title: 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: Department of Pediatrics, Division of Hematology, The Children's Hospital of Philadelphia, Philadelphia, PA; and.
authors: Giulia
authors: G
authors: Pavani
authors: Department of Pediatrics, Division of Hematology, The Children's Hospital of Philadelphia, Philadelphia, PA; and.
authors: Lacramioara
authors: L
authors: Ivanciu
authors: Department of Pediatrics, Division of Hematology, The Children's Hospital of Philadelphia, Philadelphia, PA; and.
authors: Armida
authors: A
authors: Faella
authors: Department of Pediatrics, Division of Hematology, The Children's Hospital of Philadelphia, Philadelphia, PA; and.
authors: Oscar A
authors: OA
authors: Marcos-Contreras
authors: Department of Pediatrics, Division of Hematology, The Children's Hospital of Philadelphia, Philadelphia, PA; and The University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA.
authors: Paris
authors: P
authors: Margaritis
mesh_terms: D015055:1-Carboxyglutamic Acid / Q000378:metabolism; D000596:Amino Acids / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D001667:Binding, Competitive; D001777:Blood Coagulation / Q000187:drug effects; D001779:Blood Coagulation Factors / Q000235:genetics / Q000378:metabolism*; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D015942:Factor VIIa / Q000008:administration & dosage / Q000235:genetics / Q000494:pharmacology*; D006467:Hemophilia A / Q000097:blood / Q000188:drug therapy*; D006487:Hemostasis / Q000187:drug effects*; D006801:Humans; D007700:Kinetics; D008297:Male; D008810:Mice, Inbred C57BL; D011485:Protein Binding; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000235:genetics / Q000494:pharmacology; D013916:Thrombelastography; D013925:Thromboplastin / Q000378:metabolism
chemical_list: D000596:Amino Acids; D001779:Blood Coagulation Factors; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins; C091963:activated protein C receptor; D015055:1-Carboxyglutamic Acid; D013925:Thromboplastin; C103587:recombinant FVIIa; D015942:Factor VIIa