Activated protein C signals through the thrombin receptor PAR1 in endothelial cells.
The anti-inflammatory effects of activated protein C (APC) have lead to its recent approval for the treatment of sepsis. Although the endothelial cell protein C receptor (EPCR) plays a crucial role in APC's protective roles in septicemia, the precise signaling mechanism of the protease APC remains unclear. In fibroblast overexpression systems, we find that APC activates protease activated receptors (PAR) 1 and 2 in an EPCR-dependent manner. Human endothelial cells (HUVECs) express PAR1, PAR2 and EPCR. Stimulation of HUVECs with either APC, or specific receptor activating peptides for PAR1 or PAR2, show that all three agonists induce a very similar set of early response genes as assessed by high density microarray analysis. Only the transcript for monocyte chemo-attractant protein-1 (MCP-1) was selectively induced by APC and the PAR1 agonist, but not by the PAR2 agonist. APC-mediated MAP kinase phosphorylation and gene induction were inhibited by cleavage blocking antibodies to PAR1, demonstrating that APC signals exclusively through PAR1 in endothelial cells. MCP-1 is protective in animal models of endotoxemia, suggesting that APC may prevent lethality in sepsis by inducing MCP-1 expression through EPCR-dependent activation of endothelial cell PAR1. These data demonstrate unexpected protective functions of the major thrombin receptor PAR1 in endothelial cells.
Department of Immunology, The Scripps Research Institute, La Jolla, California 92037, USA. riewald@scripps.edu
Matthias
M
Riewald
Ramona J
RJ
Petrovan
Aaron
A
Donner
Wolfram
W
Ruf
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000818:Animals; D019138:Antibodies, Blocking / Q000494:pharmacology; D002460:Cell Line; D018932:Chemokine CCL2 / Q000096:biosynthesis / Q000235:genetics; D000074283:Endothelial Protein C Receptor; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D006023:Glycoproteins / Q000378:metabolism; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D011486:Protein C / Q000378:metabolism*; D044463:Receptor, PAR-1 / Q000378:metabolism*; D044464:Receptor, PAR-2 / Q000235:genetics / Q000378:metabolism; D011956:Receptors, Cell Surface; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*
D000590:Amino Acid Chloromethyl Ketones; D019138:Antibodies, Blocking; D018932:Chemokine CCL2; D000074283:Endothelial Protein C Receptor; D006023:Glycoproteins; C080248:Procr protein, mouse; D011486:Protein C; D044463:Receptor, PAR-1; D044464:Receptor, PAR-2; D011956:Receptors, Cell Surface; C027587:phenylalanyl-phenylalanyl-arginine chloromethyl ketone; D020928:Mitogen-Activated Protein Kinases