Developmental expression of NCS-1 (frequenin), a regulator of Kv4 K+ channels, in mouse heart.
The channel proteins responsible for the cardiac transient outward K+ current (Ito) of human and rodent heart are composed, in part, of pore-forming Kv4.3 or Kv4.2 principal subunits. Recent reports implicate K+ channel interacting proteins (members of the neuronal Ca2+-binding protein family) as subunits of the Ito channel complex. We reported that another Ca2+-binding protein, frequenin [or neuronal calcium center protein-1 (NCS-1)], also functions as a Kv4 auxiliary subunit in the brain. By examining cardiac expression of NCS-1, the aim of this study was to examine the potential physiologic relevance of this protein as an additional regulator of cardiac Ito. Immunoblot analysis demonstrates NCS-1 protein to be expressed in adult mouse ventricle at levels comparable to that found in some brain regions. Cardiac NCS-1 protein expression levels are much higher in fetal and neonatal mouse hearts when compared with the adult. Immunocytochemical analysis of isolated neonatal mouse ventricular myocytes demonstrates co-localization of NCS-1 and Kv4.2 proteins at the sarcolemma. Given its high levels of expression in the heart, NCS-1 should be considered an important potential Kv4 regulatory subunit, particularly in the immature heart.
Nakamura
Tomoe Y
TY
Department of Pediatric Cardiology, New York University School of Medicine, New York 10016, USA.
Sturm
Eron
E
Pountney
David J
DJ
Orenzoff
Barbara
B
Artman
Michael
M
Coetzee
William A
WA
D000818:Animals; D002135:Calcium-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D005333:Fetus; D005455:Fluorescent Antibody Technique; D018507:Gene Expression Regulation, Developmental; D006321:Heart / Q000196:embryology* / Q000502:physiology*; D006352:Heart Ventricles / Q000378:metabolism; D051379:Mice; D009206:Myocardium / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D051580:Neuronal Calcium-Sensor Proteins; D009479:Neuropeptides / Q000235:genetics* / Q000378:metabolism*; D015221:Potassium Channels / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated; D051672:Shal Potassium Channels
D002135:Calcium-Binding Proteins; C497019:Kcnd2 protein, mouse; D009419:Nerve Tissue Proteins; D051580:Neuronal Calcium-Sensor Proteins; D009479:Neuropeptides; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D051672:Shal Potassium Channels; C101464:frequenin calcium sensor proteins