Related Experiment Videos
Overexpression of the p80 TNF receptor leads to TNF-dependent apoptosis, nuclear factor-kappa B activation, and c-Jun
V Haridas1, B G Darnay, K Natarajan
1Department of Molecular Oncology, University of Texas M. D. Anderson Cancer Center, Houston 77030, USA.
Abstract:
Because they have distinct intracellular domains, it has been proposed that the p60 and p80 forms of the TNF receptor mediate different signals. Several signaling proteins have been isolated that associate with either the p60 or the p80 receptor. By using TNF muteins specific to the p60 and p80 receptors, we have previously shown that cytotoxicity and nuclear factor-kappa B (NF-kappa B) activation are mediated through the p60 form of the endogenous receptor. What signals are mediated through the p80 receptor is less clear. This study was an effort to answer that question. HeLa cells, which express only p60 receptors, were transfected with p80 receptor cDNA and then examined for apoptosis, NF-kappa B activation, and c-Jun kinase activation induced by TNF and by p60 or p80 receptor-specific muteins. The p80 mutein, like TNF and the p60 mutein, induced apoptosis and activation of NF-kappa B and c-Jun kinase in cells overexpressing recombinant p80 receptor but had no effect on cells expressing a high level of endogenous p80 receptor. The apoptosis mediated through the p60 receptor was also potentiated after overexpression of the p80 receptor, suggesting a synergistic relationship between the two receptors. Interestingly, Abs to the p80 receptor blocked apoptosis induced by all ligands but by itself activated NF-kappa B in the p80-transfected cells. Overall, our results show that the p80 receptor, which lacks the death domain, mediated apoptosis, NF-kappa B activation, and c-Jun kinase activation, but only when it was overexpressed, whereas endogenous p60 receptor mediated similar signals without overexpression.
Insights
The p80 tumor necrosis factor (TNF) receptor form can mediate apoptosis and activate nuclear factor-kappa B (NF-kappa B) and c-Jun kinase, but only when overexpressed. The p60 receptor form mediates these signals without overexpression, and p80 can potentiate p60 signaling.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- Tumor necrosis factor (TNF) receptors, p60 and p80, possess distinct intracellular domains, suggesting differential signaling capabilities.
- Previous research established that the p60 receptor form mediates cytotoxicity and nuclear factor-kappa B (NF-kappa B) activation.
- The specific signaling pathways regulated by the p80 receptor remain less understood.
Purpose of the Study:
- To elucidate the signaling functions of the p80 TNF receptor form.
- To investigate the roles of p60 and p80 TNF receptors in apoptosis, NF-kappa B, and c-Jun kinase activation.
Main Methods:
- HeLa cells, expressing only endogenous p60 receptors, were transfected with p80 receptor cDNA.
- Cells were treated with TNF, and receptor-specific muteins (p60 and p80) to assess signaling.
- Apoptosis, NF-kappa B activation, and c-Jun kinase activation were measured in response to treatments.
Main Results:
- Overexpression of p80 receptor enabled it to mediate apoptosis, NF-kappa B, and c-Jun kinase activation, similar to TNF and p60 muteins.
- Endogenous p80 receptor did not mediate these signals without overexpression, while endogenous p60 did.
- p80 receptor overexpression potentiated p60-mediated apoptosis, indicating a synergistic interaction.
Conclusions:
- The p80 TNF receptor form, despite lacking a death domain, mediates apoptosis and key signaling pathways upon overexpression.
- Endogenous p60 receptor mediates similar signals independently of overexpression.
- A synergistic relationship exists between p60 and p80 receptors in mediating apoptosis.