Activation and inactivation of cAMP-response element-mediated gene transcription in cardiac myocytes.
OBJECTIVE
Chronic beta-adrenergic stimulation of the cAMP-dependent signalling pathway is implicated in functionally relevant expressional changes in congestive heart failure. We studied activation and inactivation of the cardiac gene transcription mediated by the cAMP-response element (CRE) and the CRE-binding protein (CREB) as an important mechanism of a cAMP-dependent gene regulation.


METHODS
We investigated the transcriptional activation by forskolin, an activator of the adenylyl cyclase, in chick embryonic cardiomyocytes transfected with a CRE-controlled luciferase construct in comparison to the phosphorylation and expression of CREB determined on immunoblots.


RESULTS
Forskolin (10 micromol/l; 8 h) increased CRE-mediated transcription and phosphorylation of CREB 13- and 1.5-fold, respectively. The phosphorylation was further elevated in combination with cantharidin, an inhibitor of type 1+2A protein phosphatases. The transcriptional response to forskolin was desensitized by pretreatment with forskolin (1 micromol/l; 24 h) while CREB phosphorylation was increased. In forskolin-pretreated cells, total CREB protein levels were decreased. Cantharidin did not restore the attenuated transcriptional response.


CONCLUSIONS
In cardiomyocytes, there is an activation of the CRE-mediated gene transcription by forskolin that is attenuated after prolonged stimulation, and this attenuation is not dependent from a dephosphorylation of CREB. We suggest that attenuation of the CRE-mediated transcription through chronic stimulation of the cAMP-pathway, e.g. by elevated catecholamines, contributes to the altered expressional regulation in congestive heart failure.
Müller
F U
FU
The Institute for Pharmacology and Toxicology, University of Münster, Domagkstr. 12, D-48149, Münster, Germany. mullerf@uni-muenster.de
Bokník
P
P
Knapp
J
J
Linck
B
B
Lüss
H
H
Neumann
J
J
Schmitz
W
W
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D002193:Cantharidin / Q000494:pharmacology; D002316:Cardiotonic Agents / Q000494:pharmacology; D018797:Cell Cycle Proteins; D002478:Cells, Cultured; D002642:Chick Embryo; D005576:Colforsin / Q000494:pharmacology*; D000242:Cyclic AMP / Q000378:metabolism*; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004983:Ethanolamines; D015870:Gene Expression / Q000187:drug effects; D006333:Heart Failure / Q000378:metabolism*; D007545:Isoproterenol / Q000494:pharmacology; D008156:Luciferases / Q000235:genetics; D009206:Myocardium / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors; D010766:Phosphorylation; D010940:Plant Proteins; D011407:Propane / Q000031:analogs & derivatives*; D013268:Stimulation, Chemical; D013997:Time Factors; D014158:Transcription, Genetic / Q000187:drug effects*
D002316:Cardiotonic Agents; D018797:Cell Cycle Proteins; D017362:Cyclic AMP Response Element-Binding Protein; D004791:Enzyme Inhibitors; D004983:Ethanolamines; D010940:Plant Proteins; C081079:cyc07 protein, Catharanthus roseus; C078161:CRE 1087; D005576:Colforsin; D000242:Cyclic AMP; D008156:Luciferases; D010749:Phosphoprotein Phosphatases; D000262:Adenylyl Cyclases; D002193:Cantharidin; D007545:Isoproterenol; D011407:Propane; D015056:1-Methyl-3-isobutylxanthine