Involvement of cAMP-response element binding protein in corticotropin-releasing factor (CRF)-induced down-regulation of CRF receptor 1 gene expression in rat anterior pituitary cells.
Corticotropin-releasing factor (CRF) is a major secretagogue of adrenocorticotopic hormone from the anterior pituitary and a key activator of the hypothalamic-pituitary-adrenal axis. We previously reported that CRF down-regulates expression of the CRF type-1 receptor (CRF-R1) mRNA in cultured rat anterior pituitary cells. The present study was conducted to clarify the signal transduction systems involved in CRF-induced down-regulation of CRF-R1 gene expression in the anterior pituitary. Northern blot analysis revealed that, under serum-free conditions, 10 nM CRF decreased CRF-R1 mRNA levels in cultured rat anterior pituitary cells as we reported previously. Treatment with 5 mM 8-Br-cAMP reduced CRF-R1 mRNA levels within 2 h. The mRNA level fell to 37+/-3% of the basal level at 2 h and remained low for 16 h after treatment. This CRF-induced reduction of CRF-R1 mRNA expression was inhibited completely by pretreatment with protein kinase A (PKA) inhibitor (1 microM H-89). Further examination revealed that after pretreatment with 10 microM of antisense oligodeoxynucleotide for cyclic AMP-response element binding protein (CREB), the CRF-induced inhibition of CRF-R1 mRNA was partially decreased to 79+/-4% of the control level 2 h after administration of CRF. These findings indicate that CRF may down-regulate CRF-R1 mRNA expression via a cAMP-PKA-mediated mechanism in rat anterior pituitary cells, and that CREB may mediate at least a portion of this inhibitory effect.
Kasagi
Y
Y
Department of Bioregulation, Nippon Medical School, Kawasaki, Japan. yokos@nms.ac.jp
Horiba
N
N
Sakai
K
K
Fukuda
Y
Y
Suda
T
T
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000324:Adrenocorticotropic Hormone / Q000032:analysis / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D003346:Corticotropin-Releasing Hormone / Q000378:metabolism*; D003470:Culture Media / Q000737:chemistry; D000242:Cyclic AMP / Q000494:pharmacology; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism* / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology; D008297:Male; D010903:Pituitary Gland, Anterior / Q000166:cytology* / Q000502:physiology; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D018019:Receptors, Corticotropin-Releasing Hormone / Q000235:genetics*; D000099052:CRF Receptor, Type 1
D003470:Culture Media; D017362:Cyclic AMP Response Element-Binding Protein; D012333:RNA, Messenger; D018019:Receptors, Corticotropin-Releasing Hormone; D015124:8-Bromo Cyclic Adenosine Monophosphate; D000099052:CRF Receptor, Type 1; D000324:Adrenocorticotropic Hormone; D003346:Corticotropin-Releasing Hormone; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases