Regulation of KChIP2 potassium channel beta subunit gene expression underlies the gradient of transient outward current in canine and human ventricle.
Expression of four members of the KChIP family of potassium channel beta subunits was examined in canine heart. Only one member of the gene family, KChIP2, was expressed in heart. There was a steep gradient of KChIP2 mRNA expression across the canine ventricular free wall. KChIP2 mRNA was 25-fold more abundant in the epicardium than in the endocardium, and this gradient paralleled the gradient in transient outward current (Ito) expression. In contrast, Kv4.3 potassium channel alpha subunit mRNA was expressed at equal levels across the ventricular wall. There was no difference in the pharmacological sensitivity of epicardial and endocardial Ito channels to flecainide, suggesting that the current is produced by the same channel in the two tissues. A similar gradient of KChIP2 expression was found across the ventricular wall of human heart, but not rat heart. It is concluded that transcriptional regulation of the KChIP2 beta subunit gene, rather than the Kv4.3 [alpha] subunit gene, is the primary determinant regulating the transmural gradient of Ito expression in the ventricular free wall of canine and human heart.
Rosati
B
B
Institute of Molecular Cardiology and Department of Physiology and Biophysics, State University of New York, Stony Brook, NY 11794, USA.
Pan
Z
Z
Lypen
S
S
Wang
H S
HS
Cohen
I
I
Dixon
J E
JE
McKinnon
D
D
D000818:Animals; D002135:Calcium-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D017931:DNA Primers; D004285:Dogs; D004594:Electrophysiology; D004699:Endocardium / Q000166:cytology / Q000378:metabolism; D015870:Gene Expression / Q000502:physiology; D006352:Heart Ventricles / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D051605:Kv Channel-Interacting Proteins; D018485:Muscle Fibers, Skeletal / Q000378:metabolism; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D009865:Oocytes / Q000502:physiology; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism; D024642:Potassium Channels, Voltage-Gated; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D012097:Repressor Proteins; D051672:Shal Potassium Channels; D014981:Xenopus
D002135:Calcium-Binding Proteins; D017931:DNA Primers; C497021:KCND3 protein, human; C496752:KCNIP2 protein, human; C496749:KCNIP3 protein, human; C497023:Kcnd3 protein, rat; C496758:Kcnip2 protein, rat; C496760:Kcnip3 protein, rat; D051605:Kv Channel-Interacting Proteins; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D012333:RNA, Messenger; D012097:Repressor Proteins; D051672:Shal Potassium Channels; D011188:Potassium