Abstract
Tumor necrosis factor α (TNF-α) is a pro-inflammatory cytokine capable of inducing extrinsic apoptosis and necroptosis. Tumor necrosis factor receptor-associated factor 6 (TRAF6), an E3 ligase, is a member of the TRAF family of proteins, which mediates inflammatory signals by activating nuclear factor kappa B (NFкB) and mitogen-activated protein kinase (MAPK). Although the functions of TRAF6 have been identified, its role in TNF-α-induced cell death remains poorly understood. Here, we report that TRAF6 is a negative modulator of TNF-α-induced cell death but does not affect TNF-α-induced NFκB activation. TRAF6 deficiency accelerates both TNF-α-induced apoptosis and necroptosis; however, the acceleration can be reversed by reconstituting TRAF6 or TRAF6C70A, suggesting that E3 ligase activity is not required for this activity. Mechanistically, TRAF6 directly interacts with RIPK1 during TNF-α-induced cell death signaling, which prevents RIPK1 from interacting with components of the cell death complex such as itself, FADD or RIPK3. These processes suppress the assembly of the death complex. Notably, IKK was required for TRAF6 to interact with RIPK1. In vivo, Traf6-/- embryos exhibited higher levels of cell death in the liver but could be rescued by the simultaneous knockout of Tnf. Finally, TRAF6 knockdown xenografts were highly sensitive to necroptotic stimuli. We concluded that TRAF6 suppresses TNF-α-induced cell death in coordination with IKK complexes in vivo and in vitro by suppressing the assembly of cell death complex.
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Acknowledgements
This work was supported by a grant from the National Research Foundation of Korea (NRF), funded by the Ministry of Science, ICT, and Future Planning (MSIP) (2015R1A3A2066581), in part by a National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) (No. NRF-2020R1A5A1019023), and in part by the Brain Korea 21(BK21) FOUR program.
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C-SL designed, performed, and interpreted all experiments and prepared the manuscript. GH prepared materials and performed the xenograft model experiment. YWN and CHH designed and interpreted the experimental results. JS directed the experiments and revised the manuscript.
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The mouse embryo and xenograft model studies were approved by the Yonsei University Institutional Animal Care and Use Committee (IACUC-A-202111-1368-01 and IACUC-A-202205-1465-01).
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Lee, CS., Hwang, G., Nam, Y.W. et al. IKK-mediated TRAF6 and RIPK1 interaction stifles cell death complex assembly leading to the suppression of TNF-α-induced cell death. Cell Death Differ 30, 1575–1584 (2023). https://doi.org/10.1038/s41418-023-01161-w
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DOI: https://doi.org/10.1038/s41418-023-01161-w
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