Protein kinase C-mediated down-regulation of beta1-adrenergic receptor gene expression in rat C6 glioma cells

Mol Pharmacol. 1998 Jul;54(1):14-21. doi: 10.1124/mol.54.1.14.

Abstract

In the current study, we investigated the mechanism by which protein kinase C (PKC) regulates the expression of beta1-adrenergic receptor (beta1AR) mRNA in rat C6 glioma cells. Exposure of the cells to 4beta-phorbol-12-myristate-13-acetate (PMA), an activator PKC, resulted in a down-regulation of both beta1AR binding sites and mRNA levels in a time- and concentration-dependent manner. This effect was not observed with phorbol esters that do not activate PKC and was blocked by bisindolylmaleimide, a specific PKC inhibitor. Activation of PKC did not reduce the half-life of beta1AR mRNA but significantly decreased the activity of the beta1AR promoter, as determined by reporter analysis. A putative response element, with partial homology to a consensus cAMP response element, was identified by mutation analysis of the promoter at positions -343 to -336, relative to the translational start site. Mutation of this putative regulatory element, referred to as a beta1AR-PKC response element, completely blocked the PKC-mediated down-regulation of beta1AR promoter activity. Gel mobility shift analysis detected two specific bands when C6 cell extracts were incubated with a labeled DNA probe containing the beta1AR-PKC response element sequence. Formation of one of these bands was inhibited by an oligonucleotide probe containing a consensus CRE and disrupted by an antibody for cAMP response element binding protein. Based on these studies, we propose that the PKC-induced down-regulation of beta1AR gene transcription in C6 cells is mediated in part by a cAMP response element binding protein-dependent mechanism acting on a novel response element.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Carcinogens / pharmacology*
  • Cyclic AMP / metabolism
  • Down-Regulation
  • Glioma / genetics
  • Glioma / metabolism
  • Promoter Regions, Genetic / drug effects
  • Protein Kinase C / metabolism*
  • RNA, Messenger / drug effects*
  • RNA, Messenger / metabolism
  • Rats
  • Receptors, Adrenergic, beta-1 / drug effects*
  • Receptors, Adrenergic, beta-1 / genetics
  • Tetradecanoylphorbol Acetate / pharmacology*
  • Tumor Cells, Cultured / drug effects

Substances

  • Carcinogens
  • RNA, Messenger
  • Receptors, Adrenergic, beta-1
  • Cyclic AMP
  • Protein Kinase C
  • Tetradecanoylphorbol Acetate