title: Proteasome inhibition activates the transport and the ectodomain shedding of TNF-alpha receptors in human endothelial cells.
abstract: Binding of tumor necrosis factor-alpha (TNF-alpha) to its transmembrane receptors (TNFRs) mediates proinflammatory, apoptotic and survival responses in several cell types including vascular endothelial cells. Because ectodomain shedding of cell surface molecules can be modified by proteasome activity, we studied in human endothelial cells whether the TNF-alpha-TNFRs axis can be regulated by the cleavage of their transmembrane forms in a proteasome-dependent manner. We show that proteasome inhibition increases the release of TNF-alpha and TNFRs from human endothelial cells and decreases their cellular and cell surface expression. This phenomenon involves the transient activation of mitogen-activated protein kinase p42/p44 that triggers the dispersion of TNF-alpha and TNFRs from their intracellular Golgi-complex-associated pool towards the plasma membrane. This results in their enhanced cleavage by TNF-alpha converting enzyme (TACE) because it is reduced by synthetic metalloprotease inhibitors, recombinant TIMP-3 and by a dominant negative form of TACE. In the presence of TACE inhibitor, proteasome inhibition increases the cell surface expression of TNFRs and enhances the sensitivity of these cells to the proapoptotic effect of recombinant TNF-alpha. In conclusion, our data provide evidence that proteasome inhibitors increase TACE-dependent TNFR-shedding in endothelial cells, supporting the use of these molecules in inflammatory disorders. In association with TACE inhibitor, proteasome inhibitors increase the amount of TNFRs at the cell surface and enhance the sensitivity to the proapoptotic effect of TNF-alpha, which might be of interest in the antitumor therapy.
authors.affiliation: INSERM UMR626, IFR125 IPHM, Faculté de Médecine, 27 Bd Jean Moulin, Marseilles 13385 Cedex 5, France.
authors.forename: Franck
authors.initials: F
authors.lastname: Peiretti
authors.forename: Matthias
authors.initials: M
authors.lastname: Canault
authors.forename: Denis
authors.initials: D
authors.lastname: Bernot
authors.forename: Bernadette
authors.initials: B
authors.lastname: Bonardo
authors.forename: Paule
authors.initials: P
authors.lastname: Deprez-Beauclair
authors.forename: Irène
authors.initials: I
authors.lastname: Juhan-Vague
authors.forename: Gilles
authors.initials: G
authors.lastname: Nalbone
mesh_terms: D051722:ADAM Proteins; D000072198:ADAM17 Protein; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis; D001692:Biological Transport; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D004727:Endothelium / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005434:Flow Cytometry; D005799:Genes, Dominant; D005822:Genetic Vectors; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D007249:Inflammation; D008666:Metalloendopeptidases / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D017434:Protein Structure, Tertiary; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D019717:Tissue Inhibitor of Metalloproteinase-3 / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; D061988:Proteasome Inhibitors; D018124:Receptors, Tumor Necrosis Factor; D011994:Recombinant Proteins; D019717:Tissue Inhibitor of Metalloproteinase-3; D014409:Tumor Necrosis Factor-alpha; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D051722:ADAM Proteins; D008666:Metalloendopeptidases; D000072198:ADAM17 Protein; C000606462:ADAM17 protein, human; D046988:Proteasome Endopeptidase Complex