Protein kinase C‐mediated down‐regulation of β2‐adrenergic receptor and gene expression in rat C6 glioma cells

• Published in: Journal of neurochemistry 2001-05, Vol.77 (3), p.823-829
• Main Authors: Leavitt, Maria, Setola, Vincent, Fishman, Peter H.
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Cell receptors; Cell structures and functions; down‐regulation; Fundamental and applied biological sciences. Psychology; gene transcription; Molecular and cellular biology; Monoamines receptors (catecholamine, serotonine, histamine, acetylcholine); mRNA; protein kinase C; β2‐adrenergic receptor
• ISSN: 0022-3042; 1471-4159
• DOI: 10.1046/j.1471-4159.2001.00279.x

We investigated the regulation of β2‐adrenergic receptors (β2AR) by protein kinase C (PKC) in rat C6 glioma cells at the levels of receptor activity, protein expression and gene expression. Cells exposed to 4β‐phorbol‐12‐myristate‐13‐acetate (PMA), a potent activator of PKC, exhibited a time‐ and concentration‐dependent decrease in β2AR binding activity. Maximum down‐regulation was ∼50% by 24 h and western blot analysis revealed a parallel decrease in β2AR protein. In addition, PMA treatment resulted in an acute desensitization of β2AR‐stimulated cyclic AMP response prior to any reduction in receptor levels. PMA exposure also affected steady‐state β2AR mRNA levels in a time‐dependent, biphasic manner. During the first 4 h, levels decreased by ∼60% and then slowly recovered to ∼75% of control by 24 h. As the reduction in receptor mRNA was not due to a decrease in its stability, we examined β2AR gene transcription by nuclear run‐on assays. Transcriptional activity in nuclei from C6 cells treated with PMA for 2 h was reduced by 70% compared to controls. Thus PKC can regulate β2AR at least two levels: the first being an acute desensitization of receptor function, and the second being a more prolonged repression of receptor gene transcription that in turn results in decreased receptor expression.