The ligand occupancy of endothelial protein C receptor switches the protease-activated receptor 1-dependent signaling specificity of thrombin from a permeability-enhancing to a barrier-protective response in endothelial cells

• Published in: Blood Vol. 110; no. 12; pp. 3909 - 3916
• Main Authors: Bae, Jong-Sup, Yang, Likui, Manithody, Chandrashekhara, Rezaie, Alireza R.
• Format: Journal Article
• Language: English
• Published: Washington, DC Elsevier Inc 01-12-2007; The Americain Society of Hematology; American Society of Hematology
• Series: Hemostasis, Thrombosis, and Vascular Biology
• Subjects: Antigens, CD - metabolism; Biological and medical sciences; Blood coagulation. Blood cells; Caveolin 1 - metabolism; Cell Line; Cell Membrane Permeability - drug effects; Endothelial Cells - metabolism; Endothelial Cells - pathology; Endothelial Protein C Receptor; Fundamental and applied biological sciences. Psychology; General aspects, investigation methods, hemostasis, fibrinolysis; GTP-Binding Protein alpha Subunits, Gi-Go - metabolism; Hematologic and hematopoietic diseases; Hemostasis, Thrombosis, and Vascular Biology; Hemostatics - metabolism; Hemostatics - pharmacology; Humans; Inflammation - metabolism; Inflammation - pathology; Ligands; Medical sciences; Membrane Microdomains - metabolism; Membrane Microdomains - pathology; Molecular and cellular biology; Protein C - metabolism; Protein C - pharmacology; Receptor, PAR-1 - metabolism; Receptors, Cell Surface - metabolism; Recombinant Proteins - metabolism; Recombinant Proteins - pharmacology; Signal Transduction - drug effects; Thrombin - metabolism; Thrombin - pharmacology; Human; Endothelial cell; Lipid raft; Serine endopeptidases; Hematology; Enzyme; Ligand; Protein C; Thrombin; Peptidases; Signal transduction; Protease activated receptor 1; Caveolin 1; Carboxylic acid; Hydrolases; Biological receptor
• DOI: 10.1182/blood-2007-06-096651
• EISSN: 1528-0020
• ISSN: 0006-4971

Recent studies have indicated that activated protein C (APC) may exert its cytoprotective and anti-inflammatory activities through the endothelial protein C receptor (EPCR)-dependent cleavage of protease-activated receptor 1 (PAR-1) on vascular endothelial cells. Noting that (1) the activation of protein C on endothelial cells requires thrombin, (2) relative to APC, thrombin cleaves PAR-1 with approximately 3 to 4 orders of magnitude higher catalytic efficiency, and (3) PAR-1 is a target for the proinflammatory activity of thrombin, it is not understood how APC can elicit a protective signaling response through the cleavage of PAR-1 when thrombin is present. In this study, we demonstrate that EPCR is associated with caveolin-1 in lipid rafts of endothelial cells and that its occupancy by the γ-carboxyglutamic acid (Gla) domain of protein C/APC leads to its dissociation from caveolin-1 and recruitment of PAR-1 to a protective signaling pathway through coupling of PAR-1 to the pertussis toxin–sensitive Gi-protein. Thus, when EPCR is bound by protein C, the PAR-1 cleavage-dependent protective signaling responses in endothelial cells can be mediated by either thrombin or APC. These results provide a new paradigm for understanding how PAR-1 and EPCR participate in protective signaling events in endothelial cells.