Mechanism of release of soluble forms of tumor necrosis factor/lymphotoxin receptors by phorbol myristate acetate-stimulated human THP-1 cells in vitro

• Published in: The Journal of immunology (1950) Vol. 151; no. 10; pp. 5631 - 5638
• Main Authors: Hwang, C, Gatanaga, M, Granger, GA, Gatanaga, T
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Am Assoc Immnol 15.11.1993; American Association of Immunologists
• Subjects: Biological and medical sciences; Cell Line; Colchicine - pharmacology; Fundamental and applied biological sciences. Psychology; Fundamental immunology; Humans; Immunobiology; Molecular Weight; Monocytes - drug effects; Monocytes - metabolism; Monocytes, macrophages; Myeloid cells: ontogeny, maturation, markers, receptors; Phenylmethylsulfonyl Fluoride - pharmacology; Receptors, Tumor Necrosis Factor - drug effects; Receptors, Tumor Necrosis Factor - metabolism; Serine Endopeptidases - physiology; Serine Proteinase Inhibitors - pharmacology; Tetradecanoylphorbol Acetate - pharmacology; Human; Lymphotoxin; Cell culture; Monocyte; Enzyme; Cytokine; Stimulation; Soluble form; Membrane receptor; Cell line; Tumor necrosis factor; Proteolysis; N terminal-Sequence
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.151.10.5631

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.