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

Abstract

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.

• Authors: Rehana Parvin, Akiko Saito-Hakoda, Hiroki Shimada, Kyoko Shimizu, Erika Noro, Yasumasa Iwasaki, Ken Fujiwara, Atsushi Yokoyama, Akira Sugawara
• Journal: PloS one (PLoS One) Vol. 12 Issue 4 Pg. e0175435 ( 2017) ISSN: 1932-6203 [Electronic] United States
• PMID: 28406939 (Publication Type: Journal Article)

Chemical References

• Basic Helix-Loop-Helix Transcription Factors
• Glucocorticoids
• Neoplasm Proteins
• Neurod1 protein, mouse
• RNA, Messenger
• RNA, Neoplasm
• Pro-Opiomelanocortin
• Dexamethasone

Topics

• ACTH-Secreting Pituitary Adenoma (genetics, metabolism, pathology)
• Adenoma (metabolism, pathology)
• Animals
• Basic Helix-Loop-Helix Transcription Factors (biosynthesis, genetics)
• Cell Line, Tumor
• Dexamethasone (pharmacology)
• Dose-Response Relationship, Drug
• Gene Expression Regulation, Neoplastic (drug effects)
• Glucocorticoids (pharmacology)
• Mice
• Neoplasm Proteins (biosynthesis)
• Pro-Opiomelanocortin (genetics)
• Promoter Regions, Genetic
• RNA, Messenger (biosynthesis, genetics)
• RNA, Neoplasm (biosynthesis, genetics)
• Rats