Phorbol esters and norepinephrine destabilize alpha 1B-adrenergic receptor mRNA in vascular smooth muscle cells.
The mechanism by which norepinephrine (NE) down-regulates alpha 1B-adrenergic receptor (alpha-AR) mRNA was studied in rabbit aortic smooth muscle cells. NE, phorbol esters, and bradykinin each decreased alpha-AR mRNA levels by 70-80%. The protein kinase C inhibitor (+)-1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (H-7) abolished the effects of phorbol esters and NE and decreased basal mRNA levels by 52 +/- 3%. Neither ryanodine nor EGTA inhibited down-regulation of alpha-AR mRNA by NE. Actinomycin D caused alpha-AR mRNA level to decrease with a half-life of 3.2 +/- 0.4 h and blocked the effect of H-7 to decrease basal alpha-AR mRNA level. Both NE and phorbol esters increased the rate of alpha-AR mRNA degradation. In NE-desensitized cells, phorbol esters and bradykinin each caused the expected down-regulation of alpha-AR mRNA. The protein phosphatase inhibitor okadaic acid prolonged the normally transient effect of NE for at least 24 h. We conclude that protein kinase C exerts two opposing effects on alpha-AR mRNA levels, 1) a decrease in the stability of the mRNA that requires the sustained phosphorylation of a protein kinase C substrate and 2) a permissive effect on alpha-AR gene transcription.
Izzo
N J
NJ
Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts 02115.
Tulenko
T N
TN
Colucci
W S
WS
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000378:metabolism; D001920:Bradykinin / Q000494:pharmacology; D002478:Cells, Cultured; D004075:Diglycerides / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects; D004988:Ethers, Cyclic / Q000494:pharmacology; D007295:Inositol Phosphates / Q000378:metabolism; D007546:Isoquinolines / Q000494:pharmacology; D007700:Kinetics; D008954:Models, Biological; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology*; D019319:Okadaic Acid; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology*; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors; D010879:Piperazines / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism*; D011817:Rabbits; D018340:Receptors, Adrenergic, alpha-1 / Q000096:biosynthesis*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
D004075:Diglycerides; D004988:Ethers, Cyclic; D007295:Inositol Phosphates; D007546:Isoquinolines; D010879:Piperazines; D012333:RNA, Messenger; D018340:Receptors, Adrenergic, alpha-1; D019319:Okadaic Acid; D015240:Phorbol 12,13-Dibutyrate; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D011493:Protein Kinase C; D010749:Phosphoprotein Phosphatases; D013755:Tetradecanoylphorbol Acetate; D001920:Bradykinin; D009638:Norepinephrine