title: Mechanisms involved in the processing of the p55 and the p75 tumor necrosis factor (TNF) receptors to soluble receptor forms.
abstract: The two tumor necrosis factor (TNF) receptors (TNF-R55 and TNF-R75) can release soluble TNF-binding proteins (TNF-R55-BP and TNF-R75-BP) by proteolytic cleavage. The proteolytic processing of the TNF receptors was investigated in monoblastic THP-1 and promyelocytic HL-60-10 leukemic cell lines. The release of soluble forms of both receptors was rapidly stimulated by staurosporine-sensitive protein kinase C activation by phorbol myristate acetate (PMA) and more slowly stimulated by TNF. No receptor release was seen below a temperature of 16 degrees C. NH4Cl (10 mmol/liter) and monensin (1 mumol/liter), known to increase intracellular pH, inhibited to some extent PMA- and TNF-induced release of both TNF-R55-BP and TNF-R75-BP. The inhibitory effect of monensin might be explained by a diminished translocation of newly synthesized receptor to the plasma membrane. The weak inhibitory effect of NH4Cl on PMA-induced release of soluble receptor forms could be due to effects on a pH-sensitive compartment. PMA-induced down-regulation of receptors was not dependent on acidity as it occurred also in the presence of monensin and NH4Cl when the release of TNF-BPs is partially blocked. Dibutyryl cAMP inhibited the PMA-induced release of TNF-R55-BP but not of TNF-R75-BP in both cell lines investigated. In addition, dibutyryl cAMP alone stimulated the release of both receptors but only in THP-1 cells. Our data show that the generation of soluble forms of both TNF receptors can be regulated by both PKC and PKA.
authors.affiliation: Department of Medicine, University of Lund, Sweden.
authors.forename: F
authors.initials: F
authors.lastname: Björnberg
authors.forename: M
authors.initials: M
authors.lastname: Lantz
authors.forename: I
authors.initials: I
authors.lastname: Olsson
authors.forename: U
authors.initials: U
authors.lastname: Gullberg
mesh_terms: D000470:Alkaloids / Q000494:pharmacology; D000643:Ammonium Chloride / Q000494:pharmacology; D003994:Bucladesine / Q000494:pharmacology; D002352:Carrier Proteins / Q000145:classification / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D015536:Down-Regulation; D010450:Endopeptidases / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D006367:HeLa Cells; D006801:Humans; D007948:Leukemia, Monocytic, Acute / Q000473:pathology; D015473:Leukemia, Promyelocytic, Acute / Q000473:pathology; D008985:Monensin / Q000494:pharmacology; D009363:Neoplasm Proteins / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism*; D047888:Receptors, Tumor Necrosis Factor, Type I; D012995:Solubility; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D053319:Tumor Necrosis Factor Decoy Receptors
chemical_list: D000470:Alkaloids; D002352:Carrier Proteins; D009363:Neoplasm Proteins; D018124:Receptors, Tumor Necrosis Factor; D047888:Receptors, Tumor Necrosis Factor, Type I; D053319:Tumor Necrosis Factor Decoy Receptors; D000643:Ammonium Chloride; C069521:recombinant human tumor necrosis factor-binding protein-1; D003994:Bucladesine; D008985:Monensin; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D010450:Endopeptidases; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate