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Sleiman Y, Lacampagne A, Meli AC. "Ryanopathies" and RyR2 dysfunctions: can we further decipher them using in vitro human disease models? Cell Death Dis 2021; 12:1041. [PMID: 34725342 PMCID: PMC8560800 DOI: 10.1038/s41419-021-04337-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Revised: 10/08/2021] [Accepted: 10/14/2021] [Indexed: 12/23/2022]
Abstract
The regulation of intracellular calcium (Ca2+) homeostasis is fundamental to maintain normal functions in many cell types. The ryanodine receptor (RyR), the largest intracellular calcium release channel located on the sarco/endoplasmic reticulum (SR/ER), plays a key role in the intracellular Ca2+ handling. Abnormal type 2 ryanodine receptor (RyR2) function, associated to mutations (ryanopathies) or pathological remodeling, has been reported, not only in cardiac diseases, but also in neuronal and pancreatic disorders. While animal models and in vitro studies provided valuable contributions to our knowledge on RyR2 dysfunctions, the human cell models derived from patients’ cells offer new hope for improving our understanding of human clinical diseases and enrich the development of great medical advances. We here discuss the current knowledge on RyR2 dysfunctions associated with mutations and post-translational remodeling. We then reviewed the novel human cellular technologies allowing the correlation of patient’s genome with their cellular environment and providing approaches for personalized RyR-targeted therapeutics.
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Affiliation(s)
- Yvonne Sleiman
- PhyMedExp, University of Montpellier, INSERM, CNRS, Montpellier, France
| | - Alain Lacampagne
- PhyMedExp, University of Montpellier, INSERM, CNRS, Montpellier, France
| | - Albano C Meli
- PhyMedExp, University of Montpellier, INSERM, CNRS, Montpellier, France.
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2
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Shkodra B, Press AT, Vollrath A, Nischang I, Schubert S, Hoeppener S, Haas D, Enzensperger C, Lehmann M, Babic P, Benecke KJ, Traeger A, Bauer M, Schubert US. Formulation of Liver-Specific PLGA-DY-635 Nanoparticles Loaded with the Protein Kinase C Inhibitor Bisindolylmaleimide I. Pharmaceutics 2020; 12:pharmaceutics12111110. [PMID: 33218172 PMCID: PMC7698893 DOI: 10.3390/pharmaceutics12111110] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2020] [Revised: 11/12/2020] [Accepted: 11/13/2020] [Indexed: 12/20/2022] Open
Abstract
Bisindolylmaleimide I (BIM-I) is a competitive pan protein kinase C inhibitor with anti-inflammatory and anti-metastatic properties, suggested to treat inflammatory diseases and various cancer entities. However, despite its therapeutic potential, BIM-I has two major drawbacks, i.e., it has a poor water solubility, and it binds the human ether-à-go-go-related gene (hERG) ion channels, potentially causing deadly arrhythmias. In this case, a targeted delivery of BIM-I is imperative to minimize peripheral side effects. To circumvent these drawbacks BIM-I was encapsulated into nanoparticles prepared from poly(lactic-co-glycolic acid) (PLGA) functionalized by the near-infrared dye DY-635. DY-635 served as an active targeting moiety since it selectively binds the OATP1B1 and OATP1B3 transporters that are highly expressed in liver and cancer cells. PLGA-DY-635 (BIM-I) nanoparticles were produced by nanoprecipitation and characterized using dynamic light scattering, analytical ultracentrifugation, and cryogenic transmission electron microscopy. Particle sizes were found to be in the range of 20 to 70 nm, while a difference in sizes between the drug-loaded and unloaded particles was observed by all analytical techniques. In vitro studies demonstrated that PLGA-DY-635 (BIM-I) NPs prevent the PKC activation efficiently, proving the efficacy of the inhibitor after its encapsulation, and suggesting that BIM-I is released from the PLGA-NPs. Ultimately, our results present a feasible formulation strategy that improved the cytotoxicity profile of BIM-I and showed a high cellular uptake in the liver as demonstrated in vivo by intravital microscopy investigations.
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Affiliation(s)
- Blerina Shkodra
- Laboratory of Organic and Macromolecular Chemistry (IOMC), Friedrich Schiller University Jena, Humboldtstrasse 10, 07743 Jena, Germany; (B.S.); (A.V.); (I.N.); (S.H.); (D.H.); (A.T.)
- Jena Center for Soft Matter (JCSM), Friedrich Schiller University Jena, Philosophenweg 7, 07743 Jena, Germany; (S.S.); (M.B.)
| | - Adrian T. Press
- Department of Anesthesiology and Intensive Care Medicine, Nanophysiology Group, Jena University Hospital, Am Klinikum 1, 07747 Jena, Germany; (A.T.P.); (P.B.); (K.J.B.)
- Center for Sepsis Control and Care, Jena University Hospital, 07747 Jena, Germany
| | - Antje Vollrath
- Laboratory of Organic and Macromolecular Chemistry (IOMC), Friedrich Schiller University Jena, Humboldtstrasse 10, 07743 Jena, Germany; (B.S.); (A.V.); (I.N.); (S.H.); (D.H.); (A.T.)
- Jena Center for Soft Matter (JCSM), Friedrich Schiller University Jena, Philosophenweg 7, 07743 Jena, Germany; (S.S.); (M.B.)
| | - Ivo Nischang
- Laboratory of Organic and Macromolecular Chemistry (IOMC), Friedrich Schiller University Jena, Humboldtstrasse 10, 07743 Jena, Germany; (B.S.); (A.V.); (I.N.); (S.H.); (D.H.); (A.T.)
- Jena Center for Soft Matter (JCSM), Friedrich Schiller University Jena, Philosophenweg 7, 07743 Jena, Germany; (S.S.); (M.B.)
| | - Stephanie Schubert
- Jena Center for Soft Matter (JCSM), Friedrich Schiller University Jena, Philosophenweg 7, 07743 Jena, Germany; (S.S.); (M.B.)
- Institute of Pharmacy, Department of Pharmaceutical Technology and Biopharmacy, Friedrich Schiller University Jena, Lessingstrasse 8, 07743 Jena, Germany
| | - Stephanie Hoeppener
- Laboratory of Organic and Macromolecular Chemistry (IOMC), Friedrich Schiller University Jena, Humboldtstrasse 10, 07743 Jena, Germany; (B.S.); (A.V.); (I.N.); (S.H.); (D.H.); (A.T.)
- Jena Center for Soft Matter (JCSM), Friedrich Schiller University Jena, Philosophenweg 7, 07743 Jena, Germany; (S.S.); (M.B.)
| | - Dorothee Haas
- Laboratory of Organic and Macromolecular Chemistry (IOMC), Friedrich Schiller University Jena, Humboldtstrasse 10, 07743 Jena, Germany; (B.S.); (A.V.); (I.N.); (S.H.); (D.H.); (A.T.)
| | | | - Marc Lehmann
- SmartDyeLivery GmbH, Botzstrasse 5, 07743 Jena, Germany; (C.E.); (M.L.)
| | - Petra Babic
- Department of Anesthesiology and Intensive Care Medicine, Nanophysiology Group, Jena University Hospital, Am Klinikum 1, 07747 Jena, Germany; (A.T.P.); (P.B.); (K.J.B.)
- Center for Sepsis Control and Care, Jena University Hospital, 07747 Jena, Germany
| | - Kay Jovana Benecke
- Department of Anesthesiology and Intensive Care Medicine, Nanophysiology Group, Jena University Hospital, Am Klinikum 1, 07747 Jena, Germany; (A.T.P.); (P.B.); (K.J.B.)
- Center for Sepsis Control and Care, Jena University Hospital, 07747 Jena, Germany
| | - Anja Traeger
- Laboratory of Organic and Macromolecular Chemistry (IOMC), Friedrich Schiller University Jena, Humboldtstrasse 10, 07743 Jena, Germany; (B.S.); (A.V.); (I.N.); (S.H.); (D.H.); (A.T.)
- Jena Center for Soft Matter (JCSM), Friedrich Schiller University Jena, Philosophenweg 7, 07743 Jena, Germany; (S.S.); (M.B.)
| | - Michael Bauer
- Jena Center for Soft Matter (JCSM), Friedrich Schiller University Jena, Philosophenweg 7, 07743 Jena, Germany; (S.S.); (M.B.)
- Department of Anesthesiology and Intensive Care Medicine, Nanophysiology Group, Jena University Hospital, Am Klinikum 1, 07747 Jena, Germany; (A.T.P.); (P.B.); (K.J.B.)
- Center for Sepsis Control and Care, Jena University Hospital, 07747 Jena, Germany
| | - Ulrich S. Schubert
- Laboratory of Organic and Macromolecular Chemistry (IOMC), Friedrich Schiller University Jena, Humboldtstrasse 10, 07743 Jena, Germany; (B.S.); (A.V.); (I.N.); (S.H.); (D.H.); (A.T.)
- Jena Center for Soft Matter (JCSM), Friedrich Schiller University Jena, Philosophenweg 7, 07743 Jena, Germany; (S.S.); (M.B.)
- Correspondence: ; Tel.: +49-(0)-3641-9482-00
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Sutherland-Deveen ME, Wang T, Lamothe SM, Tschirhart JN, Guo J, Li W, Yang T, Du Y, Zhang S. Differential Regulation of Human Ether-à-Go-Go–Related Gene (hERG) Current and Expression by Activation of Protein Kinase C. Mol Pharmacol 2019; 96:1-12. [DOI: 10.1124/mol.118.115188] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Accepted: 04/17/2019] [Indexed: 01/14/2023] Open
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Al-Owais MM, Hettiarachchi NT, Kirton HM, Hardy ME, Boyle JP, Scragg JL, Steele DS, Peers C. A key role for peroxynitrite-mediated inhibition of cardiac ERG (Kv11.1) K + channels in carbon monoxide-induced proarrhythmic early afterdepolarizations. FASEB J 2017; 31:4845-4854. [PMID: 28743763 PMCID: PMC5636698 DOI: 10.1096/fj.201700259r] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Accepted: 07/05/2017] [Indexed: 12/20/2022]
Abstract
Exposure to CO causes early afterdepolarization arrhythmias. Previous studies in rats have indicated that arrhythmias arose as a result of augmentation of the late Na+ current. The purpose of the present study was to examine the basis for CO-induced arrhythmias in guinea pig myocytes in which action potentials (APs) more closely resemble those of human myocytes. Whole-cell current- and voltage-clamp recordings were made from isolated guinea pig myocytes as well as from human embryonic kidney 293 (HEK293) cells that express wild-type or a C723S mutant form of ether-a-go-go-related gene (ERG; Kv11.1). We also monitored the formation of peroxynitrite (ONOO-) in HEK293 cells fluorimetrically. CO-applied as the CO-releasing molecule, CORM-2-prolonged the APs and induced early afterdepolarizations in guinea pig myocytes. In HEK293 cells, CO inhibited wild-type, but not C723S mutant, Kv11.1 K+ currents. Inhibition was prevented by an antioxidant, mitochondrial inhibitors, or inhibition of NO formation. CO also raised ONOO- levels, an effect that was reversed by the ONOO- scavenger, FeTPPS [5,10,15,20-tetrakis-(4-sulfonatophenyl)-porphyrinato-iron(III)], which also prevented the CO inhibition of Kv11.1 currents and abolished the effects of CO on Kv11.1 tail currents and APs in guinea pig myocytes. Our data suggest that CO induces arrhythmias in guinea pig cardiac myocytes via the ONOO--mediated inhibition of Kv11.1 K+ channels.-Al-Owais, M. M., Hettiarachchi, N. T., Kirton, H. M., Hardy, M. E., Boyle, J. P., Scragg, J. L., Steele, D. S., Peers, C. A key role for peroxynitrite-mediated inhibition of cardiac ERG (Kv11.1) K+ channels in carbon monoxide-induced proarrhythmic early afterdepolarizations.
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Affiliation(s)
- Moza M Al-Owais
- Division of Cardiovascular and Diabetes Research, Leeds Institute of Cardiovascular and Metabolic Medicine, Faculty of Medicine and Health, University of Leeds, Leeds, United Kingdom; and
| | - Nishani T Hettiarachchi
- Division of Cardiovascular and Diabetes Research, Leeds Institute of Cardiovascular and Metabolic Medicine, Faculty of Medicine and Health, University of Leeds, Leeds, United Kingdom; and
| | - Hannah M Kirton
- Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Matthew E Hardy
- Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - John P Boyle
- Division of Cardiovascular and Diabetes Research, Leeds Institute of Cardiovascular and Metabolic Medicine, Faculty of Medicine and Health, University of Leeds, Leeds, United Kingdom; and
| | - Jason L Scragg
- Division of Cardiovascular and Diabetes Research, Leeds Institute of Cardiovascular and Metabolic Medicine, Faculty of Medicine and Health, University of Leeds, Leeds, United Kingdom; and
| | - Derek S Steele
- Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Chris Peers
- Division of Cardiovascular and Diabetes Research, Leeds Institute of Cardiovascular and Metabolic Medicine, Faculty of Medicine and Health, University of Leeds, Leeds, United Kingdom; and
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Yue J, López JM. JNK does not regulate meiotic progression in Xenopus oocytes: The strange case of pJNK and pERK. Dev Biol 2016; 416:42-51. [DOI: 10.1016/j.ydbio.2016.06.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Revised: 06/09/2016] [Accepted: 06/09/2016] [Indexed: 01/13/2023]
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Yue J, Ben Messaoud N, López JM. Hyperosmotic Shock Engages Two Positive Feedback Loops through Caspase-3-dependent Proteolysis of JNK1-2 and Bid. J Biol Chem 2015; 290:30375-89. [PMID: 26511318 DOI: 10.1074/jbc.m115.660506] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Indexed: 01/07/2023] Open
Abstract
Hyperosmotic shock induces early calpain activation, Smac/DIABLO release from the mitochondria, and p38/JNK activation in Xenopus oocytes. These pathways regulate late cytochrome c release and caspase-3 activation. Here, we show that JNK1-1 and JNK1-2 are activated early by osmostress, and sustained activation of both isoforms accelerates the apoptotic program. When caspase-3 is activated, JNK1-2 is proteolyzed at Asp-385 increasing the release of cytochrome c and caspase-3 activity, thereby creating a positive feedback loop. Expression of Bcl-xL markedly reduces hyperosmotic shock-induced apoptosis. In contrast, expression of Bid induces rapid caspase-3 activation, even in the absence of osmostress, which is blocked by Bcl-xL co-expression. In these conditions a significant amount of Bid in the cytosol is mono- and bi-ubiquitinated. Caspase-3 activation by hyperosmotic shock induces proteolysis of Bid and mono-ubiquitinated Bid at Asp-52 increasing the release of cytochrome c and caspase-3 activation, and thus creating a second positive feedback loop. Revealing the JNK isoforms and the loops activated by osmostress could help to design better treatments for human diseases caused by perturbations in fluid osmolarity.
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Affiliation(s)
- Jicheng Yue
- From the Institut de Neurociències, Departament de Bioquímica i Biologia Molecular, Unitat de Bioquímica, Facultad de Medicina, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Barcelona, Spain
| | - Nabil Ben Messaoud
- From the Institut de Neurociències, Departament de Bioquímica i Biologia Molecular, Unitat de Bioquímica, Facultad de Medicina, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Barcelona, Spain
| | - José M López
- From the Institut de Neurociències, Departament de Bioquímica i Biologia Molecular, Unitat de Bioquímica, Facultad de Medicina, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Barcelona, Spain
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Carretero L, Llavona P, López-Hernández A, Casado P, Cutillas PR, de la Peña P, Barros F, Domínguez P. ERK and RSK are necessary for TRH-induced inhibition of r-ERG potassium currents in rat pituitary GH3 cells. Cell Signal 2015; 27:1720-30. [PMID: 26022182 DOI: 10.1016/j.cellsig.2015.05.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2015] [Revised: 05/04/2015] [Accepted: 05/20/2015] [Indexed: 11/16/2022]
Abstract
The transduction pathway mediating the inhibitory effect that TRH exerts on r-ERG channels has been thoroughly studied in GH3 rat pituitary cells but some elements have yet to be discovered, including those involved in a phosphorylation event(s). Using a quantitative phosphoproteomic approach we studied the changes in phosphorylation caused by treatment with 1μM TRH for 5min in GH3 cells. The activating residues of Erk2 and Erk1 undergo phosphorylation increases of 5.26 and 4.87 fold, respectively, in agreement with previous reports of ERK activation by TRH in GH3 cells. Thus, we studied the possible involvement of ERK pathway in the signal transduction from TRH receptor to r-ERG channels. The MEK inhibitor U0126 at 0.5μM caused no major blockade of the basal r-ERG current, but impaired the TRH inhibitory effect on r-ERG. Indeed, the TRH effect on r-ERG was also reduced when GH3 cells were transfected with siRNAs against either Erk1 or Erk2. Using antibodies, we found that TRH treatment also causes activating phosphorylation of Rsk. The TRH effect on r-ERG current was also impaired when cells were transfected with any of two different siRNAs mixtures against Rsk1. However, treatment of GH3 cells with 20nM EGF for 5min, which causes ERK and RSK activation, had no effect on the r-ERG currents. Therefore, we conclude that in the native GH3 cell system, ERK and RSK are involved in the pathway linking TRH receptor to r-ERG channel inhibition, but additional components must participate to cause such inhibition.
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Affiliation(s)
- Luis Carretero
- Departamento de Bioquímica y Biología Molecular, Edificio Santiago Gascón, Campus de El Cristo, Universidad de Oviedo, 33006 Oviedo, Spain
| | - Pablo Llavona
- Departamento de Bioquímica y Biología Molecular, Edificio Santiago Gascón, Campus de El Cristo, Universidad de Oviedo, 33006 Oviedo, Spain
| | - Alejandro López-Hernández
- Departamento de Bioquímica y Biología Molecular, Edificio Santiago Gascón, Campus de El Cristo, Universidad de Oviedo, 33006 Oviedo, Spain
| | - Pedro Casado
- Integrative Cell Signalling and Proteomics, Centre for Haemato-Oncology, Barts Cancer Institute, Queen Mary University of London, Barts School of Medicine and Dentistry, London EC1M 6BQ, United Kingdom
| | - Pedro R Cutillas
- Integrative Cell Signalling and Proteomics, Centre for Haemato-Oncology, Barts Cancer Institute, Queen Mary University of London, Barts School of Medicine and Dentistry, London EC1M 6BQ, United Kingdom
| | - Pilar de la Peña
- Departamento de Bioquímica y Biología Molecular, Edificio Santiago Gascón, Campus de El Cristo, Universidad de Oviedo, 33006 Oviedo, Spain
| | - Francisco Barros
- Departamento de Bioquímica y Biología Molecular, Edificio Santiago Gascón, Campus de El Cristo, Universidad de Oviedo, 33006 Oviedo, Spain
| | - Pedro Domínguez
- Departamento de Bioquímica y Biología Molecular, Edificio Santiago Gascón, Campus de El Cristo, Universidad de Oviedo, 33006 Oviedo, Spain.
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Messaoud NB, Yue J, Valent D, Katzarova I, López JM. Osmostress-induced apoptosis in Xenopus oocytes: role of stress protein kinases, calpains and Smac/DIABLO. PLoS One 2015; 10:e0124482. [PMID: 25866890 PMCID: PMC4395108 DOI: 10.1371/journal.pone.0124482] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Accepted: 03/02/2015] [Indexed: 12/22/2022] Open
Abstract
Hyperosmotic shock induces cytochrome c release and caspase-3 activation in Xenopus oocytes, but the regulators and signaling pathways involved are not well characterized. Here we show that hyperosmotic shock induces rapid calpain activation and high levels of Smac/DIABLO release from the mitochondria before significant amounts of cytochrome c are released to promote caspase-3 activation. Calpain inhibitors or EGTA microinjection delays osmostress-induced apoptosis, and blockage of Smac/DIABLO with antibodies markedly reduces cytochrome c release and caspase-3 activation. Hyperosmotic shock also activates the p38 and JNK signaling pathways very quickly. Simultaneous inhibition of both p38 and JNK pathways reduces osmostress-induced apoptosis, while sustained activation of these kinases accelerates the release of cytochrome c and caspase-3 activation. Therefore, at least four different pathways early induced by osmostress converge on the mitochondria to trigger apoptosis. Deciphering the mechanisms of hyperosmotic shock-induced apoptosis gives insight for potential treatments of human diseases that are caused by perturbations in fluid osmolarity.
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Affiliation(s)
- Nabil Ben Messaoud
- Institut de Neurociències, Departament de Bioquímica i Biologia Molecular, Unitat de Bioquímica, Facultad de Medicina, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Barcelona, Spain
| | - Jicheng Yue
- Institut de Neurociències, Departament de Bioquímica i Biologia Molecular, Unitat de Bioquímica, Facultad de Medicina, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Barcelona, Spain
| | - Daniel Valent
- Institut de Neurociències, Departament de Bioquímica i Biologia Molecular, Unitat de Bioquímica, Facultad de Medicina, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Barcelona, Spain
| | - Ilina Katzarova
- Institut de Neurociències, Departament de Bioquímica i Biologia Molecular, Unitat de Bioquímica, Facultad de Medicina, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Barcelona, Spain
| | - José M. López
- Institut de Neurociències, Departament de Bioquímica i Biologia Molecular, Unitat de Bioquímica, Facultad de Medicina, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Barcelona, Spain
- * E-mail:
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Protein kinase C enhances human sodium channel hNav1.7 resurgent currents via a serine residue in the domain III-IV linker. FEBS Lett 2014; 588:3964-9. [PMID: 25240195 DOI: 10.1016/j.febslet.2014.09.011] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Revised: 08/30/2014] [Accepted: 09/02/2014] [Indexed: 11/20/2022]
Abstract
Resurgent sodium currents likely play a role in modulating neuronal excitability. Here we studied whether protein kinase C (PKC) activation can increase resurgent currents produced by the human sodium channel hNav1.7. We found that a PKC agonist significantly enhanced hNav1.7-mediated resurgent currents and this was prevented by PKC antagonists. The enhancing effects were replicated by two phosphorylation-mimicking mutations and were prevented by a phosphorylation-deficient mutation at a conserved PKC phosphorylation site (Serine 1479). Our results suggest that PKC can increase sodium resurgent currents through phosphorylation of a conserved Serine residue located in the domain III-IV linker of sodium channels.
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Wang T, Hogan-Cann A, Kang Y, Cui Z, Guo J, Yang T, Lamothe SM, Li W, Ma A, Fisher JT, Zhang S. Muscarinic receptor activation increases hERG channel expression through phosphorylation of ubiquitin ligase Nedd4-2. Mol Pharmacol 2014; 85:877-86. [PMID: 24688054 DOI: 10.1124/mol.113.091553] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The human ether-à-go-go-related gene (hERG) encodes the pore-forming subunit of the rapidly activating delayed rectifier potassium channel, which is important for cardiac repolarization. Reduction of hERG current due to genetic mutations or drug interferences causes long QT syndrome, leading to cardiac arrhythmias and sudden death. To date, there is no effective therapeutic method to restore or enhance hERG channel function. Using cell biology and electrophysiological methods, we found that the muscarinic receptor agonist carbachol increased the expression and function of hERG, but not ether-à-go-go or Kv1.5 channels stably expressed in human embryonic kidney cells. The carbachol-mediated increase in hERG expression was abolished by the selective M3 antagonist 4-DAMP (1,1-dimethyl-4-diphenylacetoxypiperidinium iodide) but not by the M2 antagonist AF-DX 116 (11[[2-[(diethylamino)methyl]-1-piperidinyl]-acetyl]-5,11-dihydro-6H-pyrido[2,3-b] [1,4]benzodiazepine-6-one). Treatment of cells with carbachol reduced the hERG-ubiquitin interaction and slowed the rate of hERG degradation. We previously showed that the E3 ubiquitin ligase Nedd4-2 mediates degradation of hERG channels. Here, we found that disrupting the Nedd4-2 binding domain in hERG completely eliminated the effect of carbachol on hERG channels. Carbachol treatment enhanced the phosphorylation level, but not the total level, of Nedd4-2. Blockade of the protein kinase C (PKC) pathway abolished the carbachol-induced enhancement of hERG channels. Our data suggest that muscarinic activation increases hERG channel expression by phosphorylating Nedd4-2 via the PKC pathway.
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Affiliation(s)
- Tingzhong Wang
- Department of Cardiovascular Medicine, First Affiliated Hospital of Xi'an Jiaotong University School of Medicine, Xi'an, China (T.W., A.M.); and Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada (T.W., A.H.-C., Y.K., Z.C., J.G., T.Y., S.M.L., W.L., J.T.F., S.Z.)
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Seyler C, Li J, Schweizer PA, Katus HA, Thomas D. Inhibition of cardiac two-pore-domain K+ (K2P) channels by the antiarrhythmic drug vernakalant--comparison with flecainide. Eur J Pharmacol 2013; 724:51-7. [PMID: 24374008 DOI: 10.1016/j.ejphar.2013.12.030] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2013] [Revised: 12/16/2013] [Accepted: 12/18/2013] [Indexed: 01/25/2023]
Abstract
The mixed ion channel blocker, vernakalant (RSD1235), is effective in rapid conversion of atrial fibrillation (AF) to sinus rhythm (SR). Suppression of cardiac two-pore-domain potassium (K2P) channels causes action potential prolongation and has recently been proposed as a novel antiarrhythmic strategy. The objective of this study was to investigate acute effects of vernakalant on human K2P2.1 (TREK-1) and K2P3.1 (TASK-1) channels to provide a more complete picture of its antiarrhythmic mechanism of action. The class IC antiarrhythmic drug flecainide was studied as a comparator agent. Two-electrode voltage clamp and whole-cell patch clamp electrophysiology was used to record K2P currents from Xenopus oocytes and Chinese hamster ovary (CHO) cells. Vernakalant inhibited cardiac K2P2.1 channels expressed in Xenopus oocytes and in CHO cells. The IC50 value obtained from mammalian cells (13.3 µM) was close to the range of vernakalant levels reported in patients (2-8 µM), indicating potential clinical significance of K2P2.1 blockade. Open rectification characteristics and current-voltage relationships of K2P2.1 currents were not affected by vernakalant. Vernakalant did not significantly reduce K2P3.1 currents. Finally, the class I antiarrhythmic drug flecainide had no effect on K2P2.1 or K2P3.1 channels. In conclusion, the recently developed antiarrhythmic drug vernakalant targets human K2P2.1 K(+) background channels. This previously unrecognized inhibitory property adds to the multichannel blocking profile of vernakalant and extends the mechanistic basis for its anti-fibrillatory effect.
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Affiliation(s)
- Claudia Seyler
- Department of Cardiology, Medical University Hospital, Heidelberg, Im Neuenheimer Feld 410, D-69120 Heidelberg, Germany
| | - Jin Li
- Department of Cardiology, Medical University Hospital, Heidelberg, Im Neuenheimer Feld 410, D-69120 Heidelberg, Germany
| | - Patrick A Schweizer
- Department of Cardiology, Medical University Hospital, Heidelberg, Im Neuenheimer Feld 410, D-69120 Heidelberg, Germany
| | - Hugo A Katus
- Department of Cardiology, Medical University Hospital, Heidelberg, Im Neuenheimer Feld 410, D-69120 Heidelberg, Germany
| | - Dierk Thomas
- Department of Cardiology, Medical University Hospital, Heidelberg, Im Neuenheimer Feld 410, D-69120 Heidelberg, Germany.
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12
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Zhang P, Xing J, Luo A, Feng J, Liu Z, Gao C, Ma J. Blockade of the human ether-a-go-go-related gene potassium channel by ketamine. ACTA ACUST UNITED AC 2013; 65:1321-8. [PMID: 23927470 DOI: 10.1111/jphp.12095] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2013] [Accepted: 05/12/2013] [Indexed: 11/27/2022]
Abstract
OBJECTIVES The inhibition of the cardiac rapid delayed rectifier potassium current (IKr ) and its cloned equivalent human ether-a-go-go-related gene (hERG) channel illustrate QT interval prolonging effects of a wide range of clinically used drugs. In this study, the direct interaction of the intravenous anaesthetic ketamine with wild-type (WT) and mutation hERG currents (IhERG ) was investigated. METHODS The hERG channel (WT, Y652A and F656A) was expressed in Xenopus oocytes and studied using standard two-microelectrode voltage-clamp techniques. KEY FINDINGS WT hERG is blocked in a concentration-dependent manner with IC50 = 12.05 ± 1.38 μm by ketamine, and the steady-state inactivation curves are shifted to more negative potentials (about -27 mV). The mutation to Ala of Y652 and F656 located on the S6 domain attenuate IhERG blockade by ketamine, and produced approximately 9-fold and 2.5-fold increases in IC50 compared with that of WT hERG channel, respectively. CONCLUSIONS Ketamine blocks WT IhERG expressed in Xenopus oocytes in a concentration-dependent manner and predominantly interacts with the open hERG channels. The interaction of ketamine with hERG channel may involve the aromatic residues Tyr652 and Phe656.
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Affiliation(s)
- Peihua Zhang
- Cardio-Electrophysiological Research Laboratory, Medical College, Wuhan University of Science and Technology, Wuhan, China
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13
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Mukherjee S, Thomas NL, Williams AJ. A mechanistic description of gating of the human cardiac ryanodine receptor in a regulated minimal environment. ACTA ACUST UNITED AC 2012; 140:139-58. [PMID: 22802361 PMCID: PMC3409104 DOI: 10.1085/jgp.201110706] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Cardiac muscle contraction, triggered by the action potential, is mediated by the release of Ca2+ from the sarcoplasmic reticulum through ryanodine receptor (RyR)2 channels. In situ, RyR2 gating is modulated by numerous physiological and pharmacological agents, and altered RyR2 function underlies the occurrence of arrhythmias in both inherited and acquired diseases. To understand fully the mechanisms underpinning the regulation of RyR2 in the normal heart and how these systems are altered in pathological conditions, we must first gain a detailed knowledge of the fundamental processes of RyR2 gating. In this investigation, we provide key novel mechanistic insights into the physical reality of RyR2 gating revealed by new experimental and analytical approaches. We have examined in detail the single-channel gating kinetics of the purified human RyR2 when activated by cytosolic Ca2+ in a stringently regulated environment where the modulatory influence of factors external to the channel were minimized. The resulting gating schemes are based on an accurate description of single-channel kinetics using hidden Markov model analysis and reveal several novel aspects of RyR2 gating behavior: (a) constitutive gating is observed as unliganded opening events; (b) binding of Ca2+ to the channel stabilizes it in different open states; (c) RyR2 exists in two preopening closed conformations in equilibrium, one of which binds Ca2+ more readily than the other; (d) the gating of RyR2 when bound to Ca2+ can be described by a kinetic scheme incorporating bursts; and (e) analysis of flicker closing events within bursts reveals gating activity that is not influenced by ligand binding. The gating schemes generated in this investigation provide a framework for future studies in which the mechanisms of action of key physiological regulatory factors, disease-linked mutations, and potential therapeutic compounds can be described precisely.
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Affiliation(s)
- Saptarshi Mukherjee
- Institute of Molecular and Experimental Medicine, Wales Heart Research Institute, Cardiff University School of Medicine, Cardiff CF14 4XN, Wales, UK
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14
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Vandenberg JI, Perry MD, Perrin MJ, Mann SA, Ke Y, Hill AP. hERG K+ Channels: Structure, Function, and Clinical Significance. Physiol Rev 2012; 92:1393-478. [DOI: 10.1152/physrev.00036.2011] [Citation(s) in RCA: 463] [Impact Index Per Article: 38.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The human ether-a-go-go related gene (hERG) encodes the pore-forming subunit of the rapid component of the delayed rectifier K+ channel, Kv11.1, which are expressed in the heart, various brain regions, smooth muscle cells, endocrine cells, and a wide range of tumor cell lines. However, it is the role that Kv11.1 channels play in the heart that has been best characterized, for two main reasons. First, it is the gene product involved in chromosome 7-associated long QT syndrome (LQTS), an inherited disorder associated with a markedly increased risk of ventricular arrhythmias and sudden cardiac death. Second, blockade of Kv11.1, by a wide range of prescription medications, causes drug-induced QT prolongation with an increase in risk of sudden cardiac arrest. In the first part of this review, the properties of Kv11.1 channels, including biogenesis, trafficking, gating, and pharmacology are discussed, while the second part focuses on the pathophysiology of Kv11.1 channels.
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Affiliation(s)
- Jamie I. Vandenberg
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Matthew D. Perry
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Mark J. Perrin
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Stefan A. Mann
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Ying Ke
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Adam P. Hill
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
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15
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Son YK, Hong DH, Choi TH, Choi SW, Shin DH, Kim SJ, Jung ID, Park YM, Jung WK, Kim DJ, Choi IW, Park WS. The inhibitory effect of BIM (I) on L-type Ca²⁺ channels in rat ventricular cells. Biochem Biophys Res Commun 2012; 423:110-5. [PMID: 22634012 DOI: 10.1016/j.bbrc.2012.05.091] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Accepted: 05/16/2012] [Indexed: 02/04/2023]
Abstract
We investigated the effect of a specific protein kinase C (PKC) inhibitor, bisindolylmaleimide I [BIM (I)], on L-type Ca(2+) channels in rat ventricular myocytes. BIM (I) alone inhibited the L-type Ca(2+) current in a concentration-dependent manner, with a K(d) value of 3.31 ± 0.25 μM, and a Hill coefficient of 2.34 ± 0.23. Inhibition was immediate after applying BIM (I) in the bath solution and then it partially washed out. The steady-state activation curve was not altered by applying 3μ M BIM (I), but the steady-state inactivation curve shifted to a more negative potential with a change in the slope factor. Other PKC inhibitors, PKC-IP and chelerythrine, showed no significant effects either on the L-type Ca(2+) current or on the inhibitory effect of BIM (I) on the L-type Ca(2+) current. The results suggest that the inhibitory effect of BIM (I) on the L-type Ca(2+) current is independent of the PKC pathway. Thus, our results should be considered in studies using BIM (I) to inhibit PKC activity and ion channel modulation.
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Affiliation(s)
- Youn Kyoung Son
- Department of Physiology, Kangwon National University School of Medicine, Chuncheon, Republic of Korea
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16
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Donovan AJ, Lansu K, Williams JG, Denning MF, Gentile S. Long QT2 mutation on the Kv11.1 ion channel inhibits current activity by ablating a protein kinase Cα consensus site. Mol Pharmacol 2012; 82:428-37. [PMID: 22653970 DOI: 10.1124/mol.112.077966] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Mutations that inhibit Kv11.1 ion channel activity contribute to abnormalities of cardiac repolarization that can lead to long QT2 (LQT2) cardiac arrhythmias and sudden death. However, for most of these mutations, nothing is known about the molecular mechanism linking Kv11.1 malfunction to cardiac death. We have previously demonstrated that disease-related mutations that create consensus sites for kinases on ion channels can dramatically change ion channel activity. Here, we show that a LQT2-associated mutation can inhibit Kv11.1 ion channel activity by perturbing a consensus site for the Ser/Thr protein kinase C α (PKCα). We first reveal by mass spectrometry analysis that Ser890 of the Kv11.1 ion channel is phosphorylated. Then, we demonstrate by a phospho-detection immunoassay combined with genetic manipulation that PKCα phosphorylates Ser890. Furthermore, we show that Ser890 phosphorylation is associated with an increase in Kv11.1 membrane density with alteration of recovery from inactivation. In addition, a newly discovered and as yet uncharacterized LQT2-associated nonsynonymous single nucleotide polymorphism 2660 G→A within the human ether-á-go-go-related gene 1 coding sequence, which replaces arginine 887 with a histidine residue (R887H), strongly inhibits PKCα-dependent phosphorylation of residue Ser890 on Kv11.1, and ultimately inhibits surface expression and current density. Taken together, our data provide a functional link between this channel mutation and LQT2.
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Affiliation(s)
- Alexander J Donovan
- Departments of Molecular Pharmacology and Therapeutics, Loyola University, Chicago, Illinois, USA
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17
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Ferreira JCB, Mochly-Rosen D, Boutjdir M. Regulation of cardiac excitability by protein kinase C isozymes. Front Biosci (Schol Ed) 2012. [PMID: 22202075 DOI: 10.2741/283] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Cardiac excitability and electrical activity are determined by the sum of individual ion channels, gap junctions and exchanger activities. Electrophysiological remodeling during heart disease involves changes in membrane properties of cardiomyocytes and is related to higher prevalence of arrhythmia-associated morbidity and mortality. Pharmacological and genetic manipulation of cardiac cells as well as animal models of cardiovascular diseases are used to identity changes in electrophysiological properties and the molecular mechanisms associated with the disease. Protein kinase C (PKC) and several other kinases play a pivotal role in cardiac electrophysiological remodeling. Therefore, identifying specific therapies that regulate these kinases is the main focus of current research. PKC, a family of serine/threonine kinases, has been implicated as potential signaling nodes associated with biochemical and biophysical stress in cardiovascular diseases. In this review, we describe the role of PKC isozymes that are involved in cardiac excitability and discuss both genetic and pharmacological tools that were used, their attributes and limitations. Selective and effective pharmacological interventions to normalize cardiac electrical activities and correct cardiac arrhythmias will be of great clinical benefit.
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18
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Son YK, Hong DH, Kim DJ, Firth AL, Park WS. Direct effect of protein kinase C inhibitors on cardiovascular ion channels. BMB Rep 2011; 44:559-65. [DOI: 10.5483/bmbrep.2011.44.9.559] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
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19
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Harmati G, Papp F, Szentandrássy N, Bárándi L, Ruzsnavszky F, Horváth B, Bányász T, Magyar J, Panyi G, Krasznai Z, Nánási PP. Effects of the PKC inhibitors chelerythrine and bisindolylmaleimide I (GF 109203X) on delayed rectifier K+ currents. Naunyn Schmiedebergs Arch Pharmacol 2010; 383:141-8. [PMID: 21120453 DOI: 10.1007/s00210-010-0584-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2010] [Accepted: 11/19/2010] [Indexed: 11/30/2022]
Abstract
Protein kinase C (PKC) inhibitors are useful tools for studying PKC-dependent regulation of ion channels. For this purpose, high PKC specificity is a basic requirement excluding any direct interaction between the PKC inhibitor and the ion channel. In the present study, the effects of two frequently applied PKC inhibitors, chelerythine and bisindolylmaleimide I, were studied on the rapid and slow components of the delayed rectifier K(+) current (I(Kr) and I(Ks)) in canine ventricular cardiomyocytes and on the human ether-à-go-go-related gene (hERG) channels expressed in human embryonic kidney (HEK) cells. The whole cell version of the patch clamp technique was used in all experiments. Chelerythrine and bisindolylmaleimide I (both 1 μM) suppressed I(Kr) in canine ventricular cells. This inhibition developed rapidly, suggesting a direct drug-channel interaction. In HEK cells heterologously expressing hERG channels, chelerythrine and bisindolylmaleimide I blocked hERG current in a concentration-dependent manner, having EC(50) values of 0.11 ± 0.01 and 0.76 ± 0.04 μM, respectively. Both chelerythrine and bisindolylmaleimide I strongly modified gating kinetics of hERG--voltage dependence of activation was shifted towards more negative voltages and activation was accelerated. Deactivation was slowed by bisindolylmaleimide I but not by chelerythrine. I(Ks) was not significantly altered by bisindolylmaleimide I and chelerythrine. No significant effect of 0.1 μM bisindolylmaleimide I or 0.1 μM PMA (PKC activator) was observed on I(Kr) arguing against significant contribution of PKC to regulation of I(Kr). It is concluded that neither chelerythrine nor bisindolylmaleimide I is suitable for selective PKC blockade due to their direct blocking actions on the hERG channel.
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Affiliation(s)
- Gábor Harmati
- Department of Physiology, University of Debrecen, 4012, Debrecen, P.O. Box 22, Hungary
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20
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Betzenhauser MJ, Marks AR. Ryanodine receptor channelopathies. Pflugers Arch 2010; 460:467-80. [PMID: 20179962 PMCID: PMC2885589 DOI: 10.1007/s00424-010-0794-4] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2010] [Revised: 01/26/2010] [Accepted: 01/28/2010] [Indexed: 02/07/2023]
Abstract
Ryanodine receptors (RyR) are intracellular Ca2+-permeable channels that provide the sarcoplasmic reticulum Ca2+ release required for skeletal and cardiac muscle contractions. RyR1 underlies skeletal muscle contraction, and RyR2 fulfills this role in cardiac muscle. Over the past 20 years, numerous mutations in both RyR isoforms have been identified and linked to skeletal and cardiac diseases. Malignant hyperthermia, central core disease, and catecholaminergic polymorphic ventricular tachycardia have been genetically linked to mutations in either RyR1 or RyR2. Thus, RyR channelopathies are both of interest because they cause significant human diseases and provide model systems that can be studied to elucidate important structure-function relationships of these ion channels.
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Affiliation(s)
- Matthew J Betzenhauser
- Department of Physiology, Clyde and Helen Wu Center for Molecular Cardiology, Columbia University College of Physicians and Surgeons, 630 West 168th Street, New York, NY 10032, USA
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21
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Coi A, Massarelli I, Saraceno M, Carli N, Testai L, Calderone V, Bianucci AM. Quantitative Structure-Activity Relationship Models for Predicting Biological Properties, Developed by Combining Structure- and Ligand-Based Approaches: An Application to the Human Ether-a-go-go-Related Gene Potassium Channel Inhibition. Chem Biol Drug Des 2009; 74:416-33. [DOI: 10.1111/j.1747-0285.2009.00873.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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22
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Polak S, Wiśniowska B, Brandys J. Collation, assessment and analysis of literature in vitro data on hERG receptor blocking potency for subsequent modeling of drugs' cardiotoxic properties. J Appl Toxicol 2009; 29:183-206. [PMID: 18988205 DOI: 10.1002/jat.1395] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The assessment of the torsadogenic potency of a new chemical entity is a crucial issue during lead optimization and the drug development process. It is required by the regulatory agencies during the registration process. In recent years, there has been a considerable interest in developing in silico models, which allow prediction of drug-hERG channel interaction at the early stage of a drug development process. The main mechanism underlying an acquired QT syndrome and a potentially fatal arrhythmia called torsades de pointes is the inhibition of potassium channel encoded by hERG (the human ether-a-go-go-related gene). The concentration producing half-maximal block of the hERG potassium current (IC(50)) is a surrogate marker for proarrhythmic properties of compounds and is considered a test for cardiac safety of drugs or drug candidates. The IC(50) values, obtained from data collected during electrophysiological studies, are highly dependent on experimental conditions (i.e. model, temperature, voltage protocol). For the in silico models' quality and performance, the data quality and consistency is a crucial issue. Therefore the main objective of our work was to collect and assess the hERG IC(50) data available in accessible scientific literature to provide a high-quality data set for further studies.
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Affiliation(s)
- Sebastian Polak
- Toxicology Department, Faculty of Pharmacy, Medical Collage, Jagiellonian University, Poland.
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23
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Ganapathi SB, Kester M, Elmslie KS. State-dependent block of HERG potassium channels by R-roscovitine: implications for cancer therapy. Am J Physiol Cell Physiol 2009; 296:C701-10. [PMID: 19244476 DOI: 10.1152/ajpcell.00633.2008] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Human ether-a-go-go-related gene (HERG) potassium channel acts as a delayed rectifier in cardiac myocytes and is an important target for both pro- and antiarrhythmic drugs. Many drugs have been pulled from the market for unintended HERG block causing arrhythmias. Conversely, recent evidence has shown that HERG plays a role in cell proliferation and is overexpressed both in multiple tumor cell lines and in primary tumor cells, which makes HERG an attractive target for cancer treatment. Therefore, a drug that can block HERG but that does not induce cardiac arrhythmias would have great therapeutic potential. Roscovitine is a cyclin-dependent kinase (CDK) inhibitor that is in phase II clinical trials as an anticancer agent. In the present study we show that R-roscovitine blocks HERG potassium current (human embryonic kidney-293 cells stably expressing HERG) at clinically relevant concentrations. The block (IC(50) = 27 microM) was rapid (tau = 20 ms) and reversible (tau = 25 ms) and increased with channel activation, which supports an open channel mechanism. Kinetic study of wild-type and inactivation mutant HERG channels supported block of activated channels by roscovitine with relatively little effect on either closed or inactivated channels. A HERG gating model reproduced all roscovitine effects. Our model of open channel block by roscovitine may offer an explanation of the lack of arrhythmias in clinical trials using roscovitine, which suggests the utility of a dual CDK/HERG channel block as an adjuvant cancer therapy.
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Affiliation(s)
- Sindura B Ganapathi
- Department of Pharmacology, Penn State College of Medicine, Milton S. Hershey Medical Center, 500 University Dr., Hershey, PA 17033, USA
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24
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Brennführer A, Neumann H, Pews-Davtyan A, Beller M. Catalytic and Stoichiometric Synthesis of Novel 3-Aminocarbonyl-, 3-Alkoxycarbonyl-, and 3-Amino-4-indolylmaleimides. European J Org Chem 2008. [DOI: 10.1002/ejoc.200800964] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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25
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Loss of luminal Ca2+ activation in the cardiac ryanodine receptor is associated with ventricular fibrillation and sudden death. Proc Natl Acad Sci U S A 2007; 104:18309-14. [PMID: 17984046 DOI: 10.1073/pnas.0706573104] [Citation(s) in RCA: 113] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Different forms of ventricular arrhythmias have been linked to mutations in the cardiac ryanodine receptor (RyR)2, but the molecular basis for this phenotypic heterogeneity is unknown. We have recently demonstrated that an enhanced sensitivity to luminal Ca(2+) and an increased propensity for spontaneous Ca(2+) release or store-overload-induced Ca(2+) release (SOICR) are common defects of RyR2 mutations associated with catecholaminergic polymorphic or bidirectional ventricular tachycardia. Here, we investigated the properties of a unique RyR2 mutation associated with catecholaminergic idiopathic ventricular fibrillation, A4860G. Single-channel analyses revealed that, unlike all other disease-linked RyR2 mutations characterized previously, the A4860G mutation diminished the response of RyR2 to activation by luminal Ca(2+), but had little effect on the sensitivity of the channel to activation by cytosolic Ca(2+). This specific impact of the A4860G mutation indicates that the luminal Ca(2+) activation of RyR2 is distinct from its cytosolic Ca(2+) activation. Stable, inducible HEK293 cells expressing the A4860G mutant showed caffeine-induced Ca(2+) release but exhibited no SOICR. Importantly, HL-1 cardiac cells transfected with the A4860G mutant displayed attenuated SOICR activity compared with cells transfected with RyR2 WT. These observations provide the first evidence that a loss of luminal Ca(2+) activation and SOICR activity can cause ventricular fibrillation and sudden death. These findings also indicate that although suppressing enhanced SOICR is a promising antiarrhythmic strategy, its oversuppression can also lead to arrhythmias.
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26
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Ryanodine receptor mutations in arrhythmias: advances in understanding the mechanisms of channel dysfunction. Biochem Soc Trans 2007; 35:946-51. [DOI: 10.1042/bst0350946] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The cardiac ryanodine receptor (RyR2) mediates rapid Ca2+ efflux from intracellular stores to effect myocyte contraction during the process of EC (excitation–contraction) coupling. It is now known that mutations in this channel perturb Ca2+ release function, leading to triggered arrhythmias that may cause SCD (sudden cardiac death). Resolving the precise molecular mechanisms by which SCD-linked RyR2 dysfunction occurs currently constitutes a burgeoning area of cardiac research. So far, defective channel phosphorylation, accessory protein binding, luminal/cytosolic Ca2+ sensing, and the disruption of interdomain interactions represent the main candidate mechanisms for explaining aberrant SR (sarcoplasmic reticulum) Ca2+ release via mutants of RyR2. It appears increasingly unlikely that a single exclusive common mechanism underlies every case of mutant channel dysfunction, and that each of these potential mechanisms may contribute to the resultant phenotype. The present review will consider very recent mechanistic developments in this field, including new observations from mutant RyR2 transgenic mouse models, peptide-probe studies, and the implications of functional and phenotypic heterogeneity of RyR2 mutations and polymorphisms.
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Nilles KM, London B. Knockin Animal Models of Inherited Arrhythmogenic Diseases: What Have We Learned From Them? J Cardiovasc Electrophysiol 2007; 18:1117-25. [PMID: 17573834 DOI: 10.1111/j.1540-8167.2007.00884.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Mouse models are becoming an increasingly accepted method of studying human diseases. Knockin and knockout techniques have several advantages over traditional transgenic overexpression, and the versatility of the knockin mouse allows the study of both gain of function mutations through targeted mutagenesis, as well as the replacement of one gene by another functional gene. Here, we will review the methods available to generate knockin mice; provide an overview of the techniques used to study electrophysiology in the mice at the cellular, organ, and whole animal level; and highlight knockin mice that have implications for inherited arrhythmias. Specifically, we will focus on models that used knockin mice to clarify gene expression, identify similarities and differences between related genes, and model human arrhythmia syndromes. Our goal is to provide the reader with a general understanding of studies done on knockin mouse models of inherited arrhythmias as well as ideas for future directions.
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Affiliation(s)
- Kathy M Nilles
- Cardiovascular Institute, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA
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28
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Bian JS, McDonald TV. Phosphatidylinositol 4,5-bisphosphate interactions with the HERG K(+) channel. Pflugers Arch 2007; 455:105-13. [PMID: 17622552 DOI: 10.1007/s00424-007-0292-5] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2007] [Accepted: 05/18/2007] [Indexed: 12/20/2022]
Abstract
Regulation of ion channel activity plays a central role in controlling heart rate, rhythm, and contractility responses to cardiovascular demands. Dynamic beat-to-beat regulation of ion channels is precisely adjusted by autonomic stimulation of cardiac G protein-coupled receptors. The rapidly activating delayed rectifier K(+) current (I (Kr)) is produced by the channel that is encoded by human ether-a-gogo-related gene (HERG) and is essential for the proper repolarization of the cardiac myocyte at the end of each action potential. Reduction of I (Kr) via HERG mutations or drug block can lead to lethal cardiac tachyarrhythmias. Autonomic regulation of HERG channels is an area of active investigation with the emerging picture of a complex interplay of signal transduction events, including kinases, second messengers, and protein-protein interactions. A recently described pathway for regulation of HERG is through channel interaction with the phospholipid phosphatidylinositol 4,5-bisphosphate (PIP2). Changes in cellular PIP2 concentrations may occur with Gq-coupled receptor activation. Here, we review the evidence for PIP2-HERG interactions, its potential biological significance, and unfilled gaps in our understanding of this regulatory mechanism.
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Affiliation(s)
- Jin-Song Bian
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117597, Singapore
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29
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Scherer D, Kiesecker C, Kulzer M, Günth M, Scholz EP, Kathöfer S, Thomas D, Maurer M, Kreuzer J, Bauer A, Katus HA, Karle CA, Zitron E. Activation of inwardly rectifying Kir2.x potassium channels by beta 3-adrenoceptors is mediated via different signaling pathways with a predominant role of PKC for Kir2.1 and of PKA for Kir2.2. Naunyn Schmiedebergs Arch Pharmacol 2007; 375:311-22. [PMID: 17534603 DOI: 10.1007/s00210-007-0167-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2006] [Accepted: 05/07/2007] [Indexed: 01/22/2023]
Abstract
beta(3)-adrenoceptors have recently been shown to induce a complex modulation of intracellular signaling pathways including cyclic guanine monophosphate, cyclic adenosine monophosphate, nitric oxide, and protein kinases A and C. They are expressed in a broad variety of tissues including the myocardium, vascular smooth muscle, and endothelium. In those tissues, resting membrane potential is controlled mainly by inwardly rectifying potassium channels of the Kir2 family namely, Kir2.1 in the vascular smooth muscle, Kir2.1-2.3 in the myocardium, and Kir2.1-2.2 in the endothelium. In the present study, we investigated the possible modulation of Kir2 channel function by beta(3)-adrenoceptors in an expression system. Human-cloned beta(3)-adrenoceptors and Kir2.1 (KCNJ2), Kir2.2 (KCNJ12), and Kir2.3 (KCNJ4) channels were coexpressed in Xenopus oocytes, and currents were measured with double-microelectrode voltage clamp. Activation of beta(3)-adrenoceptors with isoproterenol resulted in markedly increased currents in Kir2.1 and in Kir2.2 potassium channels with EC50 values of 27 and 18 nM, respectively. In contrast, Kir2.3 currents were not modulated. Coapplication of specific inhibitors of protein kinase A (KT-5720) and calmodulin kinase II (KN-93) had no effects on the observed regulation in Kir2.1. However, coapplication of protein kinase C (PKC) inhibitors staurosporine and chelerythrine suppressed the observed effect. In Kir2.2, coapplication of KT-5720 reduced the effect of beta(3)-adrenoceptor activation. No differences in current increase after application of isoproterenol were observed between mutant Kir2.2 potassium channels lacking all functional PKC phosphorylation sites and Kir2.2 wild-type channels. In heteromeric Kir2.x channels, all types of heteromers were activated. The effect was most pronounced in Kir2.1/Kir2.2 and in Kir2.2/Kir2.3 channels. In summary, homomeric and heteromeric Kir2.x channels are activated by beta(3)-adrenoceptors via different protein kinase-dependent pathways: Kir2.1 subunits are modulated by PKC, whereas Kir2.2 is modulated by protein kinase A. In heteromeric composition, a marked activation of currents can be observed particularly with involvement of Kir2.2 subunits. This regulation may contribute to the hyperpolarizing effects of beta(3)-adrenoceptors in tissues that exhibit modulation by Kir2 channel function.
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Affiliation(s)
- Daniel Scherer
- Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld 410, 69120, Heidelberg, Germany
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Thomas NL, George CH, Lai FA. Role of ryanodine receptor mutations in cardiac pathology: more questions than answers? Biochem Soc Trans 2007; 34:913-8. [PMID: 17052226 DOI: 10.1042/bst0340913] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The RyR (ryanodine receptor) mediates rapid Ca2+ efflux from the ER (endoplasmic reticulum) and is responsible for triggering numerous Ca2+-activated physiological processes. The most studied RyR-mediated process is excitation-contraction coupling in striated muscle, where plasma membrane excitation is transmitted to the cell interior and results in Ca2+ efflux that triggers myocyte contraction. Recently, single-residue mutations in the cardiac RyR (RyR2) have been identified in families that exhibit CPVT (catecholaminergic polymorphic ventricular tachycardia), a condition in which physical or emotional stress can trigger severe tachyarrhythmias that can lead to sudden cardiac death. The RyR2 mutations in CPVT are clustered in the N- and C-terminal domains, as well as in a central domain. Further, a critical signalling role for dysfunctional RyR2 has also been implicated in the generation of arrhythmias in the common condition of HF (heart failure). We have prepared cardiac RyR2 plasmids with various CPVT mutations to enable expression and analysis of Ca2+ release mediated by the wild-type and mutated RyR2. These studies suggest that the mutational locus may be important in the mechanism of Ca2+ channel dysfunction. Understanding the causes of aberrant Ca2+ release via RyR2 may assist in the development of effective treatments for the ventricular arrhythmias that often leads to sudden death in HF and in CPVT.
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Affiliation(s)
- N L Thomas
- Department of Cardiology, Wales Heart Research Institute, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK.
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Sánchez C, Méndez C, Salas JA. Indolocarbazole natural products: occurrence, biosynthesis, and biological activity. Nat Prod Rep 2006; 23:1007-45. [PMID: 17119643 DOI: 10.1039/b601930g] [Citation(s) in RCA: 303] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The indolocarbazole family of natural products, including the biosynthetically related bisindolylmaleimides, is reviewed (with 316 references cited). The isolation of indolocarbazoles from natural sources and the biosynthesis of this class of compounds are thoroughly reviewed, including recent developments in molecular genetics, enzymology and metabolic engineering. The biological activities and underlying modes of action displayed by natural and synthetic indolocarbazoles is also presented, with an emphasis on the development of analogs that have entered clinical trials for its future use against cancer or other diseases.
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Affiliation(s)
- César Sánchez
- Departamento de Biología Funcional & Instituto Universitario de Oncología del Principado de Asturias (I.U.O.P.A.), Universidad de Oviedo, 33006, Oviedo, Spain
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Ekins S, Balakin KV, Savchuk N, Ivanenkov Y. Insights for Human Ether-a-Go-Go-Related Gene Potassium Channel Inhibition Using Recursive Partitioning and Kohonen and Sammon Mapping Techniques. J Med Chem 2006; 49:5059-71. [PMID: 16913696 DOI: 10.1021/jm060076r] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The human ether-a-go-go related gene (hERG) can be inhibited by marketed drugs, and this inhibition may lead to QT prolongation and possibly fatal cardiac arrhythmia. We have collated literature data for 99 diverse hERG inhibitors to generate Kohonen maps, Sammon maps, and recursive partitioning models. Our aim was to investigate whether these computational models could be used either individually or together in a consensus approach to predict the binding of a prospectively selected test set of 35 diverse molecules and at the same time to offer further insights into hERG inhibition. The recursive partitioning model provided a quantitative prediction, which was markedly improved when Tanimoto similarity was included as a filter to remove molecules from the test set that were too dissimilar to the training set (r2 = 0.83, Spearman rho = 0.75, p = 0.0003 for the 18 remaining molecules, >0.77 similarity). This model was also used to screen and prioritize a database of drugs, recovering several hERG inhibitors not used in model building. The mapping approaches used molecular descriptors required for hERG inhibition that were not reported previously and in particular highlighted the importance of molecular shape. The Sammon map model provided the best qualitative classification of the test set (95% correct) compared with the Kohonen map model (81% correct), and this result was also superior to the consensus approach. This study illustrates that patch clamping data from various literature sources can be combined to generate valid models of hERG inhibition for prospective predictions.
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Affiliation(s)
- Sean Ekins
- ACT LLC, 601 Runnymede Avenue, Jenkintown, Pennsylvania 19046, USA.
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Kannankeril PJ, Mitchell BM, Goonasekera SA, Chelu MG, Zhang W, Sood S, Kearney DL, Danila CI, De Biasi M, Wehrens XHT, Pautler RG, Roden DM, Taffet GE, Dirksen RT, Anderson ME, Hamilton SL. Mice with the R176Q cardiac ryanodine receptor mutation exhibit catecholamine-induced ventricular tachycardia and cardiomyopathy. Proc Natl Acad Sci U S A 2006; 103:12179-84. [PMID: 16873551 PMCID: PMC1567715 DOI: 10.1073/pnas.0600268103] [Citation(s) in RCA: 146] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Mutations in the cardiac ryanodine receptor 2 (RyR2) have been associated with catecholaminergic polymorphic ventricular tachycardia and a form of arrhythmogenic right ventricular dysplasia. To study the relationship between RyR2 function and these phenotypes, we developed knockin mice with the human disease-associated RyR2 mutation R176Q. Histologic analysis of hearts from RyR2(R176Q/+) mice revealed no evidence of fibrofatty infiltration or structural abnormalities characteristic of arrhythmogenic right ventricular dysplasia, but right ventricular end-diastolic volume was decreased in RyR2(R176Q/+) mice compared with controls, indicating subtle functional impairment due to the presence of a single mutant allele. Ventricular tachycardia (VT) was observed after caffeine and epinephrine injection in RyR2(R176Q/+), but not in WT, mice. Intracardiac electrophysiology studies with programmed stimulation also elicited VT in RyR2(R176Q/+) mice. Isoproterenol administration during programmed stimulation increased both the number and duration of VT episodes in RyR2(R176Q/+) mice, but not in controls. Isolated cardiomyocytes from RyR2(R176Q/+) mice exhibited a higher incidence of spontaneous Ca(2+) oscillations in the absence and presence of isoproterenol compared with controls. Our results suggest that the R176Q mutation in RyR2 predisposes the heart to catecholamine-induced oscillatory calcium-release events that trigger a calcium-dependent ventricular arrhythmia.
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Affiliation(s)
| | | | - Sanjeewa A. Goonasekera
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY 14627; and
| | | | - Wei Zhang
- Medicine and Pharmacology, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Subeena Sood
- Departments of Molecular Physiology and Biophysics
| | | | | | - Mariella De Biasi
- Departments of Medicine and Physiology and Biophysics, University of Iowa Roy J. and Lucille A. Carver College of Medicine, Iowa City, IA 52242
| | - Xander H. T. Wehrens
- Departments of Molecular Physiology and Biophysics
- Medicine, Baylor College of Medicine, Houston, TX 77030
| | | | - Dan M. Roden
- Medicine and Pharmacology, Vanderbilt University School of Medicine, Nashville, TN 37232
| | | | - Robert T. Dirksen
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY 14627; and
| | - Mark E. Anderson
- Departments of Medicine and Physiology and Biophysics, University of Iowa Roy J. and Lucille A. Carver College of Medicine, Iowa City, IA 52242
| | - Susan L. Hamilton
- Departments of Molecular Physiology and Biophysics
- To whom correspondence should be addressed at:
Department of Molecular Physiology and Biophysics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030. E-mail:
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Yano M, Yamamoto T, Ikeda Y, Matsuzaki M. Mechanisms of Disease: ryanodine receptor defects in heart failure and fatal arrhythmia. ACTA ACUST UNITED AC 2006; 3:43-52. [PMID: 16391617 DOI: 10.1038/ncpcardio0419] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2005] [Accepted: 09/27/2005] [Indexed: 11/08/2022]
Abstract
Abnormal regulation of intracellular Ca(2+) by sarcoplasmic reticulum plays a part in the mechanism underlying contractile and relaxation dysfunction in heart failure (HF). The protein-kinase-A-mediated hyperphosphorylation of ryanodine receptors in the sarcoplasmic reticulum has been shown to cause the dissociation of FKBP12.6 (also known as calstabin-2) from ryanodine receptors in HF. In addition, several disease-linked mutations in the ryanodine receptors have been reported in patients with catecholaminergic polymorphic ventricular tachycardia or arrhythmogenic right ventricular cardiomyopathy type 2. The unique distribution of these mutation sites has led to the concept that the interaction among the putative regulatory domains within the ryanodine receptors has a key role in regulating channel opening. The knowledge gained from various studies of ryanodine receptors under pathologic conditions might lead to the development of new pharmacological or genetic strategies for the treatment of HF or cardiac arrhythmia. In this review, we focus on the role of the Ca(2+)-release channel, the ryanodine receptor, in the pathogenesis of HF and fatal arrhythmia, and the possibility of developing new therapeutic strategies for targeting this receptor.
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Affiliation(s)
- Masafumi Yano
- Department of Medical Bioregulation, Division of Cardiovascular Medicine, Yamaguchi University Graduate School of Medicine, Yamaguchi, Japan
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35
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Roy S, Eastman A, Gribble GW. Synthesis of bisindolylmaleimides related to GF109203x and their efficient conversion to the bioactive indolocarbazoles. Org Biomol Chem 2006; 4:3228-34. [PMID: 17036110 DOI: 10.1039/b607504e] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
From a structure-activity relationship perspective, the new indolocarbazoles 11 and 12 have been synthesized and evaluated biologically as novel Chk1 inhibitors. Compounds 11 and 12 were synthesized in high yield from indole via bisindolylmaleimides 18 and 24.
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Affiliation(s)
- Sudipta Roy
- Department of Chemistry, Dartmouth College, Hanover, NH 03755, USA
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Cockerill SL, Mitcheson JS. Direct block of human ether-a-go-go-related gene potassium channels by caffeine. J Pharmacol Exp Ther 2005; 316:860-8. [PMID: 16227470 DOI: 10.1124/jpet.105.094755] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The human ether-a-go-go-related gene (hERG) potassium channel is expressed in a variety of cell types, including neurons, tumor cells, and cardiac myocytes. In the heart, it is important for repolarization of the cardiac action potential. Attenuation of hERG current can cause long QT syndrome and cardiac arrhythmias such as torsades de pointes. Caffeine is frequently used as a pharmacological tool to study calcium-dependent transduction pathways in cellular preparations. It raises cytosolic calcium by opening ryanodine receptors and may also inhibit phosphodiesterases to increase cytosolic cAMP. In this study, we show 5 mM caffeine rapidly and reversibly attenuates hERG currents expressed in human embryonic kidney 293 cells to 61.1 +/- 2.2% of control. Caffeine-dependent inhibition of hERG current is not altered by raising cAMP with forskolin, buffering cytosolic calcium with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid, or inhibition of protein kinase C. Thus, the effects of caffeine are unlikely to be mediated by cAMP or intracellular calcium-dependent mechanisms. Further experiments showed caffeine directly blocks hERG in an open state-dependent manner. Furthermore, caffeine inhibition is greatly reduced by the pore mutants Y562A and F656A hERG, which disrupt block of most previously tested hERG antagonists. Thus, caffeine attenuates hERG currents by binding to a drug receptor located within the inner cavity of the channel. Dietary intake of caffeine is unlikely to cause long QT syndrome because plasma concentrations do not reach sufficiently high levels to significantly inhibit hERG currents. However, the effects of caffeine have implications for its use in examining calcium-dependent pathways in cellular preparations expressing hERG.
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Affiliation(s)
- S L Cockerill
- Department of Cell Physiology and Pharmacology, University of Leicester, UK
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38
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Newton PM, Messing RO. Intracellular signaling pathways that regulate behavioral responses to ethanol. Pharmacol Ther 2005; 109:227-37. [PMID: 16102840 DOI: 10.1016/j.pharmthera.2005.07.004] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2005] [Accepted: 07/13/2005] [Indexed: 10/25/2022]
Abstract
Recent evidence indicates that ethanol modulates the function of specific intracellular signaling cascades, including those that contain cyclic adenosine 3', 5'-monophosphate (cAMP)-dependent protein kinase A (PKA), protein kinase C (PKC), the tyrosine kinase Fyn, and phospholipase D (PLD). In some cases, the specific components of these cascades appear to mediate the effects of ethanol, whereas other components indirectly modify responses to ethanol. Studies utilizing selective inhibitors and genetically modified mice have identified specific isoforms of proteins involved in responses to ethanol. The effects of ethanol on neuronal signaling appear restricted to certain brain regions, partly due to the restricted distribution of these proteins. This likely contributes specificity to ethanol's actions on behavior. This review summarizes recent work on ethanol and intracellular signal transduction, emphasizing studies that have identified specific molecular events that underlie behavioral responses to ethanol.
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Affiliation(s)
- P M Newton
- The Ernest Gallo Clinic and Research Center, Department of Neurology, University of California at San Francisco, 5858 Horton Street, Suite 200, Emeryville, CA 94608, United States
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George CH, Thomas NL, Lai FA. Ryanodine receptor dysfunction in arrhythmia and sudden cardiac death. Future Cardiol 2005; 1:531-41. [DOI: 10.2217/14796678.1.4.531] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Mutations in ryanodine receptor calcium ion-release channels (RyR2) have emerged as important causative players in exercise/stress-induced ventricular arrhythmia leading to sudden cardiac death (SCD). Thus, RyR2 represents an attractive therapeutic target, and a detailed understanding of the mechanistic basis of RyR2 dysfunction at the molecular, cellular and organ level is essential for the development of novel, more effective therapeutic approaches to prevent arrhythmia and SCD. Such advances will translate into a tremendous improvement in the survival and quality of life of SCD-susceptible individuals. In this review, the authors consider how recent knowledge gained from mutation identification, phenotypic manifestation and functional evaluation of RyR2 mutants, are being used to develop novel therapeutic strategies in RyR2-dependent arrhythmia.
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Affiliation(s)
- Christopher H George
- Cardiff University School of Medicine, Department of Cardiology, Wales Heart Research Institute, Heath Park, Cardiff, CF14 4XN, UK
| | - N Lowri Thomas
- Cardiff University School of Medicine, Department of Cardiology, Wales Heart Research Institute, Heath Park, Cardiff, CF14 4XN, UK
| | - F Anthony Lai
- Cardiff University School of Medicine, Department of Cardiology, Wales Heart Research Institute, Heath Park, Cardiff, CF14 4XN, UK
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40
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Zissimopoulos S, Lai FA. Interaction of FKBP12.6 with the cardiac ryanodine receptor C-terminal domain. J Biol Chem 2004; 280:5475-85. [PMID: 15591045 DOI: 10.1074/jbc.m412954200] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The ryanodine receptor-calcium release channel complex (RyR) plays a pivotal role in excitation-contraction coupling in skeletal and cardiac muscle. RyR channel activity is modulated by interaction with FK506-binding protein (FKBP), and disruption of the RyR-FKBP association has been implicated in cardiomyopathy, cardiac hypertrophy, and heart failure. Evidence for an interaction between RyR and FKBP is well documented, both in skeletal muscle (RyR1-FKBP12) and in cardiac muscle (RyR2-FKBP12.6), however definition of the FKBP-binding site remains elusive. Early reports proposed interaction of a short RyR central domain with FKBP12/12.6, however this site has been questioned, and recently an alternative FKBP12.6 interaction site has been identified within the N-terminal half of RyR2. In this study, we report evidence for the human RyR2 C-terminal domain as a novel FKBP12.6-binding site. Using competition binding assays, we find that short C-terminal RyR2 fragments can displace bound FKBP12.6 from the native RyR2, although they are unable to exclusively support interaction with FKBP12.6. However, expression of a large RyR2 C-terminal construct in mammalian cells encompassing the pore-forming transmembrane domains exhibits rapamycin-sensitive binding specifically to FKBP12.6 but not to FKBP12. We also obtained some evidence for involvement of the RyR2 N-terminal, but not the central domain, in FKBP12.6 interaction. Our studies suggest that a novel interaction site for FKBP12.6 may be present at the RyR2 C terminus, proximal to the channel pore, a sterically appropriate location that would enable this protein to play a central role in the modulation of this critical ion channel.
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Affiliation(s)
- Spyros Zissimopoulos
- Wales Heart Research Institute, Department of Cardiology, University of Wales College of Medicine, Cardiff CF14 4XN, UK
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