title: Elevation of NR4A3 expression and its possible role in modulating insulin expression in the pancreatic beta cell.
abstract: BACKGROUND
  NR4A3/NOR-1 is a member of the NR4A orphan nuclear receptor subfamily, which contains early response genes that sense and respond to a variety of stimuli in the cellular environment. The role of NR4A3 in insulin expression in pancreatic beta cells remains unknown.
  
  
  METHODS
  Dynamic changes in NR4A3 were examined in a pancreatic beta-cell line, MIN6, treated with thapsigargin (TG), palmitate (PA), tunicamycin (TM), and dithiothreitol (DTT), chemicals that produce cell stress and even apoptosis. We exploited virus infection techniques to induce expression of NR4A3 or three deletion mutants, and determined expression of insulin and insulin regulatory genes in MIN6 cells.
  
  
  RESULTS
  TG and PA, two endoplasmic reticulum (ER) stress inducers, were able to induce unfolded protein response (UPR) activation and elevation of NR4A3 expression in MIN6 cells, whereas TM and DTT, two other ER stress inducers, were able to induce UPR activation but not NR4A3 elevation. MIN6 cells over-expressing NR4A3 protein after adenoviral infection exhibited reduced transcription of the insulin genes Ins1 and Ins2, and reduced insulin protein secretion, which were negatively correlated with NR4A3 expression levels. Functional analysis of different deletion mutants of NR4A3 showed that deleting the activation domain AF1 or the DNA-binding domain abolished the down-regulation of insulin transcription by NR4A3 in MIN6 cells, indicating that this down-regulative role was closely related to the NR4A3 trans-activation activity. Over-expression of NR4A3 in MIN6 cells resulted in reduced mRNA transcription of the insulin positive-regulation genes, Pdx1 and NeuroD1.
  
  
  CONCLUSIONS
  Some ER stress inducers, such as TG or PA, are able to elevate NR4A3 expression in MIN6 cells, while others, such as TM or DTT, are not. Over-expression of NR4A3 in MIN6 cells results in down-regulation of insulin gene transcription and insulin secretion. NR4A3 reduces insulin gene expression by modulating the expression of Pdx1 and NeuroD1.
authors.affiliation: Department of Cell Biology, Shandong University School of Medicine, Jinan, China; School of Medical Technology and Engineering, Henan University of Science and Technology, Luoyang, China.
authors.forename: Weina
authors.initials: W
authors.lastname: Gao
authors.affiliation: Department of Nutrition Sciences, University of Alabama at Birmingham, Birmingham, Alabama, United States of America.
authors.forename: Yuchang
authors.initials: Y
authors.lastname: Fu
authors.affiliation: Department of Cell Biology, Shandong University School of Medicine, Jinan, China.
authors.forename: Cong
authors.initials: C
authors.lastname: Yu
authors.affiliation: Department of Cell Biology, Shandong University School of Medicine, Jinan, China.
authors.forename: Shunke
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of Cell Biology, Shandong University School of Medicine, Jinan, China.
authors.forename: Yuchao
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Cell Biology, Shandong University School of Medicine, Jinan, China.
authors.forename: Chen
authors.initials: C
authors.lastname: Zong
authors.affiliation: Department of Cell Biology, Shandong University School of Medicine, Jinan, China.
authors.forename: Tongfu
authors.initials: T
authors.lastname: Xu
authors.affiliation: The Institute for Nutritional Sciences, Chinese Academy of Science, Shanghai, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Cell Biology, Shandong University School of Medicine, Jinan, China.
authors.forename: Xia
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Cell Biology, Shandong University School of Medicine, Jinan, China; Key Laboratory of Protein Sciences for Chronic Degenerative Diseases in Universities of Shandong (Shandong University), Jinan, China.
authors.forename: Xiangdong
authors.initials: X
authors.lastname: Wang
mesh_terms: D000818:Animals; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D007328:Insulin / Q000235:genetics* / Q000378:metabolism; D050417:Insulin-Secreting Cells / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D010168:Palmitates / Q000494:pharmacology; D054730:Protein Interaction Domains and Motifs; D011987:Receptors, Steroid / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D011988:Receptors, Thyroid Hormone / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D019284:Thapsigargin / Q000494:pharmacology; D014158:Transcription, Genetic; D014415:Tunicamycin / Q000494:pharmacology; D056811:Unfolded Protein Response / Q000187:drug effects
chemical_list: D004268:DNA-Binding Proteins; D007328:Insulin; D009419:Nerve Tissue Proteins; C490411:Nr4a3 protein, mouse; D010168:Palmitates; D011987:Receptors, Steroid; D011988:Receptors, Thyroid Hormone; D014415:Tunicamycin; D019284:Thapsigargin