Tumor necrosis factor receptor signaling. A dominant negative mutation suppresses the activation of the 55-kDa tumor necrosis factor receptor.

To investigate the signaling mechanism of the 55-kDa tumor necrosis factor (TNF) receptor a functional transfection based assay was developed. The human 55-kDa TNF receptor, stably expressed in mouse L929 cells, was demonstrated to be activated specifically by agonist antibodies and to initiate a signal for cellular cytotoxicity. A deletion mutant of the human TNF receptor lacking most of the cytoplasmic domain was found to be completely defective in generating the signal for cytotoxicity. Additionally, expression of the truncated receptor substantially suppressed signaling by endogenous mouse TNF receptors in response to TNF, but not in response to specific anti-murine TNF receptor antibodies. These results suggest that aggregation of 55-kDa TNF receptor intracellular domains, which are not associated in the absence of ligand, is an important component of the signal for cellular toxicity. This work also provides an example of a dominant negative mutation in a transmembrane receptor that lacks a tyrosine kinase domain, and suggests a more general utility of dominant negative mutations in the investigation of cytokine receptor function.