Role of heteromultimers in the generation of myocardial transient outward K+ currents.
Previous studies have demonstrated a role for Kv4 alpha subunits in the generation of the fast transient outward K+ current, I(to,f), in the mammalian myocardium. The experiments here were undertaken to explore the role of homomeric/heteromeric assembly of Kv4.2 and Kv4.3 and of the Kv channel accessory subunit, KChIP2, in the generation of mouse ventricular I(to,f). Western blots reveal that the expression of Kv4.2 parallels the regional heterogeneity in I(to,f) density, whereas Kv4.3 and KChIP2 are uniformly expressed in adult mouse ventricles. Antisense oligodeoxynucleotides (AsODNs) targeted against Kv4.2 or Kv4.3 selectively attenuate I(to,f) in mouse ventricular cells. Adenoviral-mediated coexpression of Kv4.2 and Kv4.3 in HEK-293 cells and in mouse ventricular myocytes produces transient outward K+ currents with properties distinct from those produced on expression of Kv4.2 or Kv4.3 alone, and the gating properties of the heteromeric Kv4.2/Kv4.3 channels in ventricular cells are more similar to native I(to,f) than are the homomeric Kv4.2 or Kv4.3 channels. Biochemical studies reveal that Kv4.2, Kv4.3, and KChIP2 coimmunoprecipitate from adult mouse ventricles. In addition, most of the Kv4.2 and KChIP2 are associated with Kv4.3 in situ. Taken together, these results demonstrate that functional mouse ventricular I(to,f) channels are heteromeric, comprising Kv4.2/Kv4.3 alpha subunits and KChIP2. The results here also suggest that Kv4.2 is the primary determinant of the regional heterogeneity in I(to,f) expression in adult mouse ventricle.
Guo
Weinong
W
Department of Molecular Biology and Pharmacology, Washington University School of Medicine, St. Louis, Mo 63110, USA.
Li
Huilin
H
Aimond
Franck
F
Johns
David C
DC
Rhodes
Kenneth J
KJ
Trimmer
James S
JS
Nerbonne
Jeanne M
JM
D000818:Animals; D015153:Blotting, Western; D002135:Calcium-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D018929:Cell Culture Techniques; D006352:Heart Ventricles / Q000166:cytology / Q000378:metabolism*; D015640:Ion Channel Gating / Q000187:drug effects; D051605:Kv Channel-Interacting Proteins; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism*; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated; D011233:Precipitin Tests; D020836:Protein Structure, Quaternary / Q000502:physiology; D021122:Protein Subunits; D051672:Shal Potassium Channels
D002135:Calcium-Binding Proteins; C497019:Kcnd2 protein, mouse; C497022:Kcnd3 protein, mouse; C496755:Kcnip2 protein, mouse; D051605:Kv Channel-Interacting Proteins; D016376:Oligonucleotides, Antisense; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D021122:Protein Subunits; D051672:Shal Potassium Channels; D011188:Potassium