The Fas-associated death domain protein suppresses activation of NF-κB by LPS and IL-1β
Douglas D. Bannerman, … , Robert K. Winn, John M. Harlan
Douglas D. Bannerman, … , Robert K. Winn, John M. Harlan
Published February 1, 2002
Citation Information: J Clin Invest. 2002;109(3):419-425. https://doi.org/10.1172/JCI14774.
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Article

The Fas-associated death domain protein suppresses activation of NF-κB by LPS and IL-1β

Abstract

Activation of NF-κB by bacterial LPS promotes the upregulation of proinflammatory cytokines that contribute to the pathogenesis of Gram-negative septic shock. LPS activation of NF-κB is dependent upon the interaction of two death domain–containing (DD-containing) proteins, MyD88 and IL-1 receptor–associated kinase IRAK. Another DD-containing protein, Fas-associated death domain (FADD), also binds MyD88 through respective DD-DD interactions. Although FADD has been classically described as a proapoptotic signaling molecule, several reports have implicated a role for FADD in mediating NF-κB activation. In the present report, we investigated whether FADD could mediate LPS activation of NF-κB. Overexpression of FADD blocked LPS-induced NF-κB activation, whereas absence of FADD enhanced activation of NF-κB by LPS. Further, LPS-induced expression of two NF-κB–dependent gene products, IL-6 and KC, was enhanced in FADD–/– mouse embryo fibroblasts (MEFs) compared with wild-type. This increase in NF-κB activity correlated with enhanced IκB degradation. FADD–/– MEFs were also resistant to NF-κB activation induced by IL-1β. Finally, reconstitution of full-length FADD in the FADD–/– MEFs completely reversed the enhanced activation of NF-κB elicited by either LPS or IL-1β. Together, these data indicate that FADD negatively regulates LPS- and IL-1β–induced NF-κB activation and that this regulation occurs upstream of IκB degradation.

Authors

Douglas D. Bannerman, Joan C. Tupper, James D. Kelly, Robert K. Winn, John M. Harlan

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Figure 1

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Overexpression of FADD or the DD of FADD inhibits LPS- and IL-1β–induced...
Overexpression of FADD or the DD of FADD inhibits LPS- and IL-1β–induced NF-κB activation. HMEC-1 cells were stably transfected with GFP vector alone (a–d), the DD of FADD (a and b), or full-length FADD (c and d), and expression was confirmed by Western blot analysis (a and c). In separate studies, these cells were treated for 4.5 hours with medium, LPS (100 ng/ml), or hIL-1β (100 ng/ml), lysed, and assayed for luciferase activity (b and d). Vertical bars represent mean (± SE) luciferase activity in arbitrary units. *Significantly decreased compared with HMEC-1 cells transfected with vector alone that were exposed to identical treatment.