Regulation of endothelial protein C receptor shedding by cytokines is mediated through differential activation of MAP kinase signaling pathways.
The endothelial protein C receptor (EPCR) plays a pivotal role in coagulation, inflammation, cell proliferation, and cancer, but its activity is markedly changed by ectodomain cleavage and release as the soluble protein (sEPCR). In this study we examined the mechanisms involved in the regulation of EPCR shedding in human umbilical endothelial cells (HUVEC). Interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha), but not interferon-gamma and interleukin-6, suppressed EPCR mRNA transcription and cell-associated EPCR expression in HUVEC. The release of sEPCR induced by IL-1beta and TNF-alpha correlated with activation of p38 MAPK and c-Jun N-terminal kinase (JNK). EPCR shedding was also induced by phorbol 12-myristate 13-acetate, ionomycin, anisomycin, thiol oxidants or alkylators, thrombin, and disruptors of lipid rafts. Both basal and induced shedding of EPCR was blocked by the metalloproteinase inhibitors, TAPI-0 and GM6001, and by the reduced non-protein thiols, glutathione, dihydrolipoic acid, dithiothreitol, and N-acetyl-l-cysteine. Because other antioxidants and scavengers of reactive oxygen species failed to block the cleavage of EPCR, a direct suppression of metalloproteinase activity seems responsible for the observed effects of reduced thiols. In summary, the shedding of EPCR in HUVEC is effectively regulated by IL-1beta and TNF-alpha, and downstream by MAP kinase signaling pathways and metalloproteinases.
Menschikowski
Mario
M
Institute of Clinical Chemistry and Laboratory Medicine, Technical University of Dresden, Medical Faculty Carl Gustav Carus, Fetscherstrasse 74, Dresden, Germany.
Hagelgans
Albert
A
Eisenhofer
Graeme
G
Siegert
Gabriele
G
D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D016207:Cytokines / Q000378:metabolism*; D000074283:Endothelial Protein C Receptor; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000378:metabolism; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism; D053583:Interleukin-1beta / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000502:physiology*; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*
D015703:Antigens, CD; D016207:Cytokines; D000074283:Endothelial Protein C Receptor; D004791:Enzyme Inhibitors; D053583:Interleukin-1beta; D015850:Interleukin-6; C478370:PROCR protein, human; D011956:Receptors, Cell Surface; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D013755:Tetradecanoylphorbol Acetate