title: Human vascular smooth muscle cells express functionally active endothelial cell protein C receptor.
abstract: The endothelial cell protein C receptor (EPCR) is expressed on endothelial cells and regulates the protein C anticoagulant pathway via the thrombin-thrombomodulin complex. Independent of its anticoagulant activity, activated protein C (APC) can directly signal to endothelial cells and upregulate antiapoptotic and antiinflammatory genes. Here we show that vascular smooth muscle cells (SMCs) also express EPCR. EPCR protein on SMCs was detected by flow cytometry and Western blotting. EPCR mRNA was identified by quantitative RT-PCR. To examine the functionality of EPCR, intracellular signaling in APC-stimulated SMCs was analyzed by determination of intracellular free calcium transients using confocal laser scanning microscopy. Phosphorylation of extracellular signal-regulated kinases 1 and 2 (ERK-1/2) was detected by immunoblotting. APC-induced ERK-1/2 phosphorylation was inhibited by an anti-EPCR antibody and by a cleavage site blocking anti-PAR-1 antibody, indicating that binding of APC to EPCR and cleavage of protease-activated receptor-1 (PAR-1) were involved. APC elicited an increase in [(3)H]-thymidine incorporation. The mitogenic effect of APC was significantly enhanced in the presence of thrombin. EPCR expression was also detected in SMCs in the fibrous cap of human carotid artery plaques. The present data demonstrate functionally active EPCR in SMCs and suggest that EPCR-bound APC might modulate PAR-1-mediated responses of SMCs to vascular injury.
authors.affiliation: Institut für Vaskuläre Medizin, Klinikum der Friedrich-Schiller-Universität Jena, Germany.
authors.forename: Ellen
authors.initials: E
authors.lastname: Bretschneider
authors.forename: Barbara
authors.initials: B
authors.lastname: Uzonyi
authors.forename: Artur-Aron
authors.initials: AA
authors.lastname: Weber
authors.forename: Jens W
authors.initials: JW
authors.lastname: Fischer
authors.forename: Robert
authors.initials: R
authors.lastname: Pape
authors.forename: Katharina
authors.initials: K
authors.lastname: Lötzer
authors.forename: Karsten
authors.initials: K
authors.lastname: Schrör
mesh_terms: D015703:Antigens, CD / Q000096:biosynthesis* / Q000235:genetics* / Q000502:physiology; D016893:Carotid Stenosis / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D002478:Cells, Cultured; D018920:Coculture Techniques; D000074283:Endothelial Protein C Receptor; D004730:Endothelium, Vascular / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D005786:Gene Expression Regulation / Q000502:physiology*; D006801:Humans; D009131:Muscle, Smooth, Vascular / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D032389:Myocytes, Smooth Muscle / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D011485:Protein Binding / Q000502:physiology; D011486:Protein C / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000096:biosynthesis* / Q000235:genetics* / Q000502:physiology
chemical_list: D015703:Antigens, CD; D000074283:Endothelial Protein C Receptor; C478370:PROCR protein, human; D011486:Protein C; D011956:Receptors, Cell Surface