title: Bz-423 superoxide signals B cell apoptosis via Mcl-1, Bak, and Bax.
abstract: Bz-423 is a pro-apoptotic 1,4-benzodiazepine with therapeutic properties in murine models of lupus demonstrating selectivity for autoreactive lymphocytes. Bz-423 modulates the F(1)F(0)-ATPase, inducing the formation of superoxide within the mitochondrial respiratory chain, which then functions as a second messenger initiating apoptosis. In order to understand some of the features that contribute to the increased sensitivity of lymphocytes, we report the signaling pathway engaged by Bz-423 in a Burkitt lymphoma cell line (Ramos). Following the generation of superoxide, Bz-423-induced apoptosis requires the activation of Bax and Bak to induce mitochondrial outer membrane permeabilization and cytochrome c release. Knockdown of the BH3-only proteins Bad, Bim, Bik, and Puma inhibits Bz-423 apoptosis, suggesting that these proteins serve as upstream sensors of the oxidant stress induced by Bz-423. Treatment with Bz-423 results in superoxide-dependent Mcl-1 degradation, implicating this protein as the link between Bz-423-induced superoxide and Bax and Bak activation. In contrast to fibroblasts, B cell death induced by Bz-423 is independent of c-Jun N-terminal kinase. These results demonstrate that superoxide generated from the mitochondrial respiratory chain as a consequence of a respiratory transition can signal a specific apoptotic response that differs across cell types.
authors.affiliation: Department of Pediatrics and Communicable Diseases, University of Michigan, F6865 Mott SPC 5297, 1500 E. Medical Center Drive, Ann Arbor, MI 48109-5297, United States. nblatt@umich.edu
authors.forename: Neal B
authors.initials: NB
authors.lastname: Blatt
authors.forename: Anthony E
authors.initials: AE
authors.lastname: Boitano
authors.forename: Costas A
authors.initials: CA
authors.lastname: Lyssiotis
authors.forename: Anthony W
authors.initials: AW
authors.lastname: Opipari
authors.forename: Gary D
authors.initials: GD
authors.lastname: Glick
mesh_terms: D017209:Apoptosis / Q000502:physiology*; D001360:Avidin / Q000378:metabolism; D001402:B-Lymphocytes / Q000378:metabolism; D001569:Benzodiazepines / Q000494:pharmacology*; D019921:Biotinylation; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004396:Coloring Agents / Q000378:metabolism; D018274:Electroporation; D005452:Fluoresceins / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D011419:Propidium / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013481:Superoxides / Q000378:metabolism; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000378:metabolism*; D051028:bcl-2-Associated X Protein / Q000378:metabolism*
chemical_list: C494826:BAX protein, human; D004396:Coloring Agents; D005452:Fluoresceins; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; D013481:Superoxides; D001569:Benzodiazepines; D001360:Avidin; D011419:Propidium; C468549:Bz-423