Binding of factor VIIa to the endothelial cell protein C receptor reduces its coagulant activity.
BACKGROUND
Endothelial cell protein C receptor (EPCR) binds protein C through its gamma-carboxyglutamic acid (Gla) domain and enhances its thrombin-thrombomodulin complex-dependent activation. So far, only protein C/activated protein C has been shown to interact with EPCR. Factor VII (FVII), the coagulation trigger upon tissue factor (TF) interaction, is a serine protease whose Gla domain is highly homologous to the Gla domain of protein C.


OBJECTIVE
To characterize the binding of FVII/FVIIa to EPCR and its functional consequences.


RESULTS
We demonstrated by surface plasmon resonance (SPR) that FVII/FVIIa binds to EPCR through its Gla domain. At therapeutic concentrations, FVIIa reduced the activation of protein C by 40%. Soluble EPCR (sEPCR) was also able to prolong dose-dependently the clotting time induced by the FVIIa-TF complex. SPR and amidolytic experiments showed that FVIIa is able to interact simultaneously with TF and EPCR, thus ruling out the possibility that the effect of EPCR on clotting time was due to the inhibition of the binding between FVIIa and TF. sEPCR inhibited dose-dependently the activation of FX by the FVIIa-TF complex. Notably, blocking the binding site of EPCR on the endothelial surface increased the generation of FXa 2-fold.


CONCLUSIONS
EPCR binds to FVII/FVIIa and inhibits the procoagulant activity of the FVIIa-TF complex.
López-Sagaseta
J
J
Haematology Department and the Division of Cardiovascular Sciences, Laboratory of Thrombosis and Haemostasis, Clínica Universitaria/School of Medicine, Centre for Applied Medical Research, University of Navarra, Pamplona, Spain.
Montes
R
R
Puy
C
C
Díez
N
N
Fukudome
K
K
Hermida
J
J
D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism*; D003029:Coagulants / Q000378:metabolism*; D000074283:Endothelial Protein C Receptor; D015942:Factor VIIa / Q000378:metabolism*; D006801:Humans; D010843:Pichia / Q000235:genetics; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism
D015703:Antigens, CD; D003029:Coagulants; D000074283:Endothelial Protein C Receptor; C478370:PROCR protein, human; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins; D015942:Factor VIIa