title: Transcriptional regulation of steroid receptor coactivator-1 (SRC-1) in glucocorticoid action.
abstract: Diverse mechanisms of steroid receptor action have been clarified in recent years, as a consequence of the discovery of multiple coactivators. Among them, steroid receptor coactivator-1 (SRC-1) is a member of the p160 coactivator families, which are 160 kDa proteins that interact with steroid receptors in a hormone-sensitive manner. Since coactivators function as transcriptional power boosters, subtle changes in coactivator expression levels in certain cells markedly change of receptor-mediated transcriptional activity. Expression of the glucocorticoid receptor (GR) has been shown to be autoregulated in glucocorticoid action, i.e., GR is downregulated by its cognate ligand, indicating that this autoregulation of GR may protect target cells against excessive hormone action. In the present study, we examined whether coactivator expression levels are also regulated by glucocorticoids. Among several coactivators, the SRC-1 mRNA level was downregulated by dexamethasone treatment in rat tissues, such as liver, heart, kidney, stomach, and cerebrum, in vivo. We also demonstrated dexamethasone-mediated downregulation of SRC-1 mRNA and its protein levels in rat renal mesangial cells in vitro. These results suggest that ligand-mediated downregulation of SRC-1 is crucial in the physiology of glucocorticoid action.
authors.affiliation: Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan.
authors.forename: I
authors.initials: I
authors.lastname: Kurihara
authors.forename: H
authors.initials: H
authors.lastname: Shibata
authors.forename: T
authors.initials: T
authors.lastname: Suzuki
authors.forename: T
authors.initials: T
authors.lastname: Ando
authors.forename: S
authors.initials: S
authors.lastname: Kobayashi
authors.forename: M
authors.initials: M
authors.lastname: Hayashi
authors.forename: I
authors.initials: I
authors.lastname: Saito
authors.forename: T
authors.initials: T
authors.lastname: Saruta
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D003907:Dexamethasone / Q000494:pharmacology*; D015536:Down-Regulation; D005920:Glomerular Mesangium / Q000166:cytology / Q000378:metabolism; D005938:Glucocorticoids / Q000494:pharmacology*; D051548:Histone Acetyltransferases; D008297:Male; D056920:Nuclear Receptor Coactivator 1; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic / Q000502:physiology*
chemical_list: D005938:Glucocorticoids; D012333:RNA, Messenger; D014157:Transcription Factors; D003907:Dexamethasone; D051548:Histone Acetyltransferases; D056920:Nuclear Receptor Coactivator 1