Regulation of human β₁-adrenergic receptors and their mRNA in neuroepithelioma SK-N-MC cells: effects of agonist, forskolin, and protein kinase A

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• 作者：Bahouth ; Suleiman W. ; Sowinski ; Kevin M. ; Lima ; John J.
• 关键词：β ; ₁-Adrenergic receptors ; β ; ₁-Adrenergic receptor mRNA ; Protein kinase A ; Isoproterenol ; Ribonuclease protection assay ; SK-N-MC cells
• 刊名：Biochemical Pharmacology
• 出版年：2001
• 出版时间：November 1, 2001
• 年：2001
• 卷：62
• 期：9
• 页码：1211-1220
• 全文大小：166 K

文摘

We determined the effect of long-term exposure to β-agonists on β₁-adrenergic receptors (β₁-AR) in human neuroepithelioma SK-N-MC cells because earlier studies have indicated that β₁-AR in this cell line are resistant to agonist-induced down-regulation. Exposing SK-N-MC cells to isoproterenol for 24 hr reduced the density of β₁-AR by 72 % , whereas forskolin, an activator of all the isoforms of adenylyl cyclase, failed to affect the density of β₁-AR. Measurement of β₁-AR mRNA levels by the ribonuclease protection assay revealed that isoproterenol-induced down-regulation of β₁-AR was associated with a sharp decline in β₁-AR mRNA, while forskolin also failed to affect this parameter. The differences between the effects of isoproterenol and forskolin on β₁-AR were unrelated to cyclic AMP levels, since both agents increased cyclic AMP equally. Next, we determined the role of cyclic AMP-dependent protein kinase A (PKA) in this phenomenon. Inhibition of PKA by its specific inhibitor, H-89 {N-[2-((p-bromocinnamyl)amino)ethyl]-5-isoquinolinesulfonamide, 2HCl}, markedly reduced the magnitude of the isoproterenol-mediated down-regulation of the β₁-AR and its mRNA. Transient expression of the catalytic subunit of PKA in SK-N-MC cells down-regulated β₁-AR independently of isoproterenol. Therefore, PKA is central to the effect of β-agonists in down-regulating β₁-AR, and its spacial compartmentalization and access to the receptor appear to be essential components of its action.