title: Bax inhibitor-1 regulates endoplasmic reticulum stress-associated reactive oxygen species and heme oxygenase-1 expression.
abstract: The Bax inhibitor-1 (BI-1) is an anti-apoptotic protein that is located in endoplasmic reticulum (ER) membranes and protects cells from ER stress-induced apoptosis. The ER is associated with generation of reactive oxygen species (ROS) through oxidative protein folding. This study examined the role of BI-1 in the regulation of ER stress-induced accumulation of ROS and expression of unfolded protein response-associated proteins. BI-1 reduced the expression levels of glucose response protein 78, C/EBP homologous protein, phospho-eukaryotic initiation factor 2alpha, IRE1alpha, XBP-1, and phospho-JNK and inhibited the cleavage of ATF-6alpha p-90, leading to the inhibition of ROS. Although ROS scavengers offer some protection against ER stress-induced apoptosis, the expression of pro-apoptotic ER stress proteins was not affected. This study shows that the response of unfolded proteins is followed by ROS accumulation under ER stress, which is regulated in BI-1 cells. The mechanism for these BI-1-associated functions involves the expression of heme oxygenase-1 (HO-1) through nuclear factor erythroid 2-related factor 2. In BI-1 cells, the transfection of HO-1 small interfering RNA completely abolished the BI-1-induced protection. The endogenous expression of HO-1 through ER stress-initiated ROS is believed to be as a protection signal. In conclusion, these observations suggest that BI-1 can inhibit the ER stress proteins as well as the accumulation of ROS, thereby protecting the cells. Moreover, HO-1 plays an important role in the BI-1-associated protection against ER stress.
authors.affiliation: Department of Pharmacology and Institute of Cardiovascular Research, School of Medicine, Chonbuk National University, Jeonju, Chonbuk, South Korea.
authors.forename: Geum-Hwa
authors.initials: GH
authors.lastname: Lee
authors.forename: Hyun-Kyung
authors.initials: HK
authors.lastname: Kim
authors.forename: Soo-Wan
authors.initials: SW
authors.lastname: Chae
authors.forename: Do-Sung
authors.initials: DS
authors.lastname: Kim
authors.forename: Ki-Chan
authors.initials: KC
authors.lastname: Ha
authors.forename: Mike
authors.initials: M
authors.lastname: Cuddy
authors.forename: Christina
authors.initials: C
authors.lastname: Kress
authors.forename: John C
authors.initials: JC
authors.lastname: Reed
authors.forename: Hyung-Ryong
authors.initials: HR
authors.lastname: Kim
authors.forename: Han-Jung
authors.initials: HJ
authors.lastname: Chae
mesh_terms: D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000502:physiology*; D002232:Carbocyanines / Q000494:pharmacology; D045744:Cell Line, Tumor; D053938:DNA Fragmentation; D004721:Endoplasmic Reticulum / Q000502:physiology*; D005354:Fibrosarcoma; D051547:Heme Oxygenase-1 / Q000378:metabolism*; D006801:Humans; D008565:Membrane Proteins / Q000502:physiology*; D051267:NF-E2-Related Factor 2 / Q000235:genetics; D011401:Promoter Regions, Genetic; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013314:Stress, Mechanical
chemical_list: D051017:Apoptosis Regulatory Proteins; D002232:Carbocyanines; D008565:Membrane Proteins; D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; D017382:Reactive Oxygen Species; C484209:TMBIM6 protein, human; C007392:3,3'-dihexyl-2,2'-oxacarbocyanine; D051547:Heme Oxygenase-1