Agonist-induced destabilization of beta-adrenergic receptor mRNA. Attenuation of glucocorticoid-induced up-regulation of beta-adrenergic receptors.
beta-Adrenergic receptor expression and receptor mRNA levels are down-regulated by beta-adrenergic agonists and up-regulated by glucocorticoids. The interaction between these two opposing regulatory pathways was investigated at the levels of receptor and receptor mRNA in DDT1 MF-2 hamster vas deferens cells. Dexamethasone blunted a marked decrease in receptor expression induced by isoproterenol alone, as made visible by indirect immunofluorescence using antireceptor antibodies. Receptor mRNA levels were quantified by DNA-excess solution hybridization. Dexamethasone stimulated a sharp increase in receptor mRNA at 4 h following the addition of steroid in either the absence or the presence of isoproterenol. By 12 h, dexamethasone treatment resulted in a new steady-state level of receptor mRNA double that observed in untreated cells. Isoproterenol blunted the dexamethasone effect observed at 12 h. Cells treated with isoproterenol and dexamethasone in combination displayed a new steady-state level only 30% greater than untreated cells. Measured by nuclear run-on assays, transcription rates of the receptor gene were unaffected in cells challenged with isoproterenol alone. Dexamethasone, in contrast, stimulated a 4-fold increase in beta 2-adrenergic receptor gene transcription. Isoproterenol and dexamethasone in combination promoted a transcription rate comparable to dexamethasone alone. The half-life of receptor mRNA in untreated and dexamethasone-treated cells was 12 h. In contrast, beta-adrenergic receptor mRNA half-life declined to 5 h in cells that were treated with isoproterenol in the presence or absence of dexamethasone. Agonist-promoted destabilization and steroid-induced transcription provide mechanisms for the interplay of two opposing pathways controlling receptor mRNA levels.
Hadcock
J R
JR
Department of Pharmacological Sciences, School of Medicine, New York, Stony Brook 11794-8651.
Wang
H Y
HY
Malbon
C C
CC
D000818:Animals; D002460:Cell Line; D006224:Cricetinae; D003907:Dexamethasone / Q000494:pharmacology*; D005455:Fluorescent Antibody Technique; D015870:Gene Expression / Q000187:drug effects; D005796:Genes / Q000187:drug effects; D007545:Isoproterenol / Q000494:pharmacology*; D007700:Kinetics; D009693:Nucleic Acid Hybridization; D012333:RNA, Messenger / Q000187:drug effects* / Q000235:genetics; D011943:Receptors, Adrenergic, beta / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects
D012333:RNA, Messenger; D011943:Receptors, Adrenergic, beta; D003907:Dexamethasone; D007545:Isoproterenol