Mechanism of release of soluble forms of tumor necrosis factor/lymphotoxin receptors by phorbol myristate acetate-stimulated human THP-1 cells in vitro.
The mechanism involved in the release of the soluble forms of 55 and 75 kDa TNF and lymphotoxin (LT) membrane receptors was studied in a continuous human monocytic cell line, THP-1, in vitro. THP-1 cells were found to spontaneously release soluble forms of both 55 and 75 kDa TNF/LT receptors. Release was up-regulated by PMA, and optimal release was achieved at 10(-8) M PMA. Serine protease inhibitors such as PMSF,3,4 dichloroisocoumarin, N alpha-p-tosyl-L-lysine chloromethyl ketone (TLCK), and N-tosyl-L-phenylalanine chloromethyl ketone (TPCK) were found to inhibit the production of both soluble TNF/LT receptors. PMSF (2 mM) also blocked receptors shedding from paraformaldehyde-fixed THP-1 cells coincubated with conditioned media from PMA-stimulated THP-1 cells. Colchicine at 1 and 10 microM stimulated the production of both soluble TNF/LT receptors, but the PMA-induced release of both soluble TNF/LT receptors was inhibited. It appears that the PMA-induced release of soluble TNF/LT receptors involves serine proteases in the extracellular space where the soluble parts of the TNF/LT receptors are cleaved directly off the cell membrane.
Hwang
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Department of Molecular Biology and Biochemistry, University of California at Irvine 92717.
Gatanaga
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Granger
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Gatanaga
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D002460:Cell Line; D003078:Colchicine / Q000494:pharmacology; D006801:Humans; D008970:Molecular Weight; D009000:Monocytes / Q000187:drug effects / Q000378:metabolism*; D010664:Phenylmethylsulfonyl Fluoride / Q000494:pharmacology; D018124:Receptors, Tumor Necrosis Factor / Q000187:drug effects / Q000378:metabolism*; D012697:Serine Endopeptidases / Q000502:physiology; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
D018124:Receptors, Tumor Necrosis Factor; D015842:Serine Proteinase Inhibitors; D010664:Phenylmethylsulfonyl Fluoride; D012697:Serine Endopeptidases; D013755:Tetradecanoylphorbol Acetate; D003078:Colchicine