title: TNFα-induced lysosomal membrane permeability is downstream of MOMP and triggered by caspase-mediated NDUFS1 cleavage and ROS formation.
abstract: When NF-κB activation or protein synthesis is inhibited, tumor necrosis factor alpha (TNFα) can induce apoptosis through Bax- and Bak-mediated mitochondrial outer membrane permeabilization (MOMP) leading to caspase-3 activation. Additionally, previous studies have implicated lysosomal membrane permeability (LMP) and formation of reactive oxygen species (ROS) as early steps of TNFα-induced apoptosis. However, how these two events connect to MOMP and caspase-3 activation has been largely debated. Here, we present the novel finding that LMP induced by the addition of TNFα plus cycloheximide (CHX), the release of lysosomal cathepsins and ROS formation do not occur upstream but downstream of MOMP and require the caspase-3-mediated cleavage of the p75 NDUFS1 subunit of respiratory complex I. Both a caspase non-cleavable p75 mutant and the mitochondrially localized antioxidant MitoQ prevent LMP mediated by TNFα plus CHX and partially interfere with apoptosis induction. Moreover, LMP is completely blocked in cells deficient in both Bax and Bak, Apaf-1, caspase-9 or both caspase-3 and -7. Thus, after MOMP, active caspase-3 exerts a feedback action on complex I to produce ROS. ROS then provoke LMP, cathepsin release and further caspase activation to amplify TNFα apoptosis signaling.
authors.affiliation: Institute of Molecular Medicine and Cell Research (ZBMZ), Albert Ludwigs University Freiburg, Stefan Meier Strasse 17, D-79104 Freiburg, Germany. jisen.huai@unimedizin-mainz.de
authors.forename: Jisen
authors.initials: J
authors.lastname: Huai
authors.forename: F-Nora
authors.initials: FN
authors.lastname: Vögtle
authors.forename: Lars
authors.initials: L
authors.lastname: Jöckel
authors.forename: Yunbo
authors.initials: Y
authors.lastname: Li
authors.forename: Thomas
authors.initials: T
authors.lastname: Kiefer
authors.forename: Jean-Ehrland
authors.initials: JE
authors.lastname: Ricci
authors.forename: Christoph
authors.initials: C
authors.lastname: Borner
mesh_terms: D000818:Animals; D017209:Apoptosis; D053477:Apoptotic Protease-Activating Factor 1 / Q000172:deficiency / Q000378:metabolism; D053148:Caspase 3 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D053179:Caspase 7 / Q000172:deficiency / Q000235:genetics; D053453:Caspase 9 / Q000172:deficiency / Q000378:metabolism; D002401:Cathepsin B / Q000172:deficiency / Q000235:genetics; D056668:Cathepsin L / Q000172:deficiency / Q000235:genetics; D002462:Cell Membrane / Q000378:metabolism; D002463:Cell Membrane Permeability / Q000502:physiology*; D003513:Cycloheximide / Q000494:pharmacology; D042967:Electron Transport Complex I / Q000378:metabolism*; D004789:Enzyme Activation; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008928:Mitochondria / Q000378:metabolism; D051336:Mitochondrial Membranes / Q000378:metabolism; D009245:NADH Dehydrogenase / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D009943:Organophosphorus Compounds / Q000494:pharmacology; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D017382:Reactive Oxygen Species; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D014451:Ubiquinone / Q000031:analogs & derivatives / Q000494:pharmacology; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000172:deficiency / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000172:deficiency / Q000378:metabolism
chemical_list: C506593:Apaf1 protein, mouse; D053477:Apoptotic Protease-Activating Factor 1; C494773:Bak1 protein, mouse; D009943:Organophosphorus Compounds; D011500:Protein Synthesis Inhibitors; D017382:Reactive Oxygen Species; D014409:Tumor Necrosis Factor-alpha; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; D014451:Ubiquinone; C429014:mitoquinone; D003513:Cycloheximide; D009245:NADH Dehydrogenase; D053148:Caspase 3; D053179:Caspase 7; D053453:Caspase 9; D002401:Cathepsin B; D056668:Cathepsin L; D042967:Electron Transport Complex I; C588006:NDUFS1 protein, mouse
keywords: Apoptosis; Apoptosome; Bak; Bax; Caspase; LMP; MOMP; MitoQ; ROS; TNFα