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MADD, a novel death domain protein that interacts with the type 1 tumor necrosis factor receptor and activates
A R Schievella1, J H Chen, J R Graham
1Small Molecule Drug Discovery Group, Genetics Institute, Inc., Cambridge, Massachusetts 02140, USA.
Abstract:
The death domain of the type 1 tumor necrosis factor receptor (TNFR1) mediates interactions with several proteins involved in signaling the downstream effects of TNF. We have used the yeast interaction trap to isolate a protein, MADD, that associates with the death domain of TNFR1 through its own C-terminal death domain. MADD interacts with TNFR1 residues that are critical for signal generation and coimmunoprecipitates with TNFR1, implicating MADD as a component of the TNFR1 signaling complex. Importantly, we have found that overexpression of MADD activates the mitogen-activated protein (MAP) kinase extracellular signal-regulated kinase (ERK), and expression of the MADD death domain stimulates both the ERK and c-JUN N-terminal kinase MAP kinases and induces the phosphorylation of cytosolic phospholipase A2. These data indicate that MADD links TNFR1 with MAP kinase activation and arachidonic acid release and provide further insight into the mechanisms by which TNF exerts its pleiotropic effects.
Insights
MADD protein links TNFR1 signaling to MAP kinase activation. This discovery sheds light on how TNF triggers cellular responses, including arachidonic acid release.
Area of Science:
- Molecular Biology
- Cell Signaling
- Immunology
Background:
- The type 1 tumor necrosis factor receptor (TNFR1) death domain is crucial for mediating downstream signaling pathways activated by TNF.
- Understanding the molecular components of the TNFR1 signaling complex is essential for elucidating TNF's diverse cellular effects.
Purpose of the Study:
- To identify novel proteins interacting with the TNFR1 death domain.
- To investigate the role of MADD in TNFR1-mediated signaling pathways.
- To explore the connection between MADD, MAP kinase activation, and arachidonic acid release.
Main Methods:
- Yeast interaction trap assay to identify MADD.
- Co-immunoprecipitation to confirm MADD-TNFR1 interaction.
- Overexpression studies to assess MADD's effect on MAP kinase pathways (ERK, JNK) and phospholipase A2 phosphorylation.
Main Results:
- MADD was identified as a protein that binds to the TNFR1 death domain.
- MADD interacts with critical TNFR1 residues involved in signal generation and is part of the TNFR1 signaling complex.
- Overexpression of MADD activates ERK, while MADD death domain expression activates ERK and JNK, leading to cytosolic phospholipase A2 phosphorylation.
Conclusions:
- MADD serves as a crucial link between TNFR1 and the activation of mitogen-activated protein (MAP) kinases.
- MADD mediates TNF-induced arachidonic acid release through MAP kinase activation.
- These findings provide new insights into the complex mechanisms underlying TNF's pleiotropic effects.