title: TRAF2 is a biologically important necroptosis suppressor.
abstract: Tumor necrosis factor α (TNFα) triggers necroptotic cell death through an intracellular signaling complex containing receptor-interacting protein kinase (RIPK) 1 and RIPK3, called the necrosome. RIPK1 phosphorylates RIPK3, which phosphorylates the pseudokinase mixed lineage kinase-domain-like (MLKL)-driving its oligomerization and membrane-disrupting necroptotic activity. Here, we show that TNF receptor-associated factor 2 (TRAF2)-previously implicated in apoptosis suppression-also inhibits necroptotic signaling by TNFα. TRAF2 disruption in mouse fibroblasts augmented TNFα-driven necrosome formation and RIPK3-MLKL association, promoting necroptosis. TRAF2 constitutively associated with MLKL, whereas TNFα reversed this via cylindromatosis-dependent TRAF2 deubiquitination. Ectopic interaction of TRAF2 and MLKL required the C-terminal portion but not the N-terminal, RING, or CIM region of TRAF2. Induced TRAF2 knockout (KO) in adult mice caused rapid lethality, in conjunction with increased hepatic necrosome assembly. By contrast, TRAF2 KO on a RIPK3 KO background caused delayed mortality, in concert with elevated intestinal caspase-8 protein and activity. Combined injection of TNFR1-Fc, Fas-Fc and DR5-Fc decoys prevented death upon TRAF2 KO. However, Fas-Fc and DR5-Fc were ineffective, whereas TNFR1-Fc and interferon α receptor (IFNAR1)-Fc were partially protective against lethality upon combined TRAF2 and RIPK3 KO. These results identify TRAF2 as an important biological suppressor of necroptosis in vitro and in vivo.
authors.affiliation: Cancer Immunology, Genentech, Inc., 1 DNA Way, South San Francisco, CA 94080, USA.
authors.forename: S L
authors.initials: SL
authors.lastname: Petersen
authors.affiliation: Cancer Immunology, Genentech, Inc., 1 DNA Way, South San Francisco, CA 94080, USA.
authors.forename: T T
authors.initials: TT
authors.lastname: Chen
authors.affiliation: Cancer Immunology, Genentech, Inc., 1 DNA Way, South San Francisco, CA 94080, USA.
authors.forename: D A
authors.initials: DA
authors.lastname: Lawrence
authors.affiliation: Cancer Immunology, Genentech, Inc., 1 DNA Way, South San Francisco, CA 94080, USA.
authors.forename: S A
authors.initials: SA
authors.lastname: Marsters
authors.affiliation: Cancer Immunology, Genentech, Inc., 1 DNA Way, South San Francisco, CA 94080, USA.
authors.forename: F
authors.initials: F
authors.lastname: Gonzalvez
authors.affiliation: Cancer Immunology, Genentech, Inc., 1 DNA Way, South San Francisco, CA 94080, USA.
authors.forename: A
authors.initials: A
authors.lastname: Ashkenazi
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics / Q000502:physiology; D016923:Cell Death / Q000235:genetics / Q000502:physiology; D005347:Fibroblasts / Q000378:metabolism; D007150:Immunohistochemistry; D051379:Mice; D018345:Mice, Knockout; D011485:Protein Binding; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D053422:Receptor-Interacting Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D047992:TNF Receptor-Associated Factor 2 / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination / Q000235:genetics / Q000502:physiology
chemical_list: D047992:TNF Receptor-Associated Factor 2; C570694:MLKL protein, mouse; D011494:Protein Kinases; D053422:Receptor-Interacting Protein Serine-Threonine Kinases; C506251:Ripk1 protein, mouse; C485615:Ripk3 protein, mouse