title: Facilitation of mitochondrial outer and inner membrane permeabilization and cell death in oxidative stress by a novel Bcl-2 homology 3 domain protein.
abstract: We identified a sequence homologous to the Bcl-2 homology 3 (BH3) domain of Bcl-2 proteins in SOUL. Tissues expressed the protein to different extents. It was predominantly located in the cytoplasm, although a fraction of SOUL was associated with the mitochondria that increased upon oxidative stress. Recombinant SOUL protein facilitated mitochondrial permeability transition and collapse of mitochondrial membrane potential (MMP) and facilitated the release of proapoptotic mitochondrial intermembrane proteins (PMIP) at low calcium and phosphate concentrations in a cyclosporine A-dependent manner in vitro in isolated mitochondria. Suppression of endogenous SOUL by diced small interfering RNA in HeLa cells increased their viability in oxidative stress. Overexpression of SOUL in NIH3T3 cells promoted hydrogen peroxide-induced cell death and stimulated the release of PMIP but did not enhance caspase-3 activation. Despite the release of PMIP, SOUL facilitated predominantly necrotic cell death, as revealed by annexin V and propidium iodide staining. This necrotic death could be the result of SOUL-facilitated collapse of MMP demonstrated by JC-1 fluorescence. Deletion of the putative BH3 domain sequence prevented all of these effects of SOUL. Suppression of cyclophilin D prevented these effects too, indicating that SOUL facilitated mitochondrial permeability transition in vivo. Overexpression of Bcl-2 and Bcl-x(L), which can counteract the mitochondria-permeabilizing effect of BH3 domain proteins, also prevented SOUL-facilitated collapse of MMP and cell death. These data indicate that SOUL can be a novel member of the BH3 domain-only proteins that cannot induce cell death alone but can facilitate both outer and inner mitochondrial membrane permeabilization and predominantly necrotic cell death in oxidative stress.
authors.affiliation: Institute of Oncotherapy, University of Pécs, 12 Szigeti Street, Pécs H-7624, Hungary.
authors.forename: Andras
authors.initials: A
authors.lastname: Szigeti
authors.forename: Eniko
authors.initials: E
authors.lastname: Hocsak
authors.forename: Edit
authors.initials: E
authors.lastname: Rapolti
authors.forename: Boglarka
authors.initials: B
authors.lastname: Racz
authors.forename: Arpad
authors.initials: A
authors.lastname: Boronkai
authors.forename: Eva
authors.initials: E
authors.lastname: Pozsgai
authors.forename: Balazs
authors.initials: B
authors.lastname: Debreceni
authors.forename: Zita
authors.initials: Z
authors.lastname: Bognar
authors.forename: Szabolcs
authors.initials: S
authors.lastname: Bellyei
authors.forename: Balazs
authors.initials: B
authors.lastname: Sumegi
authors.forename: Ferenc
authors.initials: F
authors.lastname: Gallyas
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D002417:Cattle; D002463:Cell Membrane Permeability / Q000187:drug effects; D002470:Cell Survival; D000081406:Peptidyl-Prolyl Isomerase F; D021983:Cyclophilins / Q000494:pharmacology; D005786:Gene Expression Regulation; D006367:HeLa Cells; D000081062:Heme-Binding Proteins; D006420:Hemeproteins / Q000737:chemistry* / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D051379:Mice; D051336:Mitochondrial Membranes / Q000187:drug effects / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D041681:NIH 3T3 Cells; D018384:Oxidative Stress / Q000187:drug effects; D011257:Pregnancy Proteins / Q000737:chemistry* / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000737:chemistry*; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid
chemical_list: D000081406:Peptidyl-Prolyl Isomerase F; C516258:HEBP2 protein, human; D000081062:Heme-Binding Proteins; D006420:Hemeproteins; D024101:Mitochondrial Proteins; C000631446:PPIF protein, mouse; D011257:Pregnancy Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; D006861:Hydrogen Peroxide; D021983:Cyclophilins