The endothelial protein C receptor enhances hemostasis of FVIIa administration in hemophilic mice in vivo.

Abstract

Recombinant activated human factor VII (rhFVIIa) is an established hemostatic agent in hemophilia, but its mechanism of action remains unclear. Although tissue factor (TF) is its natural receptor, rhFVIIa also interacts with the endothelial protein C receptor (EPCR) through its γ-carboxyglutamic acid (Gla) domain, with unknown hemostatic consequences in vivo. Here, we study whether EPCR facilitates rhFVIIa hemostasis in hemophilia using a mouse model system. Mouse activated FVII (mFVIIa) is functionally homologous to rhFVIIa, but binds poorly to mouse EPCR (mEPCR). We modified mFVIIa to gain mEPCR binding using 3 amino acid changes in its Gla domain (L4F/L8M/W9R). The resulting molecule mFVIIa-FMR specifically bound mEPCR in vitro and in vivo and was identical to mFVIIa with respect to TF affinity and procoagulant functions. In macrovascular injury models, hemophilic mice administered mFVIIa-FMR exhibited superior hemostatic activity compared with mFVIIa. This was abolished by blocking mEPCR and was absent in ex vivo whole blood coagulation assays, implicating a specific mFVIIa-FMR and endothelial mEPCR interaction. Because mFVIIa-FMR models the TF-dependent and EPCR binding properties of rhFVIIa, our data unmask a novel contribution of EPCR on the action of rhFVIIa administration in hemophilia, prompting the rational design of improved and safer rhFVIIa therapeutics.

• Authors: Giulia Pavani, Lacramioara Ivanciu, Armida Faella, Oscar A Marcos-Contreras, Paris Margaritis
• Journal: Blood (Blood) Vol. 124 Issue 7 Pg. 1157-65 (Aug 14 2014) ISSN: 1528-0020 [Electronic] United States
• PMID: 24957146 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2014 by The American Society of Hematology.

Chemical References

• Amino Acids
• Blood Coagulation Factors
• Receptors, Cell Surface
• Recombinant Proteins
• activated protein C receptor
• 1-Carboxyglutamic Acid
• Thromboplastin
• recombinant FVIIa
• Factor VIIa

Topics

• 1-Carboxyglutamic Acid (metabolism)
• Amino Acids (genetics, metabolism)
• Animals
• Binding Sites (genetics)
• Binding, Competitive
• Blood Coagulation (drug effects)
• Blood Coagulation Factors (genetics, metabolism)
• CHO Cells
• Cricetinae
• Cricetulus
• Factor VIIa (administration & dosage, genetics, pharmacology)
• Hemophilia A (blood, drug therapy)
• Hemostasis (drug effects)
• Humans
• Kinetics
• Male
• Mice, Inbred C57BL
• Protein Binding
• Receptors, Cell Surface (genetics, metabolism)
• Recombinant Proteins (administration & dosage, genetics, pharmacology)
• Thrombelastography
• Thromboplastin (metabolism)