title: RIPK1 ensures intestinal homeostasis by protecting the epithelium against apoptosis.
abstract: Receptor interacting protein kinase 1 (RIPK1) has an essential role in the signalling triggered by death receptors and pattern recognition receptors. RIPK1 is believed to function as a node driving NF-κB-mediated cell survival and inflammation as well as caspase-8 (CASP8)-dependent apoptotic or RIPK3/MLKL-dependent necroptotic cell death. The physiological relevance of this dual function has remained elusive because of the perinatal death of RIPK1 full knockout mice. To circumvent this problem, we generated RIPK1 conditional knockout mice, and show that mice lacking RIPK1 in intestinal epithelial cells (IECs) spontaneously develop severe intestinal inflammation associated with IEC apoptosis leading to early death. This early lethality was rescued by antibiotic treatment, MYD88 deficiency or tumour-necrosis factor (TNF) receptor 1 deficiency, demonstrating the importance of commensal bacteria and TNF in the IEC Ripk1 knockout phenotype. CASP8 deficiency, but not RIPK3 deficiency, rescued the inflammatory phenotype completely, indicating the indispensable role of RIPK1 in suppressing CASP8-dependent apoptosis but not RIPK3-dependent necroptosis in the intestine. RIPK1 kinase-dead knock-in mice did not exhibit any sign of inflammation, suggesting that RIPK1-mediated protection resides in its kinase-independent platform function. Depletion of RIPK1 in intestinal organoid cultures sensitized them to TNF-induced apoptosis, confirming the in vivo observations. Unexpectedly, TNF-mediated NF-κB activation remained intact in these organoids. Our results demonstrate that RIPK1 is essential for survival of IECs, ensuring epithelial homeostasis by protecting the epithelium from CASP8-mediated IEC apoptosis independently of its kinase activity and NF-κB activation.
authors.affiliation: 1] VIB Inflammation Research Center, Technologiepark 927, B-9052 Ghent, Belgium [2] Department of Biomedical Molecular Biology, Ghent University, Technologiepark 927, B-9052 Ghent, Belgium.
authors.forename: Nozomi
authors.initials: N
authors.lastname: Takahashi
authors.affiliation: 1] VIB Inflammation Research Center, Technologiepark 927, B-9052 Ghent, Belgium [2] Department of Biomedical Molecular Biology, Ghent University, Technologiepark 927, B-9052 Ghent, Belgium.
authors.forename: Lars
authors.initials: L
authors.lastname: Vereecke
authors.affiliation: 1] VIB Inflammation Research Center, Technologiepark 927, B-9052 Ghent, Belgium [2] Department of Biomedical Molecular Biology, Ghent University, Technologiepark 927, B-9052 Ghent, Belgium.
authors.forename: Mathieu J M
authors.initials: MJ
authors.lastname: Bertrand
authors.affiliation: 1] VIB Inflammation Research Center, Technologiepark 927, B-9052 Ghent, Belgium [2] Department of Biomedical Molecular Biology, Ghent University, Technologiepark 927, B-9052 Ghent, Belgium.
authors.forename: Linde
authors.initials: L
authors.lastname: Duprez
authors.affiliation: Pattern Recognition Receptor Discovery Performance Unit, Immuno-inflammation Therapeutic Area, GlaxoSmithKline, Collegeville, Pennsylvania 19426, USA.
authors.forename: Scott B
authors.initials: SB
authors.lastname: Berger
authors.affiliation: 1] VIB Inflammation Research Center, Technologiepark 927, B-9052 Ghent, Belgium [2] Department of Biomedical Molecular Biology, Ghent University, Technologiepark 927, B-9052 Ghent, Belgium.
authors.forename: Tatyana
authors.initials: T
authors.lastname: Divert
authors.affiliation: 1] VIB Inflammation Research Center, Technologiepark 927, B-9052 Ghent, Belgium [2] Department of Biomedical Molecular Biology, Ghent University, Technologiepark 927, B-9052 Ghent, Belgium [3] VIB Bio Imaging Core Gent, Technologiepark 927, B-9052 Ghent, Belgium.
authors.forename: Amanda
authors.initials: A
authors.lastname: Gonçalves
authors.affiliation: 1] VIB Inflammation Research Center, Technologiepark 927, B-9052 Ghent, Belgium [2] Department of Biomedical Molecular Biology, Ghent University, Technologiepark 927, B-9052 Ghent, Belgium.
authors.forename: Mozes
authors.initials: M
authors.lastname: Sze
authors.affiliation: 1] VIB Inflammation Research Center, Technologiepark 927, B-9052 Ghent, Belgium [2] Department of Biomedical Molecular Biology, Ghent University, Technologiepark 927, B-9052 Ghent, Belgium.
authors.forename: Barbara
authors.initials: B
authors.lastname: Gilbert
authors.affiliation: 1] VIB Inflammation Research Center, Technologiepark 927, B-9052 Ghent, Belgium [2] Department of Biomedical Molecular Biology, Ghent University, Technologiepark 927, B-9052 Ghent, Belgium.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Kourula
authors.affiliation: 1] VIB Inflammation Research Center, Technologiepark 927, B-9052 Ghent, Belgium [2] Department of Biomedical Molecular Biology, Ghent University, Technologiepark 927, B-9052 Ghent, Belgium.
authors.forename: Vera
authors.initials: V
authors.lastname: Goossens
authors.affiliation: 1] VIB Inflammation Research Center, Technologiepark 927, B-9052 Ghent, Belgium [2] Department of Biomedical Molecular Biology, Ghent University, Technologiepark 927, B-9052 Ghent, Belgium.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Lefebvre
authors.affiliation: Department of Medicine 1, Friedrich-Alexander-University, D-91054 Erlangen, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Günther
authors.affiliation: Department of Medicine 1, Friedrich-Alexander-University, D-91054 Erlangen, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Becker
authors.affiliation: Pattern Recognition Receptor Discovery Performance Unit, Immuno-inflammation Therapeutic Area, GlaxoSmithKline, Collegeville, Pennsylvania 19426, USA.
authors.forename: John
authors.initials: J
authors.lastname: Bertin
authors.affiliation: Pattern Recognition Receptor Discovery Performance Unit, Immuno-inflammation Therapeutic Area, GlaxoSmithKline, Collegeville, Pennsylvania 19426, USA.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Gough
authors.affiliation: 1] VIB Inflammation Research Center, Technologiepark 927, B-9052 Ghent, Belgium [2] Department of Biomedical Molecular Biology, Ghent University, Technologiepark 927, B-9052 Ghent, Belgium.
authors.forename: Wim
authors.initials: W
authors.lastname: Declercq
authors.affiliation: 1] VIB Inflammation Research Center, Technologiepark 927, B-9052 Ghent, Belgium [2] Department of Biomedical Molecular Biology, Ghent University, Technologiepark 927, B-9052 Ghent, Belgium.
authors.forename: Geert
authors.initials: G
authors.lastname: van Loo
authors.affiliation: 1] VIB Inflammation Research Center, Technologiepark 927, B-9052 Ghent, Belgium [2] Department of Biomedical Molecular Biology, Ghent University, Technologiepark 927, B-9052 Ghent, Belgium [3] Methusalem program, Ghent University, Technologiepark 927, B-9052 Ghent, Belgium.
authors.forename: Peter
authors.initials: P
authors.lastname: Vandenabeele
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D053181:Caspase 8 / Q000235:genetics / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D004847:Epithelial Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D005260:Female; D017353:Gene Deletion; D006706:Homeostasis / Q000187:drug effects; D007249:Inflammation / Q000378:metabolism / Q000473:pathology; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000166:cytology* / Q000187:drug effects / Q000473:pathology; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D053594:Myeloid Differentiation Factor 88 / Q000172:deficiency; D016328:NF-kappa B / Q000378:metabolism; D009336:Necrosis; D009940:Organoids / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D053422:Receptor-Interacting Protein Serine-Threonine Kinases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000172:deficiency; D016019:Survival Analysis; D048069:Tumor Necrosis Factors / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; C507780:Myd88 protein, mouse; D053594:Myeloid Differentiation Factor 88; D016328:NF-kappa B; D047888:Receptors, Tumor Necrosis Factor, Type I; C506236:Tnfrsf1a protein, mouse; D048069:Tumor Necrosis Factors; C570694:MLKL protein, mouse; D011494:Protein Kinases; D053422:Receptor-Interacting Protein Serine-Threonine Kinases; C506251:Ripk1 protein, mouse; C485615:Ripk3 protein, mouse; C505526:Casp8 protein, mouse; D053181:Caspase 8