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Protein kinase C‐mediated down‐regulation of β 2 ‐adrenergic receptor and gene expression in rat C6 glioma cells
Author(s) -
Leavitt Maria,
Setola Vincent,
Fishman Peter H.
Publication year - 2001
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.2001.00279.x
Subject(s) - protein kinase c , receptor , microbiology and biotechnology , activator (genetics) , gene expression , biology , messenger rna , protein kinase a , endocrinology , medicine , northern blot , phorbol , kinase , gene , biochemistry
We investigated the regulation of β 2 ‐adrenergic receptors (β 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 4β‐phorbol‐12‐myristate‐13‐acetate (PMA), a potent activator of PKC, exhibited a time‐ and concentration‐dependent decrease in β 2 AR binding activity. Maximum down‐regulation was ∼50% by 24 h and western blot analysis revealed a parallel decrease in β 2 AR protein. In addition, PMA treatment resulted in an acute desensitization of β 2 AR‐stimulated cyclic AMP response prior to any reduction in receptor levels. PMA exposure also affected steady‐state β 2 AR 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 β 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 β 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.