title: Novel mechanisms for activated protein C cytoprotective activities involving noncanonical activation of protease-activated receptor 3.
abstract: The direct cytoprotective activities of activated protein C (APC) on cells convey therapeutic, relevant, beneficial effects in injury and disease models in vivo and require the endothelial protein C receptor (EPCR) and protease activated receptor 1 (PAR1). Thrombin also activates PAR1, but its effects on cells contrast APC's cytoprotective effects. To gain insights into mechanisms for these contrasting cellular effects, protease activated receptor 3 (PAR3) activation by APC and thrombin was studied. APC cleaved PAR3 on transfected and endothelial cells in the presence of EPCR. Remarkably, APC cleaved a synthetic PAR3 N-terminal peptide at Arg41, whereas thrombin cleaved at Lys38. On cells, APC failed to cleave R41Q-PAR3, whereas K38Q-PAR3 was still cleaved by APC but not by thrombin. PAR3 tethered-ligand peptides beginning at amino acid 42, but not those beginning at amino acid 39, conveyed endothelial barrier-protective effects. In vivo, the APC-derived PAR3 tethered-ligand peptide, but not the thrombin-derived PAR3 peptide, blunted vascular endothelial growth factor (VEGF)-induced vascular permeability. These data indicate that PAR3 cleavage by APC at Arg41 can initiate distinctive APC-like cytoprotective effects. These novel insights help explain the differentiation of APC's cytoprotective versus thrombin's proinflammatory effects on cells and suggest a unique contributory role for PAR3 in the complex mechanisms underlying APC cytoprotective effects.
authors.affiliation: Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA.
authors.forename: Laurent
authors.initials: L
authors.lastname: Burnier
authors.forename: Laurent O
authors.initials: LO
authors.lastname: Mosnier
mesh_terms: D019943:Amino Acid Substitution / Q000502:physiology; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D002199:Capillary Permeability / Q000502:physiology; D020134:Catalytic Domain / Q000235:genetics; D000074283:Endothelial Protein C Receptor; D004730:Endothelium, Vascular / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D011486:Protein C / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D011499:Protein Processing, Post-Translational / Q000235:genetics; D059748:Proteolysis; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D018179:Receptors, Thrombin / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D013917:Thrombin / Q000378:metabolism / Q000502:physiology; D014162:Transfection
chemical_list: D015703:Antigens, CD; D000074283:Endothelial Protein C Receptor; D050505:Mutant Proteins; C478370:PROCR protein, human; D011486:Protein C; D011956:Receptors, Cell Surface; D018179:Receptors, Thrombin; C105295:protease-activated receptor 3; D013917:Thrombin