Biology subjects

Jalife, J.

Publications and source records attributed to Jalife, J..

8 recordsLinked to original sources

bioRxiv2025

Repurposing polyamines to prevent arrhythmias in Short QT Syndrome type 3, a potentially lethal disease

Short QT Syndrome type 3 (SQTS3) is a channelopathy characterized by the abbreviation of the QT interval on electrocardiogram and life-threatening arrhythmias. SQTS3 is caused by gain-of-function mutations in KCNJ2, which codes the strong inward rectifier potassium channel Kir2.1 responsible for the repolarizing current IK1. Inward- going rectification of IK1 is due to a voltage-dependent block by intracellular magnesium and polyamines. We evaluated the therapeutic potential of extrinsic polyamine administration to restore normal cardiac repolarization and prevent life-threatening arrhythmias in an AAV9-mediated mouse model of SQTS3 carrying the Kir2.1M301K mutation, which shortens the QT interval to a minimum of 194ms in patients. Compared to Kir2.1WT, the QT interval was significantly shortened in Kir2.1M301K mice. Intracardiac stimulation induced long-lasting, high-frequency ventricular tachycardia. Patch-clamping demonstrated an extremely abbreviated action potential duration (APD) in Kir2.1M301K cardiomyocytes due to a Kir2.1 lack of inward rectification. These IK1 defects decreased INa density and NaV1.5 expression. The mechanistically targeted Kir2.1 blockage by exogenous polyamines (spermine intraperitoneally or spermidine orally) prolonged the APD and the QT interval, and significantly reduced arrhythmia inducibility in Kir2.1M301K mice. Polyamines significantly reduced the IK1 gain-of-function, an effect that alleviated the INa reduction in mutant cardiomyocytes. Therefore, repurposing polyamine administration might be a novel and effective therapeutic strategy for managing cardiac arrhythmias in SQTS3 patients.

physiology↗

bioRxiv2024

Novel insights into IKur modulation by Lgi3-4: Implications in atrial fibrillation

BackgroundPatients with atrial fibrillation (AF) exhibit a reduction in the ultrarapid outward potassium current (IKur) conducted by KV1.5 channels. Ion channels are closely modulated by regulatory subunits, forming macromolecular complexes known as channelosomes. One such regulatory family is the leucine-rich glioma-inactivated protein family (Lgi1-4), which has been shown to interact with KV1, modifying their trafficking and/or biophysical properties in neurons. However, the expression and impact of these proteins in the heart is still unknown. We investigated the role of Lgi3-4 proteins in cardiac electrophysiology, focusing specifically on IKur, and their potential contribution to the pathophysiology of AF. MethodsWe used three complementary biological systems, including heterologous COS-7, HEK297 and CHO cells, AAV-mediated cardiac-specific Lgi4 gene transfer in mice (Lgi4 mice), and human samples from patients in sinus rhythm and AF. Our multidisciplinary approach included immunolocalization, patch clamping, surface ECG, transvenous catheter-mediated intracardiac stimulation, and molecular biology techniques. ResultsOnly Lgi3 and Lgi4 were expressed in the human heart. In human atrial tissue and heterologous cells, Lgi3 and Lgi4 interacted with KV1.5 channels. In HEK293 cells, Lgi3-4 impaired KV1.5/KV{beta} association, partially reversing the KV{beta}-induced N-type inactivation and reducing IKur amplitude. On surface ECG, the QRS interval was prolonged, and impulse conduction was impaired in cardiac-specific Lgi4 mice compared with control. In isolated ventricular cardiomyocytes from Lgi4 mice, early action potential repolarization was prolonged compared to control cardiomyocytes. These results correlated with the reduced KV1.5 membrane expression and IKur density observed in Lgi4 cardiomyocytes and HEK293 cells. Notably, Lgi4 protein expression was lower in atrial tissue from patients with AF than sinus rhythm patients. The reduction in Lgi4 protein levels in AF was also associated with an altered colocalization with KV1.5 channels, suggesting potential disruptions in their functional interactions. ConclusionsLgi3-4 proteins are new components of the KV1.5 channelosome. They modulate IKur by interfering with KV1.5 interaction with the KV{beta} subunit. Importantly, Lgi4 is dysregulated differently in paroxysmal versus permanent AF. The results improved the understanding of this most common type of arrhythmia and identified Lgi proteins as a new potential target for treatment. NOVELTY AND SIGNIFICANCEWhat is known? O_LILeucine-rich glioma-inactivated protein family (Lgi1-4) exert an important role in the nervous system and neurological diseases. In neurons, certain Lgi proteins interact with KV1 channels, modifying their trafficking and/or biophysical properties. C_LIO_LIIn cardiomyocytes, the activation of KV1.5 channels generates the ultrarapid outward potassium current (IKur), which is essential for the initial phase of human atrial repolarization, and it is dysregulated in AF. C_LIO_LIChanges in the properties or functional expression of some KV1.5 interacting proteins have crucial pathophysiological consequences. C_LI What new information does this article contribute? O_LIWe demonstrate that Lgi3-4 are novel components of KV1.5 channelosome, modulating IKur and hence human atrial electrophysiology. Lgi3-4 proteins decrease IKur by interfering with the interaction between KV1.5 and KV{beta} subunits. C_LIO_LIThe decrease in IKur in cardiac-specific mouse model expressing Lgi4 slows the early repolarization in the action potential, as well as produce electrophysiological changes in the surface ECG and the cardiac conduction system. C_LIO_LILgi4 is dysregulated differently in paroxysmal (PX) versus permanent (PM) AF, thus shedding light into the mechanisms underlying this cardiac arrhythmia. C_LI

physiology↗

bioRxiv2023

Extracellular cysteine disulfide bond break at Cys122 disrupts PIP2-dependent Kir2.1 channel function and leads to arrhythmias in Andersen-Tawil Syndrome

BackgroundAndersen-Tawil Syndrome Type 1 (ATS1) is a rare heritable disease caused by mutations in the strong inwardly rectifying K+ channel Kir2.1. The extracellular Cys122-to-Cys154 disulfide bond in the Kir2.1 channel structure is crucial for proper folding, but has not been associated with correct channel function at the membrane. We tested whether a human mutation at the Cys122-to-Cys154 disulfide bridge leads to Kir2.1 channel dysfunction and arrhythmias by reorganizing the overall Kir2.1 channel structure and destabilizing the open state of the channel. Methods and ResultsWe identified a Kir2.1 loss-of-function mutation in Cys122 (c.366 A>T; p.Cys122Tyr) in a family with ATS1. To study the consequences of this mutation on Kir2.1 function we generated a cardiac specific mouse model expressing the Kir2.1C122Y mutation. Kir2.1C122Y animals recapitulated the abnormal ECG features of ATS1, like QT prolongation, conduction defects, and increased arrhythmia susceptibility. Kir2.1C122Y mouse cardiomyocytes showed significantly reduced inward rectifier K+ (IK1) and inward Na+ (INa) current densities independently of normal trafficking ability and localization at the sarcolemma and the sarcoplasmic reticulum. Kir2.1C122Y formed heterotetramers with wildtype (WT) subunits. However, molecular dynamic modeling predicted that the Cys122-to-Cys154 disulfide-bond break induced by the C122Y mutation provoked a conformational change over the 2000 ns simulation, characterized by larger loss of the hydrogen bonds between Kir2.1 and phosphatidylinositol-4,5-bisphosphate (PIP2) than WT. Therefore, consistent with the inability of Kir2.1C122Y channels to bind directly to PIP2 in bioluminescence resonance energy transfer experiments, the PIP2 binding pocket was destabilized, resulting in a lower conductance state compared with WT. Accordingly, on inside-out patch-clamping the C122Y mutation significantly blunted Kir2.1 sensitivity to increasing PIP2 concentrations. ConclusionThe extracellular Cys122-to-Cys154 disulfide bond in the tridimensional Kir2.1 channel structure is essential to channel function. We demonstrated that ATS1 mutations that break disulfide bonds in the extracellular domain disrupt PIP2-dependent regulation, leading to channel dysfunction and life-threatening arrhythmias. CLINICAL PERSPECTIVEO_ST_ABSNOVELTY AND SIGNIFICANCEC_ST_ABSWhat is known? O_LIAndersen-Tawil Syndrome Type 1 (ATS1) is a rare arrhythmogenic disease caused by loss-of-function mutations in KCNJ2, the gene encoding the strong inward rectifier potassium channel Kir2.1 responsible for IK1. C_LIO_LIExtracellular Cys122 and Cys154 form an intramolecular disulfide bond that is essential for proper Kir2.1 channel folding but not considered vital for channel function. C_LIO_LIReplacement of Cys122 or Cys154 residues in the Kir2.1 channel with either alanine or serine abolished ionic current in Xenopus laevis oocytes. C_LI What new information does this article contribute? O_LIWe generated a mouse model that recapitulates the main cardiac electrical abnormalities of ATS1 patients carrying the C122Y mutation, including prolonged QT interval and life-threatening ventricular arrhythmias. C_LIO_LIWe demonstrate for the first time that a single residue mutation causing a break in the extracellular Cys122-to-Cys154 disulfide-bond leads to Kir2.1 channel dysfunction and arrhythmias in part by reorganizing the overall Kir2.1 channel structure, disrupting PIP2-dependent Kir2.1 channel function and destabilizing the open state of the channel. C_LIO_LIDefects in Kir2.1 energetic stability alter the functional expression of the voltage-gated cardiac sodium channel Nav1.5, one of the main Kir2.1 interactors in the macromolecular channelosome complex, contributing to the arrhythmias. C_LIO_LIThe data support the idea that susceptibility to arrhythmias and SCD in ATS1 are specific to the type and location of the mutation, so that clinical management should be different for each patient. C_LIO_LIAltogether, the results may lead to the identification of new molecular targets in the future design of drugs to treat a human disease that currently has no defined therapy. C_LI

molecular biology↗

bioRxiv2023

Intermediate molecular phenotypes to identify genetic markers of anthracycline-induced cardiotoxicity risk

Cardiotoxicity due to anthracyclines (CDA) affects cancer patients, but we cannot predict who may suffer from this complication. CDA is a complex disease whose polygenic component is mainly unidentified. We propose that levels of intermediate molecular phenotypes in the myocardium associated with histopathological damage could explain CDA susceptibility; so that variants of genes encoding these intermediate molecular phenotypes could identify patients susceptible to this complication. A genetically heterogeneous cohort of mice generated by backcrossing (N = 165) was treated with doxorubicin and docetaxel. Cardiac histopathological damage was measured by fibrosis and cardiomyocyte size by an Ariol slide scanner. We determine intramyocardial levels of intermediate molecular phenotypes of CDA associated with histopathological damage and quantitative trait loci (ipQTLs) linked to them. These ipQTLs seem to contribute to the missing heritability of CDA because they improve the heritability explained by QTL directly linked to CDA (cda-QTLs) through genetic models. Genes encoding these molecular subphenotypes were evaluated as genetic markers of CDA in three cancer patient cohorts (N = 517) whose cardiac damage was quantified by echocardiography or Cardiac Magnetic Resonance. Many SNPs associated with CDA were found using genetic models. LASSO multivariate regression identified two risk score models, one for pediatric cancer patients and the other for women with breast cancer. Molecular intermediate phenotypes associated with heart damage can identify genetic markers of CDA risk, thereby allowing a more personalized patient management. A similar strategy could be applied to identify genetic markers of other complex trait diseases.

genetics↗

bioRxiv2022

SNTA1 GeneRescues Ion Channel Function in Cardiomyocytes Derived from Induced Pluripotent Stem Cells Reprogrammed from Muscular Dystrophy Patients with Arrhythmias

Patients with cardiomyopathy of Duchenne Muscular Dystrophy (DMD) are at risk of developing life-threatening arrhythmias, but the mechanisms are unknown. We aimed to determine the role of cardiac ion channels controlling cardiac excitability in the mechanisms of arrhythmias in DMD patients. To test whether cardiac dystrophin mutations lead to defective NaV1.5-Kir2.1 channelosomes and arrhythmias, we generated iPSC-CMs from two hemizygous DMD males, a heterozygous female, and two unrelated controls. Two Patients had abnormal ECGs with frequent runs of ventricular tachycardia. iPSC-CMs from all DMD patients showed abnormal action potential profiles, slowed conduction velocities, and reduced sodium (INa) and inward rectifier potassium (IK1) currents. Membrane NaV1.5 and Kir2.1 protein levels were reduced in hemizygous DMD iPSC-CMs but not in heterozygous iPSC-CMs. Remarkably, transfecting just one component of the dystrophin protein complex (1-syntrophin) in hemizygous iPSC-CMs restored channelosome function, INa and IK1 densities and action potential profile. We provide the first demonstration that iPSC-CMs reprogrammed from skin fibroblasts of DMD patients with cardiomyopathy have a dysfunction of the NaV1.5-Kir2.1 channelosome, with consequent reduction of cardiac excitability and conduction. Altogether, iPSC-CMs from patients with DMD cardiomyopathy have a NaV1.5-Kir2.1 channelosome dysfunction, which can be rescued by the scaffolding protein 1-syntrophin to restore excitability.

cell biology↗

bioRxiv2021

MKK6 deficiency promotes cardiac dysfunction through MKK3-p38γ/δ-mTOR hyperactivation

Stress-activated p38 kinases control a plethora of functions and their dysregulation has been linked to development of steatosis, obesity, immune disorders and cancer. Therefore, they have been identified as potential targets for novel therapeutic strategies. There are four p38 family members (p38, p38{beta}, p38{gamma}, and p38{delta}) that are activated by MKK3 and MKK6. Here we demonstrate that lack of MKK6 reduces the life span in mice. Longitudinal study of cardiac function in Mkk6-/- mice showed that young mice have cardiac hypertrophy which progresses to cardiac dilatation and fibrosis with age. Mechanistically, lack of MKK6 blunts p38 activation while causing MKK3-p38{gamma}/{delta} hyperphosphorylation and increased mTOR signaling, resulting in cardiac hypertrophy. Cardiac hypertrophy in Mkk6-/- mice is reverted by knocking out either p38{gamma} or p38{delta}, or by inhibiting mTOR pathway with rapamycin. In conclusion, we have identified a key role for the MKK3/6-p38{gamma}/{delta} pathway in the development of cardiac hypertrophy, which has important implications for the clinical use of p38 inhibitors in the long-term treatment since they might result in cardiotoxicity. eLifes Review ProcesseLife works to improve the process of peer review so that it more effectively conveys the assessment of expert reviewers to authors, readers and other interested parties. In the future we envision a system in which research is first published as a preprint and the outputs of peer review are the primary way research is assessed, rather than journal title. Our editorial process produces two outputs: i) an assessment by peers designed to be posted alongside a preprint for the benefit of the readers; ii) detailed feedback on the manuscript for the authors, including requests for revisions and suggestions for improvement. Therefore we want to change how we construct and write peer reviews to make them useful to both authors and readers in a way that better reflects the work you put into reading and thinking about a paper. eLife reviews now have three parts: O_LIAn evaluation summary (in two or three sentences) that captures the major conclusions of the review in a concise manner, accessible to a wide audience. C_LIO_LIA public review that details the strengths and weaknesses of the manuscript before you, and discusses whether the authors claims and conclusions are justified by their data. C_LIO_LIA set of private recommendations for the authors that outline how you think the science and its presentation could be strengthened. C_LI All three sections will be used as the basis for an eLife publishing decision, which will, as always, be made after a consultation among the reviewers and editor. Each of the public reviews will be published (anonymously) alongside the preprint, together with a response from the authors if they choose. In the case of papers we reject after review, the authors can choose to delay posting until their paper has been published elsewhere. If this is your first time going through this new process, we ask that you take some time to read our Reviewer Guide, which discusses how we see each section will be used, what it should contain, and what we hope it accomplishes. And we remind you that, with the shift of reviews from private correspondence to public discourse, it is more important than ever that reviews are written in a clear and constructive manner appropriate for a public audience and mindful of the impact language choices might have on the authors.

molecular biology↗

bioRxiv2021

Dual Dysfunction of Kir2.1 Underlies Conduction and Excitation-Contraction Coupling Defects Promoting Arrhythmias in a Mouse Model of Andersen-Tawil Syndrome Type 1

Andersen-Tawil Syndrome (ATS) is associated with life threatening arrhythmias of unknown mechanism. We report on a mouse model carrying the trafficking-deficient mutant Kir2.1{Delta}314-315. The mouse recapitulates the electrophysiological phenotype of type 1 (ATS1), with slower conduction velocities in response to flecainide, QT prolongation exacerbated by isoproterenol, and increased vulnerability to calcium-mediated arrhythmias resembling catecholaminergic polymorphic ventricular tachycardia (CPVT). Kir2.1{Delta}314-315 expression significantly reduced inward rectifier K+ and Na+ inward currents, depolarized resting membrane potential and prolonged action potential duration. Immunolocalization in wildtype cardiomyocytes and skeletal muscle cells revealed a novel sarcoplasmic reticulum (SR) microdomain of functional Kir2.1 channels contributing to intracellular Ca2+ homeostasis. Kir2.1{Delta}314-315 cardiomyocytes showed defects in SR Kir2.1 localization and function, which contributed to abnormal spontaneous Ca2+ release events. This is the first in-vivo demonstration of a dual arrhythmogenic mechanism of ATS1 defects in Kir2.1 channel function at the sarcolemma and the SR, with overlap between ATS1 and CPVT.

cell biology↗

bioRxiv2018

Genome-wide association study of 1 million people identifies 111 loci for atrial fibrillation

To understand the genetic variation underlying atrial fibrillation (AF), the most common cardiac arrhythmia, we performed a genome-wide association study (GWAS) of > 1 million people, including 60,620 AF cases and 970,216 controls. We identified 163 independent risk variants at 111 loci and prioritized 165 candidate genes likely to be involved in AF. Many of the identified risk variants fall near genes where more deleterious mutations have been reported to cause serious heart defects in humans or mice (MYH6, NKX2-5, PITX2, TBC1D32, TBX5),1,2 or near genes important for striated muscle function and integrity (e.g. MYH7, PKP2, SSPN, SGCA). Experiments in rabbits with heart failure and left atrial dilation identified a heterogeneous distributed molecular switch from MYH6 to MYH7 in the left atrium, which resulted in contractile and functional heterogeneity and may predispose to initiation and maintenance of atrial arrhythmia.

genetics↗