TNF-Induced shedding of TNF receptors in human polymorphonuclear leukocytes: role of the 55-kDa TNF receptor and involvement of a membrane-bound and non-matrix metalloproteinase.
A down-modulation of both the 55-kDa (TNF-R55) and the 75-kDa (TNF-R75) TNF receptors is observed in neutrophils exposed to a variety of stimuli. Proteolytic cleavage of the extracellular region of both receptors (shedding) and, with TNF, internalization of TNF-R55 and shedding of TNF-R75 are the proposed mechanisms. We have characterized the TNF-induced shedding of TNF receptors in neutrophils and determined the nature of the involved proteinase. Neutrophils exposed to TNF release both TNF receptors. A release of TNF receptors comparable to that observed with TNF was induced with TNF-R55-specific reagents (mAbs and a mutant of TNF) but not with the corresponding TNF-R75-specific reagents. A hydroxamic acid compound (KB8301) almost completely inhibited shedding of TNF-R55 and to a lesser degree shedding of TNF-R75. KB8301 also inhibited FMLP-induced shedding to a similar extent. Shedding was also inhibited by 1,10-phenanthroline, but this effect was considered nonspecific as the compound, at variance with KB8301, almost completely inhibited TNF and FMLP-induced PMN activation. Diisopropylfluorophosphate partially inhibited shedding of TNF-R75, suggesting the contribution of a serine proteinase to the release of this receptor. Shedding activity was not affected by matrix metalloproteinases inhibitors nor was it released in the supernatants of FMLP-stimulated neutrophils. These results suggest that TNF induces release of its receptors, that such a release is mediated via TNF-R55, and that a membrane-bound and non-matrix metalloproteinase is involved in the process. The possibility that ADAM-17, which we show to be expressed in neutrophils, might be the involved proteinase is discussed.
Department of Physiology and Pathology, University of Trieste, Trieste, Italy. dri@univ.trieste.it
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Dri
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Gasparini
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Menegazzi
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Cramer
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Albéri
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Presani
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Garbisa
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Patriarca
D051722:ADAM Proteins; D000072199:ADAM12 Protein; D000072198:ADAM17 Protein; D015703:Antigens, CD / Q000378:metabolism / Q000502:physiology*; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology / Q000276:immunology; D006801:Humans; D061965:Matrix Metalloproteinase Inhibitors; D020782:Matrix Metalloproteinases / Q000502:physiology*; D008565:Membrane Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000502:physiology*; D008666:Metalloendopeptidases / Q000096:biosynthesis / Q000737:chemistry / Q000502:physiology*; D009124:Muscle Proteins / Q000096:biosynthesis / Q000502:physiology; D009504:Neutrophils / Q000187:drug effects / Q000201:enzymology* / Q000276:immunology* / Q000378:metabolism; D010618:Phenanthrolines / Q000494:pharmacology; D018124:Receptors, Tumor Necrosis Factor / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D047888:Receptors, Tumor Necrosis Factor, Type I; D047889:Receptors, Tumor Necrosis Factor, Type II; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000494:pharmacology; D019716:Tissue Inhibitor of Metalloproteinase-2 / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D020298:U937 Cells
D015703:Antigens, CD; D061965:Matrix Metalloproteinase Inhibitors; D008565:Membrane Proteins; D009124:Muscle Proteins; D010618:Phenanthrolines; D018124:Receptors, Tumor Necrosis Factor; D047888:Receptors, Tumor Necrosis Factor, Type I; D047889:Receptors, Tumor Necrosis Factor, Type II; D019715:Tissue Inhibitor of Metalloproteinase-1; D014409:Tumor Necrosis Factor-alpha; D019716:Tissue Inhibitor of Metalloproteinase-2; D051722:ADAM Proteins; D000072199:ADAM12 Protein; C096115:Adam12 protein, mouse; D020782:Matrix Metalloproteinases; D008666:Metalloendopeptidases; D000072198:ADAM17 Protein; C000606462:ADAM17 protein, human; C000606463:Adam17 protein, mouse; C025205:1,10-phenanthroline