Molecular mechanisms underlying forskolin-mediated up-regulation of human dopamine D2L receptors

Cell Mol Neurobiol. 1997 Oct;17(5):547-55. doi: 10.1023/a:1026367023458.


1. Human dopamine (DA) D2long (hD2L) receptors, expressed by Ltk- cells, can be up-regulated by treating the cells with forskolin for 16 hr (Johansson and Westlind-Danielsson, 1994). We have examined some of the molecular mechanisms underlying this forskolin-mediated up-regulation. 2. Forskolin (100 microM, 16 hr), but not 1,9-dideoxyforskolin, a forskolin analogue that is unable to activate adenylyl cyclase and raise intracellular cAMP concentrations, up-regulates the hD2L receptor population by 43%. The implication of a cAMP-dependent increase in the receptor up-regulation was further substantiated by treating the cells with 8-bromo-cAMP or prostaglandin E1 (PGE1). The forskolin-mediated rise in receptor number was blocked by cycloheximide or an antisense phosphorothioate oligodeoxynucleotide (ODN) directed toward the hD2L mRNA. KT5720, a specific protein kinase A (PKA) inhibitor, completely blocked the receptor rise, whereas pertussis toxin (PTX) attenuated the increase considerably. Forskolin also produced an increase in the level of the DA hD2short (hD2S) receptor expressed by Ltk- cells. This increase was 2.5-fold higher than that found for the hD2L receptor. 3. The forskolin-mediated hD2L receptor rise is dependent on de novo protein synthesis, a rise in cAMP levels, PKA activation, and, at least partially, PTX-sensitive G proteins. 4. Long-term increases in intracellular cAMP levels may change the sensitivity of a DA receptor expressing cell to DA by increasing D2 receptor density through enhanced cAMP-dependent transcription.

MeSH terms

  • Adenylate Cyclase Toxin
  • Amino Acid Sequence
  • Animals
  • Cells, Cultured
  • Colforsin / pharmacology*
  • Cyclic AMP / metabolism
  • Cyclic AMP-Dependent Protein Kinases / metabolism
  • Dopamine Antagonists / pharmacology
  • Fibroblasts / chemistry
  • Fibroblasts / cytology
  • Fibroblasts / enzymology
  • GTP-Binding Proteins / metabolism
  • Humans
  • Mice
  • Peptide Fragments / physiology
  • Pertussis Toxin
  • Raclopride
  • Receptors, Dopamine D2 / biosynthesis
  • Receptors, Dopamine D2 / chemistry
  • Receptors, Dopamine D2 / metabolism*
  • Salicylamides / pharmacology
  • Transfection
  • Tritium
  • Up-Regulation / drug effects*
  • Virulence Factors, Bordetella


  • Adenylate Cyclase Toxin
  • Dopamine Antagonists
  • Peptide Fragments
  • Receptors, Dopamine D2
  • Salicylamides
  • Virulence Factors, Bordetella
  • Tritium
  • Colforsin
  • Raclopride
  • Cyclic AMP
  • Pertussis Toxin
  • Cyclic AMP-Dependent Protein Kinases
  • GTP-Binding Proteins