Cytoplasmic truncation of the p55 tumour necrosis factor (TNF) receptor abolishes signalling, but not induced shedding of the receptor.

Abstract

The mechanistic relationship between the signalling for the TNF effects by the human p55 TNF receptor (hup55-TNF-R) and the formation of a soluble form of the receptor, which is inhibitory to these effects, was explored by examining the function of C-terminally truncated mutants of the receptor, expressed in rodent cells. The 'wild-type' receptor signalled for a cytocidal effect when cross-linked with specific antibodies and exhibited spontaneous shedding. Shedding of the receptor was not affected by TNF but was markedly enhanced by 4,(-phorbol-12-myristate-13-acetate (PMA). Receptor mutants with 53%, 83% and 96% C-terminal deletions could not signal for the cytocidal effect. Furthermore, they were found to associate with the endogenous rodent receptors, interfering with their signalling. Yet even the deletion of 96% of the intracellular domain did not abolish shedding of the receptor in response to PMA. These findings suggest that signalling and shedding of the p55 TNF-R are mechanistically distinct.

The Death Domain of Tumor Necrosis Factor Receptor 1 Is Necessary but Not Sufficient for Golgi Retention of the Receptor and Mediates Receptor Desensitization

“…The intracellular domains of these clustered receptor monomers bind intracellular adaptor molecules, which in turn initiate signaling cascades leading either to cell activation or cell death (reviewed in Tartaglia and Goeddel, 1992b). Receptors mutated to remove the intracellular regions may act as dominant negative mutants, presumably by forming receptor complexes that are unable to recruit the relevant adaptor molecules (Brakebusch et al, 1992;Tartaglia and Goeddel, 1992a).…”

“…This difference may reflect the mechanism of desensitization caused by ligand versus that caused by receptor overexpression. This inhibitory effect of overexpressed TNFR1 also contrasts with the sensitization to TNF-mediated apoptosis observed in other cell lines transfected with the receptor Brakebusch et al, 1992); however, HUVEC are generally resistant to TNF-induced apoptosis in the absence of a second signal (eg, actinomycin or ceramide) and therefore the pathways leading to TNFinduced apoptosis may differ from those leading to NF-B examined in this study.…”

“…As reported previously in the murine L929 and A9 cells (Brakebusch et al, 1992;Tartaglia and Goeddel, 1992a), TNFR1 lacking the death domain had a dominant negative effect on TNF signaling. Surprisingly, both gfpTNFR1 and gfpTNFR2 ϩDD also inhibited the response to TNF.…”

“…The C-terminal half of the intracellular region of TNFR1 contains a protein-protein interaction motif dubbed the "death domain" that is homologous with other proteins involved in induction of apoptosis (Cleveland and Ihle, 1995;Feinstein et al, 1995;Tartaglia et al, 1993). Surprisingly, this region of TNFR1 has been shown to be necessary for TNF-mediated activation of gene transcription as well as death responses Brakebusch et al, 1992;Machleidt et al, 1996;Tartaglia et al, 1993). The death domain of TNFR1 interacts with the death domain of the adaptor protein TRADD (TNF receptor-associated death domain protein), which is the first step in signal transduction leading both to the activation of the transcription factors NF-B and AP-1 and to the activation of apoptosis-mediating caspases (Hsu et al, 1995;Park and Baichwal, 1996).…”

Alteration of the Sphingomyelin/Ceramide Pathway Is Associated with Resistance of Human Breast Carcinoma MCF7 Cells to Tumor Necrosis Factor-α-mediated Cytotoxicity

“…Although functional wild-type p55 receptor expression was reestablished in R-A1 cells by gene transfer as well as subsequent NF-B activation in response to TNF, these cells remained totally resistant to the cytotoxic action of TNF. It should be noted that transfection of rodent cells using the same vector efficiently triggered the cytotoxic effect of TNF (26). Our observations suggest that NF-B is not sufficient to induce cell killing, and confirm that the activation of this nuclear factor and apoptosis are coincidental but that these two activities are separable.…”