Immunolocalization of KATP channel subunits in mouse and rat cardiac myocytes and the coronary vasculature.
BACKGROUND
Electrophysiological data suggest that cardiac KATP channels consist of Kir6.2 and SUR2A subunits, but the distribution of these (and other KATP channel subunits) is poorly defined. We examined the localization of each of the KATP channel subunits in the mouse and rat heart.


RESULTS
Immunohistochemistry of cardiac cryosections demonstrate Kir6.1 protein to be expressed in ventricular myocytes, as well as in the smooth muscle and endothelial cells of coronary resistance vessels. Endothelial capillaries also stained positive for Kir6.1 protein. Kir6.2 protein expression was found predominantly in ventricular myocytes and also in endothelial cells, but not in smooth muscle cells. SUR1 subunits are strongly expressed at the sarcolemmal surface of ventricular myocytes (but not in the coronary vasculature), whereas SUR2 protein was found to be localized predominantly in cardiac myocytes and coronary vessels (mostly in smaller vessels). Immunocytochemistry of isolated ventricular myocytes shows co-localization of Kir6.2 and SUR2 proteins in a striated sarcomeric pattern, suggesting t-tubular expression of these proteins. Both Kir6.1 and SUR1 subunits were found to express strongly at the sarcolemma. The role(s) of these subunits in cardiomyocytes remain to be defined and may require a reassessment of the molecular nature of ventricular KATP channels.


CONCLUSIONS
Collectively, our data demonstrate unique cellular and subcellular KATP channel subunit expression patterns in the heart. These results suggest distinct roles for KATP channel subunits in diverse cardiac structures.
Morrissey
Alison
A
Pediatric Cardiology, NYU School of Medicine, New York, USA. amorrissey@tpna.com <amorrissey@tpna.com>
Rosner
Erika
E
Lanning
Jennifer
J
Parachuru
Lavanya
L
Dhar Chowdhury
Piyali
P
Han
Sandra
S
Lopez
Gwendolyn
G
Tong
XiaoYong
X
Yoshida
Hidetada
H
Nakamura
Tomoe Y
TY
Artman
Michael
M
Giblin
Jonathan P
JP
Tinker
Andrew
A
Coetzee
William A
WA
D018528:ATP-Binding Cassette Transporters / Q000378:metabolism*; D000818:Animals; D003331:Coronary Vessels / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000378:metabolism; D006352:Heart Ventricles; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D054086:KATP Channels; D051379:Mice; D008929:Mitochondria, Heart / Q000378:metabolism; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying / Q000378:metabolism*; D051381:Rats; D011955:Receptors, Drug; D013347:Subcellular Fractions / Q000378:metabolism; D064233:Sulfonylurea Receptors; D014018:Tissue Distribution; D000099161:Kcnj11 Channel
D018528:ATP-Binding Cassette Transporters; D054086:KATP Channels; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D024661:Potassium Channels, Inwardly Rectifying; D011955:Receptors, Drug; D064233:Sulfonylurea Receptors; D000099161:Kcnj11 Channel; C577508:Abcc8 protein, mouse; C577509:Abcc8 protein, rat; C577511:Abcc9 protein, mouse; C577512:Abcc9 protein, rat; C092520:uK-ATP-1 potassium channel