Protein kinase C-mediated down-regulation of beta(2)-adrenergic receptor and gene expression in rat C6 glioma cells.
We investigated the regulation of beta(2)-adrenergic receptors (beta(2)AR) by protein kinase C (PKC) in rat C6 glioma cells at the levels of receptor activity, protein expression and gene expression. Cells exposed to 4beta-phorbol-12-myristate-13-acetate (PMA), a potent activator of PKC, exhibited a time- and concentration-dependent decrease in beta(2)AR binding activity. Maximum down-regulation was approximately 50% by 24 h and western blot analysis revealed a parallel decrease in beta(2)AR protein. In addition, PMA treatment resulted in an acute desensitization of beta(2)AR-stimulated cyclic AMP response prior to any reduction in receptor levels. PMA exposure also affected steady-state beta(2)AR mRNA levels in a time-dependent, biphasic manner. During the first 4 h, levels decreased by approximately 60% and then slowly recovered to approximately 75% of control by 24 h. As the reduction in receptor mRNA was not due to a decrease in its stability, we examined beta(2)AR 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 beta(2)AR 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.
Leavitt
M
M
Membrane Biochemistry Section, Laboratory of Molecular and Cellular Neurobiology, National Institute of Neurological Disorders and Stroke, The National Institutes of Health, Bethesda, Maryland 20892-4440, USA.
Setola
V
V
Fishman
P H
PH
D000818:Animals; D015153:Blotting, Western; D000242:Cyclic AMP / Q000378:metabolism; D015536:Down-Regulation; D004789:Enzyme Activation / Q000187:drug effects; D015870:Gene Expression; D005910:Glioma / Q000378:metabolism*; D007700:Kinetics; D011493:Protein Kinase C / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D018343:Receptors, Adrenergic, beta-2 / Q000032:analysis / Q000235:genetics*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
D012333:RNA, Messenger; D018343:Receptors, Adrenergic, beta-2; D000242:Cyclic AMP; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate