Facilitation of mitochondrial outer and inner membrane permeabilization and cell death in oxidative stress by a novel Bcl-2 homology 3 domain protein

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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,SOULfacilitated 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 cyclophilinD prevented these effects too, indicating that SOUL facilitated mitochondrial permeability transition in vivo. Overexpression of Bcl-2 and Bcl-xL, which can counteract the mitochondriapermeabilizing 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.

Original languageEnglish
Pages (from-to)2140-2151
Number of pages12
JournalJournal of Biological Chemistry
Volume285
Issue number3
DOIs
Publication statusPublished - Jan 15 2010

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ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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