scholarly journals Insights into Cardiac IKs (KCNQ1/KCNE1) Channels Regulation

2020 ◽  
Vol 21 (24) ◽  
pp. 9440
Author(s):  
Xiaoan Wu ◽  
H. Peter Larsson
Keyword(s):  
Cardiac Arrhythmias ◽  
Cardiac Death ◽  
Delayed Rectifier ◽  
Long Qt ◽  
Voltage Gated ◽  
Important Regulator ◽  
Functional Knowledge ◽  
Qt Syndrome ◽  
Channel Properties ◽  
Iks Channel

The delayed rectifier potassium IKs channel is an important regulator of the duration of the ventricular action potential. Hundreds of mutations in the genes (KCNQ1 and KCNE1) encoding the IKs channel cause long QT syndrome (LQTS). LQTS is a heart disorder that can lead to severe cardiac arrhythmias and sudden cardiac death. A better understanding of the IKs channel (here called the KCNQ1/KCNE1 channel) properties and activities is of great importance to find the causes of LQTS and thus potentially treat LQTS. The KCNQ1/KCNE1 channel belongs to the superfamily of voltage-gated potassium channels. The KCNQ1/KCNE1 channel consists of both the pore-forming subunit KCNQ1 and the modulatory subunit KCNE1. KCNE1 regulates the function of the KCNQ1 channel in several ways. This review aims to describe the current structural and functional knowledge about the cardiac KCNQ1/KCNE1 channel. In addition, we focus on the modulation of the KCNQ1/KCNE1 channel and its potential as a target therapeutic of LQTS.

scholarly journals Impact of Dietary Factors on Brugada Syndrome and Long QT Syndrome

Nutrients ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 2482
Author(s):  
Sara D’Imperio ◽  
Michelle M. Monasky ◽  
Emanuele Micaglio ◽  
Gabriele Negro ◽  
Carlo Pappone
Keyword(s):  
Risk Factors ◽  
Sudden Cardiac Death ◽  
Long Qt Syndrome ◽  
Cardiac Arrhythmias ◽  
Brugada Syndrome ◽  
Cardiac Death ◽  
Dietary Factors ◽  
Long Qt ◽  
Qt Syndrome ◽  
The Relationship

A healthy regime is fundamental for the prevention of cardiovascular diseases (CVD). In inherited channelopathies, such as Brugada syndrome (BrS) and Long QT syndrome (LQTS), unfortunately, sudden cardiac death could be the first sign for patients affected by these syndromes. Several known factors are used to stratify the risk of developing cardiac arrhythmias, although none are determinative. The risk factors can be affected by adjusting lifestyle habits, such as a particular diet, impacting the risk of arrhythmogenic events and mortality. To date, the importance of understanding the relationship between diet and inherited channelopathies has been underrated. Therefore, we describe herein the effects of dietary factors on the development of arrhythmia in patients affected by BrS and LQTS. Modifying the diet might not be enough to fully prevent arrhythmias, but it can help lower the risk.

scholarly journals Inherited heart rhythm and conduction disorders in children with infectious diseases

2020 ◽  
pp. 126-133
Author(s):  
S. N. Chuprova ◽  
E. P. Rudneva ◽  
Yu. V. Lobzin
Keyword(s):  
Sudden Cardiac Death ◽  
Body Temperature ◽  
Infectious Diseases ◽  
Long Qt Syndrome ◽  
Cardiac Arrhythmias ◽  
Brugada Syndrome ◽  
Cardiac Death ◽  
Long Qt ◽  
Qt Syndrome ◽  
Inherited Arrhythmias

Introduction. One of the causes of sudden cardiac death in children is inherited arrhythmias. In view of the links between the increase in body temperature and the manifestation of some inherited cardiac arrhythmias (including typical electrocardiographic changes), the frequency of inherited cardiac arrhythmias in children with infectious diseases have been analyzed.The relevance of the study: is initiated by the necessity of timely diagnosis of inherited cardiac arrhythmias and conduction in children in order to prevent sudden cardiac death in them.The purpose of the study: to determine the frequency of inherited arrhythmias in children with infectious diseases based on clinical and electrocardiographic analysis.Materials and methods: 3584 electrocardiograms (ECGs) of children with infectious diseases (average age 8.5 ± 5.3 years old; boys – 57.5%, girls – 42.5%) hospitalized in the Pediatric Research and Clinical Center for Infectious Diseases were analyzed. Patients with changes in the ECGs were given additional examination depending on the intended diagnosis (inherited arrhythmias): 24-Hour Holter ECG monitoring, stress test, echocardiography. The family history was also clarified, and the parents’ ECG was analyzed.Results and conclusions. ECG changes, which are typical for Brugada syndrome (type 1), were detected in two children (0.05%) at first. Long QT syndrome was also detected in two children (0,05%). Mutations in the SCN5A gene were identified in children with Brugada syndrome, and in the KCNQ1 gene with long QT syndrome. An episode of monomorphic ventricular tachycardia was recorded at night in a 5-year-old girl with atrioventricular block 1 degree, hypoadaptation of the QT interval with repeated Holter ECG monitoring during sleep. Cases of life-threatening ventricular arrhythmias have previously been described in the literature in patients with Brugada syndrome. An increase in body temperature leads to disruption of the sodium ion channels which underlie the development of this syndrome, thereby, on the one hand, increasing the risk of life-threatening arrhythmias and sudden cardiac death, on the other hand, to the clinical manifestation of the disease, allowing the diagnosis to be made in time. In the cases of long QT syndrome, in our study, the increase in the corrected QT interval (QTc) is most likely due to a change in heart rate rather than a direct effect of an increase in body temperature on the ion channels.

scholarly journals Kalium rhodopsins: Natural light-gated potassium channels

2021 ◽  
Author(s):  
Elena G. Govorunova ◽  
Yueyang Gou ◽  
Oleg A. Sineshchekov ◽  
Hai Li ◽  
Yumei Wang ◽  
...  
Keyword(s):  
Potassium Channels ◽  
Cardiac Arrhythmias ◽  
Cortical Neurons ◽  
Cardiac Diseases ◽  
Potential Treatment ◽  
Permeability Ratio ◽  
Long Qt ◽  
Voltage Gated ◽  
Cell Firing ◽  
Qt Syndrome

AbstractWe report a family of K+ channels, kalium channelrhodopsins (KCRs) from a fungus-like protist. Previously known potassium channels, widespread and mainly ligand- or voltage-gated, share a conserved pore-forming domain and K+-selectivity filter. KCRs differ in that they are light-gated and they have independently evolved an alternative K+ selectivity mechanism. The KCRs are potent, highly selective of K+ over Na+, and open in less than 1 millisecond following photoactivation. Their permeability ratio PK/PNa of ∼ 20 make KCRs powerful hyperpolarizing tools that suppress excitable cell firing upon illumination, demonstrated here in mouse cortical neurons. KCRs enable specific optogenetic photocontrol of K+ gradients promising for the study and potential treatment of potassium channelopathies such as epilepsy, Parkinson’s disease, and long-QT syndrome and other cardiac arrhythmias.One-Sentence SummaryPotassium-selective channelrhodopsins long-sought for optogenetic research and therapy of neurological and cardiac diseases.

scholarly journals Molecular Mechanism of Autosomal Recessive Long QT-Syndrome 1 without Deafness

2021 ◽  
Vol 22 (3) ◽  
pp. 1112
Author(s):  
Annemarie Oertli ◽  
Susanne Rinné ◽  
Robin Moss ◽  
Stefan Kääb ◽  
Gunnar Seemann ◽  
...  
Keyword(s):  
Action Potential ◽  
Molecular Mechanism ◽  
Long Qt Syndrome ◽  
Autosomal Recessive ◽  
Delayed Rectifier ◽  
Loss Of Function ◽  
Wild Type ◽  
Long Qt ◽  
Qt Syndrome ◽  
Iks Channel

KCNQ1 encodes the voltage-gated potassium (Kv) channel KCNQ1, also known as KvLQT1 or Kv7.1. Together with its ß-subunit KCNE1, also denoted as minK, this channel generates the slowly activating cardiac delayed rectifier current IKs, which is a key regulator of the heart rate dependent adaptation of the cardiac action potential duration (APD). Loss-of-function mutations in KCNQ1 cause congenital long QT1 (LQT1) syndrome, characterized by a delayed cardiac repolarization and a prolonged QT interval in the surface electrocardiogram. Autosomal dominant loss-of-function mutations in KCNQ1 result in long QT syndrome, called Romano–Ward Syndrome (RWS), while autosomal recessive mutations lead to Jervell and Lange-Nielsen syndrome (JLNS), associated with deafness. Here, we identified a homozygous KCNQ1 mutation, c.1892_1893insC (p.P631fs*20), in a patient with an isolated LQT syndrome (LQTS) without hearing loss. Nevertheless, the inheritance trait is autosomal recessive, with heterozygous family members being asymptomatic. The results of the electrophysiological characterization of the mutant, using voltage-clamp recordings in Xenopus laevis oocytes, are in agreement with an autosomal recessive disorder, since the IKs reduction was only observed in homomeric mutants, but not in heteromeric IKs channel complexes containing wild-type channel subunits. We found that KCNE1 rescues the KCNQ1 loss-of-function in mutant IKs channel complexes when they contain wild-type KCNQ1 subunits, as found in the heterozygous state. Action potential modellings confirmed that the recessive c.1892_1893insC LQT1 mutation only affects the APD of homozygous mutation carriers. Thus, our study provides the molecular mechanism for an atypical autosomal recessive LQT trait that lacks hearing impairment.

scholarly journals A novel KCNH2 frameshift mutation (c.46delG) associated with high risk of sudden death in a family with congenital long QT syndrome type 2

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Hyun Sok Yoo ◽  
Nancy Medina ◽  
María Alejandra von Wulffen ◽  
Natalia Ciampi ◽  
Analia Paolucci ◽  
...  
Keyword(s):  
Sudden Cardiac Death ◽  
Long Qt Syndrome ◽  
Cardiac Death ◽  
Frameshift Mutation ◽  
Alpha Subunit ◽  
Syndrome Type ◽  
Long Qt ◽  
Qt Syndrome ◽  
Congenital Long Qt Syndrome

Abstract Background The congenital long QT syndrome type 2 is caused by mutations in KCNH2 gene that encodes the alpha subunit of potassium channel Kv11.1. The carriers of the pathogenic variant of KCNH2 gene manifest a phenotype characterized by prolongation of QT interval and increased risk of sudden cardiac death due to life-threatening ventricular tachyarrhythmias. Results A family composed of 17 members with a family history of sudden death and recurrent syncopes was studied. The DNA of proband with clinical manifestations of long QT syndrome was analyzed using a massive DNA sequencer that included the following genes: KCNQ1, KCNH2, SCN5A, KCNE1, KCNE2, ANK2, KCNJ2, CACNA1, CAV3, SCN1B, SCN4B, AKAP9, SNTA1, CALM1, KCNJ5, RYR2 and TRDN. DNA sequencing of proband identified a novel pathogenic variant of KCNH2 gene produced by a heterozygous frameshift mutation c.46delG, pAsp16Thrfs*44 resulting in the synthesis of a truncated alpha subunit of the Kv11.1 ion channel. Eight family members manifested the phenotype of long QT syndrome. The study of family segregation using Sanger sequencing revealed the identical variant in several members of the family with a positive phenotype. Conclusions The clinical and genetic findings of this family demonstrate that the novel frameshift mutation causing haploinsufficiency can result in a congenital long QT syndrome with a severe phenotypic manifestation and an elevated risk of sudden cardiac death.

scholarly journals Fatty acid analogue N-arachidonoyl taurine restores function of IKs channels with diverse long QT mutations

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Sara I Liin ◽  
Johan E Larsson ◽  
Rene Barro-Soria ◽  
Bo Hjorth Bentzen ◽  
H Peter Larsson
Keyword(s):  
Fatty Acid ◽  
Long Qt Syndrome ◽  
Molecular Mechanisms ◽  
Loss Of Function ◽  
Long Qt ◽  
Acid Analogue ◽  
Fatty Acid Analogue ◽  
Qt Syndrome ◽  
Channel Currents ◽  
Iks Channel

About 300 loss-of-function mutations in the IKs channel have been identified in patients with Long QT syndrome and cardiac arrhythmia. How specific mutations cause arrhythmia is largely unknown and there are no approved IKs channel activators for treatment of these arrhythmias. We find that several Long QT syndrome-associated IKs channel mutations shift channel voltage dependence and accelerate channel closing. Voltage-clamp fluorometry experiments and kinetic modeling suggest that similar mutation-induced alterations in IKs channel currents may be caused by different molecular mechanisms. Finally, we find that the fatty acid analogue N-arachidonoyl taurine restores channel gating of many different mutant channels, even though the mutations are in different domains of the IKs channel and affect the channel by different molecular mechanisms. N-arachidonoyl taurine is therefore an interesting prototype compound that may inspire development of future IKs channel activators to treat Long QT syndrome caused by diverse IKs channel mutations.

scholarly journals Trafficking-deficient hERG K+ channels linked to long QT syndrome are regulated by a microtubule-dependent quality control compartment in the ER

2011 ◽  
Vol 301 (1) ◽  
pp. C75-C85 ◽  
Author(s):  
Jennifer L. Smith ◽  
Christie M. McBride ◽  
Parvathi S. Nataraj ◽  
Daniel C. Bartos ◽  
Craig T. January ◽  
...  
Keyword(s):  
Golgi Apparatus ◽  
Long Qt Syndrome ◽  
Functional Expression ◽  
Delayed Rectifier ◽  
Temperature Sensitive ◽  
Missense Mutations ◽  
Long Qt ◽  
Delayed Rectifier Current ◽  
Golgi Compartment ◽  
Qt Syndrome

The human ether-a-go-go related gene ( hERG) encodes the voltage-gated K+ channel that underlies the rapidly activating delayed-rectifier current in cardiac myocytes. hERG is synthesized in the endoplasmic reticulum (ER) as an “immature” N-linked glycoprotein and is terminally glycosylated in the Golgi apparatus. Most hERG missense mutations linked to long QT syndrome type 2 (LQT2) reduce the terminal glycosylation and functional expression. We tested the hypothesis that a distinct pre-Golgi compartment negatively regulates the trafficking of some LQT2 mutations to the Golgi apparatus. We found that treating cells in nocodazole, a microtubule depolymerizing agent, altered the subcellular localization, functional expression, and glycosylation of the LQT2 mutation G601S-hERG differently from wild-type hERG (WT-hERG). G601S-hERG quickly redistributed to peripheral compartments that partially colocalized with KDEL (Lys-Asp-Glu-Leu) chaperones but not calnexin, Sec31, or the ER golgi intermediate compartment (ERGIC). Treating cells in E-4031, a drug that increases the functional expression of G601S-hERG, prevented the accumulation of G601S-hERG to the peripheral compartments and increased G601S-hERG colocalization with the ERGIC. Coexpressing the temperature-sensitive mutant G protein from vesicular stomatitis virus, a mutant N-linked glycoprotein that is retained in the ER, showed it was not restricted to the same peripheral compartments as G601S-hERG at nonpermissive temperatures. We conclude that the trafficking of G601S-hERG is negatively regulated by a microtubule-dependent compartment within the ER. Identifying mechanisms that prevent the sorting or promote the release of LQT2 channels from this compartment may represent a novel therapeutic strategy for LQT2.

Indications for genetic testing in athletes and its application in daily practice

2019 ◽  
pp. 166-176
Author(s):  
Andrea Mazzanti ◽  
Katherine Underwood ◽  
Silvia G. Priori
Keyword(s):  
Cardiovascular Disease ◽  
Genetic Testing ◽  
Genetic Information ◽  
Cardiac Death ◽  
Arrhythmogenic Right Ventricular Cardiomyopathy ◽  
Daily Practice ◽  
Polymorphic Ventricular Tachycardia ◽  
Molecular Testing ◽  
Long Qt ◽  
Qt Syndrome

Genetic information is fundamental for the management of patients with primary arrhythmia syndromes (e.g. long QT syndrome or catecholaminergic polymorphic ventricular tachycardia) and cardiomyopathies (e.g. arrhythmogenic right ventricular cardiomyopathy or hypertrophic cardiomyopathy) which increase the risk of sudden cardiac death. Importantly, molecular testing can play a pivotal role in establishing a clinical diagnosis of an inherited cardiovascular disease, particularly when the phenotype in unclear and overlaps with the normal adaptations induced in the heart by chronic exercise. However, the decision to undergo genetic testing needs to be justified on a clinical basis and handled by professionals who are capable of framing the results in the correct perspective. In this chapter we will answer the following questions. When should genetic testing be performed in athletes? Which genetic tests should be requested for athletes? What impact should a positive genetic result have on sports eligibility?

scholarly journals Balance Between Rapid Delayed Rectifier K + Current and Late Na + Current on Ventricular Repolarization

2020 ◽  
Vol 13 (4) ◽  
Author(s):  
Bence Hegyi ◽  
Ye Chen-Izu ◽  
Leighton T. Izu ◽  
Sridharan Rajamani ◽  
Luiz Belardinelli ◽  
...  
Keyword(s):  
Heart Failure ◽  
Long Qt Syndrome ◽  
Therapeutic Potential ◽  
Heart Diseases ◽  
Ionic Currents ◽  
Close Correlation ◽  
Delayed Rectifier ◽  
Long Qt ◽  
Comparable Amount ◽  
Qt Syndrome

Background: Rapid delayed rectifier K + current (I Kr ) and late Na + current (I NaL ) significantly shape the cardiac action potential (AP). Changes in their magnitudes can cause either long or short QT syndromes associated with malignant ventricular arrhythmias and sudden cardiac death. Methods: Physiological self AP-clamp was used to measure I NaL and I Kr during the AP in rabbit and porcine ventricular cardiomyocytes to test our hypothesis that the balance between I Kr and I NaL affects repolarization stability in health and disease conditions. Results: We found comparable amount of net charge carried by I Kr and I NaL during the physiological AP, suggesting that outward K + current via I Kr and inward Na + current via I NaL are in balance during physiological repolarization. Remarkably, I Kr and I NaL integrals in each control myocyte were highly correlated in both healthy rabbit and pig myocytes, despite high overall cell-to-cell variability. This close correlation was lost in heart failure myocytes from both species. Pretreatment with E-4031 to block I Kr (mimicking long QT syndrome 2) or with sea anemone toxin II to impair Na + channel inactivation (mimicking long QT syndrome 3) prolonged AP duration (APD); however, using GS-967 to inhibit I NaL sufficiently restored APD to control in both cases. Importantly, I NaL inhibition significantly reduced the beat-to-beat and short-term variabilities of APD. Moreover, I NaL inhibition also restored APD and repolarization stability in heart failure. Conversely, pretreatment with GS-967 shortened APD (mimicking short QT syndrome), and E-4031 reverted APD shortening. Furthermore, the amplitude of AP alternans occurring at high pacing frequency was decreased by I NaL inhibition, increased by I Kr inhibition, and restored by combined I NaL and I Kr inhibitions. Conclusions: Our data demonstrate that I Kr and I NaL are counterbalancing currents during the physiological ventricular AP and their integrals covary in individual myocytes. Targeting these ionic currents to normalize their balance may have significant therapeutic potential in heart diseases with repolarization abnormalities. Visual Overview: A visual overview is available for this article.

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