title: HL-1 cells express an inwardly rectifying K+ current activated via muscarinic receptors comparable to that in mouse atrial myocytes.
abstract: An inwardly rectifying K(+) current is present in atrial cardiac myocytes that is activated by acetylcholine (I(KACh)). Physiologically, activation of the current in the SA node is important in slowing the heart rate with increased parasympathetic tone. It is a paradigm for the direct regulation of signaling effectors by the Gbetagamma G-protein subunit. Many questions have been addressed in heterologous expression systems with less focus on the behaviour in native myocytes partly because of the technical difficulties in undertaking comparable studies in native cells. In this study, we characterise a potassium current in the atrial-derived cell line HL-1. Using an electrophysiological approach, we compare the characteristics of the potassium current with those in native atrial cells and in a HEK cell line expressing the cloned Kir3.1/3.4 channel. The potassium current recorded in HL-1 is inwardly rectifying and activated by the muscarinic agonist carbachol. Carbachol-activated currents were inhibited by pertussis toxin and tertiapin-Q. The basal current was time-dependently increased when GTP was substituted in the patch-clamp pipette by the non-hydrolysable analogue GTPgammaS. We compared the kinetics of current modulation in HL-1 with those of freshly isolated atrial mouse cardiomyocytes. The current activation and deactivation kinetics in HL-1 cells are comparable to those measured in atrial cardiomyocytes. Using immunofluorescence, we found GIRK4 at the membrane in HL-1 cells. Real-time RT-PCR confirms the presence of mRNA for the main G-protein subunits, as well as for M2 muscarinic and A1 adenosine receptors. The data suggest HL-1 cells are a good model to study IKAch.
authors.affiliation: Department of Medicine, BHF Laboratories, University College London, The Rayne Institute, 5 University Street, London, WC1E 6JJ, UK.
authors.forename: Muriel
authors.initials: M
authors.lastname: Nobles
authors.forename: Sonia
authors.initials: S
authors.lastname: Sebastian
authors.forename: Andrew
authors.initials: A
authors.lastname: Tinker
mesh_terms: D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D001514:Bee Venoms / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D002460:Cell Line; D018679:Cholinergic Agonists / Q000494:pharmacology; D005260:Female; D005455:Fluorescent Antibody Technique; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006325:Heart Atria / Q000378:metabolism; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects; D007700:Kinetics; D008297:Male; D051379:Mice; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D037342:Pertussis Toxin / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D024661:Potassium Channels, Inwardly Rectifying / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D043585:Receptor, Muscarinic M2 / Q000187:drug effects / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection
chemical_list: D001514:Bee Venoms; D018679:Cholinergic Agonists; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; C497067:Kcnj3 protein, mouse; C484273:Kcnj5 protein, mouse; D026902:Potassium Channel Blockers; D024661:Potassium Channels, Inwardly Rectifying; D012333:RNA, Messenger; D043585:Receptor, Muscarinic M2; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C029738:tertiapin; D002217:Carbachol; D037342:Pertussis Toxin; D000109:Acetylcholine; D011188:Potassium