title: The Orphan Nuclear Receptor NR4A1 Protects Pancreatic β-Cells from Endoplasmic Reticulum (ER) Stress-mediated Apoptosis.
abstract: The role of NR4A1 in apoptosis is controversial. Pancreatic β-cells often face endoplasmic reticulum (ER) stress under adverse conditions such as high free fatty acid (FFA) concentrations and sustained hyperglycemia. Severe ER stress results in β-cell apoptosis. The aim of this study was to analyze the role of NR4A1 in ER stress-mediated β-cell apoptosis and to characterize the related mechanisms. We confirmed that upon treatment with the ER stress inducers thapsigargin (TG) or palmitic acid (PA), the mRNA and protein levels of NR4A1 rapidly increased in both MIN6 cells and mouse islets. NR4A1 overexpression in MIN6 cells conferred resistance to cell loss induced by TG or PA, as assessed by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, and TUNEL assays indicated that NR4A1 overexpression also protected against ER stress-induced apoptosis. This conclusion was further confirmed by experiments exploiting siRNA to knockdown NR4A1 expression in MIN6 cells or exploiting NR4A1 knock-out mice. NR4A1 overexpression in MIN6 cells reduced C/EBP homologous protein (CHOP) expression and Caspase3 activation induced by TG or PA. NR4A1 overexpression in MIN6 cells or mouse islets resulted in Survivin up-regulation. A critical regulatory element was identified in Survivin promoter (-1872 bp to -1866 bp) with a putative NR4A1 binding site; ChIP assays demonstrated that NR4A1 physically associates with the Survivin promoter. In conclusion, NR4A1 protects pancreatic β-cells against ER stress-mediated apoptosis by up-regulating Survivin expression and down-regulating CHOP expression, which we termed as "positive and negative regulation."
authors.affiliation: The Department of Cell Biology, Shandong University School of Medicine, Jinan, China, 250012.
authors.forename: Cong
authors.initials: C
authors.lastname: Yu
authors.affiliation: The Department of Cell Biology, Shandong University School of Medicine, Jinan, China, 250012.
authors.forename: Shang
authors.initials: S
authors.lastname: Cui
authors.affiliation: The Department of Cell Biology, Shandong University School of Medicine, Jinan, China, 250012.
authors.forename: Chen
authors.initials: C
authors.lastname: Zong
authors.affiliation: The Department of Cell Biology, Shandong University School of Medicine, Jinan, China, 250012.
authors.forename: Weina
authors.initials: W
authors.lastname: Gao
authors.affiliation: The Department of Cell Biology, Shandong University School of Medicine, Jinan, China, 250012.
authors.forename: Tongfu
authors.initials: T
authors.lastname: Xu
authors.affiliation: The Department of Cell Biology, Shandong University School of Medicine, Jinan, China, 250012.
authors.forename: Peng
authors.initials: P
authors.lastname: Gao
authors.affiliation: The Department of Cell Biology, Shandong University School of Medicine, Jinan, China, 250012.
authors.forename: Jicui
authors.initials: J
authors.lastname: Chen
authors.affiliation: The Department of Cell Biology, Shandong University School of Medicine, Jinan, China, 250012.
authors.forename: Dandan
authors.initials: D
authors.lastname: Qin
authors.affiliation: The Department of Endocrinology, Provincial Hospital affiliated to Shandong University, Jinan, China, 250021.
authors.forename: Qingbo
authors.initials: Q
authors.lastname: Guan
authors.affiliation: Department of Endocrinology, Qingdao Municipal Hospital, Qingdao, China, 266071.
authors.forename: Yuantao
authors.initials: Y
authors.lastname: Liu
authors.affiliation: The Department of Nutrition Sciences, University of Alabama at Birmingham, Alabama 35294.
authors.forename: Yuchang
authors.initials: Y
authors.lastname: Fu
authors.affiliation: The Department of Cell Biology, Shandong University School of Medicine, Jinan, China, 250012. Electronic address: lixia1666@sdu.edu.cn.
authors.forename: Xia
authors.initials: X
authors.lastname: Li
authors.affiliation: The Department of Cell Biology, Shandong University School of Medicine, Jinan, China, 250012; Key Laboratory of Protein Sciences for Chronic Degenerative Diseases in Universities of Shandong (Shandong University), Jinan, China 250012. Electronic address: xdongw@sdu.edu.cn.
authors.forename: Xiangdong
authors.initials: X
authors.lastname: Wang
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics*; D001483:Base Sequence; D001665:Binding Sites; D053148:Caspase 3 / Q000235:genetics / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects / Q000235:genetics*; D005786:Gene Expression Regulation; D051034:Inhibitor of Apoptosis Proteins / Q000235:genetics* / Q000378:metabolism; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1 / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D019308:Palmitic Acid / Q000494:pharmacology; D061251:Primary Cell Culture; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012333:RNA, Messenger / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D000077022:Survivin; D019284:Thapsigargin / Q000494:pharmacology; D051742:Transcription Factor CHOP / Q000235:genetics* / Q000378:metabolism
chemical_list: C117749:Birc5 protein, mouse; C497250:Ddit3 protein, mouse; D051034:Inhibitor of Apoptosis Proteins; C539818:Nr4a1 protein, mouse; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D012097:Repressor Proteins; D000077022:Survivin; D051742:Transcription Factor CHOP; D019308:Palmitic Acid; D019284:Thapsigargin; C505409:Casp3 protein, mouse; D053148:Caspase 3
keywords: NR4A1; apoptosis; beta cell (B-cell); endoplasmic reticulum stress (ER stress); pancreatic islet; survivin