagulation / Q000502:physiology*; D001779:Blood Coagulation Factors / Q000037:antagonists & inhibitors*; D002417:Cattle; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D004357:Drug Synergism; D015949:Factor IXa / Q000037:antagonists & inhibitors*; D005165:Factor V / Q000494:pharmacology*; D015944:Factor VIIIa / Q000037:antagonists & inhibitors*; D006801:Humans; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors*; D011486:Protein C / Q000378:metabolism*; D017293:Protein S / Q000494:pharmacology*; D013045:Species Specificity
D001779:Blood Coagulation Factors; D009363:Neoplasm Proteins; D011486:Protein C; D017293:Protein S; D015944:Factor VIIIa; D005165:Factor V; D015949:Factor IXa; D003546:Cysteine Endopeptidases; C030910:cancer procoagulant