Tumor necrosis factor up-regulates gamma-interferon binding in a human carcinoma cell line.
WiDR colorectal carcinoma cells are highly sensitive to the synergistic cytotoxic effects of tumor necrosis factor (TNF) and gamma-interferon (IFN-gamma). In the present study, we have investigated the effects of recombinant human (rh) TNF and IFN-gamma on the binding of both ligands in this cell line. WiDR cells exhibited high affinity binding sites for both 125I-rhTNF (Kd = 1.66 x 10(-10) M, 920 sites/cell) and 125I-rhIFN-gamma (Kd = 4.15 x 10(-10) M, 18,960 sites/cell). Preincubation of the cells with rhTNF (24 h) increased cell-associated 125I-rhIFN-gamma radioactivity by 129% when binding was carried out at 37 degrees C, as a result of an increase in both surface bound and internalized 125I-rhIFN-gamma. However, rhTNF did not alter the degradation profile of released 125I-rhIFN-gamma radioactivity. Scatchard analysis of 125I-rhIFN-gamama binding data (4 degrees C) revealed that rhTNF induced a 245% increase in 125I-rhIFN-gamma binding sites. Conversely, rhIFN-gamma caused a 68% increase in 125I-rhTNF binding sites and a 58% increase in receptor affinity. rhIFN-gamma also increased the subsequent binding of 125I-rhIFN-gamma, whereas rhTNF increased the subsequent binding of 125I-rhTNF. Furthermore, preincubation of the cells with both rhTNF and rhIFN-gamma also resulted in an increase in the binding of both ligands. Actinomycin D and cycloheximide blocked all the effects of rhTNF and rhIFN-gamma on ligand binding. However, the basal level of 125I-rhIFN-gamma binding was insensitive to either inhibitor, whereas the basal level of 125I-rhTNF binding was decreased by both inhibitors. These data indicate that in some cell types TNF and IFN-gamma may induce an increase in their own receptors (homologous up-regulation) and concomitantly increase each other's receptors (heterologous up-regulation) and that these actions are due, in part, to enhanced receptor synthesis.
Raitano
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Department of Microbiology and Immunology, University of Arizona, Tucson 85724.
Korc
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D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism* / Q000494:pharmacology; D007700:Kinetics; D011971:Receptors, Immunologic / Q000187:drug effects / Q000378:metabolism*; D017471:Receptors, Interferon; D011994:Recombinant Proteins / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000166:cytology / Q000187:drug effects / Q000276:immunology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D015854:Up-Regulation
D011971:Receptors, Immunologic; D017471:Receptors, Interferon; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D003609:Dactinomycin; D007371:Interferon-gamma; D003513:Cycloheximide