title: BAX/BAK-independent mitoptosis during cell death induced by proteasome inhibition?
abstract: Proteasome inhibitors induce rapid death of cancer cells. We show that in epithelial cancer cells, such death is associated with dramatic and simultaneous up-regulation of several BH3-only proteins, including BIK, BIM, MCL-1S, NOXA, and PUMA, as well as p53. Elevated levels of these proteins seem to be the result of direct inhibition of their proteasomal degradation, induction of transcription, and active translation. Subsequent cell death is independent of BAX, and probably BAK, and proceeds through the intrinsic mitochondrial apoptosis pathway. We identify the cascade of molecular events responsible for cell death induced by a prototypical proteasome inhibitor, MG132, starting with rapid accumulation of BH3-only proteins in the mitochondria, proceeding through mitochondrial membrane permeabilization and subsequent loss of DeltaPsi(m), and leading to irreversible changes of mitochondrial ultrastructure, degradation of mitochondrial network, and detrimental impairment of crucial mitochondrial functions. Our results also establish a rationale for the broader use of proteasome inhibitors to kill apoptosis-resistant tumor cells that lack functional BAX/BAK proteins.
authors: Institute for Molecular Virology, Saint Louis University School of Medicine, St. Louis, Missouri, USA.
authors: Elena
authors: E
authors: Lomonosova
authors: Jan
authors: J
authors: Ryerse
authors: G
authors: G
authors: Chinnadurai
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D045325:HCT116 Cells; D006801:Humans; D007976:Leupeptins / Q000494:pharmacology*; D051379:Mice; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism* / Q000648:ultrastructure; D051336:Mitochondrial Membranes / Q000187:drug effects / Q000648:ultrastructure; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D010539:Permeability / Q000187:drug effects; D061988:Proteasome Inhibitors; D014176:Protein Biosynthesis / Q000187:drug effects; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: D007976:Leupeptins; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D061988:Proteasome Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; D016159:Tumor Suppressor Protein p53; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde