Journal Article

Role of NeuroD1 on the negative regulation of Pomc expression by glucocorticoid

Noro, Erika, Iwasaki, Yasumasa, Fujiwara, Ken, Parvin, Rehana, Shimizu, Kyoko, Shimada, Hiroki, Sugawara, Akira, Saito-Hakoda, Akiko, Yokoyama, Atsushi

2017

Overview

The mechanism of the negative regulation of proopiomelanocortin gene (Pomc) by glucocorticoids (Gcs) is still unclear in many points. Here, we demonstrated the involvement of neurogenic differentiation factor 1 (NeuroD1) in the Gc-mediated negative regulation of Pomc. Murine pituitary adrenocorticotropic hormone (ACTH) producing corticotroph tumor-derived AtT20 cells were treated with dexamethasone (DEX) (1-100 nM) and cultured for 24 hrs. Thereafter, Pomc mRNA expression was studied by quantitative real-time PCR and rat Pomc promoter (-703/+58) activity was examined by luciferase assay. Both Pomc mRNA expression and Pomc promoter activity were inhibited by DEX in a dose-dependent manner. Deletion and point mutant analyses of Pomc promoter suggested that the DEX-mediated transcriptional repression was mediated via E-box that exists at -376/-371 in the promoter. Since NeuroD1 is known to bind to and activate E-box of the Pomc promoter, we next examined the effect of DEX on NeuroD1 expression. Interestingly, DEX dose-dependently inhibited NeuroD1 mRNA expression, mouse NeuroD1 promoter (-2.2-kb) activity, and NeuroD1 protein expression in AtT20 cells. In addition, we confirmed the inhibitory effect of DEX on the interaction of NeuroD1 and E-box on Pomc promoter by chromatin immunoprecipitation (ChIP) assay. Finally, overexpression of mouse NeuroD1 could rescue the DEX-mediated inhibition of Pomc mRNA expression and Pomc promoter activity. Taken together, it is suggested that the suppression of NeuroD1 expression and the inhibition of NeuroD1/E-box interaction may play an important role in the Gc-mediated negative regulation of Pomc.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: ACTH-Secreting Pituitary Adenoma - genetics / ACTH-Secreting Pituitary Adenoma - metabolism / ACTH-Secreting Pituitary Adenoma - pathology / Adenoma - metabolism / Adenoma - pathology / Adrenocorticotropic hormone / American Type Culture Collection / Anatomy / Animals / Antibodies / Basic Helix-Loop-Helix Transcription Factors - biosynthesis / Basic Helix-Loop-Helix Transcription Factors - genetics / Beta2 protein / Binding sites / Biochemistry / Biology and life sciences / Carbon dioxide / Cascades / Cell activation / Cell culture / Cell Line, Tumor / Cells (biology) / Cytoplasm / Deoxyribonucleic acid / Dexamethasone - pharmacology / Diabetes mellitus / Differentiation / Digestive tract / Dilution / DNA / Dose-Response Relationship, Drug / Down-regulation / Endocrinology / Ethanol / Gastrointestinal tract / Gene expression / Gene Expression Regulation, Neoplastic - drug effects / Gene regulation / Gene silencing / Glucocorticoids / Glucocorticoids - pharmacology / Histology / Hormones / Immune system / Insulin / Medicine / Medicine and Health Sciences / Mice / Morphogenesis / Neoplasm Proteins - biosynthesis / Nervous system / Neural stem cells / Neurogenesis / Nuclei / Nucleotide sequence / Peptides / Physical Sciences / Pituitary (anterior) / Plasmids / Pro-opiomelanocortin / Pro-Opiomelanocortin - genetics / Promoter Regions, Genetic / Proteins / Rats / Reagents / Research and Analysis Methods / Ribonucleic acid / RNA / RNA, Messenger - biosynthesis / RNA, Messenger - genetics / RNA, Neoplasm - biosynthesis / RNA, Neoplasm - genetics / Rodents / Skin / Splicing / Tissues / Transcription factors / University graduates