title: A murder mystery in the liver: who done it and how?
abstract: Hepatocyte death, which can be apoptosis or necrosis depending on the context, is a prominent feature of liver disease. The lectin concanavalin A (ConA) activates immune cells, resulting in inflammatory liver injury and hepatocyte necrosis. In this issue of the JCI, Günther et al. demonstrate that the pseudokinase mixed lineage kinase domain-like protein (MLKL) participates in hepatocyte death in ConA injury and that MLKL-mediated death is independent of the receptor-interacting protein kinase RIPK3. RIPK3 was absent in hepatocytes, and MLKL-deficient mice, but not RIPK3-deficient mice, were protected from ConA-induced liver injury. The authors also present evidence that an unidentified kinase activates MLKL, as RIPK1 bound MLKL but did not phosphorylate it. Moreover, ConA rapidly induced MLKL, mediated by the IFN-γ/STAT1 pathway, while activation and translocation to the plasma membrane required TNF. Increased phospho-MLKL staining in liver biopsies from patients with autoimmune hepatitis suggests a role for MLKL in this disease. This study describes a previously unrecognized form of cell death in the liver that should be further explored as a potential therapeutic target in immune-mediated liver injury.
authors.forename: Lily
authors.initials: L
authors.lastname: Dara
authors.forename: Zhang-Xu
authors.initials: ZX
authors.lastname: Liu
authors.forename: Neil
authors.initials: N
authors.lastname: Kaplowitz
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics / Q000276:immunology*; D056486:Chemical and Drug Induced Liver Injury / Q000235:genetics / Q000276:immunology* / Q000473:pathology; D003208:Concanavalin A / Q000633:toxicity; D019693:Hepatitis, Autoimmune / Q000235:genetics / Q000276:immunology* / Q000473:pathology; D022781:Hepatocytes / Q000276:immunology* / Q000473:pathology; D006801:Humans; D007371:Interferon-gamma / Q000235:genetics / Q000276:immunology; D008099:Liver / Q000276:immunology* / Q000473:pathology; D051379:Mice; D008817:Mice, Mutant Strains; D009336:Necrosis; D011494:Protein Kinases / Q000235:genetics / Q000276:immunology; D053422:Receptor-Interacting Protein Serine-Threonine Kinases / Q000235:genetics / Q000276:immunology; D050794:STAT1 Transcription Factor / Q000235:genetics / Q000276:immunology
chemical_list: C573415:IFNG protein, human; C000611649:IFNG protein, mouse; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; C494080:Stat1 protein, mouse; D003208:Concanavalin A; D007371:Interferon-gamma; C570693:MLKL protein, human; C570694:MLKL protein, mouse; D011494:Protein Kinases; C506249:RIPK1 protein, human; D053422:Receptor-Interacting Protein Serine-Threonine Kinases; C506251:Ripk1 protein, mouse