Christiane Koppe1, Patricia Verheugd2, Jérémie Gautheron1, Florian Reisinger3, Karina Kreggenwinkel1, Christoph Roderburg1, Luca Quagliata4, Luigi Terracciano4, Nikolaus Gassler5, René H Tolba6, Yannick Boege7, Achim Weber7, Michael Karin8, Mark Luedde9, Ulf P Neumann10, Ralf Weiskirchen11, Frank Tacke1, Mihael Vucur1, Christian Trautwein1, Bernhard Lüscher2, Christian Preisinger12, Mathias Heikenwalder3,13, Tom Luedde14. 1. Department of Medicine III, Division of Gastroenterology, Hepatology and Hepatobiliary Oncology, University Hospital RWTH Aachen, Aachen, Germany. 2. Institute of Biochemistry and Molecular Biology, University Hospital RWTH Aachen University, Aachen, Germany. 3. Department of Virology, Technische Universität München/Helmholtz Zentrum München für Gesundheit und Umwelt (HMGU), Munich, Germany. 4. Institute of Pathology, University Hospital of Basel, Basel, Switzerland. 5. Institute of Pathology, Hospital of Braunschweig, Braunschweig, Germany. 6. Department of Laboratory Animal Research, University Hospital RWTH Aachen, Aachen, Germany. 7. Institute of Surgical Pathology, University Hospital Zurich, Zurich, Switzerland. 8. Department of Pharmacology and Pathology, School of Medicine, UCSD, La Jolla, CA. 9. Department of Cardiology and Angiology, University Hospital Schleswig-Holstein, Kiel, Germany. 10. Department of Visceral and Transplantation Surgery, University Hospital RWTH Aachen, Aachen, Germany. 11. Institute of Molecular Pathobiochemistry, Experimental Gene Therapy and Clinical Chemistry, University Hospital RWTH Aachen, Aachen, Germany. 12. Proteomics Facility, Interdisciplinary Center for Clinical Research (IZKF) Aachen, University Hospital RWTH Aachen, Aachen, Germany. 13. Division of Chronic Inflammation and Cancer, German Cancer Research Center (DKFZ), Heidelberg, Germany. 14. Department of Medicine III, Division of Gastroenterology, Hepatology and Hepatobiliary Oncology, University Hospital RWTH Aachen, Aachen, Germany. tluedde@ukaachen.de.
Abstract
UNLABELLED: The IκB-Kinase (IKK) complex-consisting of the catalytic subunits, IKKα and IKKβ, as well as the regulatory subunit, NEMO-mediates activation of the nuclear factor κB (NF-κB) pathway, but previous studies suggested the existence of NF-κB-independent functions of IKK subunits with potential impact on liver physiology and disease. Programmed cell death is a crucial factor in the progression of liver diseases, and receptor-interacting kinases (RIPKs) exerts strategic control over multiple pathways involved in regulating novel programmed cell-death pathways and inflammation. We hypothesized that RIPKs might be unrecognized targets of the catalytic IKK-complex subunits, thereby regulating hepatocarcinogenesis and cholestasis. In this present study, mice with specific genetic inhibition of catalytic IKK activity in liver parenchymal cells (LPCs; IKKα/β(LPC-KO) ) were intercrossed with RIPK1(LPC-KO) or RIPK3(-/-) mice to examine whether RIPK1 or RIPK3 might be downstream targets of IKKs. Moreover, we performed in vivo phospho-proteome analyses and in vitro kinase assays, mass spectrometry, and mutagenesis experiments. These analyses revealed that IKKα and IKKβ-in addition to their known function in NF-κB activation-directly phosphorylate RIPK1 at distinct regions of the protein, thereby regulating cell viability. Loss of this IKKα/β-dependent RIPK1 phosphorylation in LPCs inhibits compensatory proliferation of hepatocytes and intrahepatic biliary cells, thus impeding HCC development, but promoting biliary cell paucity and lethal cholestasis. CONCLUSIONS: IKK-complex subunits transmit a previously unrecognized signal through RIPK1, which is fundamental for the long-term consequences of chronic hepatic inflammation and might have potential implications for future pharmacological strategies against cholestatic liver disease and cancer. (Hepatology 2016;64:1217-1231).
UNLABELLED: The IκB-Kinase (IKK) complex-consisting of the catalytic subunits, IKKα and IKKβ, as well as the regulatory subunit, NEMO-mediates activation of the nuclear factor κB (NF-κB) pathway, but previous studies suggested the existence of NF-κB-independent functions of IKK subunits with potential impact on liver physiology and disease. Programmed cell death is a crucial factor in the progression of liver diseases, and receptor-interacting kinases (RIPKs) exerts strategic control over multiple pathways involved in regulating novel programmed cell-death pathways and inflammation. We hypothesized that RIPKs might be unrecognized targets of the catalytic IKK-complex subunits, thereby regulating hepatocarcinogenesis and cholestasis. In this present study, mice with specific genetic inhibition of catalytic IKK activity in liver parenchymal cells (LPCs; IKKα/β(LPC-KO) ) were intercrossed with RIPK1(LPC-KO) or RIPK3(-/-) mice to examine whether RIPK1 or RIPK3 might be downstream targets of IKKs. Moreover, we performed in vivo phospho-proteome analyses and in vitro kinase assays, mass spectrometry, and mutagenesis experiments. These analyses revealed that IKKα and IKKβ-in addition to their known function in NF-κB activation-directly phosphorylate RIPK1 at distinct regions of the protein, thereby regulating cell viability. Loss of this IKKα/β-dependent RIPK1 phosphorylation in LPCs inhibits compensatory proliferation of hepatocytes and intrahepatic biliary cells, thus impeding HCC development, but promoting biliary cell paucity and lethal cholestasis. CONCLUSIONS: IKK-complex subunits transmit a previously unrecognized signal through RIPK1, which is fundamental for the long-term consequences of chronic hepatic inflammation and might have potential implications for future pharmacological strategies against cholestatic liver disease and cancer. (Hepatology 2016;64:1217-1231).
Authors: Nadine Gehrke; Marcus A Wörns; Amrit Mann; Nadine Hövelmeyer; Ari Waisman; Beate K Straub; Peter R Galle; Jörn M Schattenberg Journal: Cell Death Dis Date: 2022-05-31 Impact factor: 9.685