Overexpression of beta2-adrenergic receptors cAMP-dependent protein kinase phosphorylates and modulates slow delayed rectifier potassium channels expressed in murine heart: evidence for receptor/channel co-localization.
The cardiac slow delayed rectifier potassium channel (IKs), comprised of (KCNQ1) and beta (KCNE1) subunits, is regulated by sympathetic nervous stimulation, with activation of beta-adrenergic receptors PKA phosphorylating IKs channels. We examined the effects of 2-adrenergic receptors (beta2-AR) on IKs in cardiac ventricular myocytes from transgenic mice expressing fusion proteins of IKs subunits and hbeta2-ARs. KCNQ1 and beta2-ARs were localized to the same subcellular regions, sharing intimate localization within nanometers of each other. In IKs/B2-AR myocytes, IKs density was increased, and activation shifted in the hyperpolarizing direction; IKs was not further modulated by exposure to isoproterenol, and KCNQ1 was found to be PKA-phosphorylated. Conversely, beta2-AR overexpression did not affect L-type calcium channel current (ICaL) under basal conditions with ICaL remaining responsive to cAMP. These data indicate intimate association of KCNQ1 and beta2-ARs and that beta2-AR signaling can modulate the function of IKs channels under conditions of increased beta2-AR expression, even in the absence of exogenous beta-AR agonist.
Dilly
Keith W
KW
Department of Pharmacology, Center for Molecular Cardiology, College of Physicians & Surgeons, Columbia University, New York, New York 10032, USA.
Kurokawa
Junko
J
Terrenoire
Cecile
C
Reiken
Steven
S
Lederer
W J
WJ
Marks
Andrew R
AR
Kass
Robert S
RS
D000818:Animals; D015153:Blotting, Western; D015220:Calcium Channels / Q000737:chemistry; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004594:Electrophysiology; D031541:Fluorescence Resonance Energy Transfer; D006352:Heart Ventricles / Q000378:metabolism; D007150:Immunohistochemistry; D051656:KCNQ Potassium Channels; D051657:KCNQ1 Potassium Channel; D051379:Mice; D008822:Mice, Transgenic; D008856:Microscopy, Fluorescence; D032383:Myocytes, Cardiac / Q000378:metabolism; D010766:Phosphorylation; D015221:Potassium Channels / Q000096:biosynthesis* / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated; D011233:Precipitin Tests; D018343:Receptors, Adrenergic, beta-2 / Q000096:biosynthesis*; D015854:Up-Regulation
D015220:Calcium Channels; D051656:KCNQ Potassium Channels; D051657:KCNQ1 Potassium Channel; C496910:Kcnq1 protein, mouse; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D018343:Receptors, Adrenergic, beta-2; C059983:potassium channel protein I(sk); D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases