Molecular components of transient outward potassium current in cultured neonatal rat ventricular myocytes.
We have previously reported that K(v1.4), K(v4.2), and K(v4.3) mRNAs are present in adult and neonatal rat ventricular myocytes, and that transient outward potassium current (I(to)) recovers from inactivation with a slow (I(to,s)) and a fast (I(to,f)) time course. This study was designed to determine the molecular correlates of I(to,s) and I(to,f) in cultured neonatal rat ventricular myocytes (NRVM) employing dominant-negative adenoviral infections to manipulate the function of endogenous I(to)-encoding K+ channels. Western blot data from cultured NRVM showed that K(v1.4), K(v4.2), and K(v4.3) channel proteins are present in these myocytes. The biphasic recovery from inactivation of I(to) in control GFP-infected myocytes demonstrated equal contribution of I(to,s) and I(to,f) in NRVM. Infection of cultured NRVM with adenoviruses expressing full-length K(v1.4) or K(v4.2) genes generated currents with recovery from inactivation kinetics similar to native I(to,s) and I(to,f) in GFP-infected myocytes, respectively. Overexpression of dominant-negative truncated K(v1.4) transgene (K(v1.4)N) caused a 51% reduction in I(to), selectively removing the slowly recovering I(to,s). Overexpression of dominant-negative K(v4.2)N reduced I(to) by 53% and eliminated the fast-recovering I(to,f). Our results establish that, in neonatal rat ventricular myocytes, the shaker K(v1) family (probably K(v1.4) and/or K(v1.7)) underlies I(to,s), and that the shal K(v4) family (probably K(v4.2) and K(v4.3)) is responsible for I(to,f).
Kassiri
Zamaneh
Z
Department of Physiology and Medicine, Heart and Stroke, Richard Lewar Center, and Division of Cardiology, University Health Network, University of Toronto, 150 College St., Toronto, Ontario M5G 3E2, Canada.
Hajjar
Roger
R
Backx
Peter H
PH
D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D004594:Electrophysiology / Q000379:methods; D005786:Gene Expression Regulation; D005799:Genes, Dominant; D049452:Green Fluorescent Proteins; D006352:Heart Ventricles / Q000737:chemistry / Q000378:metabolism*; D051665:Kv1.4 Potassium Channel; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D051672:Shal Potassium Channels
C496979:Kcna4 protein, rat; D051665:Kv1.4 Potassium Channel; D008164:Luminescent Proteins; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D011994:Recombinant Proteins; D051672:Shal Potassium Channels; D049452:Green Fluorescent Proteins; D011188:Potassium