title: Phenylephrine preconditioning in embryonic heart H9c2 cells is mediated by up-regulation of SUR2B/Kir6.2: A first evidence for functional role of SUR2B in sarcolemmal KATP channels and cardioprotection.
abstract: ATP-sensitive K(+) (KATP) channels were originally described in cardiomyocytes, where physiological levels of intracellular ATP keep them in a closed state. Structurally, these channels are composed of pore-forming inward rectifier, Kir6.1 or Kir6.2, and a regulatory, ATP-binding subunit, SUR1, SUR2A or SUR2B. SUR1 and Kir6.2 form pancreatic type of KATP channels, SUR2A and Kir6.2 form cardiac type of KATP channels, SUR2B and Kir6.1 form vascular smooth muscle type of KATP channels. The presence of SUR2B has been described in cardiomyocytes, but its functional significance and role has remained unknown. Pretreatment with phenylephrine (100nM) for 24h increased mRNA levels of SUR2B and Kir6.2, without affecting those levels of SUR1, SUR2A and Kir6.1 in embryonic heart H9c2 cells. Such increase was associated with increased K(+) current through KATP channels and Kir6.2/SUR2B protein complexes as revealed by whole cell patch clamp electrophysiology and immunoprecipitation/Western blotting respectively. Pretreatment with phenylephrine (100nM) generated a cellular phenotype that acquired resistance to chemical hypoxia induced by 2,4-dinitrophenol (DNP; 10mM), which was accompanied by increased in K(+) current in response to DNP (10mM). Cytoprotection afforded by phenylephrine (100nM) was abolished by infection of H9c2 cells with adenovirus containing Kir6.2AFA, a mutant form of Kir6.2 with largely reduced K(+) conductance. Taking all together, the present findings demonstrate that the activation of α1-adrenoceptors up-regulates SUR2B/Kir6.2 to confer cardioprotection. This is the first account of possible physiological role of SUR2B in cardiomyocytes.
authors.affiliation: Medical Research Institute, Division of Cardiovascular & Diabetic Medicine, Ninewells Hospital & Medical School, University of Dundee, UK.
authors.forename: Sofija
authors.initials: S
authors.lastname: Jovanović
authors.affiliation: Medical Research Institute, Division of Cardiovascular & Diabetic Medicine, Ninewells Hospital & Medical School, University of Dundee, UK.
authors.forename: Thomas
authors.initials: T
authors.lastname: Ballantyne
authors.affiliation: Medical Research Institute, Division of Cardiovascular & Diabetic Medicine, Ninewells Hospital & Medical School, University of Dundee, UK.
authors.forename: Qingyou
authors.initials: Q
authors.lastname: Du
authors.affiliation: Department of Anatomy, Faculty of Veterinary Medicine, University of Belgrade, Belgrade, Serbia.
authors.forename: Miloš
authors.initials: M
authors.lastname: Blagojević
authors.affiliation: Medical Research Institute, Division of Cardiovascular & Diabetic Medicine, Ninewells Hospital & Medical School, University of Dundee, UK. Electronic address: a.jovanovic@dundee.ac.uk.
authors.forename: Aleksandar
authors.initials: A
authors.lastname: Jovanović
mesh_terms: D019297:2,4-Dinitrophenol / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism; D058646:Adrenergic alpha-1 Receptor Agonists / Q000494:pharmacology*; D000818:Animals; D002316:Cardiotonic Agents / Q000494:pharmacology*; D015687:Cell Hypoxia / Q000187:drug effects; D002460:Cell Line; D004622:Embryo, Mammalian; D005786:Gene Expression Regulation; D054086:KATP Channels / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010656:Phenylephrine / Q000494:pharmacology*; D024661:Potassium Channels, Inwardly Rectifying / Q000819:agonists / Q000235:genetics* / Q000378:metabolism; D020033:Protein Isoforms / Q000819:agonists / Q000235:genetics / Q000378:metabolism; D021122:Protein Subunits / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction; D064233:Sulfonylurea Receptors / Q000235:genetics / Q000378:metabolism; D000099161:Kcnj11 Channel
chemical_list: D019297:2,4-Dinitrophenol; D000255:Adenosine Triphosphate; D058646:Adrenergic alpha-1 Receptor Agonists; D002316:Cardiotonic Agents; D054086:KATP Channels; D010656:Phenylephrine; D024661:Potassium Channels, Inwardly Rectifying; D020033:Protein Isoforms; D021122:Protein Subunits; D012333:RNA, Messenger; D064233:Sulfonylurea Receptors; D000099161:Kcnj11 Channel; C577509:Abcc8 protein, rat; C092520:uK-ATP-1 potassium channel
keywords: Cardiomyocytes; Cardioprotection; H9c2 cells; Preconditioning; SUR2B