1
|
Trayanova NA, Lyon A, Shade J, Heijman J. Computational modeling of cardiac electrophysiology and arrhythmogenesis: toward clinical translation. Physiol Rev 2024; 104:1265-1333. [PMID: 38153307 DOI: 10.1152/physrev.00017.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Revised: 12/19/2023] [Accepted: 12/21/2023] [Indexed: 12/29/2023] Open
Abstract
The complexity of cardiac electrophysiology, involving dynamic changes in numerous components across multiple spatial (from ion channel to organ) and temporal (from milliseconds to days) scales, makes an intuitive or empirical analysis of cardiac arrhythmogenesis challenging. Multiscale mechanistic computational models of cardiac electrophysiology provide precise control over individual parameters, and their reproducibility enables a thorough assessment of arrhythmia mechanisms. This review provides a comprehensive analysis of models of cardiac electrophysiology and arrhythmias, from the single cell to the organ level, and how they can be leveraged to better understand rhythm disorders in cardiac disease and to improve heart patient care. Key issues related to model development based on experimental data are discussed, and major families of human cardiomyocyte models and their applications are highlighted. An overview of organ-level computational modeling of cardiac electrophysiology and its clinical applications in personalized arrhythmia risk assessment and patient-specific therapy of atrial and ventricular arrhythmias is provided. The advancements presented here highlight how patient-specific computational models of the heart reconstructed from patient data have achieved success in predicting risk of sudden cardiac death and guiding optimal treatments of heart rhythm disorders. Finally, an outlook toward potential future advances, including the combination of mechanistic modeling and machine learning/artificial intelligence, is provided. As the field of cardiology is embarking on a journey toward precision medicine, personalized modeling of the heart is expected to become a key technology to guide pharmaceutical therapy, deployment of devices, and surgical interventions.
Collapse
Affiliation(s)
- Natalia A Trayanova
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland, United States
- Alliance for Cardiovascular Diagnostic and Treatment Innovation, Johns Hopkins University, Baltimore, Maryland, United States
| | - Aurore Lyon
- Department of Biomedical Engineering, CARIM School for Cardiovascular Diseases, Maastricht University, Maastricht, The Netherlands
- Division of Heart and Lungs, Department of Medical Physiology, University Medical Centre Utrecht, Utrecht, The Netherlands
| | - Julie Shade
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland, United States
- Alliance for Cardiovascular Diagnostic and Treatment Innovation, Johns Hopkins University, Baltimore, Maryland, United States
| | - Jordi Heijman
- Department of Cardiology, CARIM School for Cardiovascular Diseases, Maastricht University, Maastricht, The Netherlands
| |
Collapse
|
2
|
Egly CL, Barny LA, Do T, McDonald EF, Knollmann BC, Plate L. The proteostasis interactomes of trafficking-deficient variants of the voltage-gated potassium channel K V11.1 associated with long QT syndrome. J Biol Chem 2024; 300:107465. [PMID: 38876300 PMCID: PMC11284683 DOI: 10.1016/j.jbc.2024.107465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2024] [Revised: 05/16/2024] [Accepted: 06/04/2024] [Indexed: 06/16/2024] Open
Abstract
The voltage-gated potassium ion channel KV11.1 plays a critical role in cardiac repolarization. Genetic variants that render Kv11.1 dysfunctional cause long QT syndrome (LQTS), which is associated with fatal arrhythmias. Approximately 90% of LQTS-associated variants cause intracellular protein transport (trafficking) dysfunction, which pharmacological chaperones like E-4031 can rescue. Protein folding and trafficking decisions are regulated by chaperones, protein quality control factors, and trafficking machinery comprising the cellular proteostasis network. Here, we test whether trafficking dysfunction is associated with alterations in the proteostasis network of pathogenic Kv11.1 variants and whether pharmacological chaperones can normalize the proteostasis network of responsive variants. We used affinity-purification coupled with tandem mass tag-based quantitative mass spectrometry to assess protein interaction changes of WT KV11.1 or trafficking-deficient channel variants in the presence or absence of E-4031. We identified 572 core KV11.1 protein interactors. Trafficking-deficient variants KV11.1-G601S and KV11.1-G601S-G965∗ had significantly increased interactions with proteins responsible for folding, trafficking, and degradation compared to WT. We confirmed previous findings that the proteasome is critical for KV11.1 degradation. Our report provides the first comprehensive characterization of protein quality control mechanisms of KV11.1. We find extensive interactome remodeling associated with trafficking-deficient KV11.1 variants and with pharmacological chaperone rescue of KV11.1 cell surface expression. The identified protein interactions could be targeted therapeutically to improve KV11.1 trafficking and treat LQTS.
Collapse
Affiliation(s)
- Christian L Egly
- Department of Medicine, Vanderbilt University Medical Center, Nasville, Tennessee, USA
| | - Lea A Barny
- Program in Chemical and Physical Biology, Vanderbilt University, Nashville, Tennessee, USA; Department of Chemistry, Vanderbilt University, Nashville, Tennessee, USA
| | - Tri Do
- Department of Medicine, Vanderbilt University Medical Center, Nasville, Tennessee, USA
| | - Eli F McDonald
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee, USA
| | - Björn C Knollmann
- Department of Medicine, Vanderbilt University Medical Center, Nasville, Tennessee, USA.
| | - Lars Plate
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee, USA; Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, USA; Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, USA.
| |
Collapse
|
3
|
Sun S, Xu Z, Lin Z, Chen W, Zhang Y, Yan M, Ren S, Liu Q, Zhu H, Tian B, Zhang J, Zhang W, Jiang S, Sheng C, Ge J, Chen F, Dong Z. A biomimetic ion channel shortens the QT interval of type 2 long QT syndrome through efficient transmembrane transport of potassium ions. Acta Biomater 2024; 181:391-401. [PMID: 38704114 DOI: 10.1016/j.actbio.2024.04.046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Revised: 04/28/2024] [Accepted: 04/30/2024] [Indexed: 05/06/2024]
Abstract
Potassium ion transport across myocardial cell membrane is essential for type 2 long QT syndrome (LQT2). However, the dysfunction of potassium ion transport due to genetic mutations limits the therapeutic effect in treating LQT2. Biomimetic ion channels that selectively and efficiently transport potassium ions across the cellular membranes are promising for the treatment of LQT2. To corroborate this, we synthesized a series of foldamer-based ion channels with different side chains, and found a biomimetic ion channel of K+ (BICK) with the highest transport activity among them. The selected BICK can restore potassium ion transport and increase transmembrane potassium ion current, thus shortening phase 3 of action potential (AP) repolarization and QT interval in LQT2. Moreover, BICK does not affect heart rate and cardiac rhythm in treating LQT2 model induced by E4031 in isolated heart as well as in guinea pigs. By restoring ion transmembrane transport tactic, biomimetic ion channels, such as BICK, will show great potential in treating diseases related to ion transport blockade. STATEMENT OF SIGNIFICANCE: Type 2 long QT syndrome (LQT2) is a disease caused by K+ transport disorder, which can cause malignant arrhythmia and even death. There is currently no radical cure, so it is critical to explore ways to improve K+ transmembrane transport. In this study, we report that a small-molecule biomimetic ion channel BICK can efficiently simulate natural K+ channel proteins on the cardiomyocyte and cure E4031-induced LQT2 in guinea pig by restoring K+ transport function for the first time. This study found that the potassium transmembrane transport by BICK significantly reduced the QT interval, which provides a conceptually new strategy for the treatment of LQT2 disease.
Collapse
Affiliation(s)
- Shuang Sun
- Key Laboratory of Pathobiology, Ministry of Education, Nanomedicine and Translational Research Center, China-Japan Union Hospital, Jilin University, Changchun 130021, China
| | - Zhaocheng Xu
- State Key Laboratory of Supramolecular Structure and Materials, and Center for Supramolecular Chemical Biology, Jilin University, Changchun 130021, China
| | - Ze Lin
- State Key Laboratory of Supramolecular Structure and Materials, and Center for Supramolecular Chemical Biology, Jilin University, Changchun 130021, China
| | - Weiwei Chen
- Department of Cardiology, China-Japan Union Hospital, Jilin University, Changchun 130021, China
| | - Yue Zhang
- Key Laboratory of Pathobiology, Ministry of Education, Nanomedicine and Translational Research Center, China-Japan Union Hospital, Jilin University, Changchun 130021, China
| | - Mengjie Yan
- Department of Cardiology, China-Japan Union Hospital, Jilin University, Changchun 130021, China
| | - Shengnan Ren
- Key Laboratory of Pathobiology, Ministry of Education, Nanomedicine and Translational Research Center, China-Japan Union Hospital, Jilin University, Changchun 130021, China
| | - Qihui Liu
- Key Laboratory of Pathobiology, Ministry of Education, Nanomedicine and Translational Research Center, China-Japan Union Hospital, Jilin University, Changchun 130021, China
| | - Huimin Zhu
- Department of Gynecology, China-Japan Union Hospital, Jilin University, Changchun 130021, China
| | - Bin Tian
- Key Laboratory of Pathobiology, Ministry of Education, Nanomedicine and Translational Research Center, China-Japan Union Hospital, Jilin University, Changchun 130021, China
| | - Jian Zhang
- Department of Anesthesiology, The First Hospital, Jilin University, Changchun 130021, China
| | - Weijia Zhang
- Department of Vascular Surgery, China-Japan Union Hospital, Jilin University, Changchun 130021, China
| | - Shan Jiang
- Key Laboratory of Pathobiology, Ministry of Education, Nanomedicine and Translational Research Center, China-Japan Union Hospital, Jilin University, Changchun 130021, China
| | - Chuqiao Sheng
- State Key Laboratory of Supramolecular Structure and Materials, and Center for Supramolecular Chemical Biology, Jilin University, Changchun 130021, China
| | - Jingyan Ge
- Department of Physiology, College of Basic Medical Sciences, Jilin University, Changchun 130021, China.
| | - Fangfang Chen
- Key Laboratory of Pathobiology, Ministry of Education, Nanomedicine and Translational Research Center, China-Japan Union Hospital, Jilin University, Changchun 130021, China.
| | - Zeyuan Dong
- State Key Laboratory of Supramolecular Structure and Materials, and Center for Supramolecular Chemical Biology, Jilin University, Changchun 130021, China.
| |
Collapse
|
4
|
Hu Y, Zhang C, Wang S, Xiong H, Xie W, Zeng Z, Cai H, Wang QK, Lu Z. 14-3-3ε/YWHAE regulates the transcriptional expression of cardiac sodium channel Na V1.5. Heart Rhythm 2024:S1547-5271(24)02557-8. [PMID: 38750908 DOI: 10.1016/j.hrthm.2024.05.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2023] [Revised: 05/02/2024] [Accepted: 05/07/2024] [Indexed: 06/12/2024]
Abstract
BACKGROUND Cardiac voltage-gated sodium channel alpha subunit 5 (NaV1.5) encoded by SCN5A is associated with arrhythmia disorders. However, the molecular mechanism underlying NaV1.5 expression remains to be fully elucidated. Previous studies have reported that the 14-3-3 family acts as an adaptor involved in regulating kinetic characteristics of cardiac ion channels. OBJECTIVE The purpose of this study was to establish 14-3-3ε/YWHAE, a member of the 14-3-3 family, as a crucial regulator of NaV1.5 and to explore the potential role of 14-3-3ε in the heart. METHODS Western blotting, patch clamping, real-time reverse transcription-polymerase chain reaction, RNA immunoprecipitation, electrocardiogram recording, echocardiography, and histologic analysis were performed. RESULTS YWHAE overexpression significantly reduced the expression level of SCN5A mRNA and sodium current density, whereas YWHAE knockdown significantly increased SCN5A mRNA expression and sodium current density in HEK293/NaV1.5 and H9c2 cells. Similar results were observed in mice injected with adeno-associated virus serotype 9-mediated YWHAE knockdown. The effect of 14-3-3ε on NaV1.5 expression was abrogated by knockdown of TBX5, a transcription factor of NaV1.5. An interaction between 14-3-3ε protein and TBX5 mRNA was identified, and YWHAE overexpression significantly decreased TBX5 mRNA stability without affecting SCN5A mRNA stability. In addition, mice subjected to adeno-associated virus serotype 9-mediated YWHAE knockdown exhibited shorter R-R intervals and higher prevalence of premature ventricular contractions. CONCLUSION Our data unveil a novel regulatory mechanism of NaV1.5 by 14-3-3ε and highlight the significance of 14-3-3ε in transcriptional regulation of NaV1.5 expression and cardiac arrhythmias.
Collapse
Affiliation(s)
- Yushuang Hu
- Department of Cardiology, Zhongnan Hospital of Wuhan University, Wuhan, Hubei, PR China; Institute of Myocardial Injury and Repair, Wuhan University, Wuhan, Hubei, PR China
| | - Chi Zhang
- Center for Human Genome Research, Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, PR China
| | - Shun Wang
- Department of Cardiology, Zhongnan Hospital of Wuhan University, Wuhan, Hubei, PR China; Institute of Myocardial Injury and Repair, Wuhan University, Wuhan, Hubei, PR China
| | - Hongbo Xiong
- Department of Cardiology, Zhongnan Hospital of Wuhan University, Wuhan, Hubei, PR China; Institute of Myocardial Injury and Repair, Wuhan University, Wuhan, Hubei, PR China
| | - Wen Xie
- Department of Basic Medicine, Xiamen Medical College, Xiamen, Fujian, PR China
| | - Ziyue Zeng
- Department of Cardiology, Zhongnan Hospital of Wuhan University, Wuhan, Hubei, PR China; Institute of Myocardial Injury and Repair, Wuhan University, Wuhan, Hubei, PR China
| | - HuanHuan Cai
- Department of Cardiology, Zhongnan Hospital of Wuhan University, Wuhan, Hubei, PR China; Institute of Myocardial Injury and Repair, Wuhan University, Wuhan, Hubei, PR China
| | - Qing Kenneth Wang
- Center for Human Genome Research, Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, PR China
| | - Zhibing Lu
- Department of Cardiology, Zhongnan Hospital of Wuhan University, Wuhan, Hubei, PR China; Institute of Myocardial Injury and Repair, Wuhan University, Wuhan, Hubei, PR China.
| |
Collapse
|
5
|
Kohansal E, Naderi N, Fazelifar AF, Maleki M, Kalayinia S. Detection of a novel pathogenic variant in KCNH2 associated with long QT syndrome 2 using whole exome sequencing. BMC Med Genomics 2024; 17:126. [PMID: 38715010 PMCID: PMC11077719 DOI: 10.1186/s12920-024-01900-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2024] [Accepted: 05/02/2024] [Indexed: 05/12/2024] Open
Abstract
BACKGROUND Long QT syndrome (LQTS) is a cardiac channelopathy characterized by impaired myocardial repolarization that predisposes to life-threatening arrhythmias. This study aimed to elucidate the genetic basis of LQTS in an affected Iranian family using whole exome sequencing (WES). METHODS A 37-year-old woman with a personal and family history of sudden cardiac arrest and LQTS was referred for genetic study after losing her teenage daughter due to sudden cardiac death (SCD). WES was performed and variants were filtered and prioritized based on quality, allele frequency, pathogenicity predictions, and conservation scores. Sanger sequencing confirmed segregation in the family. RESULTS WES identified a novel heterozygous frameshift variant (NM_000238.4:c.3257_3258insG; pGly1087Trpfs*32) in the KCNH2 encoding the α-subunit of the rapid delayed rectifier potassium channel responsible for cardiac repolarization. This variant, predicted to cause a truncated protein, is located in the C-terminal region of the channel and was classified as likely pathogenic based on ACMG guidelines. The variant was absent in population databases and unaffected family members. CONCLUSION This study reports a novel KCNH2 frameshift variant in an Iranian family with LQTS, expanding the spectrum of disease-causing variants in this gene. Our findings highlight the importance of the C-terminal region in KCNH2 for proper channel function and the utility of WES in identifying rare variants in genetically heterogeneous disorders like LQTS. Functional characterization of this variant is warranted to fully elucidate its pathogenic mechanisms and inform personalized management strategies.
Collapse
Affiliation(s)
- Erfan Kohansal
- Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Niloofar Naderi
- Cardiogenetic Research Center, Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Amir Farjam Fazelifar
- Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Majid Maleki
- Cardiogenetic Research Center, Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Samira Kalayinia
- Cardiogenetic Research Center, Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran.
| |
Collapse
|
6
|
Egly CL, Barny L, Do T, McDonald EF, Plate L, Knollmann BC. The proteostasis interactomes of trafficking-deficient K V 11.1 variants associated with Long QT Syndrome and pharmacological chaperone rescue. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.31.574410. [PMID: 38352392 PMCID: PMC10862811 DOI: 10.1101/2024.01.31.574410] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/25/2024]
Abstract
Introduction The voltage gated potassium ion channel K V 11.1 plays a critical role in cardiac repolarization. Genetic variants that render Kv11.1 dysfunctional cause Long QT Syndrome (LQTS), which is associated with fatal arrhythmias. Approximately 90% of LQTS-associated variants cause intracellular protein transport (trafficking) dysfunction, which can be rescued by pharmacological chaperones like E-4031. Protein folding and trafficking decisions are regulated by chaperones, protein quality control factors, and trafficking machinery, comprising the cellular proteostasis network. Here, we test whether trafficking dysfunction is associated with alterations in the proteostasis network of pathogenic Kv11.1 variants, and whether pharmacological chaperones can normalize the proteostasis network of responsive variants. Methods We used affinity-purification coupled with tandem mass tag-based quantitative mass spectrometry to assess protein interaction changes in human embryonic kidney (HEK293) cells expressing wild-type (WT) K V 11.1 or trafficking-deficient channel variants in the presence or absence of E-4031. Resultsa We identified 573 core K V 11.1 protein interactors. Both variants K V 11.1-G601S and K V 11.1-G601S-G965* had significantly increased interactions with proteins responsible for folding, trafficking, and degradation compared to WT. We found that proteasomal degradation is a key component for K V 11.1 degradation and that the K V 11.1-G601S-G965* variant was more responsive to E-4031 treatment. This suggests a role in the C-terminal domain and the ER retention motif of K V 11.1 in regulating trafficking. Conclusion Our report characterizes the proteostasis network of K V 11.1, two trafficking deficient K V 11.1 variants, and variants treated with a pharmacological chaperone. The identified protein interactions could be targeted therapeutically to improve K V 11.1 trafficking and treat Long QT Syndrome.
Collapse
|
7
|
Al Salmani MK, Tavakoli R, Zaman W, Al Harrasi A. Multiple mechanisms underlie reduced potassium conductance in the p.T1019PfsX38 variant of hERG. Physiol Rep 2022; 10:e15341. [PMID: 35854468 PMCID: PMC9296870 DOI: 10.14814/phy2.15341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2021] [Revised: 05/15/2022] [Accepted: 05/16/2022] [Indexed: 11/30/2022] Open
Abstract
Long QT syndrome type II (LQT2) is caused by loss-of-function mutations in the hERG K+ channel, leading to increased incidence of cardiac arrest and sudden death. Many genetic variants have been reported in the hERG gene with various consequences on channel expression, permeation, and gating. Only a small number of LQT2 causing variants has been characterized to define the underlying pathophysiological causes of the disease. We sought to determine the characteristics of the frameshift variant p.Thr1019ProfsX38 (T1019PfsX38) which affects the C-terminus of the protein. This mutation was identified in an extended Omani family of LQT2. It replaces the last 140 amino acids of hERG with 37 unique amino acids. T1019 is positioned at a distinguished region of the C-terminal tail of hERG, as predicted from the deep learning system AlphaFold v2.0. We employed the whole-cell configuration of the patch-clamp technique to study wild-type and mutant channels that were transiently expressed in human embryonic kidney 293 (HEK293) cells. Depolarizing voltages elicited slowly deactivating tail currents that appeared upon repolarization of cells that express either wild-type- or T1019PfsX38-hERG. There were no differences in the voltage and time dependencies of activation between the two variants. However, the rates of hERG channel deactivation at hyperpolarizing potentials were accelerated by T1019PfsX38. In addition, the voltage dependence of inactivation of T1019PfsX38-hERG was shifted by 20 mV in the negative direction when compared with wild-type hERG. The rates of channel inactivation were increased in the mutant channel variant. Next, we employed a step-ramp protocol to mimic membrane repolarization by the cardiac action potential. The amplitudes of outward currents and their integrals were reduced in the mutant variant when compared with the wild-type variant during repolarization. Thus, changes in the gating dynamics of hERG by the T1019PfsX38 variant contribute to the pathology seen in affected LQT2 patients.
Collapse
Affiliation(s)
| | - Rezvan Tavakoli
- Natural and Medical Sciences Research CenterUniversity of NizwaNizwaOman
| | - Wajid Zaman
- Natural and Medical Sciences Research CenterUniversity of NizwaNizwaOman
| | - Ahmed Al Harrasi
- Natural and Medical Sciences Research CenterUniversity of NizwaNizwaOman
| |
Collapse
|
8
|
Thompson WC, Goldspink PH. 14-3-3 protein regulation of excitation-contraction coupling. Pflugers Arch 2021; 474:267-279. [PMID: 34820713 PMCID: PMC8837530 DOI: 10.1007/s00424-021-02635-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 10/21/2021] [Accepted: 10/23/2021] [Indexed: 11/25/2022]
Abstract
14-3-3 proteins (14-3-3 s) are a family of highly conserved proteins that regulate many cellular processes in eukaryotes by interacting with a diverse array of client proteins. The 14-3-3 proteins have been implicated in several disease states and previous reviews have condensed the literature with respect to their structure, function, and the regulation of different cellular processes. This review focuses on the growing body of literature exploring the important role 14-3-3 proteins appear to play in regulating the biochemical and biophysical events associated with excitation-contraction coupling (ECC) in muscle. It presents both a timely and unique analysis that seeks to unite studies emphasizing the identification and diversity of 14-3-3 protein function and client protein interactions, as modulators of muscle contraction. It also highlights ideas within these two well-established but intersecting fields that support further investigation with respect to the mechanistic actions of 14-3-3 proteins in the modulation of force generation in muscle.
Collapse
Affiliation(s)
- Walter C Thompson
- Department of Physiology and Biophysics (M/C 901) and Center for Cardiovascular Research, College of Medicine, University of Illinois at Chicago, 835 South Wolcott Avenue, RM E-202, Chicago, IL, 60612, USA
| | - Paul H Goldspink
- Department of Physiology and Biophysics (M/C 901) and Center for Cardiovascular Research, College of Medicine, University of Illinois at Chicago, 835 South Wolcott Avenue, RM E-202, Chicago, IL, 60612, USA.
| |
Collapse
|
9
|
Abstract
Objective: We aimed to find crucial microRNAs (miRNAs) associated with the development of atrial fibrillation (AF), and then try to elucidate the possible molecular mechanisms of miRNAs in AF. Methods: The miRNA microarray, GSE68475, which included 10 right atrial appendage samples from patients with persistent AF and 11 samples from patients with normal sinus rhythm, was used for the analysis. After data preprocessing, differentially expressed miRNAs were screened using limma. Target genes of miRNAs were predicted using miRWalk2.0. We then conducted functional enrichment analyses for miRNA and target genes. Protein-protein interaction (PPI) network and module analyses for target genes were performed. Finally, transcription factors (TFs)-target genes regulatory network was predicted and constructed. Results: Seven genes, including CAMK2D, IGF2R, PPP2R2A, PAX6, POU3F2, YWHAE, and AP2A2, were targeted by TFs. Among these seven genes, CAMK2D (targeted by miR-31-5p), IGF2R (targeted by miR-204-5p), PAX6 (targeted by miR-223-3p), POU3F2 (targeted by miR-204-5p), YWHAE (targeted by miR-31-5p), and AP2A2 (targeted by miR-204-5p) belonged to the top 10 degree genes in the PPI network. Notably, MiR-204-5p, miR-31-5p, and miR-223-3p had more target genes. Besides, CAMK2D was enriched in some pathways, such as adrenergic signaling in cardiomyocytes pathway and cAMP signaling pathway. YWHAE was enriched in the Hippo signaling pathway. Conclusion: miR-31-5p played a crucial role in cardiomyocytes by targeting CAMK2D and YWHAE via cAMP and Hippo signaling pathways. miR-204 was involved in the progression of AF by regulating its target genes IGF2R, POU3F2, and AP2A2. On the other hand, miR-223-3p functioned in AF by targeting PAX6, which was associated with the regulation of apoptosis in AF. This study would provide a theoretical basis and potential therapeutic targets for the treatment of AF.
Collapse
|
10
|
Liu B, Li X, Zhao C, Wang Y, Lv M, Shi X, Han C, Pandey P, Qian C, Guo C, Zhang Y. Proteomic Analysis of Atrial Appendages Revealed the Pathophysiological Changes of Atrial Fibrillation. Front Physiol 2020; 11:573433. [PMID: 33041871 PMCID: PMC7526521 DOI: 10.3389/fphys.2020.573433] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Accepted: 08/13/2020] [Indexed: 11/18/2022] Open
Abstract
Atrial fibrillation (AF), known as the most common arrhythmia in the developed world, affects 1.5–2.0% of the population. Numerous basic studies have been carried out to identify the roles of electric and structural remodeling in the pathophysiological changes of AF, but more explorations are required to further understand the mechanisms of AF development. Proteomics enables researchers to identify protein alterations responsible for the pathological developing progresses of diseases. Compared to the genome, the proteome is closely related to the disease phenotype and can better manifest the progression of diseases. In this study, AF patients proteomically analyzed to identify possible mechanisms. Totally 20 patients undergoing cardiac surgery (10 with paroxysmal AF and 10 with persistent AF) and 10 healthy subjects were recruited. The differentially expressed proteins identified here included AKR1A1, LYZ, H2AFY, DDAH1, FGA, FGB, LAMB1, LAMC1, MYL2, MYBPC3, MYL5, MYH10, HNRNPU, DKK3, COPS7A, YWHAQ, and PAICS. These proteins were mainly involved in the development of structural remodeling. The differently expressed proteins may provide a new perspective for the pathological process of AF, and may enable useful targets for drug interference. Nevertheless, more research in terms of multi-omics is required to investigate possible implicated molecular pathways of AF development.
Collapse
Affiliation(s)
- Ban Liu
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Xiang Li
- Department of Cardiology, The First Affiliated Hospital of Chongqing Medical University, Chongqing Medical University, Chongqing, China
| | - Cuimei Zhao
- Department of Cardiology, Tongji Hospital, Tongji University School of Medicine, Shanghai, China
| | - Yuliang Wang
- Department of Immunology, School of Basic Medical Science, Nanjing Medical University, Nanjing, China
| | - Mengwei Lv
- Shanghai East Hospital of Clinical Medical College, Nanjing Medical University, Shanghai, China.,Department of Cardiovascular Surgery, Shanghai East Hospital, Tongji University School of Medicine, Shanghai, China
| | - Xin Shi
- Department of Pediatric Cardiology, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Chunyan Han
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Pratik Pandey
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Chunhua Qian
- Department of Endocrinology and Metabolism, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Changfa Guo
- Department of Cardiovascular Surgery, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Yangyang Zhang
- Department of Cardiovascular Surgery, Shanghai East Hospital, Tongji University School of Medicine, Shanghai, China
| |
Collapse
|
11
|
Abstract
The treatment of individual patients in cardiology practice increasingly relies on advanced imaging, genetic screening and devices. As the amount of imaging and other diagnostic data increases, paralleled by the greater capacity to personalize treatment, the difficulty of using the full array of measurements of a patient to determine an optimal treatment seems also to be paradoxically increasing. Computational models are progressively addressing this issue by providing a common framework for integrating multiple data sets from individual patients. These models, which are based on physiology and physics rather than on population statistics, enable computational simulations to reveal diagnostic information that would have otherwise remained concealed and to predict treatment outcomes for individual patients. The inherent need for patient-specific models in cardiology is clear and is driving the rapid development of tools and techniques for creating personalized methods to guide pharmaceutical therapy, deployment of devices and surgical interventions.
Collapse
|
12
|
De Zio R, Gerbino A, Forleo C, Pepe M, Milano S, Favale S, Procino G, Svelto M, Carmosino M. Functional study of a KCNH2 mutant: Novel insights on the pathogenesis of the LQT2 syndrome. J Cell Mol Med 2019; 23:6331-6342. [PMID: 31361068 PMCID: PMC6714209 DOI: 10.1111/jcmm.14521] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 06/02/2019] [Accepted: 06/08/2019] [Indexed: 12/29/2022] Open
Abstract
The K+ voltage-gated channel subfamily H member 2 (KCNH2) transports the rapid component of the cardiac delayed rectifying K+ current. The aim of this study was to characterize the biophysical properties of a C-terminus-truncated KCNH2 channel, G1006fs/49 causing long QT syndrome type II in heterozygous members of an Italian family. Mutant carriers underwent clinical workup, including 12-lead electrocardiogram, transthoracic echocardiography and 24-hour ECG recording. Electrophysiological experiments compared the biophysical properties of G1006fs/49 with those of KCNH2 both expressed either as homotetramers or as heterotetramers in HEK293 cells. Major findings of this work are as follows: (a) G1006fs/49 is functional at the plasma membrane even when co-expressed with KCNH2, (b) G1006fs/49 exerts a dominant-negative effect on KCNH2 conferring specific biophysical properties to the heterotetrameric channel such as a significant delay in the voltage-sensitive transition to the open state, faster kinetics of both inactivation and recovery from the inactivation and (c) the activation kinetics of the G1006fs/49 heterotetrameric channels is partially restored by a specific KCNH2 activator. The functional characterization of G1006fs/49 homo/heterotetramers provided crucial findings about the pathogenesis of LQTS type II in the mutant carriers, thus providing a new and potential pharmacological strategy.
Collapse
Affiliation(s)
- Roberta De Zio
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
| | - Andrea Gerbino
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
| | - Cinzia Forleo
- Cardiology Unit, Department of Emergency and Organ Transplantation, University of Bari, Bari, Italy
| | - Martino Pepe
- Cardiology Unit, Department of Emergency and Organ Transplantation, University of Bari, Bari, Italy
| | - Serena Milano
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
| | - Stefano Favale
- Cardiology Unit, Department of Emergency and Organ Transplantation, University of Bari, Bari, Italy
| | - Giuseppe Procino
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
| | - Maria Svelto
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
| | - Monica Carmosino
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy.,Department of Sciences, University of Basilicata, Potenza, Italy
| |
Collapse
|
13
|
Sergeev V, Perry F, Roston TM, Sanatani S, Tibbits GF, Claydon TW. Functional characterization of a novel hERG variant in a family with recurrent sudden infant death syndrome: Retracting a genetic diagnosis. Forensic Sci Int 2018; 284:39-45. [PMID: 29331839 DOI: 10.1016/j.forsciint.2017.12.028] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Revised: 12/05/2017] [Accepted: 12/07/2017] [Indexed: 01/25/2023]
Abstract
Long QT syndrome (LQTS) is the most common cardiac ion channelopathy and has been found to be responsible for approximately 10% of sudden infant death syndrome (SIDS) cases. Despite increasing use of broad panels and now whole exome sequencing (WES) in the investigation of SIDS, the probability of identifying a pathogenic mutation in a SIDS victim is low. We report a family-based study who are afflicted by recurrent SIDS in which several members harbor a variant, p.Pro963Thr, in the C-terminal region of the human-ether-a-go-go (hERG) gene, published to be responsible for cases of LQTS type 2. Functional characterization was undertaken due to the variable phenotype in carriers, the discrepancy with published cases, and the importance of identifying a cause for recurrent deaths in a single family. Studies of the mutated ion channel in in vitro heterologous expression systems revealed that the mutation has no detectable impact on membrane surface expression, biophysical gating properties such as activation, deactivation and inactivation, or the amplitude of the protective current conducted by hERG channels during early repolarization. These observations suggest that the p.Pro963Thr mutation is not a monogenic disease-causing LQTS mutation despite evidence of co-segregation in two siblings affected by SIDS. Our findings demonstrate some of the potential pitfalls in post-mortem molecular testing and the importance of functional testing of gene variants in determining disease-causation, especially where the impacts of cascade screening can affect multiple generations.
Collapse
Affiliation(s)
- Valentine Sergeev
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada
| | - Frances Perry
- Division of Cardiology, Department of Pediatrics, BC Children's Hospital & University of British Columbia, Vancouver, BC, Canada
| | - Thomas M Roston
- Division of Cardiology, Department of Medicine, University of British Columbia, Vancouver, BC, Canada; Department of Medicine, University of Alberta, Edmonton, AB, Canada
| | - Shubhayan Sanatani
- Division of Cardiology, Department of Pediatrics, BC Children's Hospital & University of British Columbia, Vancouver, BC, Canada
| | - Glen F Tibbits
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada
| | - Thomas W Claydon
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada.
| |
Collapse
|
14
|
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.
Collapse
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.
| |
Collapse
|
15
|
Puckerin A, Aromolaran KA, Chang DD, Zukin RS, Colecraft HM, Boutjdir M, Aromolaran AS. hERG 1a LQT2 C-terminus truncation mutants display hERG 1b-dependent dominant negative mechanisms. Heart Rhythm 2016; 13:1121-1130. [PMID: 26775140 DOI: 10.1016/j.hrthm.2016.01.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Indexed: 12/01/2022]
Abstract
BACKGROUND The human ether-à-go-go-related gene (hERG 1a) potassium channel is critical for cardiac repolarization. hERG 1b, another variant subunit, co-assembles with hERG 1a, modulates channel biophysical properties and plays an important role in repolarization. Mutations of hERG 1a lead to type 2 long QT syndrome (LQT2), and increased risk for fatal arrhythmias. The functional consequences of these mutations in the presence of hERG 1b are not known. OBJECTIVE To investigate whether hERG 1a mutants exert dominant negative gating and trafficking defects when co-expressed with hERG 1b. METHODS Electrophysiology, co-immunoprecipitation, and fluorescence resonance energy transfer (FRET) experiments in HEK293 cells and guinea pig cardiomyocytes were used to assess the mutants on gating and trafficking. Mutations of 1a-G965X and 1a-R1014X, relevant to gating and trafficking were introduced in the C-terminus region. RESULTS The hERG 1a mutants when expressed alone did not result in decreased current amplitude. Compared to wild-type hERG 1a currents, 1a-G965X currents were significantly larger, whereas those produced by the 1a-R1014X mutant were similar in magnitude. Only when co-expressed with wild-type hERG 1a and 1b did a mutant phenotype emerge, with a marked reduction in surface expression, current amplitude, and a corresponding positive shift in the V1/2 of the activation curve. Co-immunoprecipitation and FRET assays confirmed association of mutant and wild-type subunits. CONCLUSION Heterologously expressed hERG 1a C-terminus truncation mutants, exert a dominant negative gating and trafficking effect only when co-expressed with hERG 1b. These findings may have potentially profound implications for LQT2 therapy.
Collapse
Affiliation(s)
- Akil Puckerin
- Department of Physiology & Cellular Biophysics, Columbia University, New York, New York
| | - Kelly A Aromolaran
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, New York, New York
| | - Donald D Chang
- Department of Physiology & Cellular Biophysics, Columbia University, New York, New York
| | - R Suzanne Zukin
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, New York, New York
| | - Henry M Colecraft
- Department of Physiology & Cellular Biophysics, Columbia University, New York, New York
| | - Mohamed Boutjdir
- Cardiovascular Research Program, VA New York Harbor Healthcare System, Brooklyn, New York; Departments of Medicine, Cell Biology and Pharmacology, State University of New York Downstate Medical Center, Brooklyn, New York,; Department of Medicine, New York University School of Medicine, New York, New York
| | - Ademuyiwa S Aromolaran
- Department of Physiology & Cellular Biophysics, Columbia University, New York, New York.
| |
Collapse
|
16
|
Page A, Aktas MK, Soyata T, Zareba W, Couderc JP. "QT clock" to improve detection of QT prolongation in long QT syndrome patients. Heart Rhythm 2015; 13:190-8. [PMID: 26334569 DOI: 10.1016/j.hrthm.2015.08.037] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Indexed: 10/23/2022]
Abstract
BACKGROUND The QT interval is a risk marker for cardiac events such as torsades de pointes. However, QT measurements obtained from a 12-lead ECG during clinic hours may not capture the full extent of a patient's daily QT range. OBJECTIVE The purpose of this study was to evaluate the utility of 24-hour Holter ECG recording in patients with long QT syndrome (LQTS) to identify dynamic changes in the heart rate-corrected QT interval and to investigate methods of visualizing the resulting datasets. METHODS Beat-to-beat QTc (Bazett) intervals were automatically measured across 24-hour Holter recordings from 202 LQTS type 1, 89 type 2, and 14 type 3 genotyped patients and a reference group of 200 healthy individuals. We measured the percentage of beats with QTc greater than the gender-specific threshold (QTc ≥470 ms in women and QTc ≥450 ms in men). The percentage of beats with QTc prolongation was determined across the 24-hour recordings. RESULTS Based on the median percentage of heartbeats per patient with QTc prolongation, LQTS type 1 patients showed more frequent QTc prolongation during the day (~3 PM) than they did at night (~3 AM): 97% vs 48%, P ~10(-4) for men, and 68% vs 30%, P ~10(-5) for women. LQTS type 2 patients showed less frequent QTc prolongation during the day compared to nighttime: 87% vs 100%, P ~10(-4) for men, and 62% vs 100%, P ~10(-3) for women. CONCLUSION In patients with genotype-positive LQTS, significant differences exist in the degree of daytime and nocturnal QTc prolongation. Holter monitoring using the "QT clock" concept may provide an easy, fast, and accurate method for assessing the true personalized burden of QTc prolongation.
Collapse
Affiliation(s)
- Alex Page
- Electrical and Computer Engineering Department, University of Rochester, Rochester, New York
| | - Mehmet K Aktas
- Cardiology Department, University of Rochester Medical Center, Rochester, New York
| | - Tolga Soyata
- Electrical and Computer Engineering Department, University of Rochester, Rochester, New York
| | | | - Jean-Philippe Couderc
- Electrical and Computer Engineering Department, University of Rochester, Rochester, New York; Heart Research Follow Up Program, Rochester, New York.
| |
Collapse
|
17
|
Lin TF, Lin IW, Chen SC, Wu HH, Yang CS, Fang HY, Chiu MM, Jeng CJ. The subfamily-specific assembly of Eag and Erg K+ channels is determined by both the amino and the carboxyl recognition domains. J Biol Chem 2014; 289:22815-22834. [PMID: 25008323 DOI: 10.1074/jbc.m114.574814] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
A functional voltage-gated K(+) (Kv) channel comprises four pore-forming α-subunits, and only members of the same Kv channel subfamily may co-assemble to form heterotetramers. The ether-à-go-go family of Kv channels (KCNH) encompasses three distinct subfamilies: Eag (Kv10), Erg (Kv11), and Elk (Kv12). Members of different ether-à-go-go subfamilies, such as Eag and Erg, fail to form heterotetramers. Although a short stretch of amino acid sequences in the distal C-terminal section has been implicated in subfamily-specific subunit assembly, it remains unclear whether this region serves as the sole and/or principal subfamily recognition domain for Eag and Erg. Here we aim to ascertain the structural basis underlying the subfamily specificity of ether-à-go-go channels by generating various chimeric constructs between rat Eag1 and human Erg subunits. Biochemical and electrophysiological characterizations of the subunit interaction properties of a series of different chimeric and truncation constructs over the C terminus suggested that the putative C-terminal recognition domain is dispensable for subfamily-specific assembly. Further chimeric analyses over the N terminus revealed that the N-terminal region may also harbor a subfamily recognition domain. Importantly, exchanging either the N-terminal or the C-terminal domain alone led to a virtual loss of the intersubfamily assembly boundary. By contrast, simultaneously swapping both recognition domains resulted in a reversal of subfamily specificity. Our observations are consistent with the notion that both the N-terminal and the C-terminal recognition domains are required to sustain the subfamily-specific assembly of rat Eag1 and human Erg.
Collapse
Affiliation(s)
- Ting-Feng Lin
- Institute of Anatomy and Cell Biology, School of Medicine, and National Yang-Ming University, No. 155, Section 2, Li-Non Street, Taipei 12212, Taiwan
| | - I-Wen Lin
- Institute of Anatomy and Cell Biology, School of Medicine, and National Yang-Ming University, No. 155, Section 2, Li-Non Street, Taipei 12212, Taiwan
| | - Shu-Ching Chen
- Department of Medical Research, National Taiwan University Hospital, Taipei 10051, Taiwan
| | - Hao-Han Wu
- Institute of Anatomy and Cell Biology, School of Medicine, and National Yang-Ming University, No. 155, Section 2, Li-Non Street, Taipei 12212, Taiwan
| | - Chi-Sheng Yang
- Institute of Anatomy and Cell Biology, School of Medicine, and National Yang-Ming University, No. 155, Section 2, Li-Non Street, Taipei 12212, Taiwan
| | - Hsin-Yu Fang
- Institute of Anatomy and Cell Biology, School of Medicine, and National Yang-Ming University, No. 155, Section 2, Li-Non Street, Taipei 12212, Taiwan
| | - Mei-Miao Chiu
- Institute of Anatomy and Cell Biology, School of Medicine, and National Yang-Ming University, No. 155, Section 2, Li-Non Street, Taipei 12212, Taiwan
| | - Chung-Jiuan Jeng
- Institute of Anatomy and Cell Biology, School of Medicine, and National Yang-Ming University, No. 155, Section 2, Li-Non Street, Taipei 12212, Taiwan; Brain Research Center, National Yang-Ming University, No. 155, Section 2, Li-Non Street, Taipei 12212, Taiwan and.
| |
Collapse
|
18
|
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.
Collapse
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.
| |
Collapse
|
19
|
Chen CP, Chang TY, Guo WY, Wu PC, Wang LK, Chern SR, Wu PS, Su JW, Chen YT, Chen LF, Wang W. Chromosome 17p13.3 deletion syndrome: aCGH characterization, prenatal findings and diagnosis, and literature review. Gene 2013; 532:152-9. [DOI: 10.1016/j.gene.2013.09.044] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Revised: 09/06/2013] [Accepted: 09/11/2013] [Indexed: 12/17/2022]
|
20
|
Gillie DJ, Novick SJ, Donovan BT, Payne LA, Townsend C. Development of a high-throughput electrophysiological assay for the human ether-à-go-go related potassium channel hERG. J Pharmacol Toxicol Methods 2013; 67:33-44. [DOI: 10.1016/j.vascn.2012.10.002] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Revised: 10/02/2012] [Accepted: 10/18/2012] [Indexed: 01/03/2023]
|
21
|
Zhang A, Sun C, Zhang L, Lv Y, Xue X, Li G, Cui C, Yan GX. L539 fs/47, a truncated mutation of human ether-a-go-go-related gene (hERG), decreases hERG ion channel currents in HEK 293 cells. Clin Exp Pharmacol Physiol 2012; 40:28-36. [DOI: 10.1111/1440-1681.12028] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2012] [Revised: 10/12/2012] [Accepted: 11/04/2012] [Indexed: 01/09/2023]
Affiliation(s)
| | - Chaofeng Sun
- Department of Cardiovascular Medicine; MOE; Ion Channel Disease Laboratory; MOE Key Laboratory of Environment and Genes Related to Diseases, The First Affiliated Hospital of Xi'an Jiaotong University; Xi'an; Shaanxi; China
| | - Li Zhang
- Main Line Health Heart Center; Lankenau Institute for Medical Research; Wynnewood; Pennsylvania; USA
| | - Ying Lv
- Department of Cardiovascular Medicine; MOE; Ion Channel Disease Laboratory; MOE Key Laboratory of Environment and Genes Related to Diseases, The First Affiliated Hospital of Xi'an Jiaotong University; Xi'an; Shaanxi; China
| | - Xiaolin Xue
- Department of Cardiovascular Medicine; MOE; Ion Channel Disease Laboratory; MOE Key Laboratory of Environment and Genes Related to Diseases, The First Affiliated Hospital of Xi'an Jiaotong University; Xi'an; Shaanxi; China
| | - Guoliang Li
- Department of Cardiovascular Medicine; MOE; Ion Channel Disease Laboratory; MOE Key Laboratory of Environment and Genes Related to Diseases, The First Affiliated Hospital of Xi'an Jiaotong University; Xi'an; Shaanxi; China
| | - Changcong Cui
- Department of Cardiovascular Medicine; MOE; Ion Channel Disease Laboratory; MOE Key Laboratory of Environment and Genes Related to Diseases, The First Affiliated Hospital of Xi'an Jiaotong University; Xi'an; Shaanxi; China
| | - Gan-Xin Yan
- Main Line Health Heart Center; Lankenau Institute for Medical Research; Wynnewood; Pennsylvania; USA
| |
Collapse
|
22
|
Chang B, Gorbea C, Lezin G, Li L, Shan L, Sakai N, Kogaki S, Otomo T, Okinaga T, Hamaoka A, Yu X, Hata Y, Nishida N, Yost HJ, Bowles NE, Brunelli L, Ichida F. 14-3-3ε gene variants in a Japanese patient with left ventricular noncompaction and hypoplasia of the corpus callosum. Gene 2012; 515:173-80. [PMID: 23266643 DOI: 10.1016/j.gene.2012.12.049] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2012] [Accepted: 12/02/2012] [Indexed: 01/07/2023]
Abstract
BACKGROUND Left ventricular noncompaction (LVNC) is a cardiomyopathy characterized by a prominent trabecular meshwork and deep intertrabecular recesses, and is thought to be due to an arrest of normal endomyocardial morphogenesis. However, the genes contributing to this process remain poorly understood. 14-3-3ε, encoded by YWHAE, is an adapter protein belonging to the 14-3-3 protein family which plays important roles in neuronal development and is involved in Miller-Dieker syndrome. We recently showed that mice lacking this gene develop LVNC. Therefore, we hypothesized that variants in YWHAE may contribute to the pathophysiology of LVNC in humans. METHODS AND RESULTS In 77 Japanese patients with LVNC, including the probands of 29 families, mutation analysis of YWHAE by direct DNA sequencing identified 7 novel variants. One of them, c.-458G>T, in the YWHAE promoter, was identified in a familial patient with LVNC and hypoplasia of the corpus callosum. The -458G>T variant is located within a regulatory CCAAT/enhancer binding protein (C/EBP) response element of the YWHAE promoter, and it reduced promoter activity by approximately 50%. Increased binding of an inhibitory C/EBPβ isoform was implicated in decreasing YWHAE promoter activity. Interestingly, we had previously shown that C/EBPβ is a key regulator of YWHAE. CONCLUSIONS These data suggest that the -458G>T YWHAE variant contributes to the abnormal myocardial morphogenesis characteristic of LVNC as well as abnormal brain development, and implicate YWHAE as a novel candidate gene in pediatric cardiomyopathies.
Collapse
Affiliation(s)
- Bo Chang
- Department of Pediatrics, University of Toyama, Toyama, Japan
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
23
|
Niederer SA, Land S, Omholt SW, Smith NP. Interpreting genetic effects through models of cardiac electromechanics. Am J Physiol Heart Circ Physiol 2012; 303:H1294-303. [PMID: 23042948 DOI: 10.1152/ajpheart.00121.2012] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Multiscale models of cardiac electromechanics are being increasingly focused on understanding how genetic variation and environment underpin multiple disease states. In this paper we review the current state of the art in both the development of specific models and the physiological insights they have produced. This growing research body includes the development of models for capturing the effects of changes in function in both single and multiple proteins in both specific expression systems and in vivo contexts. Finally, the potential for using this approach for ultimately predicting phenotypes from genetic sequence information is discussed.
Collapse
Affiliation(s)
- S A Niederer
- Department of Biomedical Engineering, King's College London, King's Health Partners, Saint Thomas' Hospital, London, UK
| | | | | | | |
Collapse
|
24
|
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.
Collapse
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
| |
Collapse
|
25
|
Trudeau MC, Leung LM, Roti ER, Robertson GA. hERG1a N-terminal eag domain-containing polypeptides regulate homomeric hERG1b and heteromeric hERG1a/hERG1b channels: a possible mechanism for long QT syndrome. ACTA ACUST UNITED AC 2012; 138:581-92. [PMID: 22124116 PMCID: PMC3226966 DOI: 10.1085/jgp.201110683] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
Human ether-á-go-go–related gene (hERG) potassium channels are critical for cardiac action potential repolarization. Cardiac hERG channels comprise two primary isoforms: hERG1a, which has a regulatory N-terminal Per-Arnt-Sim (PAS) domain, and hERG1b, which does not. Isolated, PAS-containing hERG1a N-terminal regions (NTRs) directly regulate NTR-deleted hERG1a channels; however, it is unclear whether hERG1b isoforms contain sufficient machinery to support regulation by hERG1a NTRs. To test this, we constructed a series of PAS domain–containing hERG1a NTRs (encoding amino acids 1–181, 1–228, 1–319, and 1–365). The NTRs were also predicted to form from truncation mutations that were linked to type 2 long QT syndrome (LQTS), a cardiac arrhythmia disorder associated with mutations in the hERG gene. All of the hERG1a NTRs markedly regulated heteromeric hERG1a/hERG1b channels and homomeric hERG1b channels by decreasing the magnitude of the current–voltage relationship and slowing the kinetics of channel closing (deactivation). In contrast, NTRs did not measurably regulate hERG1a channels. A short NTR (encoding amino acids 1–135) composed primarily of the PAS domain was sufficient to regulate hERG1b. These results suggest that isolated hERG1a NTRs directly interact with hERG1b subunits. Our results demonstrate that deactivation is faster in hERG1a/hERG1b channels compared to hERG1a channels because of fewer PAS domains, not because of an inhibitory effect of the unique hERG1b NTR. A decrease in outward current density of hERG1a/hERG1b channels by hERG1a NTRs may be a mechanism for LQTS.
Collapse
Affiliation(s)
- Matthew C Trudeau
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
| | | | | | | |
Collapse
|
26
|
Nishimoto O, Matsuda M, Nakamoto K, Nishiyama H, Kuraoka K, Taniyama K, Tamura R, Shimizu W, Kawamoto T. Peripartum cardiomyopathy presenting with syncope due to Torsades de pointes: a case of long QT syndrome with a novel KCNH2 mutation. Intern Med 2012; 51:461-4. [PMID: 22382559 DOI: 10.2169/internalmedicine.51.5943] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Peripartum cardiomyopathy (PPCM) is a cardiomyopathy of unknown cause that occurs in the peripartum period. We report a case of PPCM presenting with syncope 1 month after an uncomplicated delivery. Electrocardiography showed Torsades de pointes (TdP) and QT interval prolongation. Echocardiography showed left ventricular systolic dysfunction and endomyocardial biopsy showed myocyte degeneration and fibrosis. Administration of magnesium sulfate and temporary pacing eliminated recurrent TdP. Genetic analyses revealed that recurrent TdP occurred via electrolyte disturbance and cardiac failure due to PPCM on the basis of a novel mutation in KCNH2, a gene responsible for inherited type 2 long QT syndrome.
Collapse
Affiliation(s)
- Orie Nishimoto
- Department of Cardiology, National Hospital Organization, Kure Medical Center and Chugoku Cancer Center, Japan
| | | | | | | | | | | | | | | | | |
Collapse
|
27
|
Rankinen T, Sung YJ, Sarzynski MA, Rice TK, Rao DC, Bouchard C. Heritability of submaximal exercise heart rate response to exercise training is accounted for by nine SNPs. J Appl Physiol (1985) 2011; 112:892-7. [PMID: 22174390 DOI: 10.1152/japplphysiol.01287.2011] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Endurance training-induced changes in hemodynamic traits are heritable. However, few genes associated with heart rate training responses have been identified. The purpose of our study was to perform a genome-wide association study to uncover DNA sequence variants associated with submaximal exercise heart rate training responses in the HERITAGE Family Study. Heart rate was measured during steady-state exercise at 50 W (HR50) on 2 separate days before and after a 20-wk endurance training program in 483 white subjects from 99 families. Illumina HumanCNV370-Quad v3.0 BeadChips were genotyped using the Illumina BeadStation 500GX platform. After quality control procedures, 320,000 single-nucleotide polymorphisms (SNPs) were available for the genome-wide association study analyses, which were performed using the MERLIN software package (single-SNP analyses and conditional heritability tests) and standard regression models (multivariate analyses). The strongest associations for HR50 training response adjusted for age, sex, body mass index, and baseline HR50 were detected with SNPs at the YWHAQ locus on chromosome 2p25 (P = 8.1 × 10(-7)), the RBPMS locus on chromosome 8p12 (P = 3.8 × 10(-6)), and the CREB1 locus on chromosome 2q34 (P = 1.6 × 10(-5)). In addition, 37 other SNPs showed P values <9.9 × 10(-5). After removal of redundant SNPs, the 10 most significant SNPs explained 35.9% of the ΔHR50 variance in a multivariate regression model. Conditional heritability tests showed that nine of these SNPs (all intragenic) accounted for 100% of the ΔHR50 heritability. Our results indicate that SNPs in nine genes related to cardiomyocyte and neuronal functions, as well as cardiac memory formation, fully account for the heritability of the submaximal heart rate training response.
Collapse
Affiliation(s)
- Tuomo Rankinen
- Human Genomics Laboratory, Pennington Biomedical Research Center, 6400 Perkins Rd., Baton Rouge, LA 70808-4124, USA.
| | | | | | | | | | | |
Collapse
|
28
|
Sroubek J, McDonald TV. Protein kinase A activity at the endoplasmic reticulum surface is responsible for augmentation of human ether-a-go-go-related gene product (HERG). J Biol Chem 2011; 286:21927-36. [PMID: 21536683 DOI: 10.1074/jbc.m110.201699] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human ether-a-go-go-related gene product (HERG) is a cardiac potassium channel commonly implicated in the pathogenesis of the long QT syndrome, type 2 (LQT2). LQT2 mutations typically have incomplete penetrance and affect individuals at various stages of their lives; this may mirror variations in intracellular signaling and HERG regulation. Previous work showed that sustained protein kinase A (PKA) activity augments HERG protein abundance by a mechanism that includes enhanced protein translation. To investigate the subcellular site of this regulation, we generated site-specific probes to the cytoplasmic surface of the endoplasmic reticulum (ER), the presumed locale of channel synthesis. Real-time FRET-based indicators demonstrated both cAMP and PKA activity at the ER. A PKA inhibitor targeted to the ER surface (termed p4PKIg) completely abolished PKA-mediated augmentation of HERG in HEK293 cells as well as rat neonatal cardiomyocytes. Immunofluorescence co-localization, targeted FRET-based PKA biosensors, phospho-specific antibodies, and in vivo phosphorylation experiments confirmed that p4PKIg is preferentially active at the ER surface rather than the plasma membrane. Rerouting this inhibitor to the outer mitochondrial membrane diminishes its ability to block cAMP-dependent HERG induction. Our results support a model where PKA-dependent regulation of HERG synthesis occurs at the ER surface. Furthermore, reagents generated for this study provide novel experimental tools to probe compartmentalized cAMP/PKA signaling within cells.
Collapse
Affiliation(s)
- Jakub Sroubek
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | | |
Collapse
|
29
|
Abstract
Since the first discovery of Kvbeta-subunits more than 15 years ago, many more ancillary Kv channel subunits were characterized, for example, KChIPs, KCNEs, and BKbeta-subunits. The ancillary subunits are often integral parts of native Kv channels, which, therefore, are mostly multiprotein complexes composed of voltage-sensing and pore-forming Kvalpha-subunits and of ancillary or beta-subunits. Apparently, Kv channels need the ancillary subunits to fulfill their many different cell physiological roles. This is reflected by the large structural diversity observed with ancillary subunit structures. They range from proteins with transmembrane segments and extracellular domains to purely cytoplasmic proteins. Ancillary subunits modulate Kv channel gating but can also have a great impact on channel assembly, on channel trafficking to and from the cellular surface, and on targeting Kv channels to different cellular compartments. The importance of the role of accessory subunits is further emphasized by the number of mutations that are associated in both humans and animals with diseases like hypertension, epilepsy, arrhythmogenesis, periodic paralysis, and hypothyroidism. Interestingly, several ancillary subunits have in vitro enzymatic activity; for example, Kvbeta-subunits are oxidoreductases, or modulate enzymatic activity, i.e., KChIP3 modulates presenilin activity. Thus different modes of beta-subunit association and of functional impact on Kv channels can be delineated, making it difficult to extract common principles underlying Kvalpha- and beta-subunit interactions. We critically review present knowledge on the physiological role of ancillary Kv channel subunits and their effects on Kv channel properties.
Collapse
Affiliation(s)
- Olaf Pongs
- Institut für Neurale Signalverarbeitung, Zentrum für Molekulare Neurobiologie Hamburg, Universitätsklinikum Hamburg-Eppendorf, Universität Hamburg, Hamburg, Germany.
| | | |
Collapse
|
30
|
Nof E, Cordeiro JM, Pérez GJ, Scornik FS, Calloe K, Love B, Burashnikov E, Caceres G, Gunsburg M, Antzelevitch C. A common single nucleotide polymorphism can exacerbate long-QT type 2 syndrome leading to sudden infant death. ACTA ACUST UNITED AC 2010; 3:199-206. [PMID: 20181576 DOI: 10.1161/circgenetics.109.898569] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
BACKGROUND Identification of infants at risk for sudden arrhythmic death remains one of the leading challenges of modern medicine. We present a family in which a common polymorphism (single nucleotide polymorphism) inherited from the father, combined with a stop codon mutation inherited from the mother (both asymptomatic), led to 2 cases of sudden infant death. METHODS AND RESULTS KCNQ1, KCNH2, SCN5A, KCNE1, KCNE2, CACNA1c, CACNB2b, and KCNJ2 genes were amplified and analyzed by direct sequencing. Functional electrophysiological studies were performed with the single nucleotide polymorphism and mutation expressed singly and in combination in Chinese ovary (CHO-K1) and COS-1 cells. An asymptomatic woman presenting after the death of her 2-day-old infant and spontaneous abortion of a second baby in the first trimester was referred for genetic analysis. The newborn infant had nearly incessant ventricular tachycardia while in utero and a prolonged QTc (560 ms). The mother was asymptomatic but displayed a prolonged QTc. Genetic screening of the mother revealed a heterozygous nonsense mutation (P926AfsX14) in KCNH2, predicting a stop codon. The father was asymptomatic with a normal QTc but had a heterozygous polymorphism (K897T) in KCNH2. The baby who died at 2 days of age and the aborted fetus inherited both K897T and P926AfsX14. Heterologous coexpression of K897T and P926AfsX14 led to loss of function of HERG current much greater than expression of K897T or P926AfsX14 alone. CONCLUSIONS Our data suggest that a common polymorphism (K897T) can markedly accentuate the loss of function of mildly defective HERG channels, leading to long-QT syndrome-mediated arrhythmias and sudden infant death.
Collapse
Affiliation(s)
- Eyal Nof
- Masonic Medical Research Laboratory, Utica, NY 13501, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
31
|
Grunnet M. Repolarization of the cardiac action potential. Does an increase in repolarization capacity constitute a new anti-arrhythmic principle? Acta Physiol (Oxf) 2010; 198 Suppl 676:1-48. [PMID: 20132149 DOI: 10.1111/j.1748-1716.2009.02072.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The cardiac action potential can be divided into five distinct phases designated phases 0-4. The exact shape of the action potential comes about primarily as an orchestrated function of ion channels. The present review will give an overview of ion channels involved in generating the cardiac action potential with special emphasis on potassium channels involved in phase 3 repolarization. In humans, these channels are primarily K(v)11.1 (hERG1), K(v)7.1 (KCNQ1) and K(ir)2.1 (KCNJ2) being the responsible alpha-subunits for conducting I(Kr), I(Ks) and I(K1). An account will be given about molecular components, biophysical properties, regulation, interaction with other proteins and involvement in diseases. Both loss and gain of function of these currents are associated with different arrhythmogenic diseases. The second part of this review will therefore elucidate arrhythmias and subsequently focus on newly developed chemical entities having the ability to increase the activity of I(Kr), I(Ks) and I(K1). An evaluation will be given addressing the possibility that this novel class of compounds have the ability to constitute a new anti-arrhythmic principle. Experimental evidence from in vitro, ex vivo and in vivo settings will be included. Furthermore, conceptual differences between the short QT syndrome and I(Kr) activation will be accounted for.
Collapse
Affiliation(s)
- M Grunnet
- NeuroSearch A/S, Ballerup, and Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Denmark.
| |
Collapse
|
32
|
Hedley PL, Jørgensen P, Schlamowitz S, Wangari R, Moolman-Smook J, Brink PA, Kanters JK, Corfield VA, Christiansen M. The genetic basis of long QT and short QT syndromes: A mutation update. Hum Mutat 2009; 30:1486-511. [DOI: 10.1002/humu.21106] [Citation(s) in RCA: 318] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
|
33
|
Kruse M, Schulze-Bahr E, Corfield V, Beckmann A, Stallmeyer B, Kurtbay G, Ohmert I, Schulze-Bahr E, Brink P, Pongs O. Impaired endocytosis of the ion channel TRPM4 is associated with human progressive familial heart block type I. J Clin Invest 2009; 119:2737-44. [PMID: 19726882 DOI: 10.1172/jci38292] [Citation(s) in RCA: 236] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2008] [Accepted: 06/10/2009] [Indexed: 01/20/2023] Open
Abstract
Progressive familial heart block type I (PFHBI) is a progressive cardiac bundle branch disease in the His-Purkinje system that exhibits autosomal-dominant inheritance. In 3 branches of a large South African Afrikaner pedigree with an autosomal-dominant form of PFHBI, we identified the mutation c.19G-->A in the transient receptor potential cation channel, subfamily M, member 4 gene (TRPM4) at chromosomal locus 19q13.3. This mutation predicted the amino acid substitution p.E7K in the TRPM4 amino terminus. TRPM4 encodes a Ca2+-activated nonselective cation (CAN) channel that belongs to the transient receptor potential melastatin ion channel family. Quantitative analysis of TRPM4 mRNA content in human cardiac tissue showed the highest expression level in Purkinje fibers. Cellular expression studies showed that the c.19G-->A missense mutation attenuated deSUMOylation of the TRPM4 channel. The resulting constitutive SUMOylation of the mutant TRPM4 channel impaired endocytosis and led to elevated TRPM4 channel density at the cell surface. Our data therefore revealed a gain-of-function mechanism underlying this type of familial heart block.
Collapse
Affiliation(s)
- Martin Kruse
- Institut für Neurale Signalverarbeitung, Zentrum für Molekulare Neurobiologie, Universität Hamburg, Hamburg, Germany
| | | | | | | | | | | | | | | | | | | |
Collapse
|
34
|
Biliczki P, Girmatsion Z, Brandes RP, Harenkamp S, Pitard B, Charpentier F, Hébert TE, Hohnloser SH, Baró I, Nattel S, Ehrlich JR. Trafficking-deficient long QT syndrome mutation KCNQ1-T587M confers severe clinical phenotype by impairment of KCNH2 membrane localization: evidence for clinically significant IKr-IKs alpha-subunit interaction. Heart Rhythm 2009; 6:1792-801. [PMID: 19959132 DOI: 10.1016/j.hrthm.2009.08.009] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2009] [Accepted: 08/06/2009] [Indexed: 12/27/2022]
Abstract
BACKGROUND KCNQ1-T587M is a trafficking-deficient long QT syndrome (LQTS) missense mutation. Affected patients exhibit severe clinical phenotypes that are not explained by the mutant's effects on I(Ks). Previous work showed a KCNH2 and KCNQ1 alpha-subunit interaction that increases KCNH2 membrane localization and function. OBJECTIVE We hypothesized that failure of trafficking-deficient KCNQ1-T587M to enhance KCNH2 membrane expression could reduce KCNH2 current versus wild-type KCNQ1 (KCNQ1-WT), contributing to the LQTS phenotype of KCNQ1-T587M carriers. METHODS Patch-clamp, protein biochemical studies, confocal imaging, and in vivo transfection of guinea pig cardiomyocytes were performed. RESULTS KCNQ1-T587M failed to generate functional current when coexpressed with KCNE1 and caused haploinsufficiency when coexpressed with KCNQ1-WT/KCNE1. Coexpression of KCNQ1-WT with KCNH2 increased I(KCNH2) versus KCNH2 alone (P <.05). Immunoblots and confocal microscopy indicated increased plasma membrane localization of KCNH2 alpha-subunits in cells cotransfected with KCNQ1-WT plasmid, while total KCNH2 protein synthesis and KCNH2 glycosylation remained unaffected, which suggests a chaperone effect of KCNQ1-WT to enhance the membrane localization of KCNH2. KCNH2 also coimmunoprecipitated with KCNQ1-WT. Although KCNQ1-T587M coprecipitated with KCNH2, the mutant was retained intracellularly and failed to increase KCNH2 membrane localization, abolishing the KCNQ1-WT chaperone function and reducing I(KCNH2) upon coexpression substantially compared with coexpression with KCNQ1-WT (P <.05). In vivo transfection of KCNQ1-T587M in guinea pigs suppressed I(Kr) in isolated cardiomyocytes. CONCLUSION The trafficking-deficient LQTS mutation KCNQ1-T587M fails to show the chaperoning function that enhances KCNH2 membrane localization with KCNQ1-WT. This novel mechanism results in reduced I(KCNH2), which would be expected to decrease repolarization reserve and synergize with reduced I(KCNQ1) caused directly by the mutation, potentially explaining the malignant clinical phenotype in affected patients.
Collapse
Affiliation(s)
- Peter Biliczki
- Div. of Cardiology, Section of Electrophysiology, Goethe-Universität, Frankfurt, Germany
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
35
|
Clinical and genetic analysis of long QT syndrome in children from six families in Saudi Arabia: are they different? Pediatr Cardiol 2009; 30:490-501. [PMID: 19184172 DOI: 10.1007/s00246-008-9377-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/02/2008] [Revised: 11/13/2008] [Accepted: 12/24/2008] [Indexed: 10/21/2022]
Abstract
Congenital long QT syndrome (LQTS) is an inherited cardiac arrhythmia disorder characterized by prolongation of the QT interval; patients are predisposed to ventricular tachyarrhythmias and fibrillation leading to recurrent syncope or sudden cardiac death. We performed clinical and genetic studies in six Saudi Arabian families with a history of sudden unexplained death of children. Clinical symptoms, ECG phenotypes, and genetic findings led to the diagnosis of LQT1 in two families (recessive) and LQT2 in four families (three recessive and one dominant). Onset of arrhythmia was more severe in the recessive carriers and occurred during early childhood in all recessive LQT1 patients. Arrhythmia originated at the intrauterine stages of life in the recessive LQT2 patients. LQT1, causing mutation c.387-5 T > A in the KCNQ1 gene, and LQT2, causing mutation c.3208 C > T in the KCNH2 gene, are presumably founder mutations in the Assir province of Saudi Arabia. Further, all LQTS causing mutations detected in this study are novel and have not been reported in other populations.
Collapse
|
36
|
PPARδ activity in cardiovascular diseases: A potential pharmacological target. PPAR Res 2009; 2009:745821. [PMID: 19325917 PMCID: PMC2659552 DOI: 10.1155/2009/745821] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2008] [Revised: 12/21/2008] [Accepted: 02/12/2009] [Indexed: 11/17/2022] Open
Abstract
Activation of peroxisome proliferator-activated receptors (PPARs), and particularly of
PPARα and PPARγ, using selective agonists, is currently used in the treatment of metabolic diseases such as hypertriglyceridemia and type 2 diabetes mellitus. PPARα and PPARγ anti-inflammatory, antiproliferative and antiangiogenic properties in cardiovascular cells were
extensively clarified in a variety of in vitro and in vivo models. In contrast, the role of PPARδ in cardiovascular system is poorly understood. Prostacyclin, the predominant prostanoid released by
vascular cells, is a putative endogenous agonist for PPARδ, but only recently PPARδ selective synthetic agonists were found, improving studies about the physiological and pathophysiological roles of PPARδ activation. Recent reports suggest that the PPARδ activation may play a pivotal role to
regulate inflammation, apoptosis, and cell proliferation, suggesting that this transcriptional factor could become an interesting pharmacological target to regulate cardiovascular cell apoptosis, proliferation, inflammation, and metabolism.
Collapse
|
37
|
Ahrens-Nicklas RC, Clancy CE, Christini DJ. Re-evaluating the efficacy of beta-adrenergic agonists and antagonists in long QT-3 syndrome through computational modelling. Cardiovasc Res 2009; 82:439-47. [PMID: 19264765 DOI: 10.1093/cvr/cvp083] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
AIMS Long QT syndrome (LQTS) is a heterogeneous collection of inherited cardiac ion channelopathies characterized by a prolonged electrocardiogram QT interval and increased risk of sudden cardiac death. Beta-adrenergic blockers are the mainstay of treatment for LQTS. While their efficacy has been demonstrated in LQTS patients harbouring potassium channel mutations, studies of beta-blockers in subtype 3 (LQT3), which is caused by sodium channel mutations, have produced ambiguous results. In this modelling study, we explore the effects of beta-adrenergic drugs on the LQT3 phenotype. METHODS AND RESULTS In order to investigate the effects of beta-adrenergic activity and to identify sources of ambiguity in earlier studies, we developed a computational model incorporating the effects of beta-agonists and beta-blockers into an LQT3 mutant guinea pig ventricular myocyte model. Beta-activation suppressed two arrhythmogenic phenomena, transmural dispersion of repolarization and early after depolarizations, in a dose-dependent manner. However, the ability of beta-activation to prevent cardiac conduction block was pacing-rate-dependent. Low-dose beta-blockade by propranolol reversed the beneficial effects of beta-activation, while high dose (which has off-target sodium channel effects) decreased arrhythmia susceptibility. CONCLUSION These results demonstrate that beta-activation may be protective in LQT3 and help to reconcile seemingly conflicting results from different experimental models. They also highlight the need for well-controlled clinical investigations re-evaluating the use of beta-blockers in LQT3 patients.
Collapse
Affiliation(s)
- Rebecca C Ahrens-Nicklas
- Greenberg Division of Cardiology, Weill Cornell Medical College, 1300 York Ave., Box 161, New York, NY 10065, USA
| | | | | |
Collapse
|
38
|
Ke Y, Lei M, Solaro RJ. Regulation of cardiac excitation and contraction by p21 activated kinase-1. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2009; 98:238-50. [PMID: 19351515 DOI: 10.1016/j.pbiomolbio.2009.01.007] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Cardiac excitation and contraction are regulated by a variety of signaling molecules. Central to the regulatory scheme are protein kinases and phosphatases that carry out reversible phosphorylation of different effectors. The process of beta-adrenergic stimulation mediated by cAMP dependent protein kinase (PKA) forms a well-known pathway considered as the most significant control mechanism in excitation and contraction as well as many other regulatory mechanisms in cardiac function. However, although dephosphorylation pathways are critical to these regulatory processes, signaling to phosphatases is relatively poorly understood. Emerging evidence indicates that regulation of phosphatases, which dampen the effect of beta-adrenergic stimulation, is also important. We review here functional studies of p21 activated kinase-1 (Pak1) and its potential role as an upstream signal for protein phosphatase PP2A in the heart. Pak1 is a serine/threonine protein kinase directly activated by the small GTPases Cdc42 and Rac1. Pak1 is highly expressed in different regions of the heart and modulates the activities of ion channels, sarcomeric proteins, and other phosphoproteins through up-regulation of PP2A activity. Coordination of Pak1 and PP2A activities is not only potentially involved in regulation of normal cardiac function, but is likely to be important in patho-physiological conditions.
Collapse
Affiliation(s)
- Yunbo Ke
- The Department of Physiology and Biophysics and Center for Cardiovascular Research, University of Illinois at Chicago, College of Medicine, Room 202, COMRB, 835 South Wolcott Avenue, Chicago, IL 60612, USA
| | | | | |
Collapse
|
39
|
Brennan T, Fink M, Rodriguez B. Multiscale modelling of drug-induced effects on cardiac electrophysiological activity. Eur J Pharm Sci 2008; 36:62-77. [PMID: 19061955 DOI: 10.1016/j.ejps.2008.09.013] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2008] [Accepted: 09/08/2008] [Indexed: 01/09/2023]
Abstract
Many drugs fail in the clinical trials and therefore do not reach the market due to adverse effects on cardiac electrical function. This represents a growing concern for both regulatory and pharmaceutical agencies as it translates into important socio-economic costs. Drugs affecting cardiac activity come from diverse pharmacological groups and their interaction with cardiac electrophysiology can result in increased risk of potentially life threatening arrhythmias, such as Torsade de Pointes. The mechanisms of drug interaction with the heart are very complex and the effects span from the ion channel to the whole organ level. This makes their investigation using solely experimental in vitro and in vivo techniques very difficult. Computational modelling of cardiac electrophysiological behaviour has provided insight into the mechanisms of cardiac arrhythmogenesis, with high spatio-temporal resolution, from the ion channel to the whole organ level. It therefore represents a powerful tool in investigating mechanisms of drug-induced changes in cardiac behaviour and in their pro-arrhythmic potential. This article presents a comprehensive review of the recent advances in detailed models of drug action on cardiac electrophysiological activity.
Collapse
Affiliation(s)
- T Brennan
- Department of Engineering Science, University of Oxford, Oxford, United Kingdom
| | | | | |
Collapse
|
40
|
Christé G, Thériault O, Chahine M, Millat G, Rodriguez-Lafrasse C, Rousson R, Deschênes I, Ficker E, Chevalier P. A new C-terminal hERG mutation A915fs+47X associated with symptomatic LQT2 and auditory-trigger syncope. Heart Rhythm 2008; 5:1577-86. [PMID: 18984536 DOI: 10.1016/j.hrthm.2008.08.031] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2007] [Accepted: 08/26/2008] [Indexed: 11/29/2022]
Abstract
BACKGROUND A novel mutation of hERG (A915fs+47X) was discovered in a 32-year-old woman with torsades de pointes, long QTc interval (515 ms), and syncope upon auditory trigger. OBJECTIVE We explored whether the properties of this mutation could explain the pathology. METHODS Whole-cell A915fs+47X (del) and wild-type (WT) currents were recorded in transiently transfected COS7 cells or Xenopus oocytes. Western blots and sedimentation analysis of del/WT hERG were used to analyze protein expression, assembly, and trafficking. RESULTS The tail current density at -40 mV after a 2-s depolarization to +40 mV in COS7 cells expressing del was 36% of that for WT. Inactivation was 1.9-fold to 2.8-fold faster in del versus WT between -60 and +60 mV. In the range -60 to -10 mV, we found that a nondeactivating fraction of current was increased in del at the expense of a rapidly deactivating fraction, with a slowly deactivating fraction being unchanged. In Xenopus oocytes, expression of del alone produced 38% of WT currents, whereas coexpression of 1/2 WT + 1/2 del produced 49.8%. Furthermore, the expression of del protein at the cell surface was reduced by about 50%. This suggests that a partial trafficking defect of del contributes to the reduction in del current densities and to the dominant negative effect when coexpressed with WT. In model simulations, the mutation causes a 10% prolongation of action potential duration. CONCLUSION Decreased current levels caused by a trafficking defect may explain the long QT syndrome observed in our patient.
Collapse
|
41
|
Li Y, Sroubek J, Krishnan Y, McDonald TV. A-kinase anchoring protein targeting of protein kinase A and regulation of HERG channels. J Membr Biol 2008; 223:107-16. [PMID: 18679741 PMCID: PMC2522378 DOI: 10.1007/s00232-008-9118-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2008] [Accepted: 06/25/2008] [Indexed: 12/02/2022]
Abstract
Adrenergic stimulation of the heart initiates a signaling cascade in cardiac myocytes that increases the concentration of cAMP. Although cAMP elevation may occur over a large area of a target-organ cell, its effects are often more restricted due to local concentration of its main effector, protein kinase A (PKA), through A-kinase anchoring proteins (AKAPs). The HERG potassium channel, which produces the cardiac rapidly activating delayed rectifying K+ current (IKr), is a target for cAMP/PKA regulation. PKA regulation of the current may play a role in the pathogenesis of hereditary and acquired abnormalities of the channel leading to cardiac arrhythmia. We examined the possible role for AKAP-mediated regulation of HERG channels. Here, we report that the PKA-RII-specific AKAP inhibitory peptide AKAP-IS perturbs the distribution of PKA-RII and diminishes the PKA-dependent phosphorylation of HERG protein. The functional consequence of AKAP-IS is a reversal of cAMP-dependent regulation of HERG channel activity. In further support of AKAP-mediated targeting of kinase to HERG, PKA activity was coprecipitated from HERG expressed in HEK cells. Velocity gradient centrifugation of solubilized porcine cardiac membrane proteins showed that several PKA-RI and PKA-RII binding proteins cosediment with ERG channels. A physical association of HERG with several specific AKAPs with known cardiac expression, however, was not demonstrable in heterologous cotransfection studies. These results suggest that one or more AKAP(s) targets PKA to HERG channels and may contribute to the acute regulation of IKr by cAMP.
Collapse
Affiliation(s)
- Yan Li
- Department of Medicine, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
| | | | | | | |
Collapse
|
42
|
|
43
|
Bhuiyan ZA, Momenah TS, Gong Q, Amin AS, Ghamdi SA, Carvalho JS, Homfray T, Mannens MMAM, Zhou Z, Wilde AAM. Recurrent intrauterine fetal loss due to near absence of HERG: clinical and functional characterization of a homozygous nonsense HERG Q1070X mutation. Heart Rhythm 2008; 5:553-61. [PMID: 18362022 DOI: 10.1016/j.hrthm.2008.01.020] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2007] [Accepted: 01/15/2008] [Indexed: 11/25/2022]
Abstract
BACKGROUND Inherited arrhythmias may underlie intrauterine and neonatal arrhythmias. Resolving the molecular genetic nature of these rare cases provides significant insight into the role of the affected proteins in arrhythmogenesis and (extra-) cardiac development. OBJECTIVE The purpose of this study was to perform clinical, molecular, and functional studies of a consanguineous Arabian family with repeated early miscarriages and two intrauterine fetal losses in the early part of the third trimester of pregnancy due to persistent arrhythmias. METHODS In-depth clinical investigation was performed in two siblings, both of whom developed severe arrhythmia during the second trimester of pregnancy. Homozygosity mapping with microsatellite repeat polymorphic markers encompassing various cardiac ion channel genes linked to electrical instability of the heart was performed. Screening of the candidate gene in the homozygous locus was performed. Biochemical and electrophysiologic analysis was performed to elucidate the function of the mutated gene. RESULTS Screening of the HERG gene in the homozygous locus detected a homozygous nonsense mutation Q1070X in the HERG C-terminus in affected children. Biochemical and functional analysis of the Q1070X mutant showed that although the mutant HERG had the ability to traffic to the plasma membrane and to form functional channels, it was destroyed by the nonsense-mediated decay (NMD) pathway before its translation. NMD leads to near absence of HERG in homozygous Q1070X mutation carriers, causing debilitating arrhythmias (prior to birth) in homozygous carriers but no apparent phenotype in heterozygous carriers. CONCLUSION Homozygous HERG Q1070X is equivalent to near functional knockout of HERG. Clinical consequences appear early, originating during the early stages of embryonic life. The NMD pathway renders HERG Q1070X functionless before it can form a functional ion channel.
Collapse
Affiliation(s)
- Zahurul A Bhuiyan
- Department of Clinical Genetics, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
44
|
Gong Q, Zhang L, Vincent GM, Horne BD, Zhou Z. Nonsense mutations in hERG cause a decrease in mutant mRNA transcripts by nonsense-mediated mRNA decay in human long-QT syndrome. Circulation 2007; 116:17-24. [PMID: 17576861 PMCID: PMC2376840 DOI: 10.1161/circulationaha.107.708818] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Long-QT syndrome type 2 (LQT2) is caused by mutations in the human ether-a-go-go-related gene (hERG). More than 30% of the LQT2 mutations result in premature termination codons. Degradation of premature termination codon-containing mRNA transcripts by nonsense-mediated mRNA decay is increasingly recognized as a mechanism for reducing mRNA levels in a variety of human diseases. However, the role of nonsense-mediated mRNA decay in LQT2 mutations has not been explored. METHODS AND RESULTS We examined the expression of hERG mRNA in lymphocytes from patients carrying the R1014X mutation using a technique of allele-specific transcript quantification. The R1014X mutation led to a reduced level of mutant mRNA compared with that of the wild-type allele. The decrease in mutant mRNA also was observed in the LQT2 nonsense mutations W1001X and R1014X using hERG minigenes expressed in HEK293 cells or neonatal rat ventricular myocytes. Treatment with the protein synthesis inhibitor cycloheximide or RNA interference-mediated knockdown of the Upf1 protein resulted in the restoration of mutant mRNA to levels comparable to that of the wild-type minigene, suggesting that hERG nonsense mutations are subject to nonsense-mediated mRNA decay. CONCLUSIONS These results indicate that LQT2 nonsense mutations cause a decrease in mutant mRNA levels by nonsense-mediated mRNA decay rather than production of truncated proteins. Our findings suggest that the degradation of hERG mutant mRNA by nonsense-mediated mRNA decay is an important mechanism in LQT2 patients with nonsense or frameshift mutations.
Collapse
Affiliation(s)
- Qiuming Gong
- Division of Cardiovascular Medicine, Department of Medicine, Oregon Health & Science University
| | - Li Zhang
- Departments of Medicine and Cardiology, LDS Hospital, Intermountain Healthcare and University of Utah
| | - G. Michael Vincent
- Departments of Medicine and Cardiology, LDS Hospital, Intermountain Healthcare and University of Utah
| | - Benjamin D. Horne
- Genetic Epidemiology Division, LDS Hospital, Intermountain Healthcare and University of Utah
| | - Zhengfeng Zhou
- Division of Cardiovascular Medicine, Department of Medicine, Oregon Health & Science University
| |
Collapse
|
45
|
Ruknudin AM, Lakatta EG. The regulation of the Na/Ca exchanger and plasmalemmal Ca2+ ATPase by other proteins. Ann N Y Acad Sci 2007; 1099:86-102. [PMID: 17446448 DOI: 10.1196/annals.1387.045] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Na/Ca exchanger (NCX) and plasma membrane Ca2+ ATPase are the Ca2+ efflux mechanisms known in mammalian cells. NCX is the main transporter to efflux intracellular Ca2+ in the heart. NCX protein contains nine putative transmembrane domains and a large intracellular loop joining two sets of the transmembrane domains. The intracellular loop regulates the activity of the NCX by interacting with other proteins and nonprotein factors, such as ions, PIP2. Several proteins that are associated with NCX have been identified recently. Similarly, plasmalemmal Ca2+ ATPase (PMCA) has 10 putative transmembrane domains, and the C-terminal intracellular region inhibits transporter activity. There are several proteins associated with PMCA, and the roles of the associated proteins of PMCA vary from specific localization to involving PMCA in signal transduction. Elucidation of structural and functional roles played by these associated proteins of NCX and PMCA will provide opportunities to develop drugs of potential therapeutic value.
Collapse
Affiliation(s)
- Abdul M Ruknudin
- Laboratory of Cardiovascular Science, Gerontology Research Center, National Institute on Aging, NIH, Baltimore, MD 21224, USA.
| | | |
Collapse
|
46
|
Suto F, Zhu W, Chan A, Gross GJ. IKr and IKs remodeling differentially affects QT interval prolongation and dynamic adaptation to heart rate acceleration in bradycardic rabbits. Am J Physiol Heart Circ Physiol 2007; 292:H1782-8. [PMID: 17142341 DOI: 10.1152/ajpheart.00932.2006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Bradycardic ventricular electrical remodeling predisposes to lethal tachyarrhythmias. We investigated the early temporal sequence and reversibility of electrical remodeling in a rabbit complete heart block model subjected to bradycardic ventricular pacing for either 2 or 8 days, with a third group of animals undergoing 8 days of bradycardic pacing followed by 8 days of physiological-rate pacing. At specified time points after complete heart block induction and pacing initiation, steady-state QT interval measurements and variability as well as dynamic QT interval adaptation to abrupt heart rate acceleration were assessed in the absence and presence of isoproterenol. Rapidly ( IKr) and slowly ( IKs) activating delayed rectifier repolarizing K+ tail current densities were evaluated using whole cell patch clamp in isolated right ventricular myocytes. Steady-state QT interval prolongation at both 2 and 8 days was associated with moderate IKr reduction. IKs downregulation was apparent by day 2 but more profound at day 8. Dynamic QT interval adaptation was impaired under baseline conditions at day 8 but only during isoproterenol administration at day 2. Both in vivo and cellular manifestations of remodeling reverted toward control values after 8 days of physiological-rate pacing. In conclusion, in this bradycardic model, IKs downregulation 1) proceeds more gradually but more extensively than that of IKr and 2) is most prominently associated with impaired dynamic QT interval adaptation to heart rate acceleration. Isoproterenol blunts the dynamic QT interval response in animals with partially downregulated IKs, consistent with stress-related phenomena in known IKs-impaired states. Relative early sparing of IKs could explain the delay in the onset of lethal tachyarrhythmia predisposition in bradycardic electrical remodeling. Reversibility of remodeling supports the potential utility of preventive pacing intervention soon after bradycardia onset.
Collapse
Affiliation(s)
- Fumiaki Suto
- Physiology and Experimental Medicine Program, Hospital for Sick Children Research Institute, University of Toronto, Toronto, Canada
| | | | | | | |
Collapse
|
47
|
Brunelli L, Cieslik KA, Alcorn JL, Vatta M, Baldini A. Peroxisome proliferator-activated receptor-delta upregulates 14-3-3 epsilon in human endothelial cells via CCAAT/enhancer binding protein-beta. Circ Res 2007; 100:e59-71. [PMID: 17303761 DOI: 10.1161/01.res.0000260805.99076.22] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Peroxisome proliferator-activated receptor delta (PPARdelta) agonists are promising new agents for treatment of the metabolic syndrome. Although they possess antiatherosclerotic properties in vivo and promote endothelial cell survival, their mechanism of action is incompletely understood. 14-3-3epsilon is a critical component of the endothelial cell antiapoptotic machinery, which is essential to maintain homeostasis of the vascular wall. To test the hypothesis that PPARdelta targets 14-3-3epsilon in endothelial cells, we studied the response of the gene that encodes 14-3-3epsilon in humans, YWHAE, to PPARdelta ligands (L-165,041 and GW501516). We found that PPARdelta activates YWHAE promoter in a concentration and time-dependent manner. Consistent with these findings, L-165,041 increased 14-3-3epsilon mRNA and protein level, whereas PPARdelta small interfering RNA suppressed both basal and L-165,041-dependent YWHAE transcription and 14-3-3epsilon protein expression. Surprisingly, PPAR response elements in YWHAE promoter were not required for upregulation by PPARdelta, whereas a CCAAT/enhancer binding protein (C/EBP) site located at -160/-151 bp regulated both basal and PPARdelta-dependent promoter activity. Intriguingly, activation or knock down of endogenous PPARdelta regulated C/EBPbeta protein expression. Chromatin immunoprecipitation assays demonstrated that L-165,041 determines the localization of C/EBPbeta to the region spanning this C/EBP response element, whereas sequential chromatin immunoprecipitation analysis revealed that C/EBPbeta and PPARdelta form a transcriptional activating complex on this C/EBP site. Our work uncovers a novel role for C/EBPbeta as a mediator of PPARdelta-dependent 14-3-3epsilon gene regulation in human endothelial cells and provides insight into the mechanism by which PPARdelta agonists may be beneficial in atherosclerosis.
Collapse
Affiliation(s)
- Luca Brunelli
- Department of Pediatrics, The University of Texas at Houston Medical School, Houston, TX 77030-1503, USA.
| | | | | | | | | |
Collapse
|