title: Glucocorticoid regulation of corticotropin-releasing factor1 receptor expression in pituitary-derived AtT-20 cells.
abstract: Corticotropin-releasing factor (CRF) receptors represent one of the primary sites for negative feedback of the pituitary by adrenocortical glucocorticoid hormones; however, the molecular mechanisms involved have yet to be elucidated. The present study examines the mechanisms by which glucocorticoids regulate CRF-R1 expression in the pituitary cell line, AtT-20. Treatment of these cells with dexamethasone resulted in a concentration- and time-dependent inhibition of CRF-R1 mRNA that was significant by 1 hr and maximal after 4 hr. Levels of CRF-R1 mRNA then returned to control levels after 24 hr. Similar changes were observed when the cells were treated with corticosterone. Pro-opiomelanocortin mRNA was also decreased after dexamethasone pretreatment; however, the time course was much slower with a significant effect only detected after 6 hr. Further analysis of the mechanisms that mediate glucocorticoid regulation of CRF-R1 mRNA was conducted These studies demonstrated that glucocorticoid incubation significantly decreases the rate of CRF-R1 gene transcription, as determined by nuclear run-on analysis. In addition, the result demonstrate that glucocorticoid incubation significantly decreases CRF-R1 mRNA stability by approximately 50%. The down-regulation of CRF-R1 mRNA was dependent on de novo protein synthesis, as it was blocked by pretreatment with cycloheximide. This represents a novel mechanism for glucocorticoid negative feedback regulation of CRF-R1 expression.
authors.affiliation: Department of Psychiatry, Yale University School of Medicine, Connecticut Mental Health Center, New Haven 06508, USA.
authors.forename: P A
authors.initials: PA
authors.lastname: Iredale
authors.forename: R S
authors.initials: RS
authors.lastname: Duman
mesh_terms: D002460:Cell Line; D003907:Dexamethasone / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D010902:Pituitary Gland / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D018019:Receptors, Corticotropin-Releasing Hormone / Q000096:biosynthesis / Q000187:drug effects* / Q000235:genetics; D014158:Transcription, Genetic
chemical_list: D012333:RNA, Messenger; D018019:Receptors, Corticotropin-Releasing Hormone; D003907:Dexamethasone