Localization and mobility of the delayed-rectifer K+ channel Kv2.1 in adult cardiomyocytes.
The delayed-rectifier voltage-gated K(+) channel (Kv) 2.1 underlies the cardiac slow K(+) current in the rodent heart and is particularly interesting in that both its function and localization are regulated by many stimuli in neuronal systems. However, standard immunolocalization approaches do not detect cardiac Kv2.1; therefore, little is known regarding its localization in the heart. In the present study, we used recombinant adenovirus to determine the subcellular localization and lateral mobility of green fluorescent protein (GFP)-Kv2.1 and yellow fluorescent protein-Kv1.4 in atrial and ventricular myocytes. In atrial myocytes, Kv2.1 formed large clusters on the cell surface similar to those observed in hippocampal neurons, whereas Kv1.4 was evenly distributed over both the peripheral sarcolemma and the transverse tubules. However, fluorescence recovery after photobleach (FRAP) experiments indicate that atrial Kv2.1 was immobile, whereas Kv1.4 was mobile (tau = 252 +/- 42 s). In ventricular myocytes, Kv2.1 did not form clusters and was localized primarily in the transverse-axial tubules and sarcolemma. In contrast, Kv1.4 was found only in transverse tubules and sarcolemma. FRAP studies revealed that Kv2.1 has a higher mobility in ventricular myocytes (tau = 479 +/- 178 s), although its mobility is slower than Kv1.4 (tau(1) = 18.9 +/- 2.3 s; tau(2) = 305 +/- 55 s). We also observed the movement of small, intracellular transport vesicles containing GFP-Kv2.1 within ventricular myocytes. These data are the first evidence of Kv2.1 localization in living myocytes and indicate that Kv2.1 may have distinct physiological roles in atrial and ventricular myocytes.
O'Connell
Kristen M S
KM
Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA. koconnel@lamar.colostate.edu
Whitesell
Jennifer D
JD
Tamkun
Michael M
MM
D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D002460:Cell Line; D002478:Cells, Cultured; D036681:Fluorescence Recovery After Photobleaching; D005822:Genetic Vectors; D049452:Green Fluorescent Proteins; D006325:Heart Atria / Q000378:metabolism; D006352:Heart Ventricles / Q000378:metabolism; D006801:Humans; D051663:Kv1.2 Potassium Channel / Q000235:genetics / Q000378:metabolism*; D051665:Kv1.4 Potassium Channel / Q000235:genetics / Q000378:metabolism*; D008297:Male; D018613:Microscopy, Confocal; D032383:Myocytes, Cardiac / Q000378:metabolism*; D021381:Protein Transport; D051381:Rats; D017207:Rats, Sprague-Dawley; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012508:Sarcolemma / Q000378:metabolism; D013997:Time Factors; D014162:Transfection; D022161:Transport Vesicles / Q000378:metabolism
D051663:Kv1.2 Potassium Channel; D051665:Kv1.4 Potassium Channel; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins