title: Factor VIIa binding to endothelial cell protein C receptor: differences between mouse and human systems.
abstract: Recent  in vitro  studies have shown that the zymogen and activated form of factor (F)VII bind to endothelial cell protein C receptor (EPCR). At present, there is no evidence that FVIIa binds to EPCR on vascular endothelium  in vivo  in the presence of circulating protein C, a primary ligand for EPCR. The present study was carried out to investigate the interaction of murine and human ligands with murine EPCR both  in vivo  and  in vitro . Measurement of endogenous plasma levels of FVII in wild-type, EPCR-deficient and EPCR-over expressing mice showed slightly lower levels of FVII in EPCR-over expressing mice. However, infusion of high concentrations of competing ligands, either human APCi or FVIIai, to EPCR-over expressing mice failed to increase plasma levels of mouse FVII whereas they increased the plasma levels of protein C by two- to three-fold. Examining the association of exogenously administered mouse FVIIa or human FVIIa by immunohistochemistry revealed that human, but not murine FVIIa, binds to the murine endothelium in an EPCR-dependent manner.  In vitro  binding studies performed using surface plasmon resonance and endothelial cells revealed that murine FVIIa binds murine EPCR negligibly. Human FVIIa binding to EPCR, particularly to mouse EPCR, is markedly enhanced by availability of Mg2+ ions. In summary, our data show that murine FVIIa binds poorly to murine EPCR, whereas human FVIIa binds efficiently to both murine and human EPCR. Our data suggest that one should consider the use of human FVIIa in mouse models to investigate the significance of FVIIa and EPCR interaction.
authors.affiliation: Center for Biomedical Research, The University of Texas Health Science Center at Tyler, Tyler, Texas 75708, USA.
authors.forename: Prosenjit
authors.initials: P
authors.lastname: Sen
authors.forename: Curtis A
authors.initials: CA
authors.lastname: Clark
authors.forename: Ramakrishnan
authors.initials: R
authors.lastname: Gopalakrishnan
authors.forename: Ulla
authors.initials: U
authors.lastname: Hedner
authors.forename: Charles T
authors.initials: CT
authors.lastname: Esmon
authors.forename: Usha R
authors.initials: UR
authors.lastname: Pendurthi
authors.forename: L Vijaya Mohan
authors.initials: LV
authors.lastname: Rao
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD / Q000378:metabolism*; D019774:Blood Coagulation Factor Inhibitors / Q000378:metabolism; D002478:Cells, Cultured; D000074283:Endothelial Protein C Receptor; D004730:Endothelium, Vascular / Q000378:metabolism*; D015942:Factor VIIa / Q000008:administration & dosage / Q000378:metabolism*; D006023:Glycoproteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D061307:Human Umbilical Vein Endothelial Cells / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D008024:Ligands; D008274:Magnesium / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D011485:Protein Binding; D011486:Protein C / Q000378:metabolism; D018046:Protein C Inhibitor / Q000378:metabolism; D011869:Radioligand Assay; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000378:metabolism; D013045:Species Specificity; D020349:Surface Plasmon Resonance
chemical_list: D015703:Antigens, CD; D019774:Blood Coagulation Factor Inhibitors; D000074283:Endothelial Protein C Receptor; D006023:Glycoproteins; D008024:Ligands; C478370:PROCR protein, human; C080248:Procr protein, mouse; D011486:Protein C; D018046:Protein C Inhibitor; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins; C103587:recombinant FVIIa; D015942:Factor VIIa; D008274:Magnesium