title: TNF can activate RIPK3 and cause programmed necrosis in the absence of RIPK1.
abstract: Ligation of tumor necrosis factor receptor 1 (TNFR1) can cause cell death by caspase 8 or receptor-interacting protein kinase 1 (RIPK1)- and RIPK3-dependent mechanisms. It has been assumed that because RIPK1 bears a death domain (DD), but RIPK3 does not, RIPK1 is necessary for recruitment of RIPK3 into signaling and death-inducing complexes. To test this assumption, we expressed elevated levels of RIPK3 in murine embryonic fibroblasts (MEFs) from wild-type (WT) and gene-deleted mice, and exposed them to TNF. Neither treatment with TNF nor overexpression of RIPK3 alone caused MEFs to die, but when levels of RIPK3 were increased, addition of TNF killed WT, Ripk1(-/-), caspase 8(-/-), and Bax(-/-)/Bak(-/-) MEFs, even in the presence of the broad-spectrum caspase inhibitor Q-VD-OPh. In contrast, Tnfr1(-/-) and Tradd(-/-) MEFs did not die. These results show for the first time that in the absence of RIPK1, TNF can activate RIPK3 to induce cell death both by a caspase 8-dependent mechanism and by a separate Bax/Bak- and caspase-independent mechanism. RIPK1 is therefore not essential for TNF to activate RIPK3 to induce necroptosis nor for the formation of a functional ripoptosome/necrosome.
authors: The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Melbourne, Victoria, Australia.
authors: D M
authors: DM
authors: Moujalled
authors: W D
authors: WD
authors: Cook
authors: T
authors: T
authors: Okamoto
authors: J
authors: J
authors: Murphy
authors: K E
authors: KE
authors: Lawlor
authors: J E
authors: JE
authors: Vince
authors: D L
authors: DL
authors: Vaux
mesh_terms: D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D053181:Caspase 8 / Q000235:genetics / Q000378:metabolism; D061945:Caspase Inhibitors / Q000494:pharmacology; D002460:Cell Line; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D051379:Mice; D009336:Necrosis; D011804:Quinolines / Q000494:pharmacology; D053422:Receptor-Interacting Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology; D053199:TNF Receptor-Associated Death Domain Protein / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000172:deficiency / Q000235:genetics / Q000378:metabolism
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D061945:Caspase Inhibitors; D011804:Quinolines; D047888:Receptors, Tumor Necrosis Factor, Type I; D011994:Recombinant Proteins; D053199:TNF Receptor-Associated Death Domain Protein; D014409:Tumor Necrosis Factor-alpha; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; C468548:quinoline-val-asp(OMe)-CH2-OPH; D053422:Receptor-Interacting Protein Serine-Threonine Kinases; C506251:Ripk1 protein, mouse; C485615:Ripk3 protein, mouse; D053181:Caspase 8