1
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Minard AY, Clark CJ, Ahern CA, Piper RC. Beta-subunit-eliminated eHAP expression (BeHAPe) cells reveal subunit regulation of the cardiac voltage-gated sodium channel. J Biol Chem 2023; 299:105132. [PMID: 37544648 PMCID: PMC10506104 DOI: 10.1016/j.jbc.2023.105132] [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: 02/10/2023] [Revised: 07/27/2023] [Accepted: 07/31/2023] [Indexed: 08/08/2023] Open
Abstract
Voltage-gated sodium (NaV) channels drive the upstroke of the action potential and are comprised of a pore-forming α-subunit and regulatory β-subunits. The β-subunits modulate the gating, trafficking, and pharmacology of the α-subunit. These functions are routinely assessed by ectopic expression in heterologous cells. However, currently available expression systems may not capture the full range of these effects since they contain endogenous β-subunits. To better reveal β-subunit functions, we engineered a human cell line devoid of endogenous NaV β-subunits and their immediate phylogenetic relatives. This new cell line, β-subunit-eliminated eHAP expression (BeHAPe) cells, were derived from haploid eHAP cells by engineering inactivating mutations in the β-subunits SCN1B, SCN2B, SCN3B, and SCN4B, and other subfamily members MPZ (myelin protein zero(P0)), MPZL1, MPZL2, MPZL3, and JAML. In diploid BeHAPe cells, the cardiac NaV α-subunit, NaV1.5, was highly sensitive to β-subunit modulation and revealed that each β-subunit and even MPZ imparted unique gating properties. Furthermore, combining β1 and β2 with NaV1.5 generated a sodium channel with hybrid properties, distinct from the effects of the individual subunits. Thus, this approach revealed an expanded ability of β-subunits to regulate NaV1.5 activity and can be used to improve the characterization of other α/β NaV complexes.
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Affiliation(s)
- Annabel Y Minard
- Department of Molecular Physiology and Biophysics, University of Iowa College of Medicine, Iowa City, Iowa, United States
| | - Colin J Clark
- Department of Molecular Physiology and Biophysics, University of Iowa College of Medicine, Iowa City, Iowa, United States
| | - Christopher A Ahern
- Department of Molecular Physiology and Biophysics, University of Iowa College of Medicine, Iowa City, Iowa, United States.
| | - Robert C Piper
- Department of Molecular Physiology and Biophysics, University of Iowa College of Medicine, Iowa City, Iowa, United States.
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2
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Valente P, Marte A, Franchi F, Sterlini B, Casagrande S, Corradi A, Baldelli P, Benfenati F. A Push-Pull Mechanism Between PRRT2 and β4-subunit Differentially Regulates Membrane Exposure and Biophysical Properties of NaV1.2 Sodium Channels. Mol Neurobiol 2023; 60:1281-1296. [PMID: 36441479 PMCID: PMC9899197 DOI: 10.1007/s12035-022-03112-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Accepted: 10/26/2022] [Indexed: 11/29/2022]
Abstract
Proline-rich transmembrane protein 2 (PRRT2) is a neuron-specific protein implicated in the control of neurotransmitter release and neural network stability. Accordingly, PRRT2 loss-of-function mutations associate with pleiotropic paroxysmal neurological disorders, including paroxysmal kinesigenic dyskinesia, episodic ataxia, benign familial infantile seizures, and hemiplegic migraine. PRRT2 is a negative modulator of the membrane exposure and biophysical properties of Na+ channels NaV1.2/NaV1.6 predominantly expressed in brain glutamatergic neurons. NaV channels form complexes with β-subunits that facilitate the membrane targeting and the activation of the α-subunits. The opposite effects of PRRT2 and β-subunits on NaV channels raises the question of whether PRRT2 and β-subunits interact or compete for common binding sites on the α-subunit, generating Na+ channel complexes with distinct functional properties. Using a heterologous expression system, we have observed that β-subunits and PRRT2 do not interact with each other and act as independent non-competitive modulators of NaV1.2 channel trafficking and biophysical properties. PRRT2 antagonizes the β4-induced increase in expression and functional activation of the transient and persistent NaV1.2 currents, without affecting resurgent current. The data indicate that β4-subunit and PRRT2 form a push-pull system that finely tunes the membrane expression and function of NaV channels and the intrinsic neuronal excitability.
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Affiliation(s)
- Pierluigi Valente
- Department of Experimental Medicine, Section of Physiology, University of Genova, Viale Benedetto XV, 3, 16132, Genova, Italy. .,IRCCS, Ospedale Policlinico San Martino, Largo Rosanna Benzi 10, 16132, Genova, Italy.
| | - Antonella Marte
- Department of Experimental Medicine, Section of Physiology, University of Genova, Viale Benedetto XV, 3, 16132 Genova, Italy ,IRCCS, Ospedale Policlinico San Martino, Largo Rosanna Benzi 10, 16132 Genova, Italy
| | - Francesca Franchi
- Department of Experimental Medicine, Section of Physiology, University of Genova, Viale Benedetto XV, 3, 16132 Genova, Italy ,Center for Synaptic Neuroscience and Technology, Istituto Italiano Di Tecnologia, Largo Rosanna Benzi 10, 16132 Genova, Italy
| | - Bruno Sterlini
- Department of Experimental Medicine, Section of Physiology, University of Genova, Viale Benedetto XV, 3, 16132 Genova, Italy ,Center for Synaptic Neuroscience and Technology, Istituto Italiano Di Tecnologia, Largo Rosanna Benzi 10, 16132 Genova, Italy
| | - Silvia Casagrande
- Department of Experimental Medicine, Section of Physiology, University of Genova, Viale Benedetto XV, 3, 16132 Genova, Italy
| | - Anna Corradi
- Department of Experimental Medicine, Section of Physiology, University of Genova, Viale Benedetto XV, 3, 16132 Genova, Italy ,IRCCS, Ospedale Policlinico San Martino, Largo Rosanna Benzi 10, 16132 Genova, Italy
| | - Pietro Baldelli
- Department of Experimental Medicine, Section of Physiology, University of Genova, Viale Benedetto XV, 3, 16132 Genova, Italy ,IRCCS, Ospedale Policlinico San Martino, Largo Rosanna Benzi 10, 16132 Genova, Italy
| | - Fabio Benfenati
- IRCCS, Ospedale Policlinico San Martino, Largo Rosanna Benzi 10, 16132, Genova, Italy. .,Center for Synaptic Neuroscience and Technology, Istituto Italiano Di Tecnologia, Largo Rosanna Benzi 10, 16132, Genova, Italy.
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3
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Walther F, Feind D, Vom Dahl C, Müller CE, Kukaj T, Sattler C, Nagel G, Gao S, Zimmer T. Action potentials in Xenopus oocytes triggered by blue light. J Gen Physiol 2020; 152:151581. [PMID: 32211871 PMCID: PMC7201882 DOI: 10.1085/jgp.201912489] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Accepted: 02/24/2020] [Indexed: 11/20/2022] Open
Abstract
Voltage-gated sodium (Na+) channels are responsible for the fast upstroke of the action potential of excitable cells. The different α subunits of Na+ channels respond to brief membrane depolarizations above a threshold level by undergoing conformational changes that result in the opening of the pore and a subsequent inward flux of Na+. Physiologically, these initial membrane depolarizations are caused by other ion channels that are activated by a variety of stimuli such as mechanical stretch, temperature changes, and various ligands. In the present study, we developed an optogenetic approach to activate Na+ channels and elicit action potentials in Xenopus laevis oocytes. All recordings were performed by the two-microelectrode technique. We first coupled channelrhodopsin-2 (ChR2), a light-sensitive ion channel of the green alga Chlamydomonas reinhardtii, to the auxiliary β1 subunit of voltage-gated Na+ channels. The resulting fusion construct, β1-ChR2, retained the ability to modulate Na+ channel kinetics and generate photosensitive inward currents. Stimulation of Xenopus oocytes coexpressing the skeletal muscle Na+ channel Nav1.4 and β1-ChR2 with 25-ms lasting blue-light pulses resulted in rapid alterations of the membrane potential strongly resembling typical action potentials of excitable cells. Blocking Nav1.4 with tetrodotoxin prevented the fast upstroke and the reversal of the membrane potential. Coexpression of the voltage-gated K+ channel Kv2.1 facilitated action potential repolarization considerably. Light-induced action potentials were also obtained by coexpressing β1-ChR2 with either the neuronal Na+ channel Nav1.2 or the cardiac-specific isoform Nav1.5. Potential applications of this novel optogenetic tool are discussed.
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Affiliation(s)
- Florian Walther
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University, Jena, Germany
| | - Dominic Feind
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University, Jena, Germany
| | - Christian Vom Dahl
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University, Jena, Germany
| | - Christoph Emanuel Müller
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University, Jena, Germany
| | - Taulant Kukaj
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University, Jena, Germany
| | - Christian Sattler
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University, Jena, Germany
| | - Georg Nagel
- Institute of Physiology-Neurophysiology, Biocentre, Julius-Maximilians-University, Wuerzburg, Germany
| | - Shiqiang Gao
- Institute of Physiology-Neurophysiology, Biocentre, Julius-Maximilians-University, Wuerzburg, Germany
| | - Thomas Zimmer
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University, Jena, Germany
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4
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Ghatak S, Dolatabadi N, Trudler D, Zhang X, Wu Y, Mohata M, Ambasudhan R, Talantova M, Lipton SA. Mechanisms of hyperexcitability in Alzheimer's disease hiPSC-derived neurons and cerebral organoids vs isogenic controls. eLife 2019; 8:50333. [PMID: 31782729 PMCID: PMC6905854 DOI: 10.7554/elife.50333] [Citation(s) in RCA: 113] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Accepted: 11/21/2019] [Indexed: 12/21/2022] Open
Abstract
Human Alzheimer’s disease (AD) brains and transgenic AD mouse models manifest hyperexcitability. This aberrant electrical activity is caused by synaptic dysfunction that represents the major pathophysiological correlate of cognitive decline. However, the underlying mechanism for this excessive excitability remains incompletely understood. To investigate the basis for the hyperactivity, we performed electrophysiological and immunofluorescence studies on hiPSC-derived cerebrocortical neuronal cultures and cerebral organoids bearing AD-related mutations in presenilin-1 or amyloid precursor protein vs. isogenic gene corrected controls. In the AD hiPSC-derived neurons/organoids, we found increased excitatory bursting activity, which could be explained in part by a decrease in neurite length. AD hiPSC-derived neurons also displayed increased sodium current density and increased excitatory and decreased inhibitory synaptic activity. Our findings establish hiPSC-derived AD neuronal cultures and organoids as a relevant model of early AD pathophysiology and provide mechanistic insight into the observed hyperexcitability.
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Affiliation(s)
- Swagata Ghatak
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, United States
| | - Nima Dolatabadi
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, United States
| | - Dorit Trudler
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, United States
| | - XiaoTong Zhang
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, United States
| | - Yin Wu
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, United States
| | - Madhav Mohata
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, United States
| | - Rajesh Ambasudhan
- Neurodegenerative Disease Center, Scintillon Institute, San Diego, United States
| | - Maria Talantova
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, United States
| | - Stuart A Lipton
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, United States.,Neurodegenerative Disease Center, Scintillon Institute, San Diego, United States.,Department of Neuroscience, The Scripps Research Institute, La Jolla, United States.,Neuroscience Translational Center, The Scripps Research Institute, La Jolla, United States.,Department of Neurosciences, School of Medicine, University of California, San Diego, San Diego, United States
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5
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Cortada E, Brugada R, Verges M. Trafficking and Function of the Voltage-Gated Sodium Channel β2 Subunit. Biomolecules 2019; 9:biom9100604. [PMID: 31614896 PMCID: PMC6843408 DOI: 10.3390/biom9100604] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 10/07/2019] [Accepted: 10/08/2019] [Indexed: 12/15/2022] Open
Abstract
The voltage-gated sodium channel is vital for cardiomyocyte function, and consists of a protein complex containing a pore-forming α subunit and two associated β subunits. A fundamental, yet unsolved, question is to define the precise function of β subunits. While their location in vivo remains unclear, large evidence shows that they regulate localization of α and the biophysical properties of the channel. The current data support that one of these subunits, β2, promotes cell surface expression of α. The main α isoform in an adult heart is NaV1.5, and mutations in SCN5A, the gene encoding NaV1.5, often lead to hereditary arrhythmias and sudden death. The association of β2 with cardiac arrhythmias has also been described, which could be due to alterations in trafficking, anchoring, and localization of NaV1.5 at the cardiomyocyte surface. Here, we will discuss research dealing with mechanisms that regulate β2 trafficking, and how β2 could be pivotal for the correct localization of NaV1.5, which influences cellular excitability and electrical coupling of the heart. Moreover, β2 may have yet to be discovered roles on cell adhesion and signaling, implying that diverse defects leading to human disease may arise due to β2 mutations.
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Affiliation(s)
- Eric Cortada
- Cardiovascular Genetics Group, Girona Biomedical Research Institute (IDIBGI), C/ Doctor Castany, s/n-Edifici IDIBGI, 17190 Girona, Spain.
- Biomedical Research Networking Center on Cardiovascular Diseases (CIBERCV), 28029 Madrid, Spain.
| | - Ramon Brugada
- Cardiovascular Genetics Group, Girona Biomedical Research Institute (IDIBGI), C/ Doctor Castany, s/n-Edifici IDIBGI, 17190 Girona, Spain.
- Biomedical Research Networking Center on Cardiovascular Diseases (CIBERCV), 28029 Madrid, Spain.
- Medical Sciences Department, University of Girona Medical School, 17003 Girona, Spain.
- Cardiology Department, Hospital Josep Trueta, 17007 Girona, Spain.
| | - Marcel Verges
- Cardiovascular Genetics Group, Girona Biomedical Research Institute (IDIBGI), C/ Doctor Castany, s/n-Edifici IDIBGI, 17190 Girona, Spain.
- Biomedical Research Networking Center on Cardiovascular Diseases (CIBERCV), 28029 Madrid, Spain.
- Medical Sciences Department, University of Girona Medical School, 17003 Girona, Spain.
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6
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Cortada E, Brugada R, Verges M. N-Glycosylation of the voltage-gated sodium channel β2 subunit is required for efficient trafficking of Na V1.5/β2 to the plasma membrane. J Biol Chem 2019; 294:16123-16140. [PMID: 31511323 DOI: 10.1074/jbc.ra119.007903] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Revised: 09/01/2019] [Indexed: 01/25/2023] Open
Abstract
The voltage-gated sodium channel is critical for cardiomyocyte function and consists of a protein complex comprising a pore-forming α subunit and two associated β subunits. It has been shown previously that the associated β2 subunits promote cell surface expression of the α subunit. The major α isoform in the adult human heart is NaV1.5, and germline mutations in the NaV1.5-encoding gene, sodium voltage-gated channel α subunit 5 (SCN5A), often cause inherited arrhythmias. Here, we investigated the mechanisms that regulate β2 trafficking and how they may determine proper NaV1.5 cell surface localization. Using heterologous expression in polarized Madin-Darby canine kidney cells, we show that β2 is N-glycosylated in vivo and in vitro at residues 42, 66, and 74, becoming sialylated only at Asn-42. We found that fully nonglycosylated β2 was mostly retained in the endoplasmic reticulum, indicating that N-linked glycosylation is required for efficient β2 trafficking to the apical plasma membrane. The nonglycosylated variant reached the cell surface by bypassing the Golgi compartment at a rate of only approximately one-third of that of WT β2. YFP-tagged, nonglycosylated β2 displayed mobility kinetics in the plane of the membrane similar to that of WT β2. However, it was defective in promoting surface localization of NaV1.5. Interestingly, β2 with a single intact glycosylation site was as effective as the WT in promoting NaV1.5 surface localization. In conclusion, our results indicate that N-linked glycosylation of β2 is required for surface localization of NaV1.5, a property that is often defective in inherited cardiac arrhythmias.
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Affiliation(s)
- Eric Cortada
- Cardiovascular Genetics Group-Girona Biomedical Research Institute (IDIBGI), University of Girona Medical School, C/ Doctor Castany, s/n-Edifici IDIBGI, 17190 Salt-Prov. Girona, Spain.,Biomedical Research Networking Center on Cardiovascular Diseases (CIBERCV), University of Girona Medical School, C/ Doctor Castany, s/n-Edifici IDIBGI, 17190 Salt-Prov. Girona, Spain
| | - Ramon Brugada
- Cardiovascular Genetics Group-Girona Biomedical Research Institute (IDIBGI), University of Girona Medical School, C/ Doctor Castany, s/n-Edifici IDIBGI, 17190 Salt-Prov. Girona, Spain.,Biomedical Research Networking Center on Cardiovascular Diseases (CIBERCV), University of Girona Medical School, C/ Doctor Castany, s/n-Edifici IDIBGI, 17190 Salt-Prov. Girona, Spain.,Medical Sciences Department, University of Girona Medical School, C/ Doctor Castany, s/n-Edifici IDIBGI, 17190 Salt-Prov. Girona, Spain.,Cardiology Department, Hospital Josep Trueta, University of Girona Medical School, C/ Doctor Castany, s/nγÇôEdifici IDIBGI, 17190 SaltγÇôProv. Girona, Spain
| | - Marcel Verges
- Cardiovascular Genetics Group-Girona Biomedical Research Institute (IDIBGI), University of Girona Medical School, C/ Doctor Castany, s/n-Edifici IDIBGI, 17190 Salt-Prov. Girona, Spain .,Biomedical Research Networking Center on Cardiovascular Diseases (CIBERCV), University of Girona Medical School, C/ Doctor Castany, s/n-Edifici IDIBGI, 17190 Salt-Prov. Girona, Spain.,Medical Sciences Department, University of Girona Medical School, C/ Doctor Castany, s/n-Edifici IDIBGI, 17190 Salt-Prov. Girona, Spain
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7
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Hull JM, Isom LL. Voltage-gated sodium channel β subunits: The power outside the pore in brain development and disease. Neuropharmacology 2017; 132:43-57. [PMID: 28927993 DOI: 10.1016/j.neuropharm.2017.09.018] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Revised: 07/19/2017] [Accepted: 09/11/2017] [Indexed: 12/19/2022]
Abstract
Voltage gated sodium channels (VGSCs) were first identified in terms of their role in the upstroke of the action potential. The underlying proteins were later identified as saxitoxin and scorpion toxin receptors consisting of α and β subunits. We now know that VGSCs are heterotrimeric complexes consisting of a single pore forming α subunit joined by two β subunits; a noncovalently linked β1 or β3 and a covalently linked β2 or β4 subunit. VGSC α subunits contain all the machinery necessary for channel cell surface expression, ion conduction, voltage sensing, gating, and inactivation, in one central, polytopic, transmembrane protein. VGSC β subunits are more than simple accessories to α subunits. In the more than two decades since the original cloning of β1, our knowledge of their roles in physiology and pathophysiology has expanded immensely. VGSC β subunits are multifunctional. They confer unique gating mechanisms, regulate cellular excitability, affect brain development, confer distinct channel pharmacology, and have functions that are independent of the α subunits. The vast array of functions of these proteins stems from their special station in the channelome: being the only known constituents that are cell adhesion and intra/extracellular signaling molecules in addition to being part of channel complexes. This functional trifecta and how it goes awry demonstrates the power outside the pore in ion channel signaling complexes, broadening the term channelopathy beyond defects in ion conduction. This article is part of the Special Issue entitled 'Channelopathies.'
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Affiliation(s)
- Jacob M Hull
- Neuroscience Program and Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48109, United States
| | - Lori L Isom
- Neuroscience Program and Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48109, United States.
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8
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Aromolaran AS, Chahine M, Boutjdir M. Regulation of Cardiac Voltage-Gated Sodium Channel by Kinases: Roles of Protein Kinases A and C. Handb Exp Pharmacol 2017; 246:161-184. [PMID: 29032483 DOI: 10.1007/164_2017_53] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
In the heart, voltage-gated sodium (Nav) channel (Nav1.5) is defined by its pore-forming α-subunit and its auxiliary β-subunits, both of which are important for its critical contribution to the initiation and maintenance of the cardiac action potential (AP) that underlie normal heart rhythm. The physiological relevance of Nav1.5 is further marked by the fact that inherited or congenital mutations in Nav1.5 channel gene SCN5A lead to altered functional expression (including expression, trafficking, and current density), and are generally manifested in the form of distinct cardiac arrhythmic events, epilepsy, neuropathic pain, migraine, and neuromuscular disorders. However, despite significant advances in defining the pathophysiology of Nav1.5, the molecular mechanisms that underlie its regulation and contribution to cardiac disorders are poorly understood. It is rapidly becoming evident that the functional expression (localization, trafficking and gating) of Nav1.5 may be under modulation by post-translational modifications that are associated with phosphorylation. We review here the molecular basis of cardiac Na channel regulation by kinases (PKA and PKC) and the resulting functional consequences. Specifically, we discuss: (1) recent literature on the structural, molecular, and functional properties of cardiac Nav1.5 channels; (2) how these properties may be altered by phosphorylation in disease states underlain by congenital mutations in Nav1.5 channel and/or subunits such as long QT and Brugada syndromes. Our expectation is that understanding the roles of these distinct and complex phosphorylation processes on the functional expression of Nav1.5 is likely to provide crucial mechanistic insights into Na channel associated arrhythmogenic events and will facilitate the development of novel therapeutic strategies.
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Affiliation(s)
- Ademuyiwa S Aromolaran
- Cardiovascular Research Program, VA New York Harbor Healthcare System, Brooklyn, NY, USA
- Departments of Medicine, Cell Biology and Pharmacology, State University of New York Downstate Medical Center, Brooklyn, NY, USA
| | - Mohamed Chahine
- CERVO Brain Research Center, Institut Universitaire en Santé Mentale de Québec, Quebec City, QC, Canada
- Department of Medicine, Université Laval, Quebec City, QC, Canada
| | - Mohamed Boutjdir
- Cardiovascular Research Program, VA New York Harbor Healthcare System, Brooklyn, NY, USA.
- Departments of Medicine, Cell Biology and Pharmacology, State University of New York Downstate Medical Center, Brooklyn, NY, USA.
- Department of Medicine, New York University School of Medicine, New York, NY, USA.
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9
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Das S, Gilchrist J, Bosmans F, Van Petegem F. Binary architecture of the Nav1.2-β2 signaling complex. eLife 2016; 5. [PMID: 26894959 PMCID: PMC4769172 DOI: 10.7554/elife.10960] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2015] [Accepted: 01/07/2016] [Indexed: 12/15/2022] Open
Abstract
To investigate the mechanisms by which β-subunits influence Nav channel function, we solved the crystal structure of the β2 extracellular domain at 1.35Å. We combined these data with known bacterial Nav channel structural insights and novel functional studies to determine the interactions of specific residues in β2 with Nav1.2. We identified a flexible loop formed by (72)Cys and (75)Cys, a unique feature among the four β-subunit isoforms. Moreover, we found that (55)Cys helps to determine the influence of β2 on Nav1.2 toxin susceptibility. Further mutagenesis combined with the use of spider toxins reveals that (55)Cys forms a disulfide bond with (910)Cys in the Nav1.2 domain II pore loop, thereby suggesting a 1:1 stoichiometry. Our results also provide clues as to which disulfide bonds are formed between adjacent Nav1.2 (912/918)Cys residues. The concepts emerging from this work will help to form a model reflecting the β-subunit location in a Nav channel complex.
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Affiliation(s)
- Samir Das
- Department of Biochemistry and Molecular Biology, Life Sciences Institute, University of British Columbia, Vancouver, Canada
| | - John Gilchrist
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, United States
| | - Frank Bosmans
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, United States.,Solomon H Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, United States
| | - Filip Van Petegem
- Department of Biochemistry and Molecular Biology, Life Sciences Institute, University of British Columbia, Vancouver, Canada
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10
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Riuró H, Beltran-Alvarez P, Tarradas A, Selga E, Campuzano O, Vergés M, Pagans S, Iglesias A, Brugada J, Brugada P, Vázquez FM, Pérez GJ, Scornik FS, Brugada R. A missense mutation in the sodium channel β2 subunit reveals SCN2B as a new candidate gene for Brugada syndrome. Hum Mutat 2013; 34:961-6. [PMID: 23559163 DOI: 10.1002/humu.22328] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Accepted: 03/21/2013] [Indexed: 11/09/2022]
Abstract
Brugada Syndrome (BrS) is a familial disease associated with sudden cardiac death. A 20%-25% of BrS patients carry genetic defects that cause loss-of-function of the voltage-gated cardiac sodium channel. Thus, 70%-75% of patients remain without a genetic diagnosis. In this work, we identified a novel missense mutation (p.Asp211Gly) in the sodium β2 subunit encoded by SCN2B, in a woman diagnosed with BrS. We studied the sodium current (INa ) from cells coexpressing Nav 1.5 and wild-type (β2WT) or mutant (β2D211G) β2 subunits. Our electrophysiological analysis showed a 39.4% reduction in INa density when Nav 1.5 was coexpressed with the β2D211G. Single channel analysis showed that the mutation did not affect the Nav 1.5 unitary channel conductance. Instead, protein membrane detection experiments suggested that β2D211G decreases Nav 1.5 cell surface expression. The effect of the mutant β2 subunit on the INa strongly suggests that SCN2B is a new candidate gene associated with BrS.
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Affiliation(s)
- Helena Riuró
- Cardiovascular Genetics Center, Institut d'Investigació Biomèdica de Girona, Girona, Spain
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11
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Mishra S, Undrovinas NA, Maltsev VA, Reznikov V, Sabbah HN, Undrovinas A. Post-transcriptional silencing of SCN1B and SCN2B genes modulates late sodium current in cardiac myocytes from normal dogs and dogs with chronic heart failure. Am J Physiol Heart Circ Physiol 2011; 301:H1596-605. [PMID: 21705762 DOI: 10.1152/ajpheart.00948.2009] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The emerging paradigm for Na(+) current in heart failure (HF) is that its transient component (I(NaT)) responsible for the action potential (AP) upstroke is decreased, whereas the late component (I(NaL)) involved in AP plateau is augmented. Here we tested whether Na(v)β(1)- and Na(v)β(2)-subunits can modulate I(NaL) parameters in normal and failing ventricular cardiomyocytes (VCMs). Chronic HF was produced in nine dogs by multiple sequential coronary artery microembolizations, and six dogs served as a control. I(Na) and APs were measured by the whole cell and perforated patch-clamp in freshly isolated and cultured VCMs, respectively. I(NaL) was augmented with slower decay in HF VCMs compared with normal heart VCMs, and these properties remained unchanged within 5 days of culture. Post-transcriptional silencing SCN1B and SCN2B were achieved by virally delivered short interfering RNA (siRNA) specific to Na(v)β(1) and Na(v)β(2). The delivery and efficiency of siRNA were evaluated by green fluorescent protein expression, by the real-time RT-PCR, and Western blots, respectively. Five days after infection, the levels of mRNA and protein for Na(v)β(1) and Na(v)β(2) were reduced by >80%, but mRNA and protein of Na(v)1.5, as well as I(NaT), remained unchanged in HF VCMs. Na(v)β(1)-siRNA reduced I(NaL) density and accelerated I(NaL) two-exponential decay, whereas Na(v)β(2)-siRNA produced an opposite effect in VCMs from both normal and failing hearts. Physiological importance of the discovered I(NaL) modulation to affect AP shape and duration was illustrated both experimentally and by numerical simulations of a VCM excitation-contraction coupling model. We conclude that in myocytes of normal and failing dog hearts Na(v)β(1) and Na(v)β(2) exhibit oppositely directed modulation of I(NaL).
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Affiliation(s)
- Sudhish Mishra
- Department of Internal Medicine, Henry Ford Hospital, Detroit, Michigan 48202-2689, USA
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12
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Wilde AA, Brugada R. Phenotypical Manifestations of Mutations in the Genes Encoding Subunits of the Cardiac Sodium Channel. Circ Res 2011; 108:884-97. [DOI: 10.1161/circresaha.110.238469] [Citation(s) in RCA: 171] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Arthur A.M. Wilde
- From the Heart Research Centre (A.A.M.W.), Department of Clinical and Experimental Cardiology, Academic Medical Center, University Medical Center, University of Amsterdam, The Netherlands; and the Institut d'Investigació Biomèdica Girona-IdIBGi (R.B.), Universitat de Girona, Giona Spain
| | - Ramon Brugada
- From the Heart Research Centre (A.A.M.W.), Department of Clinical and Experimental Cardiology, Academic Medical Center, University Medical Center, University of Amsterdam, The Netherlands; and the Institut d'Investigació Biomèdica Girona-IdIBGi (R.B.), Universitat de Girona, Giona Spain
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13
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Yu L, Gao S, Nie L, Tang M, Huang W, Luo H, Hu X, Xi J, Zhu M, Zheng Y, Gao L, Zhang L, Song Y, Hescheler J, Liang H. Molecular and Functional Changes in Voltage-Gated Na+ Channels in Cardiomyocytes During Mouse Embryogenesis. Circ J 2011; 75:2071-9. [DOI: 10.1253/circj.cj-10-1212] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Liangzhu Yu
- Chinese-German Stem Cell Center, Department of Physiology, Tongji Medical College, Huazhong University of Science and Technology
| | - Shijun Gao
- Chinese-German Stem Cell Center, Department of Physiology, Tongji Medical College, Huazhong University of Science and Technology
| | - Li Nie
- Chinese-German Stem Cell Center, Department of Physiology, Tongji Medical College, Huazhong University of Science and Technology
| | - Ming Tang
- Chinese-German Stem Cell Center, Department of Physiology, Tongji Medical College, Huazhong University of Science and Technology
| | - Weifeng Huang
- Chinese-German Stem Cell Center, Department of Physiology, Tongji Medical College, Huazhong University of Science and Technology
| | - Hongyan Luo
- Chinese-German Stem Cell Center, Department of Physiology, Tongji Medical College, Huazhong University of Science and Technology
| | - Xinwu Hu
- Chinese-German Stem Cell Center, Department of Physiology, Tongji Medical College, Huazhong University of Science and Technology
| | - Jiaoya Xi
- Chinese-German Stem Cell Center, Department of Physiology, Tongji Medical College, Huazhong University of Science and Technology
| | - Minjie Zhu
- Chinese-German Stem Cell Center, Department of Physiology, Tongji Medical College, Huazhong University of Science and Technology
| | - Yunjie Zheng
- Chinese-German Stem Cell Center, Department of Physiology, Tongji Medical College, Huazhong University of Science and Technology
| | - Linlin Gao
- Chinese-German Stem Cell Center, Department of Physiology, Tongji Medical College, Huazhong University of Science and Technology
| | - Lanqiu Zhang
- Chinese-German Stem Cell Center, Department of Physiology, Tongji Medical College, Huazhong University of Science and Technology
| | - Yuanlong Song
- Chinese-German Stem Cell Center, Department of Physiology, Tongji Medical College, Huazhong University of Science and Technology
| | | | - Huamin Liang
- Chinese-German Stem Cell Center, Department of Physiology, Tongji Medical College, Huazhong University of Science and Technology
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14
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Kaufmann SG, Westenbroek RE, Zechner C, Maass AH, Bischoff S, Muck J, Wischmeyer E, Scheuer T, Maier SKG. Functional protein expression of multiple sodium channel alpha- and beta-subunit isoforms in neonatal cardiomyocytes. J Mol Cell Cardiol 2009; 48:261-9. [PMID: 19426735 DOI: 10.1016/j.yjmcc.2009.04.017] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2009] [Revised: 04/14/2009] [Accepted: 04/29/2009] [Indexed: 11/29/2022]
Abstract
Voltage-gated sodium channels are composed of pore-forming alpha- and auxiliary beta-subunits and are responsible for the rapid depolarization of cardiac action potentials. Recent evidence indicates that neuronal tetrodotoxin (TTX) sensitive sodium channel alpha-subunits are expressed in the heart in addition to the predominant cardiac TTX-resistant Na(v)1.5 sodium channel alpha-subunit. These TTX-sensitive isoforms are preferentially localized in the transverse tubules of rodents. Since neonatal cardiomyocytes have yet to develop transverse tubules, we determined the complement of sodium channel subunits expressed in these cells. Neonatal rat ventricular cardiomyocytes were stained with antibodies specific for individual isoforms of sodium channel alpha- and beta-subunits. alpha-actinin, a component of the z-line, was used as an intracellular marker of sarcomere boundaries. TTX-sensitive sodium channel alpha-subunit isoforms Na(v)1.1, Na(v)1.2, Na(v)1.3, Na(v)1.4 and Na(v)1.6 were detected in neonatal rat heart but at levels reduced compared to the predominant cardiac alpha-subunit isoform, Na(v)1.5. Each of the beta-subunit isoforms (beta1-beta4) was also expressed in neonatal cardiac cells. In contrast to adult cardiomyocytes, the alpha-subunits are distributed in punctate clusters across the membrane surface of neonatal cardiomyocytes; no isoform-specific subcellular localization is observed. Voltage clamp recordings in the absence and presence of 20 nM TTX provided functional evidence for the presence of TTX-sensitive sodium current in neonatal ventricular myocardium which represents between 20 and 30% of the current, depending on membrane potential and experimental conditions. Thus, as in the adult heart, a range of sodium channel alpha-subunits are expressed in neonatal myocytes in addition to the predominant TTX-resistant Na(v)1.5 alpha-subunit and they contribute to the total sodium current.
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Affiliation(s)
- Susann G Kaufmann
- Medizinische Klinik und Poliklinik I, Universität Würzburg, Josef-Schneider-Strabetae 2, 97080 Würzburg, Germany
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15
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Maltsev VA, Kyle JW, Undrovinas A. Late Na+ current produced by human cardiac Na+ channel isoform Nav1.5 is modulated by its beta1 subunit. J Physiol Sci 2009; 59:217-25. [PMID: 19340536 PMCID: PMC2744134 DOI: 10.1007/s12576-009-0029-7] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2008] [Accepted: 02/02/2009] [Indexed: 01/26/2023]
Abstract
Experimental data accumulated over the past decade show the emerging importance of the late sodium current (I(NaL)) for the function of both normal and, especially, failing myocardium, in which I(NaL) is reportedly increased. While recent molecular studies identified the cardiac Na(+) channel (NaCh) alpha subunit isoform (Na(v)1.5) as a major contributor to I (NaL), the molecular mechanisms underlying alterations of I(NaL) in heart failure (HF) are still unknown. Here we tested the hypothesis that I(NaL) is modulated by the NaCh auxiliary beta subunits. tsA201 cells were transfected simultaneously with human Na(v)1.5 (former hH1a) and cardiac beta(1) or beta(2) subunits, and whole-cell patch-clamp experiments were performed. We found that I(NaL) decay kinetics were significantly slower in cells expressing alpha + beta(1) (time constant tau = 0.73 +/- 0.16 s, n = 14, mean +/- SEM, P < 0.05) but remained unchanged in cells expressing alpha + beta(2) (tau = 0.52 +/- 0.09 s, n = 5), compared with cells expressing Na(v)1.5 alone (tau = 0.54 +/- 0.09 s, n = 20). Also, beta(1), but not beta(2), dramatically increased I(NaL) relative to the maximum peak current, I(NaT) (2.3 +/- 0.48%, n = 14 vs. 0.48 +/- 0.07%, n = 6, P < 0.05, respectively) and produced a rightward shift of the steady-state availability curve. We conclude that the auxiliary beta(1) subunit modulates I(NaL), produced by the human cardiac Na(+) channel Na(v)1.5 by slowing its decay and increasing I(NaL) amplitude relative to I(NaT). Because expression of Na(v)1.5 reportedly decreases but beta(1) remains unchanged in chronic HF, the relatively higher expression of beta(1) may contribute to the known I(NaL) increase in HF via the modulation mechanism found in this study.
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Affiliation(s)
- Victor A. Maltsev
- Department of Internal Medicine, Cardiovascular Research, Henry Ford Hospital Detroit, Education and Research Bldg. Room 4015, 2799 West Grand Boulevard, Detroit, MI 48202-2689 USA
- Present Address: Gerontology Research Center, National Institute on Aging, NIH, 5600 Nathan Shock Drive, Baltimore, MD 21224-6825 USA
| | - John W. Kyle
- Department of Neurobiology, Pharmacology, and Physiology, University of Chicago, Chicago, IL USA
| | - Albertas Undrovinas
- Department of Internal Medicine, Cardiovascular Research, Henry Ford Hospital Detroit, Education and Research Bldg. Room 4015, 2799 West Grand Boulevard, Detroit, MI 48202-2689 USA
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