The mechanism of the action of IFN-gamma and TPA on the modulation of epidermal growth factor receptors of human amnion cells.
We have examined the mechanism of synergistic action occurring between interferon (IFN)-gamma and 12-0-tetradecanoylphorbol-13-acetate (TPA) with respect to the reduction of 125I-epidermal growth factor (125I-EGF) binding to human amnion (WISH) cells [Karasaki Y et al (1989) J Biol Chem 264: 6158-6163]. The cells were treated with protein kinase C (PKC) inhibitors (H7, staurosporine) to investigate the role of PKC in the synergism between IFN-gamma and TPA, since TPA is a strong activator of PKC. The combined effect of IFN-gamma and TPA was blocked by the PKC inhibitor, suggesting that PKC plays an important role in the synergistic action of TPA and IFN-gamma on the inhibition of EGF binding to the cells. The prolonged incubation (24 h) of the cells with TPA resulted in the restoration of EGF binding to the cells. A 24 h treatment of WISH cells with both IFN-gamma and TPA, however, still exhibited greater than 50% inhibition of EGF binding. No PKC activity, however, was observed in the WISH cells treated with both IFN-gamma and TPA for 24 h as well as with TPA alone for 24 h, indicating that IFN-gamma may synergize with the second mediator induced by PKC rather than PKC itself in the reduction of EGF binding to WISH cells. In addition, IFN-gamma showed the synergistic action with calcium ionophores on the reduction of EGF binding to the cells, suggesting that Ca2+ may be one of the second mediators which was induced by TPA and which cooperated with IFN-gamma.
Katoh
T
T
Department of Biochemistry, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan.
Higashi
K
K
Karasaki
Y
Y
D000650:Amnion / Q000378:metabolism; D002118:Calcium / Q000502:physiology; D002478:Cells, Cultured; D004357:Drug Synergism; D066246:ErbB Receptors / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D007457:Iodine Radioisotopes; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
D007457:Iodine Radioisotopes; D007371:Interferon-gamma; D066246:ErbB Receptors; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium