Stimulation of androgen-regulated transactivation by modulators of protein phosphorylation

Endocrinology. 1994 Oct;135(4):1359-66. doi: 10.1210/endo.135.4.7925097.


The effect of modulators of protein phosphorylation on the transcriptional activity of the androgen receptor (AR) was studied under transient expression conditions. Activators of protein kinase-A [8-bromo-cAMP (8-Br-cAMP)] and protein kinase-C (phorbol 12-myristate 13-acetate) or an inhibitor of protein phosphatase-1 and -2A (okadaic acid) influenced minimally pMMTV-chloramphenicol acetyl-transferase (CAT) activity in CV-1 cells cotransfected with an AR expression plasmid in the absence of androgen. In the presence of testosterone, however, all compounds enhanced AR-mediated transactivation by 2- to 4-fold. A nonsteroidal antiandrogen, Casodex, behaved as a pure antagonist; it blunted the action of testosterone and was not rendered agonistic by activators of protein kinase-A. A reporter plasmid containing two androgen response elements (AREs) in front of the thymidine kinase promoter (pARE2tk-CAT) was also used to examine promoter specificity. It was activated by 8-Br-cAMP, forskolin, or okadaic acid even without AR or androgen. However, when forskolin or okadaic acid was used together with androgen and AR, the resulting AR-dependent transactivation of pARE2tk-CAT was more than additive. Intact DNA- and ligand-binding domains, but not the N-terminal amino acid residues 40-147, of the receptor were mandatory for the synergism between protein kinase-A activators and androgen. Immunoreactive AR content in transfected COS-1 cells was not influenced by exposure to 8-Br-cAMP. Similar results were obtained by ligand binding assays. Quantitative or qualitative differences were not observed in DNA-binding characteristics between receptors extracted from cells treated with testosterone with or without protein kinase-A activator. Collectively, the synergistic stimulation of AR-dependent transactivation by androgen and protein kinase activators is not due to changes in cellular AR content or affinity of the receptor for the cognate DNA element; rather, this phenomenon seems to result from altered interaction of ligand-activated AR with other proteins in the transcription machinery.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 8-Bromo Cyclic Adenosine Monophosphate / pharmacology*
  • Androgen Antagonists / pharmacology
  • Androgens / pharmacology*
  • Anilides / pharmacology
  • Animals
  • Base Sequence
  • Cell Line
  • Chloramphenicol O-Acetyltransferase / metabolism
  • Colforsin / pharmacology
  • Cyclic AMP-Dependent Protein Kinases / metabolism
  • Cyclic AMP-Dependent Protein Kinases / physiology
  • DNA / analysis
  • DNA / genetics
  • Enzyme Activation / drug effects
  • Ethers, Cyclic / pharmacology
  • HeLa Cells
  • Humans
  • Molecular Sequence Data
  • Nitriles
  • Okadaic Acid
  • Phosphoric Monoester Hydrolases / metabolism
  • Phosphoric Monoester Hydrolases / physiology
  • Phosphorylation / drug effects
  • Protein Kinase C / metabolism
  • Protein Kinase C / physiology
  • Receptors, Androgen / analysis
  • Receptors, Androgen / genetics
  • Receptors, Androgen / physiology
  • Testosterone / pharmacology
  • Tetradecanoylphorbol Acetate / pharmacology*
  • Tosyl Compounds
  • Transcriptional Activation / drug effects*


  • Androgen Antagonists
  • Androgens
  • Anilides
  • Ethers, Cyclic
  • Nitriles
  • Receptors, Androgen
  • Tosyl Compounds
  • Colforsin
  • Okadaic Acid
  • 8-Bromo Cyclic Adenosine Monophosphate
  • Testosterone
  • DNA
  • bicalutamide
  • Chloramphenicol O-Acetyltransferase
  • Cyclic AMP-Dependent Protein Kinases
  • Protein Kinase C
  • Phosphoric Monoester Hydrolases
  • Tetradecanoylphorbol Acetate