title: Overexpression of adenylyl cyclase type 5 (AC5) confers a proarrhythmic substrate to the heart.
abstract: Inhibition of β-adrenergic receptor (β-AR) signaling is one of the most common therapeutic approaches for patients with arrhythmias. Adenylyl cyclase (AC) is the key enzyme responsible for transducing β-AR stimulation to increases in cAMP. The two major AC isoforms in the heart are types 5 and 6. Therefore, it is surprising that prior studies on overexpression of AC5 and AC6 in transgenic (Tg) mice have not examined mediation of arrhythmogenesis. Our goal was to examine the proarrhythmic substrate in AC5Tg hearts. Intracellular calcium ion (Ca(2+) i) was imaged in fluo-4 AM-loaded ventricular myocytes. The sarcoplasmic reticulum (SR) Ca(2+) content, fractional Ca(2+) release, and twitch Ca(2+) transient were significantly higher in the AC5Tg vs. wild-type (WT) myocytes, indicating Ca(2+) overload in AC5Tg myocytes. Action potential (AP) duration was significantly longer in AC5Tg than in WT myocytes. Additionally, AC5Tg myocytes developed spontaneous Ca(2+) waves in a larger fraction compared with WT myocytes, particularly when cells were exposed to isoproterenol. The Ca(2+) waves further induced afterdepolarizations and triggered APs. AC5Tg hearts had increased level of SERCA2a, oxidized Ca(2+)/calmodulin-dependent protein kinase II (CaMKII), and phosphorylation of ryanodine receptors (RyR) at the CaMKII site, especially after isoproterenol treatment. This was consistent with higher reactive oxygen species production in AC5Tg myocytes after isoproterenol treatment. Isoproterenol induced more severe arrhythmias in AC5Tg than in WT mice. We conclude that AC5 overexpression promotes arrhythmogenesis, by inducing SR Ca(2+) overload and hyperactivation of RyR (phosphorylation by CaMKII), which in turn induces spontaneous Ca(2+) waves and afterdepolarizations.
authors.affiliation: Department of Pharmacology, School of Medicine, Xi'an Jiaotong University, Xi'an, People's Republic of China; Department of Cell Biology and Molecular Medicine, Rutgers University-New Jersey Medical School, Newark, New Jersey;
authors.forename: Zhenghang
authors.initials: Z
authors.lastname: Zhao
authors.affiliation: Department of Cell Biology and Molecular Medicine, Rutgers University-New Jersey Medical School, Newark, New Jersey;
authors.forename: Gopal J
authors.initials: GJ
authors.lastname: Babu
authors.affiliation: Department of Cell Biology and Molecular Medicine, Rutgers University-New Jersey Medical School, Newark, New Jersey; Department of Reproductive and Genetic Toxicology, National Center for Safety Evaluation of Drugs, National Institutes for Food and Drug Control, Beijing, People's Republic of China; and.
authors.forename: Hairuo
authors.initials: H
authors.lastname: Wen
authors.affiliation: Department of Cell Biology and Molecular Medicine, Rutgers University-New Jersey Medical School, Newark, New Jersey;
authors.forename: Nadezhda
authors.initials: N
authors.lastname: Fefelova
authors.affiliation: Department of Cell Biology and Molecular Medicine, Rutgers University-New Jersey Medical School, Newark, New Jersey;
authors.forename: Richard
authors.initials: R
authors.lastname: Gordan
authors.affiliation: Department of Cell Biology and Molecular Medicine, Rutgers University-New Jersey Medical School, Newark, New Jersey;
authors.forename: Xiangzhen
authors.initials: X
authors.lastname: Sui
authors.affiliation: Department of Cell Biology and Molecular Medicine, Rutgers University-New Jersey Medical School, Newark, New Jersey;
authors.forename: Lin
authors.initials: L
authors.lastname: Yan
authors.affiliation: Department of Cell Biology and Molecular Medicine, Rutgers University-New Jersey Medical School, Newark, New Jersey;
authors.forename: Dorothy E
authors.initials: DE
authors.lastname: Vatner
authors.affiliation: Department of Cell Biology and Molecular Medicine, Rutgers University-New Jersey Medical School, Newark, New Jersey;
authors.forename: Stephen F
authors.initials: SF
authors.lastname: Vatner
authors.affiliation: Department of Cell Biology and Molecular Medicine, Rutgers University-New Jersey Medical School, Newark, New Jersey; School of Pharmacology, Xinxiang Medical University, Xixiang, People's Republic of China xiela@njms.rutgers.edu.
authors.forename: Lai-Hua
authors.initials: LH
authors.lastname: Xie
mesh_terms: D000200:Action Potentials; D000262:Adenylyl Cyclases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000235:genetics / Q000378:metabolism; D002316:Cardiotonic Agents / Q000494:pharmacology; D002478:Cells, Cultured; D006352:Heart Ventricles / Q000166:cytology / Q000378:metabolism; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D007545:Isoproterenol / Q000494:pharmacology; D051379:Mice; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D017382:Reactive Oxygen Species / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000235:genetics / Q000378:metabolism
chemical_list: D002316:Cardiotonic Agents; D007527:Isoenzymes; D017382:Reactive Oxygen Species; D019837:Ryanodine Receptor Calcium Release Channel; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000262:Adenylyl Cyclases; D007545:Isoproterenol; D002118:Calcium
keywords: adenylyl cyclase type 5; arrhythmias; calcium handling; electrophysiology; overexpression