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Qiao S, Dou Y, Hu H, Dai Y. Curcumin Activates Vagal Afferent Neurons Through the Modulation of Ion Channels via α7 nAChR. Nat Prod Commun 2019. [DOI: 10.1177/1934578x19873738] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Curcumin, a plant polyphenol, has been previously reported to attenuate collagen-induced arthritis in rats by modulating the function of the cholinergic system, but the underlying mechanism remains to be identified. In this study, primary nodose ganglion (NG) neurons were prepared from the adult rats and the electrophysiological recording was performed using the whole-cell patch clamp technique. Curcumin was shown to reduce total potassium currents and A-type currents, without significant effect on the activation or inactivation of potassium channels. Moreover, curcumin selectively enhanced tetrodotoxin-sensitive (TTX-S) sodium channel currents. These effects could be abolished by methyllycaconitine citrate (specific antagonist of α7 nACh receptor). Interestingly, curcumin did not modulate TTX-resistant (TTX-R) or calcium channels. These results suggest that curcumin increases the excitability of NG neurons by decreasing potassium currents and increasing TTX-S sodium currents via α7 nicotinic acetylcholine receptor (nAchR).
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Affiliation(s)
- Simiao Qiao
- Department of Pharmacology of Chinese Materia Medica, School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, China
| | - Yannong Dou
- Department of Pharmacology of Chinese Materia Medica, School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, China
| | - Huijuan Hu
- Department of Anesthesiology, Rutgers New Jersey Medical School, Newark, NJ, USA
| | - Yue Dai
- Department of Pharmacology of Chinese Materia Medica, School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, China
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2
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Lei CL, Clerx M, Beattie KA, Melgari D, Hancox JC, Gavaghan DJ, Polonchuk L, Wang K, Mirams GR. Rapid Characterization of hERG Channel Kinetics II: Temperature Dependence. Biophys J 2019; 117:2455-2470. [PMID: 31451180 PMCID: PMC6990152 DOI: 10.1016/j.bpj.2019.07.030] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 06/20/2019] [Accepted: 07/17/2019] [Indexed: 11/29/2022] Open
Abstract
Ion channel behavior can depend strongly on temperature, with faster kinetics at physiological temperatures leading to considerable changes in currents relative to room temperature. These temperature-dependent changes in voltage-dependent ion channel kinetics (rates of opening, closing, inactivating, and recovery) are commonly represented with Q10 coefficients or an Eyring relationship. In this article, we assess the validity of these representations by characterizing channel kinetics at multiple temperatures. We focus on the human Ether-à-go-go-Related Gene (hERG) channel, which is important in drug safety assessment and commonly screened at room temperature so that results require extrapolation to physiological temperature. In Part I of this study, we established a reliable method for high-throughput characterization of hERG1a (Kv11.1) kinetics, using a 15-second information-rich optimized protocol. In this Part II, we use this protocol to study the temperature dependence of hERG kinetics using Chinese hamster ovary cells overexpressing hERG1a on the Nanion SyncroPatch 384PE, a 384-well automated patch-clamp platform, with temperature control. We characterize the temperature dependence of hERG gating by fitting the parameters of a mathematical model of hERG kinetics to data obtained at five distinct temperatures between 25 and 37°C and validate the models using different protocols. Our models reveal that activation is far more temperature sensitive than inactivation, and we observe that the temperature dependency of the kinetic parameters is not represented well by Q10 coefficients; it broadly follows a generalized, but not the standardly-used, Eyring relationship. We also demonstrate that experimental estimations of Q10 coefficients are protocol dependent. Our results show that a direct fit using our 15-s protocol best represents hERG kinetics at any given temperature and suggests that using the Generalized Eyring theory is preferable if no experimental data are available to derive model parameters at a given temperature.
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Affiliation(s)
- Chon Lok Lei
- Computational Biology, Department of Computer Science, University of Oxford, Oxford, United Kingdom
| | - Michael Clerx
- Computational Biology, Department of Computer Science, University of Oxford, Oxford, United Kingdom
| | - Kylie A Beattie
- Computational Biology, Department of Computer Science, University of Oxford, Oxford, United Kingdom
| | - Dario Melgari
- School of Physiology, Pharmacology and Neuroscience, and Cardiovascular Research Laboratories, School of Medical Sciences, University of Bristol, Bristol, United Kingdom
| | - Jules C Hancox
- School of Physiology, Pharmacology and Neuroscience, and Cardiovascular Research Laboratories, School of Medical Sciences, University of Bristol, Bristol, United Kingdom
| | - David J Gavaghan
- Computational Biology, Department of Computer Science, University of Oxford, Oxford, United Kingdom
| | - Liudmila Polonchuk
- Pharma Research and Early Development, Innovation Center Basel, F. Hoffmann-La Roche, Basel, Switzerland
| | - Ken Wang
- Pharma Research and Early Development, Innovation Center Basel, F. Hoffmann-La Roche, Basel, Switzerland
| | - Gary R Mirams
- Centre for Mathematical Medicine and Biology, School of Mathematical Sciences, University of Nottingham, Nottingham, United Kingdom.
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Abstract
Long QT syndrome type 2 (LQT2) is caused by mutations in the human ether-à-go-go related gene (hERG), which encodes the Kv11.1 potassium channel in the heart. Over 30% of identified LQT2 mutations are nonsense or frameshift mutations that introduce premature termination codons (PTCs). Contrary to intuition, the predominant consequence of LQT2 nonsense and frameshift mutations is not the production of truncated proteins, but rather the degradation of mutant mRNA by nonsense-mediated mRNA decay (NMD), an RNA surveillance mechanism that selectively eliminates the mRNA transcripts that contain PTCs. In this chapter, we describe methods to study NMD of hERG nonsense and frameshift mutations in long QT syndrome.
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Affiliation(s)
- Qiuming Gong
- Knight Cardiovascular Institute, Oregon Health & Science University, 3181 S.W. Sam Jackson Park Rd., Mail Code CHH14Z, Portland, OR, 97239, USA
| | - Zhengfeng Zhou
- Knight Cardiovascular Institute, Oregon Health & Science University, 3181 S.W. Sam Jackson Park Rd., Mail Code CHH14Z, Portland, OR, 97239, USA.
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Gong Q, Stump MR, Zhou Z. Position of premature termination codons determines susceptibility of hERG mutations to nonsense-mediated mRNA decay in long QT syndrome. Gene 2014; 539:190-7. [PMID: 24530480 DOI: 10.1016/j.gene.2014.02.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Revised: 02/01/2014] [Accepted: 02/10/2014] [Indexed: 01/26/2023]
Abstract
The degradation of human ether-a-go-go-related gene (hERG, KCNH2) transcripts containing premature termination codon (PTC) mutations by nonsense-mediated mRNA decay (NMD) is an important mechanism of long QT syndrome type 2 (LQT2). The mechanisms governing the recognition of PTC-containing hERG transcripts as NMD substrates have not been established. We used a minigene system to study two frameshift mutations, R1032Gfs 25 and D1037Rfs 82. R1032Gfs 25 introduces a PTC in exon 14, whereas D1037Rfs 82 causes a PTC in the last exon (exon 15). We showed that R1032Gfs 25, but not D1037Rfs 82, reduced the level of mutant mRNA compared to the wild-type minigene in an NMD-dependent manner. The deletion of intron 14 prevented degradation of R1032Gfs 25 mRNA indicating that a downstream intron is required for NMD. The recognition and elimination of PTC-containing transcripts by NMD required that the mutation be positioned >54-60 nt upstream of the 3'-most exon-exon junction. Finally, we used a full-length hERG splicing-competent construct to show that inhibition of downstream intron splicing by antisense morpholino oligonucleotides inhibited NMD and rescued the functional expression of a third LQT2 mutation, Y1078. The present study defines the positional requirements for the susceptibility of LQT2 mutations to NMD and posits that the majority of reported LQT2 nonsense and frameshift mutations are potential targets of NMD.
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Affiliation(s)
- Qiuming Gong
- Knight Cardiovascular Institute, Oregon Health & Science University, Portland, OR, USA
| | - Matthew R Stump
- Knight Cardiovascular Institute, Oregon Health & Science University, Portland, OR, USA
| | - Zhengfeng Zhou
- Knight Cardiovascular Institute, Oregon Health & Science University, Portland, OR, USA.
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5
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Mechakra A, Vincent Y, Chevalier P, Millat G, Ficker E, Jastrzebski M, Poulin H, Pouliot V, Chahine M, Christé G. The variant hERG/R148W associated with LQTS is a mutation that reduces current density on co-expression with the WT. Gene 2013; 536:348-56. [PMID: 24334129 DOI: 10.1016/j.gene.2013.11.072] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Revised: 11/08/2013] [Accepted: 11/26/2013] [Indexed: 10/25/2022]
Abstract
BACKGROUND A variant of the ether-à-go-go related channel (hERG), p.Arg148Trp (R148W) was found at heterozygous state in two infants who died from sudden infant death syndrome (SIDS), one with documented prolonged QTc and Torsade de Pointes (TdP), and in an adult woman with QTc >500 ms, atrioventricular block and TdP. This variant was previously reported in cases of severe ventricular arrhythmia but very rarely in control subjects. Its classification as mutation or polymorphism awaited electrophysiological characterization. METHODS The properties of this N-terminal, proximal domain, hERG variant were explored in Xenopus oocytes injected with the same amount of RNA encoding for either hERG/WT or hERG/R148W or their equimolar mixture. The human ventricular cell (TNNP) model was used to test the effects of changes in hERG current. RESULTS R148W alone produced a current similar to the WT (369 ± 76 nA (mean ± SEM), n=13 versus 342 ± 55 nA in WT, n=13), while the co-expression of 1/2 WT+1/2 R148W lowered the current by 29% versus WT (243 ± 35 nA, n=13, p<0.05). The voltage dependencies of steady-state activation and inactivation were not changed in the variant alone or in co-expression with the WT. The time constants of fast recovery from inactivation and of fast and slow deactivation analyzed between -120 and +20 mV were not changed. The voltage-dependent distribution of the current amplitudes among fast-, slow- and non-deactivating fractions was unaltered. A 6.6% increase in APD90 from 323.5 ms to 345 ms was observed using the human cardiac ventricular myocyte model. CONCLUSIONS Such a decrease in hERG current as evidenced here when co-expressing the hERG/R148W variant with the WT may have predisposed to the observed long QT syndrome and associated TdP. Therefore, the heterozygous carriers of hERG/R148W may be at risk of cardiac sudden death.
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Affiliation(s)
- Asma Mechakra
- Laboratoire de Neurocardiologie, EA4612, Université Lyon 1, Lyon F-69003, France
| | - Yohann Vincent
- Laboratoire de Neurocardiologie, EA4612, Université Lyon 1, Lyon F-69003, France
| | - Philippe Chevalier
- Laboratoire de Neurocardiologie, EA4612, Université Lyon 1, Lyon F-69003, France; Unité de Rythmologie, Centre National de Référence des Troubles du Rythme d'Origine Héréditaire, Hôpital Cardiovasculaire et Pneumologique L. Pradel, Hospices Civils de Lyon, Lyon F-69003, France
| | - Gilles Millat
- Laboratoire de Neurocardiologie, EA4612, Université Lyon 1, Lyon F-69003, France; Laboratoire de Cardiogénétique, Centre de Biologie Est, Hospices Civils de Lyon, Lyon F-69003, France
| | | | - Marek Jastrzebski
- Department of Cardiology and Hypertension, University Hospital, Kracow, Poland
| | - Hugo Poulin
- Le Centre de Recherche en neuroscience, Institut Universitaire en Santé Mentale de Québec and Department of Medicine, Laval University, Québec, Canada
| | - Valérie Pouliot
- Le Centre de Recherche en neuroscience, Institut Universitaire en Santé Mentale de Québec and Department of Medicine, Laval University, Québec, Canada
| | - Mohamed Chahine
- Le Centre de Recherche en neuroscience, Institut Universitaire en Santé Mentale de Québec and Department of Medicine, Laval University, Québec, Canada
| | - Georges Christé
- Laboratoire de Neurocardiologie, EA4612, Université Lyon 1, Lyon F-69003, France.
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Kaufman ES. Mutation location matters in long QT syndrome type 2 (but behavior matters more). Heart Rhythm 2012; 10:68-9. [PMID: 23041577 DOI: 10.1016/j.hrthm.2012.10.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2012] [Indexed: 11/18/2022]
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Liu L, Hayashi K, Kaneda T, Ino H, Fujino N, Uchiyama K, Konno T, Tsuda T, Kawashiri MA, Ueda K, Higashikata T, Shuai W, Kupershmidt S, Higashida H, Yamagishi M. A novel mutation in the transmembrane nonpore region of the KCNH2 gene causes severe clinical manifestations of long QT syndrome. Heart Rhythm 2012; 10:61-7. [PMID: 23010577 DOI: 10.1016/j.hrthm.2012.09.053] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2012] [Indexed: 10/27/2022]
Abstract
BACKGROUND Long QT syndrome (LQTS) is characterized by prolonged ventricular repolarization and variable clinical course with arrhythmia-related syncope and sudden death. Mutations in the nonpore region of the LQTS-associated KCNH2 gene (also known as hERG) are mostly associated with coassembly or trafficking abnormalities, resulting in haplotype insufficiency and milder clinical phenotypes compared with mutations in the pore domain. OBJECTIVE To investigate the effect of a nonpore mutation on the channel current, which was identified from an LQTS family with severe clinical phenotypes. METHODS Two members of a Japanese family with LQTS were searched for mutations in KCNQ1, KCNH2, SCN5A, KCNE1, KCNE2, and KCNJ2 genes by using automated DNA sequencing. We characterized the electrophysiological properties and glycosylation pattern of the mutant channels by using patch clamp recording and Western blot analysis. RESULTS In the LQTS patient with torsades de pointes and cardiopulmonary arrest, we identified the novel T473P mutation in the transmembrane nonpore region of KCNH2. The proband's father carried the same mutation and showed prolonged corrected QT interval and frequent torsades de pointes in the presence of hypokalemia following the administration of garenoxacin. Patch clamp analysis in heterologous cells showed that hERG T473P channels generated no current and exhibited a dominant negative effect when coexpressed with wild-type protein. Only incompletely glycosylated hERG T473P channels were observed by using Western blot analysis, suggesting impaired trafficking. CONCLUSIONS These results demonstrated that a trafficking-deficient mutation in the transmembrane nonpore region of KCNH2 causes a dominant negative effect and a severe clinical course in affected patients.
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Affiliation(s)
- Li Liu
- Department of Biophysical Genetics, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan
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Abstract
KCNE2, originally designated MinK-related peptide 1 (MiRP1), belongs to a five-strong family of potassium channel ancillary (β) subunits that, despite the diminutive size of the family and its members, has loomed large in the field of ion channel physiology. KCNE2 dictates K (+) channel gating, conductance, α subunit composition, trafficking and pharmacology, and also modifies functional properties of monovalent cation-nonselective HCN channels. The Kcne2 (-/-) mouse exhibits cardiac arrhythmia and hypertrophy, achlorhydria, gastric neoplasia, hypothyroidism, alopecia, stunted growth and choroid plexus epithelial dysfunction, illustrating the breadth and depth of the influence of KCNE2, mutations which are also associated with human cardiac arrhythmias. Here, the modus operandi and physiological roles of this potent regulator of membrane excitability and ion secretion are reviewed with particular emphasis on the ability of KCNE2 to shape the electrophysiological landscape of both excitable and non-excitable cells.
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Affiliation(s)
- Geoffrey W Abbott
- Departments of Pharmacology and Physiology and Biophysics, University of California, Irvine, Irvine, CA, USA.
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Mihic A, Chauhan VS, Gao X, Oudit GY, Tsushima RG. Trafficking defect and proteasomal degradation contribute to the phenotype of a novel KCNH2 long QT syndrome mutation. PLoS One 2011; 6:e18273. [PMID: 21483829 PMCID: PMC3069070 DOI: 10.1371/journal.pone.0018273] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2010] [Accepted: 02/25/2011] [Indexed: 12/26/2022] Open
Abstract
The Kv11.1 (hERG) K+ channel plays a fundamental role in cardiac repolarization. Missense mutations in KCNH2, the gene encoding Kv11.1, cause long QT syndrome (LQTS) and frequently cause channel trafficking-deficiencies. This study characterized the properties of a novel KCNH2 mutation discovered in a LQT2 patient resuscitated from a ventricular fibrillation arrest. Proband genotyping was performed by SSCP and DNA sequencing. The electrophysiological and biochemical properties of the mutant channel were investigated after expression in HEK293 cells. The proband manifested a QTc of 554 ms prior to electrolyte normalization. Mutation analysis revealed an autosomal dominant frameshift mutation at proline 1086 (P1086fs+32X; 3256InsG). Co-immunoprecipitation demonstrated that wild-type Kv11.1 and mutant channels coassemble. Western blot showed that the mutation did not produce mature complex-glycosylated Kv11.1 channels and coexpression resulted in reduced channel maturation. Electrophysiological recordings revealed mutant channel peak currents to be similar to untransfected cells. Co-expression of channels in a 1∶1 ratio demonstrated dominant negative suppression of peak Kv11.1 currents. Immunocytochemistry confirmed that mutant channels were not present at the plasma membrane. Mutant channel trafficking rescue was attempted by incubation at reduced temperature or with the pharmacological agents E-4031. These treatments did not significantly increase peak mutant currents or induce the formation of mature complex-glycosylated channels. The proteasomal inhibitor lactacystin increased the protein levels of the mutant channels demonstrating proteasomal degradation, but failed to induce mutant Kv11.1 protein trafficking. Our study demonstrates a novel dominant-negative Kv11.1 mutation, which results in degraded non-functional channels leading to a LQT2 phenotype.
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Affiliation(s)
- Anton Mihic
- Departments of Medicine and Physiology, University of Toronto, Toronto, Ontario, Canada
| | - Vijay S. Chauhan
- Division of Cardiology, University Health Network, Toronto, Ontario, Canada
| | - Xiaodong Gao
- Department of Biology, York University, Toronto, Ontario, Canada
| | - Gavin Y. Oudit
- Department of Medicine, Mazankowski Alberta Heart Institute and Division of Cardiology, University of Alberta, Edmonton, Alberta, Canada
- * E-mail: (GYO); (RGT)
| | - Robert G. Tsushima
- Department of Biology, York University, Toronto, Ontario, Canada
- * E-mail: (GYO); (RGT)
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Harkcom WT, Abbott GW. Emerging concepts in the pharmacogenomics of arrhythmias: ion channel trafficking. Expert Rev Cardiovasc Ther 2010; 8:1161-73. [PMID: 20670193 DOI: 10.1586/erc.10.89] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Continuous, rhythmic beating of the heart requires exquisite control of expression, localization and function of cardiac ion channels - the foundations of the cardiac myocyte action potential. Disruption of any of these processes can alter the shape of the action potential, predisposing to cardiac arrhythmias. These arrhythmias can manifest in a variety of ways depending on both the channels involved and the type of disruption (i.e., gain or loss of function). As much as 1% of the population of developed countries is affected by cardiac arrhythmia each year, and a detailed understanding of the mechanism of each arrhythmia is crucial to developing and prescribing the proper therapies. Many of the antiarrhythmic drugs currently on the market were developed before the underlying cause of the arrhythmia was known, and as a result lack specificity, causing side effects. The majority of the available drugs target the conductance of cardiac ion channels, either by blocking or enhancing current through the channel. In recent years, however, it has become apparent that specific targeting of ion channel conductance may not be the most effective means for treatment. Here we review increasing evidence that suggests defects in ion channel trafficking play an important role in the etiology of arrhythmias, and small molecule approaches to correct trafficking defects will likely play an important role in the future of arrhythmia treatment.
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Affiliation(s)
- William T Harkcom
- Department of Pharmacology, Weill Medical College of Cornell University, 520 E 70th Street, New York, NY 10021, USA
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Congenital long QT syndrome caused by the F275S KCNQ1 mutation: mechanism of impaired channel function. Biochem Biophys Res Commun 2009; 380:127-31. [PMID: 19167356 DOI: 10.1016/j.bbrc.2009.01.051] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2008] [Accepted: 01/13/2009] [Indexed: 01/22/2023]
Abstract
Congenital long QT syndrome is characterized by a prolongation of ventricular repolarization and recurrent episodes of life-threatening ventricular tachyarrhythmias, often leading to sudden death. We previously identified a missense mutation F275S located within the S5 transmembrane domain of the KCNQ1 ion channel in a Chinese family with long QT syndrome. We used oocyte expression of the KCNQ1 polypeptide to study the effects of the F275S mutation on channel properties. Expression of the F275 mutant, or co-expression with the wild-type S275 polypeptide, significantly decreased channel current amplitudes. Moreover, the F275S substitution decreased the rates of channel activation and deactivation. In transfected HEK293 cells fluorescence microscopy revealed that the F275S mutation perturbed the subcelluar localization of the ion channel. These results indicate that the F275S KCNQ1 mutation leads to impaired polypeptide trafficking that in turn leads to reduction of channel ion currents and altered gating kinetics.
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Yao Y, Teng S, Li N, Zhang Y, Boyden PA, Pu J. Aminoglycoside antibiotics restore functional expression of truncated HERG channels produced by nonsense mutations. Heart Rhythm 2009; 6:553-60. [PMID: 19324319 DOI: 10.1016/j.hrthm.2009.01.017] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2008] [Accepted: 01/11/2009] [Indexed: 11/17/2022]
Abstract
BACKGROUND Pharmacologic restoration of the trafficking defects of HERG missense mutations has been documented. However, whether correction of HERG nonsense mutations is possible is unknown. OBJECTIVE The purpose of this study was to investigate the effect of aminoglycoside antibiotics on the expression of nonsense mutants expected to produce truncated HERG channels. METHODS HERG channel and mutant currents were recorded by whole-cell patch clamp techniques. Pharmacologic rescue was applied by culturing the cells in 400 microg/mL G-418 or gentamicin for 24 hours. RESULTS Current densities were significantly reduced in cells expressing R1014X and W927X mutants compared to those of cells expressing wild-type (WT) HERG. R863X and E698X mutants failed to generate any typical HERG currents. Mean peak tail current density of R1014X mutant was significantly lower than that of WT (3.9 +/- 1.4 pA/pF, n = 8, vs 47.8 +/- 6.3 pA/pF, n = 12, P <.05) and increased to 12.7 +/- 3.3 pA/pF (n = 7, P <.05) and 18.3 +/- 3.7 pA/pF (n = 8, P <.05) after G-418 and gentamicin treatment. The voltage dependence of activation of R1014X was also restored after drug treatment. Furthermore, expression of full-length proteins for R1014X induced by drugs was detected by western blot and confocal imaging. Similar results were observed in W927X. For R863X and E698X, however, gentamicin treatment had no effect. In the cells cotransfected with WT/R1014X, gentamicin and G-418 demonstrated different results: gentamicin, but not G-418, increased the current density by 2.2-fold (n = 12, P <.05). CONCLUSION The study findings provide proof of principle that interventions designed to read through premature stop mutations may at least partially reverse the LQT2 phenotype in vitro.
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Affiliation(s)
- Yan Yao
- Center for Arrhythmia Diagnosis and Treatment, Cardiovascular Institute and Fu Wai Hospital, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China
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