title: The cAMP response element binding protein modulates expression of the transient outward current: implications for cardiac memory.
abstract: OBJECTIVE
  Long-term cardiac memory (LTCM), expressed as a specific pattern of T-wave change on ECG, is associated with 1) reduced transient outward potassium current (I(to)), 2) reduced mRNA for the pore-forming protein of I(to), Kv4.3, 3) reduced cAMP response element binding protein (CREB), and 4) diminished binding to its docking site on the DNA, the cAMP response element (CRE). We hypothesized a causal link between the decrease of the transcription factor CREB and down-regulation of I(to) and one of its channel subunits, KChIP2, in LTCM.
  
  
  METHODS
  After three weeks of left ventricular pacing to induce LTCM (8 paced, 7 sham control dogs), epicardial KChIP2 mRNA and protein levels were assessed by real-time PCR and Western blotting. Mimicking the CREB down-regulation in LTCM, CREB was knocked down in situ in other dogs using adenoviral anti-sense. Effects on the action potential notch, reflecting I(to), were investigated in situ using monophasic action potential (MAP) recordings and at the cellular level by the whole-cell patch clamp technique. CREB binding in the KChIP2 promoter region was ascertained by electrophoretic mobility-shift assays.
  
  
  RESULTS
  In LTCM, epicardial KChIP2 mRNA and protein were reduced by 62% and 76%, respectively, compared to shams (p < 0.05). CREB binding by the canine KChIP2 promoter region was demonstrated. CREB knockdown led to disappearance of the phase1 notch in MAP and ablation of I(to).
  
  
  CONCLUSIONS
  These results strengthen the hypothesis that down-regulation of CREB-mediated transcription underlies the attenuation of epicardial I(to) in LTCM. They also emphasize that ventricular pacing exerts effects at a subcellular level contributing to memory and conceivably to other forms of cardiac remodeling.
authors.affiliation: Department of Pharmacology, College of Physicians and Surgeons of Columbia University, New York, NY 10032, USA.
authors.forename: Kornelis W
authors.initials: KW
authors.lastname: Patberg
authors.forename: Maria N
authors.initials: MN
authors.lastname: Obreztchikova
authors.forename: Sarah F
authors.initials: SF
authors.lastname: Giardina
authors.forename: Aviva J
authors.initials: AJ
authors.lastname: Symes
authors.forename: Alexei N
authors.initials: AN
authors.lastname: Plotnikov
authors.forename: Jihong
authors.initials: J
authors.lastname: Qu
authors.forename: Parag
authors.initials: P
authors.lastname: Chandra
authors.forename: David
authors.initials: D
authors.lastname: McKinnon
authors.forename: Shian R
authors.initials: SR
authors.lastname: Liou
authors.forename: Andrew V
authors.initials: AV
authors.lastname: Rybin
authors.forename: Iryna
authors.initials: I
authors.lastname: Shlapakova
authors.forename: Peter
authors.initials: P
authors.lastname: Danilo
authors.forename: Jay
authors.initials: J
authors.lastname: Yang
authors.forename: Michael R
authors.initials: MR
authors.lastname: Rosen
mesh_terms: D000200:Action Potentials; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000378:metabolism* / Q000503:physiopathology*; D015153:Blotting, Western / Q000379:methods; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002304:Cardiac Pacing, Artificial; D017362:Cyclic AMP Response Element-Binding Protein / Q000276:immunology / Q000378:metabolism*; D004285:Dogs; D015536:Down-Regulation; D004562:Electrocardiography; D024202:Electrophoretic Mobility Shift Assay; D023421:Models, Animal; D009206:Myocardium / Q000378:metabolism*; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D024642:Potassium Channels, Voltage-Gated / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020257:Ventricular Remodeling
chemical_list: D002135:Calcium-Binding Proteins; D017362:Cyclic AMP Response Element-Binding Protein; D016376:Oligonucleotides, Antisense; D024642:Potassium Channels, Voltage-Gated