Death receptor-induced signaling pathways are differentially regulated by gamma interferon upstream of caspase 8 processing |
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Authors: | Siegmund Daniela Wicovsky Andreas Schmitz Ingo Schulze-Osthoff Klaus Kreuz Sebastian Leverkus Martin Dittrich-Breiholz Oliver Kracht Michael Wajant Harald |
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Affiliation: | Department of Molecular Internal Medicine, Medical Polyclinic, University of Würzburg, R?ntgenring 11, 97070 Würzburg, Germany. |
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Abstract: | FasL and gamma interferon (IFN-gamma) are produced by activated T cells and NK cells and synergistically induce apoptosis. Although both cytokines can also elicit proinflammatory responses, a possible cross talk of these ligands with respect to nonapoptotic signaling has been poorly addressed. Here, we show that IFN-gamma sensitizes KB cells for apoptosis induction by facilitating death-inducing signaling complex (DISC)-mediated caspase 8 processing. Moreover, after protection against death receptor-induced apoptosis by caspase inhibition or Bcl2 overexpression, IFN-gamma also sensitized for Fas- and TRAIL death receptor-mediated NF-kappaB activation leading to synergistic upregulation of a variety of proinflammatory genes. In contrast, Fas-mediated activation of JNK, p38, and p42/44 occurred essentially independent from IFN-gamma sensitization, indicating that the apoptosis- and NF-kappaB-related FasL-IFN-gamma cross talk was not due to a simple global enhancement of Fas signaling. Overexpression of FLIP(L) and FLIP(S) inhibited Fas- as well as TRAIL-mediated NF-kappaB activation and apoptosis induction in IFN-gamma-primed cells suggesting that both responses are coregulated at the level of the DISC. |
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