title: The endothelial protein C receptor supports tissue factor ternary coagulation initiation complex signaling through protease-activated receptors.
abstract: Protease-activated receptor (PAR) signaling is closely linked to the cellular activation of the pro- and anticoagulant pathways. The endothelial protein C receptor (EPCR) is crucial for signaling by activated protein C through PAR1, but EPCR may have additional roles by interacting with the 4-carboxyglutamic acid domains of procoagulant coagulation factors VII (FVII) and X (FX). Here we show that soluble EPCR regulates the interaction of FX with human or mouse tissue factor (TF)-FVIIa complexes. Mutagenesis of the FVIIa 4-carboxyglutamic acid domain and dose titrations with FX showed that EPCR interacted primarily with FX to attenuate FX activation in lipid-free assay systems. In human cell models of TF signaling, antibody inhibition of EPCR selectively blocked PAR activation by the ternary TF-FVIIa-FXa complex but not by the non-coagulant TF-FVIIa binary complex. Heterologous expression of EPCR promoted PAR1 and PAR2 cleavage by FXa in the ternary complex but did not alter PAR2 cleavage by TF-FVIIa. In murine smooth muscle cells that constitutively express EPCR and TF, thrombin and FVIIa/FX but not FVIIa alone induced PAR1-dependent signaling. Although thrombin signaling was unchanged, cells with genetically reduced levels of EPCR no longer showed a signaling response to the ternary complex. These results demonstrate that EPCR interacts with the ternary TF coagulation initiation complex to enable PAR signaling and suggest that EPCR may play a role in regulating the biology of TF-expressing extravascular and vessel wall cells that are exposed to limited concentrations of FVIIa and FX provided by ectopic synthesis or vascular leakage.
authors.affiliation: Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California 92037, USA.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Disse
authors.forename: Helle Heibroch
authors.initials: HH
authors.lastname: Petersen
authors.forename: Katrine S
authors.initials: KS
authors.lastname: Larsen
authors.forename: Egon
authors.initials: E
authors.lastname: Persson
authors.forename: Naomi
authors.initials: N
authors.lastname: Esmon
authors.forename: Charles T
authors.initials: CT
authors.lastname: Esmon
authors.forename: Luc
authors.initials: L
authors.lastname: Teyton
authors.forename: Lars C
authors.initials: LC
authors.lastname: Petersen
authors.forename: Wolfram
authors.initials: W
authors.lastname: Ruf
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D000074283:Endothelial Protein C Receptor; D015942:Factor VIIa / Q000235:genetics / Q000378:metabolism; D005170:Factor X / Q000235:genetics / Q000378:metabolism; D006023:Glycoproteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000378:metabolism*; D011486:Protein C / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D044463:Receptor, PAR-1 / Q000235:genetics / Q000378:metabolism*; D044464:Receptor, PAR-2 / Q000235:genetics / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D013917:Thrombin / Q000235:genetics / Q000378:metabolism; D013925:Thromboplastin / Q000235:genetics / Q000378:metabolism*
chemical_list: D015703:Antigens, CD; D000074283:Endothelial Protein C Receptor; D006023:Glycoproteins; D009097:Multienzyme Complexes; C478370:PROCR protein, human; C080248:Procr protein, mouse; D011486:Protein C; D044463:Receptor, PAR-1; D044464:Receptor, PAR-2; D011956:Receptors, Cell Surface; D005170:Factor X; D013925:Thromboplastin; D015942:Factor VIIa; D013917:Thrombin