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Molecular Determinants of Nav1.5 Multiprotein Complexes in Cardiac Cells

English title Molecular Determinants of Nav1.5 Multiprotein Complexes in Cardiac Cells
Applicant Abriel Hugues
Number 147060
Funding scheme Project funding (Div. I-III)
Research institution Department for BioMedical Research Medizinische Fakultät Universität Bern
Institution of higher education University of Berne - BE
Main discipline Cardiovascular Research
Start/End 01.04.2013 - 31.03.2016
Approved amount 713'880.00
Resource not found: 'b32db384-870a-464e-9bca-736634c1190f'

Keywords (8)

Brugada syndrome; arrhythmias; congenital long QT syndrome; cardiac conduction; ion channels; cardiac cells; voltage-gated sodium channel; cardiac electrophysiology

Lay Summary (French)

Lead
Les canaux ioniques sont de protéines qui se trouvent dans la membrane cellulaire de toutes les cellules animales. Une altération de la fonction de ces canaux ioniques, aussi nommé « canalopathie », peut conduire à diverses maladies telles qu’épilepsies, migraines, paralysies, hypertension et hypotension artérielle, et mucoviscidose.
Lay summary

 Notre projet a pour objectif d’étudier les mécanismes de régulation du canal sodique cardiaque nommé Nav1.5. Lors de nos précédentes études, nous avons pu démontrer que le gène de ce canal est fréquemment muté chez des patients et familles qui souffrent de troubles du rythme cardiaque (arythmies du cœur). Cependant, un grand nombre de détails nous manquent pour avoir une bonne compréhension des rôles de ce canal Nav1.5 dans les cellules cardiaques. Dans ce projet particulier, nous allons étudier les mécanismes moléculaires et cellulaires qui permettent une localisation précise dans les différentes parties de la membrane cellulaire des cellules cardiaques. Nous estimons que ces résultats nous permettrons de mieux comprendre les conséquences des malfonctions de Nav1.5 et permettront d’élaborer de nouvelle stratégies de traitements des patients avec des arythmies cardiaques.

Direct link to Lay Summary Last update: 30.03.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Lateral Membrane-Specific MAGUK CASK Down-Regulates NaV1.5 Channel in Cardiac Myocytes
Eichel C. A., Beuriot A., Chevalier M. Y., Rougier J. S., Louault F., Dilanian G., Amour J., Coulombe A., Abriel H., Hatem S. N., Balse E. (2016), Lateral Membrane-Specific MAGUK CASK Down-Regulates NaV1.5 Channel in Cardiac Myocytes, in Circ Res, 119, 544-56.
Cardiac-specific ablation of synapse-associated protein SAP97 in mice decreases potassium currents but not sodium current
Gillet L., Rougier Jean-Sebastien, Shy Diana, Sonntag Stephan, Mougenot Nathalie, Essers Maria, Shmerling Doron, Balse Elise, Hatem Stephane N., Abriel Hugues (2015), Cardiac-specific ablation of synapse-associated protein SAP97 in mice decreases potassium currents but not sodium current, in Heart Rhythm, 12, 181-192.
PDZ-Domain-Binding Motif Regulates Cardiomyocyte Compartment-Specific Na
Shy Diana, Gillet L., Ogrodnik Jakob, Albesa Maxime, Verkerk Arie O., Wolswinkel Rianne, Rougier Jean-Sébastien, Barc Julien, Essers Maria C., Syam Ninda, Marsman Roos F., van Mil Anneke M., Rotman Samuel, Redon Richard, Bezzina Connie R., Remme Carol Ann, Abriel Hugues (2014), PDZ-Domain-Binding Motif Regulates Cardiomyocyte Compartment-Specific Na, in Circulation, 130, 147-160.

Collaboration

Group / person Country
Types of collaboration
Prof. Stéphane Hatem, UMPC, Paris France (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication

Associated projects

Number Title Start Funding scheme
150895 Computational tools to investigate genetic channelopathies 01.09.2013 International Exploratory Workshops
165741 Multiple Nav1.5 Pools in Cardiac Cells: Molecular Determinants and Functional Roles 01.04.2016 Project funding (Div. I-III)
128016 Role of ion channel-interacting proteins in cardiac channelopathies 01.12.2009 SCOPES
135693 In vivo relevance of the PY and PDZ-domain binding motifs of the cardiac sodium channel Nav1.5 01.04.2011 Project funding (Div. I-III)
150823 Serial block face SEM 01.12.2013 R'EQUIP

Abstract

Background - The pore-forming subunit of the cardiac voltage-gated sodium channel, Nav1.5, plays a central role in physiology and diseases. It is involved in the rapid depolarization of the cardiac action potential, and thus allows the propagation of the electrical impulse throughout the myocardium. Class I anti-arrhythmic drugs are effective by reducing its activity. Furthermore, since 1995, several hundred genetic variants in its gene, SCN5A, have been detected in patients with various cardiac pathological phenotypes such as congenital and drug-acquired long QT syndromes (LQTS), Brugada syndrome (BrS), conduction disorders, sudden infant death syndrome, atrial fibrillation, and dilated cardiomyopathy. Interestingly, in many cases, patients and families display more than just one phenotype (for instance LQTS and BrS at the same time), hence defining an “Nav1.5 overlap syndrome”.

Despite already more than decades of research, the Nav1.5 field is still extremely active. The main general questions that are still to be addressed are: Is the observed phenotypic diversity in patients carrying Nav1.5 mutations a reflection of yet unknown (non-canonical) roles of Nav1.5 in the heart? In addition, what are the molecular and cellular mechanistic details of the regulation of Nav1.5 in normal and pathological states?

Over the past three years, a series of new and somewhat unexpected findings have been published. In summary, (1) our group has shown that Nav1.5 is part of at least two distinct multiprotein complexes (pools) at the intercalated discs (ID) and lateral membranes of myocytes; (2) the loss of expression of specific ID proteins such as connexin-43 and plakophilin-2 was found to be linked to reduced Nav1.5-mediated current; (3) Nav1.5 was shown to interact and to be co-regulated by an unknown mechanism with the potassium channel Kir2.1 which is responsible for the cardiac IK1 current; (4) Nav1.5 alpha-subunits were shown to be physically interacting and specific traffic-defective variants may consequently reduce the expression of wild-type proteins at the cell membrane, thus leading to a dominant-negative phenomenon; and lastly, (5) recent studies demonstrated that the biophysical properties of Nav1.5 may be modulated by the stretch of the cell membrane, thus classifying it within the list of stretch-modulated channels.

Over the past ten years, our group has actively contributed to the field by demonstrating the roles of several proteins that interact with Nav1.5. In particular, we have investigated the Nedd4-2-mediated ubiquitylation of Nav1.5, the stabilizing role of the syntrophin/dystrophin complex at the lateral membrane, the role of utrophin in dystrophin-deficient cells, and the interaction with the Membrane Associated GUanylate Kinase (MAGUK) protein, SAP97. Many of these findings were obtained by investigating genetically-modified mice and could be performed, thanks to the funding of the Swiss National Science Foundation (SNSF) and, more recently, by an FP7 grant of the European Union (Project EuTrigTreat). It is not surprising that in many instances, the results we obtained, despite being conclusive for some aspects, have raised new questions. In this proposal that can be viewed as a continuation of our previous SNSF-funded projects, our goal is to further our quest to understand the molecular and cellular determinants of the distinct multiprotein complexes of Nav1.5 that are found in cardiac cells.

Working Hypothesis - The localization and function of Nav1.5 is regulated by distinct and specific sets of proteins in different membrane compartments of ventricular cardiac cells, hence forming multiple pools/populations of Nav1.5. We propose that there are at least three pools of Nav1.5 channels found 1) at the intercalated discs, 2) at the peripheral lateral sarcolemma where it may be regulated by the MAGUK protein CASK, and 3) in the t-tubular compartment. We postulate that one of these Nav1.5 pools at the lateral membrane is regulated by PKA through a cardiac anchoring protein of the AKAP family.

In this proposal, we plan to address the three following specific aims:

1) To elucidate the role of the PDZ domain-binding motif of Nav1.5 in its anchoring to distinct membrane compartments
2) To decipher the CASK-dependent regulation of Nav1.5
3) To identify the cardiac AKAP that mediates PKA-dependent regulation of Nav1.5


Experimental Design - We plan to study Nav1.5 at the molecular and functional level using cardiomyocytes from genetically-modified mice. Mouse lines are currently available in our group, in particular, the one with a truncation of the PDZ domain-binding motif (DeltaSIV). In addition, two mouse lines are currently being generated: one constitutive and one inducible cardiac-specific KO for SAP97. In vivo cellular and biochemical phenotyping of these mice will be performed, using a set of techniques available in our laboratory and collaborating groups as stated in the proposal.



Expected Value of the Project - Nav1.5 plays a crucial role in cardiac pathology. Many of the genes and proteins that have been found to regulate Nav1.5 were also shown to be either mutated or dysregulated in different types of arrhythmias and other cardiac pathological manifestations. A continuing investigation of the regulatory mechanisms and associated proteins, and in particular, the deciphering of the molecular determinants of the distinct pools, will lead to novel genes/targets to be investigated in patients with Nav1.5-dependent cardiac disorders.

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