1
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Maurya S, Mills RW, Kahnert K, Chiang DY, Bertoli G, Lundegaard PR, Duran MPH, Zhang M, Rothenberg E, George AL, MacRae CA, Delmar M, Lundby A. Outlining cardiac ion channel protein interactors and their signature in the human electrocardiogram. NATURE CARDIOVASCULAR RESEARCH 2023; 2:673-692. [PMID: 38666184 PMCID: PMC11041666 DOI: 10.1038/s44161-023-00294-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Accepted: 05/31/2023] [Indexed: 04/28/2024]
Abstract
Protein-protein interactions are essential for normal cellular processes and signaling events. Defining these interaction networks is therefore crucial for understanding complex cellular functions and interpretation of disease-associated gene variants. We need to build a comprehensive picture of the interactions, their affinities and interdependencies in the specific organ to decipher hitherto poorly understood signaling mechanisms through ion channels. Here we report the experimental identification of the ensemble of protein interactors for 13 types of ion channels in murine cardiac tissue. Of these, we validated the functional importance of ten interactors on cardiac electrophysiology through genetic knockouts in zebrafish, gene silencing in mice, super-resolution microscopy and patch clamp experiments. Furthermore, we establish a computational framework to reconstruct human cardiomyocyte ion channel networks from deep proteome mapping of human heart tissue and human heart single-cell gene expression data. Finally, we integrate the ion channel interactome with human population genetics data to identify proteins that influence the electrocardiogram (ECG). We demonstrate that the combined channel network is enriched for proteins influencing the ECG, with 44% of the network proteins significantly associated with an ECG phenotype. Altogether, we define interactomes of 13 major cardiac ion channels, contextualize their relevance to human electrophysiology and validate functional roles of ten interactors, including two regulators of the sodium current (epsin-2 and gelsolin). Overall, our data provide a roadmap for our understanding of the molecular machinery that regulates cardiac electrophysiology.
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Affiliation(s)
- Svetlana Maurya
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Robert W. Mills
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Konstantin Kahnert
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - David Y. Chiang
- Cardiovascular Medicine Division, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA USA
| | - Giorgia Bertoli
- Division of Cardiology, NYU School of Medicine, New York, NY USA
| | - Pia R. Lundegaard
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | | | - Mingliang Zhang
- Division of Cardiology, NYU School of Medicine, New York, NY USA
| | - Eli Rothenberg
- Division of Pharmacology, NYU School of Medicine, New York, NY USA
| | - Alfred L. George
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL USA
| | - Calum A. MacRae
- Cardiovascular Medicine Division, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA USA
| | - Mario Delmar
- Division of Cardiology, NYU School of Medicine, New York, NY USA
| | - Alicia Lundby
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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2
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Álvarez M, Ruiz-Sala P, Pérez B, Desviat LR, Richard E. Dysregulated Cell Homeostasis and miRNAs in Human iPSC-Derived Cardiomyocytes from a Propionic Acidemia Patient with Cardiomyopathy. Int J Mol Sci 2023; 24:ijms24032182. [PMID: 36768524 PMCID: PMC9916417 DOI: 10.3390/ijms24032182] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Revised: 01/17/2023] [Accepted: 01/18/2023] [Indexed: 01/25/2023] Open
Abstract
Propionic acidemia (PA) disorder shows major involvement of the heart, among other alterations. A significant number of PA patients develop cardiac complications, and available evidence suggests that this cardiac dysfunction is driven mainly by the accumulation of toxic metabolites. To contribute to the elucidation of the mechanistic basis underlying this dysfunction, we have successfully generated cardiomyocytes through the differentiation of induced pluripotent stem cells (iPSCs) from a PCCB patient and its isogenic control. In this human cellular model, we aimed to examine microRNAs (miRNAs) profiles and analyze several cellular pathways to determine miRNAs activity patterns associated with PA cardiac phenotypes. We have identified a series of upregulated cardiac-enriched miRNAs and alterations in some of their regulated signaling pathways, including an increase in the expression of cardiac damage markers and cardiac channels, an increase in oxidative stress, a decrease in mitochondrial respiration and autophagy; and lipid accumulation. Our findings indicate that miRNA activity patterns from PA iPSC-derived cardiomyocytes are biologically informative and advance the understanding of the molecular mechanisms of this rare disease, providing a basis for identifying new therapeutic targets for intervention strategies.
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Affiliation(s)
- Mar Álvarez
- Centro de Biología Molecular Severo Ochoa UAM-CSIC, Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - Pedro Ruiz-Sala
- Centro de Diagnóstico de Enfermedades Moleculares (CEDEM), 28049 Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), ISCIII, 28029 Madrid, Spain
- Instituto de Investigación Sanitaria Hospital La Paz (IdiPaz), ISCIII, 28029 Madrid, Spain
| | - Belén Pérez
- Centro de Biología Molecular Severo Ochoa UAM-CSIC, Universidad Autónoma de Madrid, 28049 Madrid, Spain
- Centro de Diagnóstico de Enfermedades Moleculares (CEDEM), 28049 Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), ISCIII, 28029 Madrid, Spain
- Instituto de Investigación Sanitaria Hospital La Paz (IdiPaz), ISCIII, 28029 Madrid, Spain
| | - Lourdes Ruiz Desviat
- Centro de Biología Molecular Severo Ochoa UAM-CSIC, Universidad Autónoma de Madrid, 28049 Madrid, Spain
- Centro de Diagnóstico de Enfermedades Moleculares (CEDEM), 28049 Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), ISCIII, 28029 Madrid, Spain
- Instituto de Investigación Sanitaria Hospital La Paz (IdiPaz), ISCIII, 28029 Madrid, Spain
| | - Eva Richard
- Centro de Biología Molecular Severo Ochoa UAM-CSIC, Universidad Autónoma de Madrid, 28049 Madrid, Spain
- Centro de Diagnóstico de Enfermedades Moleculares (CEDEM), 28049 Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), ISCIII, 28029 Madrid, Spain
- Instituto de Investigación Sanitaria Hospital La Paz (IdiPaz), ISCIII, 28029 Madrid, Spain
- Correspondence:
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3
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Oda S, Nishiyama K, Furumoto Y, Yamaguchi Y, Nishimura A, Tang X, Kato Y, Numaga-Tomita T, Kaneko T, Mangmool S, Kuroda T, Okubo R, Sanbo M, Hirabayashi M, Sato Y, Nakagawa Y, Kuwahara K, Nagata R, Iribe G, Mori Y, Nishida M. Myocardial TRPC6-mediated Zn 2+ influx induces beneficial positive inotropy through β-adrenoceptors. Nat Commun 2022; 13:6374. [PMID: 36289215 PMCID: PMC9606288 DOI: 10.1038/s41467-022-34194-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Accepted: 10/12/2022] [Indexed: 12/25/2022] Open
Abstract
Baroreflex control of cardiac contraction (positive inotropy) through sympathetic nerve activation is important for cardiocirculatory homeostasis. Transient receptor potential canonical subfamily (TRPC) channels are responsible for α1-adrenoceptor (α1AR)-stimulated cation entry and their upregulation is associated with pathological cardiac remodeling. Whether TRPC channels participate in physiological pump functions remains unclear. We demonstrate that TRPC6-specific Zn2+ influx potentiates β-adrenoceptor (βAR)-stimulated positive inotropy in rodent cardiomyocytes. Deletion of trpc6 impairs sympathetic nerve-activated positive inotropy but not chronotropy in mice. TRPC6-mediated Zn2+ influx boosts α1AR-stimulated βAR/Gs-dependent signaling in rat cardiomyocytes by inhibiting β-arrestin-mediated βAR internalization. Replacing two TRPC6-specific amino acids in the pore region with TRPC3 residues diminishes the α1AR-stimulated Zn2+ influx and positive inotropic response. Pharmacological enhancement of TRPC6-mediated Zn2+ influx prevents chronic heart failure progression in mice. Our data demonstrate that TRPC6-mediated Zn2+ influx with α1AR stimulation enhances baroreflex-induced positive inotropy, which may be a new therapeutic strategy for chronic heart failure.
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Affiliation(s)
- Sayaka Oda
- grid.250358.90000 0000 9137 6732National Institute for Physiological Sciences (NIPS), National Institutes of Natural Sciences, Okazaki, 444-8787 Japan ,grid.250358.90000 0000 9137 6732Exploratory Research Center on Life and Living Systems (ExCELLS), National Institutes of Natural Sciences, Okazaki, 444-8787 Japan ,grid.275033.00000 0004 1763 208XDepartment of Physiological Sciences, SOKENDAI (School of Life Science, The Graduate University for Advanced Studies), Aichi, 444-8787 Japan
| | - Kazuhiro Nishiyama
- grid.177174.30000 0001 2242 4849Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, 812-8582 Japan
| | - Yuka Furumoto
- grid.177174.30000 0001 2242 4849Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, 812-8582 Japan
| | - Yohei Yamaguchi
- grid.252427.40000 0000 8638 2724Asahikawa Medical University, Hokkaido, 078-8510 Japan
| | - Akiyuki Nishimura
- grid.250358.90000 0000 9137 6732National Institute for Physiological Sciences (NIPS), National Institutes of Natural Sciences, Okazaki, 444-8787 Japan ,grid.250358.90000 0000 9137 6732Exploratory Research Center on Life and Living Systems (ExCELLS), National Institutes of Natural Sciences, Okazaki, 444-8787 Japan ,grid.275033.00000 0004 1763 208XDepartment of Physiological Sciences, SOKENDAI (School of Life Science, The Graduate University for Advanced Studies), Aichi, 444-8787 Japan
| | - Xiaokang Tang
- grid.250358.90000 0000 9137 6732National Institute for Physiological Sciences (NIPS), National Institutes of Natural Sciences, Okazaki, 444-8787 Japan ,grid.250358.90000 0000 9137 6732Exploratory Research Center on Life and Living Systems (ExCELLS), National Institutes of Natural Sciences, Okazaki, 444-8787 Japan ,grid.275033.00000 0004 1763 208XDepartment of Physiological Sciences, SOKENDAI (School of Life Science, The Graduate University for Advanced Studies), Aichi, 444-8787 Japan
| | - Yuri Kato
- grid.177174.30000 0001 2242 4849Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, 812-8582 Japan
| | - Takuro Numaga-Tomita
- grid.250358.90000 0000 9137 6732National Institute for Physiological Sciences (NIPS), National Institutes of Natural Sciences, Okazaki, 444-8787 Japan ,grid.250358.90000 0000 9137 6732Exploratory Research Center on Life and Living Systems (ExCELLS), National Institutes of Natural Sciences, Okazaki, 444-8787 Japan ,grid.263518.b0000 0001 1507 4692Shinshu University School of Medicine, Matsumoto, 390-8621 Japan
| | - Toshiyuki Kaneko
- grid.252427.40000 0000 8638 2724Asahikawa Medical University, Hokkaido, 078-8510 Japan
| | - Supachoke Mangmool
- grid.10223.320000 0004 1937 0490Faculty of Science, Mahidol University, Bangkok, 10400 Thailand
| | - Takuya Kuroda
- grid.410797.c0000 0001 2227 8773National Institute of Health Sciences, Kanagawa, 210-9501 Japan
| | - Reishin Okubo
- grid.177174.30000 0001 2242 4849Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, 812-8582 Japan
| | - Makoto Sanbo
- grid.250358.90000 0000 9137 6732National Institute for Physiological Sciences (NIPS), National Institutes of Natural Sciences, Okazaki, 444-8787 Japan
| | - Masumi Hirabayashi
- grid.250358.90000 0000 9137 6732National Institute for Physiological Sciences (NIPS), National Institutes of Natural Sciences, Okazaki, 444-8787 Japan
| | - Yoji Sato
- grid.410797.c0000 0001 2227 8773National Institute of Health Sciences, Kanagawa, 210-9501 Japan
| | - Yasuaki Nakagawa
- grid.258799.80000 0004 0372 2033Kyoto University Graduate School of Medicine, Kyoto, 606-8507 Japan
| | - Koichiro Kuwahara
- grid.263518.b0000 0001 1507 4692Shinshu University School of Medicine, Matsumoto, 390-8621 Japan
| | - Ryu Nagata
- grid.136593.b0000 0004 0373 3971Graduate School of Pharmaceutical Sciences, Osaka University, Osaka, 565-0871 Japan
| | - Gentaro Iribe
- grid.252427.40000 0000 8638 2724Asahikawa Medical University, Hokkaido, 078-8510 Japan
| | - Yasuo Mori
- grid.258799.80000 0004 0372 2033Graduate School of Engineering, Kyoto University, Kyoto, 615-8510 Japan
| | - Motohiro Nishida
- grid.250358.90000 0000 9137 6732National Institute for Physiological Sciences (NIPS), National Institutes of Natural Sciences, Okazaki, 444-8787 Japan ,grid.250358.90000 0000 9137 6732Exploratory Research Center on Life and Living Systems (ExCELLS), National Institutes of Natural Sciences, Okazaki, 444-8787 Japan ,grid.275033.00000 0004 1763 208XDepartment of Physiological Sciences, SOKENDAI (School of Life Science, The Graduate University for Advanced Studies), Aichi, 444-8787 Japan ,grid.177174.30000 0001 2242 4849Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, 812-8582 Japan
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Wilson ZT, Jiang M, Geng J, Kaur S, Workman SW, Hao J, Bernas T, Tseng GN. Delayed KCNQ1/KCNE1 assembly on the cell surface helps I Ks fulfil its function as a repolarization reserve in the heart. J Physiol 2021; 599:3337-3361. [PMID: 33963564 DOI: 10.1113/jp281773] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Accepted: 05/04/2021] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS In adult ventricular myocytes, the slow delayed rectifier (IKs ) channels are distributed on the surface sarcolemma, not t-tubules. In adult ventricular myocytes, KCNQ1 and KCNE1 have distinct cell surface and cytoplasmic pools. KCNQ1 and KCNE1 traffic from the endoplasmic reticulum to the plasma membrane by separate routes, and assemble into IKs channels on the cell surface. Liquid chromatography/tandem mass spectrometry applied to affinity-purified KCNQ1 and KCNE1 interacting proteins reveals novel interactors involved in protein trafficking and assembly. Microtubule plus-end binding protein 1 (EB1) binds KCNQ1 preferentially in its dimer form, and promotes KCNQ1 to reach the cell surface. An LQT1-associated mutation, Y111C, reduces KCNQ1 binding to EB1 dimer. ABSTRACT Slow delayed rectifier (IKs ) channels consist of KCNQ1 and KCNE1. IKs functions as a 'repolarization reserve' in the heart by providing extra current for ventricular action potential shortening during β-adrenergic stimulation. There has been much debate about how KCNQ1 and KCNE1 traffic in cells, where they associate to form IKs channels, and the distribution pattern of IKs channels relative to β-adrenergic signalling complex. We used experimental strategies not previously applied to KCNQ1, KCNE1 or IKs , to provide new insights into these issues. 'Retention-using-selected-hook' experiments showed that newly translated KCNE1 constitutively trafficked through the conventional secretory path to the cell surface. KCNQ1 largely stayed in the endoplasmic reticulum, although dynamic KCNQ1 vesicles were observed in the submembrane region. Disulphide-bonded KCNQ1/KCNE1 constructs reported preferential association after they had reached cell surface. An in situ proximity ligation assay detected IKs channels in surface sarcolemma but not t-tubules of ventricular myocytes, similar to the reported location of adenylate cyclase 9/yotiao. Fluorescent protein-tagged KCNQ1 and KCNE1, in conjunction with antibodies targeting their extracellular epitopes, detected distinct cell surface and cytoplasmic pools of both proteins in myocytes. We conclude that, in cardiomyocytes, KCNQ1 and KCNE1 traffic by different routes to surface sarcolemma where they assemble into IKs channels. This mode of delayed channel assembly helps IKs fulfil its function of repolarization reserve. Proteomic experiments revealed a novel KCNQ1 interactor, microtubule plus-end binding protein 1 (EB1). EB1 dimer (active form) bound KCNQ1 and increased its surface level. An LQT1 mutation, Y111C, reduced KCNQ1 binding to EB1 dimer.
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Affiliation(s)
- Zachary T Wilson
- Department of Physiology & Biophysics, Virginia Commonwealth University, Richmond, VA, USA
| | - Min Jiang
- Department of Physiology & Biophysics, Virginia Commonwealth University, Richmond, VA, USA.,Institute of Medicinal biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Jing Geng
- Institute of Medicinal biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Sukhleen Kaur
- Department of Physiology & Biophysics, Virginia Commonwealth University, Richmond, VA, USA
| | - Samuel W Workman
- Department of Physiology & Biophysics, Virginia Commonwealth University, Richmond, VA, USA.,Present address: School of Medicine, Rutgers University, Piscataway, NJ, USA
| | - Jon Hao
- Poochon Scientific, Frederick, MD, USA
| | - Tytus Bernas
- Department of Anatomy & Neurobiology, Virginia Commonwealth University, Richmond, VA, USA
| | - Gea-Ny Tseng
- Department of Physiology & Biophysics, Virginia Commonwealth University, Richmond, VA, USA
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5
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Mechanisms and Regulation of Cardiac Ca V1.2 Trafficking. Int J Mol Sci 2021; 22:ijms22115927. [PMID: 34072954 PMCID: PMC8197997 DOI: 10.3390/ijms22115927] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Revised: 05/28/2021] [Accepted: 05/29/2021] [Indexed: 01/05/2023] Open
Abstract
During cardiac excitation contraction coupling, the arrival of an action potential at the ventricular myocardium triggers voltage-dependent L-type Ca2+ (CaV1.2) channels in individual myocytes to open briefly. The level of this Ca2+ influx tunes the amplitude of Ca2+-induced Ca2+ release from ryanodine receptors (RyR2) on the junctional sarcoplasmic reticulum and thus the magnitude of the elevation in intracellular Ca2+ concentration and ultimately the downstream contraction. The number and activity of functional CaV1.2 channels at the t-tubule dyads dictates the amplitude of the Ca2+ influx. Trafficking of these channels and their auxiliary subunits to the cell surface is thus tightly controlled and regulated to ensure adequate sarcolemmal expression to sustain this critical process. To that end, recent discoveries have revealed the existence of internal reservoirs of preformed CaV1.2 channels that can be rapidly mobilized to enhance sarcolemmal expression in times of acute stress when hemodynamic and metabolic demand increases. In this review, we provide an overview of the current thinking on CaV1.2 channel trafficking dynamics in the heart. We highlight the numerous points of control including the biosynthetic pathway, the endosomal recycling pathway, ubiquitination, and lysosomal and proteasomal degradation pathways, and discuss the effects of β-adrenergic and angiotensin receptor signaling cascades on this process.
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6
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Del Villar SG, Voelker TL, Westhoff M, Reddy GR, Spooner HC, Navedo MF, Dickson EJ, Dixon RE. β-Adrenergic control of sarcolemmal Ca V1.2 abundance by small GTPase Rab proteins. Proc Natl Acad Sci U S A 2021. [PMID: 33558236 DOI: 10.1073/pnas.2017937118/-/dcsupplemental] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/31/2023] Open
Abstract
The number and activity of Cav1.2 channels in the cardiomyocyte sarcolemma tunes the magnitude of Ca2+-induced Ca2+ release and myocardial contraction. β-Adrenergic receptor (βAR) activation stimulates sarcolemmal insertion of CaV1.2. This supplements the preexisting sarcolemmal CaV1.2 population, forming large "superclusters" wherein neighboring channels undergo enhanced cooperative-gating behavior, amplifying Ca2+ influx and myocardial contractility. Here, we determine this stimulated insertion is fueled by an internal reserve of early and recycling endosome-localized, presynthesized CaV1.2 channels. βAR-activation decreased CaV1.2/endosome colocalization in ventricular myocytes, as it triggered "emptying" of endosomal CaV1.2 cargo into the t-tubule sarcolemma. We examined the rapid dynamics of this stimulated insertion process with live-myocyte imaging of channel trafficking, and discovered that CaV1.2 are often inserted into the sarcolemma as preformed, multichannel clusters. Similarly, entire clusters were removed from the sarcolemma during endocytosis, while in other cases, a more incremental process suggested removal of individual channels. The amplitude of the stimulated insertion response was doubled by coexpression of constitutively active Rab4a, halved by coexpression of dominant-negative Rab11a, and abolished by coexpression of dominant-negative mutant Rab4a. In ventricular myocytes, βAR-stimulated recycling of CaV1.2 was diminished by both nocodazole and latrunculin-A, suggesting an essential role of the cytoskeleton in this process. Functionally, cytoskeletal disruptors prevented βAR-activated Ca2+ current augmentation. Moreover, βAR-regulation of CaV1.2 was abolished when recycling was halted by coapplication of nocodazole and latrunculin-A. These findings reveal that βAR-stimulation triggers an on-demand boost in sarcolemmal CaV1.2 abundance via targeted Rab4a- and Rab11a-dependent insertion of channels that is essential for βAR-regulation of cardiac CaV1.2.
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Affiliation(s)
- Silvia G Del Villar
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA 95616
| | - Taylor L Voelker
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA 95616
| | - Maartje Westhoff
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA 95616
| | - Gopireddy R Reddy
- Department of Pharmacology, School of Medicine, University of California, Davis, CA 95616
| | - Heather C Spooner
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA 95616
| | - Manuel F Navedo
- Department of Pharmacology, School of Medicine, University of California, Davis, CA 95616
| | - Eamonn J Dickson
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA 95616
| | - Rose E Dixon
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA 95616;
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7
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Del Villar SG, Voelker TL, Westhoff M, Reddy GR, Spooner HC, Navedo MF, Dickson EJ, Dixon RE. β-Adrenergic control of sarcolemmal Ca V1.2 abundance by small GTPase Rab proteins. Proc Natl Acad Sci U S A 2021; 118:e2017937118. [PMID: 33558236 PMCID: PMC7896340 DOI: 10.1073/pnas.2017937118] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The number and activity of Cav1.2 channels in the cardiomyocyte sarcolemma tunes the magnitude of Ca2+-induced Ca2+ release and myocardial contraction. β-Adrenergic receptor (βAR) activation stimulates sarcolemmal insertion of CaV1.2. This supplements the preexisting sarcolemmal CaV1.2 population, forming large "superclusters" wherein neighboring channels undergo enhanced cooperative-gating behavior, amplifying Ca2+ influx and myocardial contractility. Here, we determine this stimulated insertion is fueled by an internal reserve of early and recycling endosome-localized, presynthesized CaV1.2 channels. βAR-activation decreased CaV1.2/endosome colocalization in ventricular myocytes, as it triggered "emptying" of endosomal CaV1.2 cargo into the t-tubule sarcolemma. We examined the rapid dynamics of this stimulated insertion process with live-myocyte imaging of channel trafficking, and discovered that CaV1.2 are often inserted into the sarcolemma as preformed, multichannel clusters. Similarly, entire clusters were removed from the sarcolemma during endocytosis, while in other cases, a more incremental process suggested removal of individual channels. The amplitude of the stimulated insertion response was doubled by coexpression of constitutively active Rab4a, halved by coexpression of dominant-negative Rab11a, and abolished by coexpression of dominant-negative mutant Rab4a. In ventricular myocytes, βAR-stimulated recycling of CaV1.2 was diminished by both nocodazole and latrunculin-A, suggesting an essential role of the cytoskeleton in this process. Functionally, cytoskeletal disruptors prevented βAR-activated Ca2+ current augmentation. Moreover, βAR-regulation of CaV1.2 was abolished when recycling was halted by coapplication of nocodazole and latrunculin-A. These findings reveal that βAR-stimulation triggers an on-demand boost in sarcolemmal CaV1.2 abundance via targeted Rab4a- and Rab11a-dependent insertion of channels that is essential for βAR-regulation of cardiac CaV1.2.
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Affiliation(s)
- Silvia G Del Villar
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA 95616
| | - Taylor L Voelker
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA 95616
| | - Maartje Westhoff
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA 95616
| | - Gopireddy R Reddy
- Department of Pharmacology, School of Medicine, University of California, Davis, CA 95616
| | - Heather C Spooner
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA 95616
| | - Manuel F Navedo
- Department of Pharmacology, School of Medicine, University of California, Davis, CA 95616
| | - Eamonn J Dickson
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA 95616
| | - Rose E Dixon
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA 95616;
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8
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Patel KHK, Jones TN, Sattler S, Mason JC, Ng FS. Proarrhythmic electrophysiological and structural remodeling in rheumatoid arthritis. Am J Physiol Heart Circ Physiol 2020; 319:H1008-H1020. [PMID: 32946265 DOI: 10.1152/ajpheart.00401.2020] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Chronic inflammatory disorders, including rheumatoid arthritis (RA), are associated with a twofold increase in the incidence of sudden cardiac death (SCD) compared with the healthy population. Although this is partly explained by an increased prevalence of coronary artery disease, growing evidence suggests that ischemia alone cannot completely account for the increased risk. The present review explores the mechanisms of cardiac electrophysiological remodeling in response to chronic inflammation in RA. In particular, it focuses on the roles of nonischemic structural remodeling, altered cardiac ionic currents, and autonomic nervous system dysfunction in ventricular arrhythmogenesis and SCD. It also explores whether common genetic elements predispose to both RA and SCD. Finally, it evaluates the potential dual effects of disease-modifying therapy in both diminishing and promoting the risk of ventricular arrhythmias and SCD.
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Affiliation(s)
| | | | - Susanne Sattler
- National Heart and Lung Institute, Imperial College London, United Kingdom
| | - Justin C Mason
- National Heart and Lung Institute, Imperial College London, United Kingdom
| | - Fu Siong Ng
- National Heart and Lung Institute, Imperial College London, United Kingdom
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9
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Oliveras A, Serrano-Novillo C, Moreno C, de la Cruz A, Valenzuela C, Soeller C, Comes N, Felipe A. The unconventional biogenesis of Kv7.1-KCNE1 complexes. SCIENCE ADVANCES 2020; 6:eaay4472. [PMID: 32270035 PMCID: PMC7112945 DOI: 10.1126/sciadv.aay4472] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 01/09/2020] [Indexed: 06/11/2023]
Abstract
The potassium channel Kv7.1 associates with the KCNE1 regulatory subunit to trigger cardiac I Ks currents. Although the Kv7.1/KCNE1 complex has received much attention, the subcellular compartment hosting the assembly is the subject of ongoing debate. Evidence suggests that the complex forms either earlier in the endoplasmic reticulum or directly at the plasma membrane. Kv7.1 and KCNE1 mutations, responsible for long QT syndromes, impair association and traffic, thereby altering I Ks currents. We found that Kv7.1 and KCNE1 do not assemble in the first stages of their biogenesis. Data support an unconventional secretory pathway for Kv7.1-KCNE1 that bypasses Golgi. This route targets channels to endoplasmic reticulum-plasma membrane junctions, where Kv7.1-KCNE1 assemble. This mechanism helps to resolve the ongoing controversy about the subcellular compartment hosting the association. Our results also provide new insights into I Ks channel localization at endoplasmic reticulum-plasma membrane junctions, highlighting an alternative anterograde trafficking mechanism for oligomeric ion channels.
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Affiliation(s)
- Anna Oliveras
- Molecular Physiology Laboratory, Departamento de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, Barcelona, Spain
| | - Clara Serrano-Novillo
- Molecular Physiology Laboratory, Departamento de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, Barcelona, Spain
| | - Cristina Moreno
- National Institute of Neurological Disorders and Stroke (NIH), Bethesda, MD, USA
| | - Alicia de la Cruz
- Instituto de Investigaciones Biomédicas Alberto Sols CSIC-UAM, Madrid, Spain
| | - Carmen Valenzuela
- Instituto de Investigaciones Biomédicas Alberto Sols CSIC-UAM, Madrid, Spain
- Spanish Network for Biomedical Research in Cardiovascular Research (CIBERCV), Instituto de Salud Carlos III, Madrid, Spain
| | - Christian Soeller
- Living Systems Institute and Biomedical Physics, University of Exeter, Exeter, UK
| | - Núria Comes
- Departamento De Biomedicina, Institut d’Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Universitat de Barcelona, Barcelona, Spain
| | - Antonio Felipe
- Molecular Physiology Laboratory, Departamento de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, Barcelona, Spain
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10
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Ito DW, Hannigan KI, Ghosh D, Xu B, Del Villar SG, Xiang YK, Dickson EJ, Navedo MF, Dixon RE. β-adrenergic-mediated dynamic augmentation of sarcolemmal Ca V 1.2 clustering and co-operativity in ventricular myocytes. J Physiol 2019; 597:2139-2162. [PMID: 30714156 PMCID: PMC6462464 DOI: 10.1113/jp277283] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Accepted: 02/03/2019] [Indexed: 01/25/2023] Open
Abstract
Key points Prevailing dogma holds that activation of the β‐adrenergic receptor/cAMP/protein kinase A signalling pathway leads to enhanced L‐type CaV1.2 channel activity, resulting in increased Ca2+ influx into ventricular myocytes and a positive inotropic response. However, the full mechanistic and molecular details underlying this phenomenon are incompletely understood. CaV1.2 channel clusters decorate T‐tubule sarcolemmas of ventricular myocytes. Within clusters, nanometer proximity between channels permits Ca2+‐dependent co‐operative gating behaviour mediated by physical interactions between adjacent channel C‐terminal tails. We report that stimulation of cardiomyocytes with isoproterenol, evokes dynamic, protein kinase A‐dependent augmentation of CaV1.2 channel abundance along cardiomyocyte T‐tubules, resulting in the appearance of channel ‘super‐clusters’, and enhanced channel co‐operativity that amplifies Ca2+ influx. On the basis of these data, we suggest a new model in which a sub‐sarcolemmal pool of pre‐synthesized CaV1.2 channels resides in cardiomyocytes and can be mobilized to the membrane in times of high haemodynamic or metabolic demand, to tune excitation–contraction coupling.
Abstract Voltage‐dependent L‐type CaV1.2 channels play an indispensable role in cardiac excitation–contraction coupling. Activation of the β‐adrenergic receptor (βAR)/cAMP/protein kinase A (PKA) signalling pathway leads to enhanced CaV1.2 activity, resulting in increased Ca2+ influx into ventricular myocytes and a positive inotropic response. CaV1.2 channels exhibit a clustered distribution along the T‐tubule sarcolemma of ventricular myocytes where nanometer proximity between channels permits Ca2+‐dependent co‐operative gating behaviour mediated by dynamic, physical, allosteric interactions between adjacent channel C‐terminal tails. This amplifies Ca2+ influx and augments myocyte Ca2+ transient and contraction amplitudes. We investigated whether βAR signalling could alter CaV1.2 channel clustering to facilitate co‐operative channel interactions and elevate Ca2+ influx in ventricular myocytes. Bimolecular fluorescence complementation experiments reveal that the βAR agonist, isoproterenol (ISO), promotes enhanced CaV1.2–CaV1.2 physical interactions. Super‐resolution nanoscopy and dynamic channel tracking indicate that these interactions are expedited by enhanced spatial proximity between channels, resulting in the appearance of CaV1.2 ‘super‐clusters’ along the z‐lines of ISO‐stimulated cardiomyocytes. The mechanism that leads to super‐cluster formation involves rapid, dynamic augmentation of sarcolemmal CaV1.2 channel abundance after ISO application. Optical and electrophysiological single channel recordings confirm that these newly inserted channels are functional and contribute to overt co‐operative gating behaviour of CaV1.2 channels in ISO stimulated myocytes. The results of the present study reveal a new facet of βAR‐mediated regulation of CaV1.2 channels in the heart and support the novel concept that a pre‐synthesized pool of sub‐sarcolemmal CaV1.2 channel‐containing vesicles/endosomes resides in cardiomyocytes and can be mobilized to the sarcolemma to tune excitation–contraction coupling to meet metabolic and/or haemodynamic demands. Prevailing dogma holds that activation of the β‐adrenergic receptor/cAMP/protein kinase A signalling pathway leads to enhanced L‐type CaV1.2 channel activity, resulting in increased Ca2+ influx into ventricular myocytes and a positive inotropic response. However, the full mechanistic and molecular details underlying this phenomenon are incompletely understood. CaV1.2 channel clusters decorate T‐tubule sarcolemmas of ventricular myocytes. Within clusters, nanometer proximity between channels permits Ca2+‐dependent co‐operative gating behaviour mediated by physical interactions between adjacent channel C‐terminal tails. We report that stimulation of cardiomyocytes with isoproterenol, evokes dynamic, protein kinase A‐dependent augmentation of CaV1.2 channel abundance along cardiomyocyte T‐tubules, resulting in the appearance of channel ‘super‐clusters’, and enhanced channel co‐operativity that amplifies Ca2+ influx. On the basis of these data, we suggest a new model in which a sub‐sarcolemmal pool of pre‐synthesized CaV1.2 channels resides in cardiomyocytes and can be mobilized to the membrane in times of high haemodynamic or metabolic demand, to tune excitation–contraction coupling.
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Affiliation(s)
- Danica W Ito
- Department of Physiology & Membrane Biology, University of California Davis, Davis, CA, USA
| | - Karen I Hannigan
- Department of Physiology & Membrane Biology, University of California Davis, Davis, CA, USA
| | - Debapriya Ghosh
- Department of Pharmacology, University of California Davis, Davis, CA, USA
| | - Bing Xu
- Department of Pharmacology, University of California Davis, Davis, CA, USA
| | - Silvia G Del Villar
- Department of Physiology & Membrane Biology, University of California Davis, Davis, CA, USA
| | - Yang K Xiang
- Department of Pharmacology, University of California Davis, Davis, CA, USA.,VA Northern California Health Care System, Mather, CA, USA
| | - Eamonn J Dickson
- Department of Physiology & Membrane Biology, University of California Davis, Davis, CA, USA
| | - Manuel F Navedo
- Department of Pharmacology, University of California Davis, Davis, CA, USA
| | - Rose E Dixon
- Department of Physiology & Membrane Biology, University of California Davis, Davis, CA, USA
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11
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Alí A, Boutjdir M, Aromolaran AS. Cardiolipotoxicity, Inflammation, and Arrhythmias: Role for Interleukin-6 Molecular Mechanisms. Front Physiol 2019; 9:1866. [PMID: 30666212 PMCID: PMC6330352 DOI: 10.3389/fphys.2018.01866] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Accepted: 12/11/2018] [Indexed: 12/12/2022] Open
Abstract
Fatty acid infiltration of the myocardium, acquired in metabolic disorders (obesity, type-2 diabetes, insulin resistance, and hyperglycemia) is critically associated with the development of lipotoxic cardiomyopathy. According to a recent Presidential Advisory from the American Heart Association published in 2017, the current average dietary intake of saturated free-fatty acid (SFFA) in the US is 11–12%, which is significantly above the recommended <10%. Increased levels of circulating SFFAs (or lipotoxicity) may represent an unappreciated link that underlies increased vulnerability to cardiac dysfunction. Thus, an important objective is to identify novel targets that will inform pharmacological and genetic interventions for cardiomyopathies acquired through excessive consumption of diets rich in SFFAs. However, the molecular mechanisms involved are poorly understood. The increasing epidemic of metabolic disorders strongly implies an undeniable and critical need to further investigate SFFA mechanisms. A rapidly emerging and promising target for modulation by lipotoxicity is cytokine secretion and activation of pro-inflammatory signaling pathways. This objective can be advanced through fundamental mechanisms of cardiac electrical remodeling. In this review, we discuss cardiac ion channel modulation by SFFAs. We further highlight the contribution of downstream signaling pathways involving toll-like receptors and pathological increases in pro-inflammatory cytokines. Our expectation is that if we understand pathological remodeling of major cardiac ion channels from a perspective of lipotoxicity and inflammation, we may be able to develop safer and more effective therapies that will be beneficial to patients.
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Affiliation(s)
- Alessandra Alí
- Cardiovascular Research Program, VA New York Harbor Healthcare System, Brooklyn, NY, United States.,Department of Medicine, State University of New York Downstate Medical Center, Brooklyn, NY, United States.,Department of Cell Biology, State University of New York Downstate Medical Center, Brooklyn, NY, United States.,Department of Pharmacology, State University of New York Downstate Medical Center, Brooklyn, NY, United States.,Department of Molecular and Developmental Medicine, University of Siena, Siena, Italy
| | - Mohamed Boutjdir
- Cardiovascular Research Program, VA New York Harbor Healthcare System, Brooklyn, NY, United States.,Department of Medicine, State University of New York Downstate Medical Center, Brooklyn, NY, United States.,Department of Cell Biology, State University of New York Downstate Medical Center, Brooklyn, NY, United States.,Department of Pharmacology, State University of New York Downstate Medical Center, Brooklyn, NY, United States.,Department of Medicine, New York University School of Medicine, New York, NY, United States
| | - Ademuyiwa S Aromolaran
- Cardiovascular Research Program, VA New York Harbor Healthcare System, Brooklyn, NY, United States.,Department of Medicine, State University of New York Downstate Medical Center, Brooklyn, NY, United States.,Department of Cell Biology, State University of New York Downstate Medical Center, Brooklyn, NY, United States.,Department of Pharmacology, State University of New York Downstate Medical Center, Brooklyn, NY, United States
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12
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Zankov DP, Salloum FN, Jiang M, Tseng GN. Chronic in vivo angiotensin II administration differentially modulates the slow delayed rectifier channels in atrial and ventricular myocytes. Heart Rhythm 2018; 16:108-116. [PMID: 30075281 DOI: 10.1016/j.hrthm.2018.07.036] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Indexed: 11/30/2022]
Abstract
BACKGROUND In the heart, slow delayed rectifier channels provide outward currents (IKs) for action potential (AP) repolarization in a region- and context-dependent manner. In diseased hearts, chronic elevation of angiotensin II (Ang II) may remodel IKs in a region-dependent manner, contributing to atrial and ventricular arrhythmias of different mechanisms. OBJECTIVE The purpose of this study was to study whether/how chronic in vivo Ang II administration remodels IKs in atrial and ventricular myocytes. METHODS We used the guinea pig (GP) model whose myocytes express robust IKs. GPs were implanted with minipumps containing Ang II or vehicle. Treatment continued for 4-6 weeks. We used patch clamp, immunofluorescence/confocal microscopy, and immunoblots to evaluate changes in IKs function and to explore the underlying mechanisms. RESULTS We confirmed the pathologic state of the heart after chronic Ang II treatment. IKs density was increased in atrial myocytes but decreased in ventricular myocytes in Ang II- vs vehicle-treated animals. The former was correlated with an increase in KCNQ1/KCNE1 colocalization in myocyte periphery, whereas the latter was correlated with a decrease in KCNQ1 protein level. Interestingly, these changes in IKs were not translated into expected alterations in AP duration or plateau voltage, indicating that other currents were involved. In atrial myocytes from Ang II-treated animals, the L-type Ca channel current was increased, contributing to AP plateau elevation and AP duration prolongation. CONCLUSION IKs is differentially modulated by chronic in vivo Ang II administration between atrial and ventricular myocytes. Other currents remodeled by Ang II treatment also contribute to changes in action potentials.
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Affiliation(s)
- Dimitar P Zankov
- Department of Physiology & Biophysics, Virginia Commonwealth University, Richmond, Virginia
| | - Fadi N Salloum
- Department of Internal Medicine, Division of Cardiology, Virginia Commonwealth University, Richmond, Virginia
| | - Min Jiang
- Department of Physiology & Biophysics, Virginia Commonwealth University, Richmond, Virginia
| | - Gea-Ny Tseng
- Department of Physiology & Biophysics, Virginia Commonwealth University, Richmond, Virginia; Department of Internal Medicine, Division of Cardiology, Virginia Commonwealth University, Richmond, Virginia.
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13
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Piccini I, Fehrmann E, Frank S, Müller FU, Greber B, Seebohm G. Adrenergic Stress Protection of Human iPS Cell-Derived Cardiomyocytes by Fast K v7.1 Recycling. Front Physiol 2017; 8:705. [PMID: 28959214 PMCID: PMC5603700 DOI: 10.3389/fphys.2017.00705] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Accepted: 08/31/2017] [Indexed: 01/09/2023] Open
Abstract
The fight-or-flight response (FFR), a physiological acute stress reaction, involves positive chronotropic and inotropic effects on heart muscle cells mediated through β-adrenoceptor activation. Increased systolic calcium is required to enable stronger heart contractions whereas elevated potassium currents are to limit the duration of the action potentials and prevent arrhythmia. The latter effect is accomplished by an increased functional activity of the Kv7.1 channel encoded by KCNQ1. Current knowledge, however, does not sufficiently explain the full extent of rapid Kv7.1 activation and may hence be incomplete. Using inducible genetic KCNQ1 complementation in KCNQ1-deficient human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs), we here reinvestigate the functional role of Kv7.1 in adapting human CMs to adrenergic stress. Under baseline conditions, Kv7.1 was barely detectable at the plasma membrane of hiPSC-CMs, yet it fully protected these from adrenergic stress-induced beat-to-beat variability of repolarization and torsade des pointes-like arrhythmia. Furthermore, isoprenaline treatment increased field potential durations specifically in KCNQ1-deficient CMs to cause these adverse macroscopic effects. Mechanistically, we find that the protective action by Kv7.1 resides in a rapid translocation of channel proteins from intracellular stores to the plasma membrane, induced by adrenergic signaling. Gene silencing experiments targeting RAB GTPases, mediators of intracellular vesicle trafficking, showed that fast Kv7.1 recycling under acute stress conditions is RAB4A-dependent.Our data reveal a key mechanism underlying the rapid adaptation of human cardiomyocytes to adrenergic stress. These findings moreover aid to the understanding of disease pathology in long QT syndrome and bear important implications for safety pharmacological screening.
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Affiliation(s)
- Ilaria Piccini
- Department of Cardiovascular Medicine, Institute of Genetics of Heart Diseases, University of Münster Medical SchoolMünster, Germany.,Human Stem Cell Pluripotency Laboratory, Max Planck Institute for Molecular BiomedicineMünster, Germany
| | - Edda Fehrmann
- Institute of Pharmacology and Toxicology, University of MünsterMünster, Germany
| | - Stefan Frank
- Human Stem Cell Pluripotency Laboratory, Max Planck Institute for Molecular BiomedicineMünster, Germany.,Chemical Genomics Centre of the Max Planck SocietyDortmund, Germany
| | - Frank U Müller
- Institute of Pharmacology and Toxicology, University of MünsterMünster, Germany
| | - Boris Greber
- Human Stem Cell Pluripotency Laboratory, Max Planck Institute for Molecular BiomedicineMünster, Germany.,Chemical Genomics Centre of the Max Planck SocietyDortmund, Germany
| | - Guiscard Seebohm
- Department of Cardiovascular Medicine, Institute of Genetics of Heart Diseases, University of Münster Medical SchoolMünster, Germany
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14
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Jiang M, Wang Y, Tseng GN. Adult Ventricular Myocytes Segregate KCNQ1 and KCNE1 to Keep the IKs Amplitude in Check Until When Larger IKs Is Needed. Circ Arrhythm Electrophysiol 2017; 10:CIRCEP.117.005084. [PMID: 28611207 DOI: 10.1161/circep.117.005084] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Accepted: 05/15/2017] [Indexed: 11/16/2022]
Abstract
BACKGROUND KCNQ1 and KCNE1 assemble to form the slow delayed rectifier (IKs) channel critical for shortening ventricular action potentials during high β-adrenergic tone. However, too much IKs under basal conditions poses an arrhythmogenic risk. Our objective is to understand how adult ventricular myocytes regulate the IKs amplitudes under basal conditions and in response to stress. METHODS AND RESULTS We express fluorescently tagged KCNQ1 and KCNE1 in adult ventricular myocytes and follow their biogenesis and trafficking paths. We also study the distribution patterns of native KCNQ1 and KCNE1, and their relationship to IKs amplitudes, in chronically stressed ventricular myocytes, and use COS-7 cell expression to probe the underlying mechanism. We show that KCNQ1 and KCNE1 are both translated in the perinuclear region but traffic by different routes, independent of each other, to their separate subcellular locations. KCNQ1 mainly resides in the jSR (junctional sarcoplasmic reticulum), whereas KCNE1 resides on the cell surface. Under basal conditions, only a small portion of KCNQ1 reaches the cell surface to support the IKs function. However, in response to chronic stress, KCNQ1 traffics from jSR to the cell surface to boost the IKs amplitude in a process depending on Ca binding to CaM (calmodulin). CONCLUSIONS In adult ventricular myocytes, KCNE1 maintains a stable presence on the cell surface, whereas KCNQ1 is dynamic in its localization. KCNQ1 is largely in an intracellular reservoir under basal conditions but can traffic to the cell surface and boost the IKs amplitude in response to stress.
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Affiliation(s)
- Min Jiang
- From the Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond (M.J., Y.W., G.-N.T.); and Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing (M.J.)
| | - Yuhong Wang
- From the Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond (M.J., Y.W., G.-N.T.); and Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing (M.J.)
| | - Gea-Ny Tseng
- From the Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond (M.J., Y.W., G.-N.T.); and Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing (M.J.).
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15
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Thompson E, Eldstrom J, Westhoff M, McAfee D, Balse E, Fedida D. cAMP-dependent regulation of IKs single-channel kinetics. J Gen Physiol 2017; 149:781-798. [PMID: 28687606 PMCID: PMC5560775 DOI: 10.1085/jgp.201611734] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Accepted: 06/20/2017] [Indexed: 02/06/2023] Open
Abstract
The delayed potassium rectifier current, IKs , is composed of KCNQ1 and KCNE1 subunits and plays an important role in cardiac action potential repolarization. During β-adrenergic stimulation, 3'-5'-cyclic adenosine monophosphate (cAMP)-dependent protein kinase A (PKA) phosphorylates KCNQ1, producing an increase in IKs current and a shortening of the action potential. Here, using cell-attached macropatches and single-channel recordings, we investigate the microscopic mechanisms underlying the cAMP-dependent increase in IKs current. A membrane-permeable cAMP analog, 8-(4-chlorophenylthio)-cAMP (8-CPT-cAMP), causes a marked leftward shift of the conductance-voltage relation in macropatches, with or without an increase in current size. Single channels exhibit fewer silent sweeps, reduced first latency to opening (control, 1.61 ± 0.13 s; cAMP, 1.06 ± 0.11 s), and increased higher-subconductance-level occupancy in the presence of cAMP. The E160R/R237E and S209F KCNQ1 mutants, which show fixed and enhanced voltage sensor activation, respectively, largely abolish the effect of cAMP. The phosphomimetic KCNQ1 mutations, S27D and S27D/S92D, are much less and not at all responsive, respectively, to the effects of PKA phosphorylation (first latency of S27D + KCNE1 channels: control, 1.81 ± 0.1 s; 8-CPT-cAMP, 1.44 ± 0.1 s, P < 0.05; latency of S27D/S92D + KCNE1: control, 1.62 ± 0.1 s; cAMP, 1.43 ± 0.1 s, nonsignificant). Using total internal reflection fluorescence microscopy, we find no overall increase in surface expression of the channel during exposure to 8-CPT-cAMP. Our data suggest that the cAMP-dependent increase in IKs current is caused by an increase in the likelihood of channel opening, combined with faster openings and greater occupancy of higher subconductance levels, and is mediated by enhanced voltage sensor activation.
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Affiliation(s)
- Emely Thompson
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, BC, Canada
| | - Jodene Eldstrom
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, BC, Canada
| | - Maartje Westhoff
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, BC, Canada
| | - Donald McAfee
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, BC, Canada
| | - Elise Balse
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, UMR_S 1166, Unité de recherche sur les maladies cardiovasculaires, le métabolisme et la nutrition, Faculté de Médecine, Site Pitié-Salpêtrière, Paris, France
| | - David Fedida
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, BC, Canada
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16
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Ahmad AA, Streiff M, Hunter C, Hu Q, Sachse FB. Physiological and pathophysiological role of transient receptor potential canonical channels in cardiac myocytes. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2017. [PMID: 28629808 DOI: 10.1016/j.pbiomolbio.2017.06.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Transient receptor potential canonical (TRPC) channels constitute a family of seven Ca2+ permeable ion channels, named TRPC1 to 7. These channels are abundantly expressed in the mammalian heart, yet mechanisms underlying activation of TRPC channels and their precise role in cardiac physiology remain poorly understood. In this review, we perused original literature regarding TRPC channels in cardiomyocytes. We first reviewed studies on TRPC channel assembly and sub-cellular localization across multiple species and cell types. Our review indicates that TRPC localization in cardiac cells is still a topic of controversy. We then examined common molecular biology tools used to infer on location and physiological roles of TRPC channels in the heart. We subsequently reviewed pharmacological tools used to modulate TRPC activity in both cardiac and non-cardiac cells. Suggested physiological roles in the heart include modulation of heart rate and sensing of mechanical strain. We examined studies on the contribution of TRPC to cardiac pathophysiology, mainly hypertrophic signaling. Several TRPC channels, particularly TRPC1, 3 and 6 were proposed to play a crucial role in hypertrophic signaling. Finally, we discussed gaps in our understanding of the location and physiological role of TRPC channels in cardiomyocytes. Closing these gaps will be crucial to gain a full understanding of the role of TRPC channels in cardiac pathophysiology and to further explore these channels as targets for treatments for cardiac diseases, in particular, hypertrophy.
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Affiliation(s)
- Azmi A Ahmad
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, USA; Bioengineering Department, University of Utah, Salt Lake City, USA
| | - Molly Streiff
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, USA; Bioengineering Department, University of Utah, Salt Lake City, USA
| | - Chris Hunter
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, USA
| | - Qinghua Hu
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, USA
| | - Frank B Sachse
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, USA; Bioengineering Department, University of Utah, Salt Lake City, USA.
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17
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Bartos DC, Morotti S, Ginsburg KS, Grandi E, Bers DM. Quantitative analysis of the Ca 2+ -dependent regulation of delayed rectifier K + current I Ks in rabbit ventricular myocytes. J Physiol 2017; 595:2253-2268. [PMID: 28008618 DOI: 10.1113/jp273676] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Accepted: 12/12/2016] [Indexed: 12/25/2022] Open
Abstract
KEY POINTS [Ca2+ ]i enhanced rabbit ventricular slowly activating delayed rectifier K+ current (IKs ) by negatively shifting the voltage dependence of activation and slowing deactivation, similar to perfusion of isoproterenol. Rabbit ventricular rapidly activating delayed rectifier K+ current (IKr ) amplitude and voltage dependence were unaffected by high [Ca2+ ]i . When measuring or simulating IKs during an action potential, IKs was not different during a physiological Ca2+ transient or when [Ca2+ ]i was buffered to 500 nm. ABSTRACT The slowly activating delayed rectifier K+ current (IKs ) contributes to repolarization of the cardiac action potential (AP). Intracellular Ca2+ ([Ca2+ ]i ) and β-adrenergic receptor (β-AR) stimulation modulate IKs amplitude and kinetics, but details of these important IKs regulators and their interaction are limited. We assessed the [Ca2+ ]i dependence of IKs in steady-state conditions and with dynamically changing membrane potential and [Ca2+ ]i during an AP. IKs was recorded from freshly isolated rabbit ventricular myocytes using whole-cell patch clamp. With intracellular pipette solutions that controlled free [Ca2+ ]i , we found that raising [Ca2+ ]i from 100 to 600 nm produced similar increases in IKs as did β-AR activation, and the effects appeared additive. Both β-AR activation and high [Ca2+ ]i increased maximally activated tail IKs , negatively shifted the voltage dependence of activation, and slowed deactivation kinetics. These data informed changes in our well-established mathematical model of the rabbit myocyte. In both AP-clamp experiments and simulations, IKs recorded during a normal physiological Ca2+ transient was similar to IKs measured with [Ca2+ ]i clamped at 500-600 nm. Thus, our study provides novel quantitative data as to how physiological [Ca2+ ]i regulates IKs amplitude and kinetics during the normal rabbit AP. Our results suggest that micromolar [Ca2+ ]i , in the submembrane or junctional cleft space, is not required to maximize [Ca2+ ]i -dependent IKs activation during normal Ca2+ transients.
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Affiliation(s)
- Daniel C Bartos
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
| | - Stefano Morotti
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
| | - Kenneth S Ginsburg
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
| | - Eleonora Grandi
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
| | - Donald M Bers
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
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18
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Grandi E, Sanguinetti MC, Bartos DC, Bers DM, Chen-Izu Y, Chiamvimonvat N, Colecraft HM, Delisle BP, Heijman J, Navedo MF, Noskov S, Proenza C, Vandenberg JI, Yarov-Yarovoy V. Potassium channels in the heart: structure, function and regulation. J Physiol 2016; 595:2209-2228. [PMID: 27861921 DOI: 10.1113/jp272864] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2016] [Accepted: 07/18/2016] [Indexed: 12/22/2022] Open
Abstract
This paper is the outcome of the fourth UC Davis Systems Approach to Understanding Cardiac Excitation-Contraction Coupling and Arrhythmias Symposium, a biannual event that aims to bring together leading experts in subfields of cardiovascular biomedicine to focus on topics of importance to the field. The theme of the 2016 symposium was 'K+ Channels and Regulation'. Experts in the field contributed their experimental and mathematical modelling perspectives and discussed emerging questions, controversies and challenges on the topic of cardiac K+ channels. This paper summarizes the topics of formal presentations and informal discussions from the symposium on the structural basis of voltage-gated K+ channel function, as well as the mechanisms involved in regulation of K+ channel gating, expression and membrane localization. Given the critical role for K+ channels in determining the rate of cardiac repolarization, it is hardly surprising that essentially every aspect of K+ channel function is exquisitely regulated in cardiac myocytes. This regulation is complex and highly interrelated to other aspects of myocardial function. K+ channel regulatory mechanisms alter, and are altered by, physiological challenges, pathophysiological conditions, and pharmacological agents. An accompanying paper focuses on the integrative role of K+ channels in cardiac electrophysiology, i.e. how K+ currents shape the cardiac action potential, and how their dysfunction can lead to arrhythmias, and discusses K+ channel-based therapeutics. A fundamental understanding of K+ channel regulatory mechanisms and disease processes is fundamental to reveal new targets for human therapy.
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Affiliation(s)
- Eleonora Grandi
- Department of Pharmacology, University of California, Davis, Davis, CA, 95616, USA
| | - Michael C Sanguinetti
- Department of Internal Medicine, University of Utah, Nora Eccles Harrison Cardiovascular Research and Training Institute, Salt Lake City, UT, 84112, USA
| | - Daniel C Bartos
- Department of Pharmacology, University of California, Davis, Davis, CA, 95616, USA
| | - Donald M Bers
- Department of Pharmacology, University of California, Davis, Davis, CA, 95616, USA
| | - Ye Chen-Izu
- Department of Pharmacology, University of California, Davis, Davis, CA, 95616, USA.,Department of Internal Medicine, Division of Cardiology, University of California, Davis, CA, 95616, USA
| | - Nipavan Chiamvimonvat
- Department of Internal Medicine, Division of Cardiology, University of California, Davis, CA, 95616, USA
| | - Henry M Colecraft
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY, 10032, USA
| | - Brian P Delisle
- Department of Physiology, University of Kentucky, Lexington, KY, 40536, USA
| | - Jordi Heijman
- Department of Cardiology, Cardiovascular Research Institute Maastricht, Faculty of Health, Medicine, and Life Sciences, Maastricht University, Maastricht, The Netherlands
| | - Manuel F Navedo
- Department of Pharmacology, University of California, Davis, Davis, CA, 95616, USA
| | - Sergei Noskov
- Centre for Molecular Simulation, Department of Biological Sciences, University of Calgary, Calgary, AB, T2N 1N4, Canada
| | - Catherine Proenza
- Department of Physiology and Biophysics, University of Colorado - Anschutz Medical Campus, Denver, CO, 80045, USA
| | - Jamie I Vandenberg
- Victor Chang Cardiac Research Institute, Darlinghurst, NSW, 2010, Australia
| | - Vladimir Yarov-Yarovoy
- Department of Physiology and Membrane Biology, University of California, Davis, CA, 95616, USA
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Jiang M, Zhang M, Howren M, Wang Y, Tan A, Balijepalli RC, Huizar JF, Tseng GN. JPH-2 interacts with Cai-handling proteins and ion channels in dyads: Contribution to premature ventricular contraction-induced cardiomyopathy. Heart Rhythm 2016; 13:743-52. [PMID: 26538326 PMCID: PMC4762763 DOI: 10.1016/j.hrthm.2015.10.037] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Indexed: 12/28/2022]
Abstract
BACKGROUND In a canine model of premature ventricular contraction-induced cardiomyopathy (PVC-CM), Cav1.2 is downregulated and misplaced from transverse tubules (T tubules). Junctophilin-2 (JPH-2) is also downregulated. OBJECTIVES The objectives of this study were to understand the role of JPH-2 in PVC-CM and to probe changes in other proteins involved in dyad structure and function. METHODS We quantify T-tubule contents (di-8-ANEPPS fluorescence in live myocytes), examine myocyte ultrastructures (electron microscopy), probe JPH-2-interacting proteins (co-immunoprecipitation), quantify dyad and nondyad protein levels (immunoblotting), and examine subcellular distributions of dyad proteins (immunofluorescence/confocal microscopy). We also test direct JPH-2 modulation of channel function (vs indirect modulation through dyad formation) using heterologous expression. RESULTS PVC myocytes have reduced T-tubule contents but otherwise normal ultrastructures. Among 19 proteins examined, only JPH-2, bridging integrator-1 (BIN-1), and Cav1.2 are highly downregulated in PVC hearts. However, statistical analysis indicates a general reduction in dyad protein levels when JPH-2 is downregulated. Furthermore, several dyad proteins, including Na/Ca exchanger, are missing or shifted from dyads to the peripheral surface in PVC myocytes. JPH-2 directly or indirectly interacts with Cai-handling proteins, Cav1.2 and KCNQ1, although not BIN-1 or other scaffolding proteins tested. Expression in mammalian cells that do not have dyads confirms direct JPH-2 modulation of the L-type Ca channel current (Cav1.2/voltage-gated Ca channel β subunit 2) and slow delayed rectifier current (KCNQ1/KCNE1). CONCLUSION JPH-2 is more than a "dyad glue": it can modulate Cai handling and ion channel function in the dyad region. Downregulation of JPH-2, BIN-1, and Cav1.2 plays a deterministic role in PVC-CM. Dissecting the hierarchical relationship among the three is necessary for the design of therapeutic interventions to prevent the progression of PVC-CM.
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Affiliation(s)
- Min Jiang
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, Virginia
| | - Mei Zhang
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, Virginia
| | - Maureen Howren
- Department of Medicine/Cardiology Division, McGuire VA Medical Center, Richmond, Virginia
| | - Yuhong Wang
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, Virginia
| | - Alex Tan
- Department of Medicine/Cardiology Division, McGuire VA Medical Center, Richmond, Virginia
| | - Ravi C Balijepalli
- Cellular and Molecular Arrhythmia Research Program, Department of Medicine, University of Wisconsin, Madison, Wisconsin
| | - Jose F Huizar
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, Virginia
| | - Gea-Ny Tseng
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, Virginia.
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Abstract
BACKGROUND Propionic acidemia (PROP) is a rare metabolic disorder caused by deficiency of propionyl-CoA carboxylase. PROP patients demonstrate QT prolongations associated with ventricular tachycardia and syncopes. Mechanisms responsible for this acquired long QT syndrome (acqLQTS) are unknown. OBJECTIVE The aim of the study was to investigate acute and chronic effects of metabolites accumulating in PROP patients on major repolarizing potassium currents (IKs and IKr) and their channel subunits. METHODS Voltage clamp studies were performed in CHO-KCNQ1/KCNE1 or HEK-KCNH2 cells to determine effects of propionic acid (PA; 1-10 mM), propionylcarnitine (PC; 25 µM-10 mM), methylcitrate (MC; 25 µM-10 mM), 0.2 M phosphate buffer (PB), or patient serum on IKs and IKr currents. Metabolite effects on action potentials were recorded in current clamp mode in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM). Protein expression of α- and β-subunits of IKs (KCNQ1/KCNE1) and IKr (KCNH2) was evaluated with Western blots. RESULTS Acute application of PA, PC, MC, and patient serum had no direct effect on net IKr densities (and KCNH2 expression), although it changed IKr gating kinetics. In contrast, PA, PC, MC, and patient serum all reduced IKs-tail (-67% ± 4.2%, -27% ± 6.7%, -16% ± 6.3%, -42.8% ± 5.15; P < .001) and IKs-end pulse currents. PA significantly prolonged action potential duration (APD) in hiPSC-CM and QT interval in wild-type but not in LQT1 rabbits lacking IKs. Moreover, PC and MC (1 mM) decreased KCNQ1 protein expression (relative density: 0.58 ± 0.08 and 0.16 ± 0.05; P < .01). Chronic exposure to 10 mM PA, in contrast, increased KCNQ1 5.4-fold (P < .001) owing to decreased protein degradation. CONCLUSION Acute reduction of IKs by PROP metabolites may be responsible for APD prolongation and acqLQTS observed in PROP patients.
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Murray CI, Westhoff M, Eldstrom J, Thompson E, Emes R, Fedida D. Unnatural amino acid photo-crosslinking of the IKs channel complex demonstrates a KCNE1:KCNQ1 stoichiometry of up to 4:4. eLife 2016; 5. [PMID: 26802629 PMCID: PMC4807126 DOI: 10.7554/elife.11815] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2015] [Accepted: 01/22/2016] [Indexed: 12/20/2022] Open
Abstract
Cardiac repolarization is determined in part by the slow delayed rectifier current (IKs), through the tetrameric voltage-gated ion channel, KCNQ1, and its β-subunit, KCNE1. The stoichiometry between α and β-subunits has been controversial with studies reporting either a strict 2 KCNE1:4 KCNQ1 or a variable ratio up to 4:4. We used IKs fusion proteins linking KCNE1 to one (EQ), two (EQQ) or four (EQQQQ) KCNQ1 subunits, to reproduce compulsory 4:4, 2:4 or 1:4 stoichiometries. Whole cell and single-channel recordings showed EQQ and EQQQQ to have increasingly hyperpolarized activation, reduced conductance, and shorter first latency of opening compared to EQ - all abolished by the addition of KCNE1. As well, using a UV-crosslinking unnatural amino acid in KCNE1, we found EQQQQ and EQQ crosslinking rates to be progressively slowed compared to KCNQ1, which demonstrates that no intrinsic mechanism limits the association of up to four β-subunits within the IKs complex. DOI:http://dx.doi.org/10.7554/eLife.11815.001 The membrane that surrounds heart muscle cells contains specialized channels that can open and close to control the movements of charged ions into and out of the cell. This ion flow generates the electrical signals that stimulate the heart muscle to contract for each heart beat. Different ion channels influence different steps in the initiation and termination of each electrical signal. For example, the IKs ion channel complex helps to return the cell to a resting state so the heart muscle can relax. This allows chambers of the heart to fill with blood before the next beat pumps blood throughout the body. Mutations that affect IKs cause serious heart conditions that affect heart rhythm, such as Long QT Syndrome. The IKs complex consists of channels that are each made of four copies of a protein called KCNQ1, through which potassium ions exit the cell. This channel opens in response to changes in the voltage across the cell membrane (known as the “membrane potential”). A small protein subunit called KCNE1 also makes up part of the complex, but it was not clear how many KCNE1 molecules combine with KCNQ1 to form a working channel complex. Several previous studies have reported two different results: that the KCNQ1 channel complex only exists with two KCNE1 molecules, or that the association is flexible, allowing the complex to contain up to four KCNE1 subunits. Murray et al. have now constructed IKs fusion channels out of different numbers of KCNQ1 and KCNE1 molecules to investigate how different KCNQ1:KCNE1 ratios affect how the channel works. Measuring the responses of these modified channels in mammalian cells revealed that channels with four KCNE1 subunits conducted ions better than channels with one or two KCNE1s. The channels containing fewer KCNE1s also opened at lower membrane potentials and after a shorter delay following a change in the membrane potential. Further experiments also supported the theory that up to four independent KCNE1 subunits may be easily added to the IKs ion channel complex. Murray et al. suggest that by being able to form channel complexes containing different numbers of KCNE1 subunits, cells can more flexibly control the rate at which ions flow out of the heart cells to tune the electrical signals that trigger each heart beat. The next challenges will be to determine the composition of the IKs channel complex in adult heart cells and to investigate how the complex might change with disease. DOI:http://dx.doi.org/10.7554/eLife.11815.002
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Affiliation(s)
- Christopher I Murray
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Maartje Westhoff
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Jodene Eldstrom
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Emely Thompson
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Robert Emes
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - David Fedida
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
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Probing binding sites and mechanisms of action of an I(Ks) activator by computations and experiments. Biophys J 2015; 108:62-75. [PMID: 25564853 DOI: 10.1016/j.bpj.2014.10.059] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Revised: 10/06/2014] [Accepted: 10/27/2014] [Indexed: 01/08/2023] Open
Abstract
The slow delayed rectifier (IKs) channel is composed of the KCNQ1 channel and KCNE1 auxiliary subunit, and functions to repolarize action potentials in the human heart. IKs activators may provide therapeutic efficacy for treating long QT syndromes. Here, we show that a new KCNQ1 activator, ML277, can enhance IKs amplitude in adult guinea pig and canine ventricular myocytes. We probe its binding site and mechanism of action by computational analysis based on our recently reported KCNQ1 and KCNQ1/KCNE1 3D models, followed by experimental validation. Results from a pocket analysis and docking exercise suggest that ML277 binds to a side pocket in KCNQ1 and the KCNE1-free side pocket of KCNQ1/KCNE1. Molecular-dynamics (MD) simulations based on the most favorable channel/ML277 docking configurations reveal a well-defined ML277 binding space surrounded by the S2-S3 loop and S4-S5 helix on the intracellular side, and by S4-S6 transmembrane helices on the lateral sides. A detailed analysis of MD trajectories suggests two mechanisms of ML277 action. First, ML277 restricts the conformational dynamics of the KCNQ1 pore, optimizing K(+) ion coordination in the selectivity filter and increasing current amplitudes. Second, ML277 binding induces global motions in the channel, including regions critical for KCNQ1 gating transitions. We conclude that ML277 activates IKs by binding to an intersubunit space and allosterically influencing pore conductance and gating transitions. KCNE1 association protects KCNQ1 from an arrhythmogenic (constitutive current-inducing) effect of ML277, but does not preclude its current-enhancing effect.
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Kienitz MC, Vladimirova D. Synergistic modulation of KCNQ1/KCNE1 K(+) channels (IKs) by phosphatidylinositol 4,5-bisphosphate (PIP2) and [ATP]i. Cell Signal 2015; 27:1457-68. [PMID: 25892084 DOI: 10.1016/j.cellsig.2015.04.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 04/08/2015] [Indexed: 01/01/2023]
Abstract
Cardiac KCNQ1/KCNE1 channels (IKs) are dependent on the concentration of membrane phosphatidylinositol-4,5-bisphosphate (PIP2) and on cytosolic ATP by two distinct mechanisms. In this study we measured IKs and FRET between PH-PLCδ-based fluorescent PIP2 sensors in a stable KCNQ1/KCNE1 CHO cell line. Effects of activating either a muscarinic M3 receptor or the switchable phosphatase Ci-VSP on IKs were analyzed. Recovery of IKs from inhibition induced by muscarinic stimulation was incomplete despite full PIP2 resynthesis. Recovery of IKs was completely suppressed under ATP-free conditions, but partially restored by the ATP analog AMP-PCP, providing evidence that depletion of intracellular ATP inhibits IKs independent of PIP2-depletion. Simultaneous patch-clamp and FRET measurements in cells co-expressing Ci-VSP and the PIP2-FRET sensor revealed a component of IKs inhibition directly related to dynamic PIP2-depletion. A second component of inhibition was independent of acute changes in PIP2 and could be mimicked by ATP-free pipette solution, suggesting that it results from intracellular ATP-depletion. The reduction of intracellular ATP upon Ci-VSP activation appears to be independent of its activity as a phosphoinositide phosphatase. Our data demonstrate that ATP-depletion slowed IKs activation but had no short-term effect on PIP2 regeneration, suggesting that impaired PIP2-resynthesis cannot account for the rapid IKs inhibition by ATP-depletion. Furthermore, the second component of IKs inhibition by Ci-VSP was reduced by AMP-PCP in the pipette filling solution, indicating that direct binding of ATP to the KCNQ1/KCNE1 complex is required for voltage activation of IKs. We suggest that fluctuations of the cellular metabolic state regulate IKs in parallel with Gq-coupled PLC activation and PIP2-depletion.
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Wang Y, Eltit JM, Kaszala K, Tan A, Jiang M, Zhang M, Tseng GN, Huizar JF. Cellular mechanism of premature ventricular contraction-induced cardiomyopathy. Heart Rhythm 2014; 11:2064-72. [PMID: 25046857 PMCID: PMC4252777 DOI: 10.1016/j.hrthm.2014.07.022] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Indexed: 11/19/2022]
Abstract
BACKGROUND Frequent premature ventricular contractions (PVCs) are associated with increased risk of sudden cardiac death and can cause secondary cardiomyopathy. OBJECTIVE We sought to determine the mechanism(s) responsible for prolonged refractory period and left ventricular (LV) dysfunction demonstrated in our canine model of PVC-induced cardiomyopathy. METHODS Single myocytes were isolated from LV free wall of PVC and control canines and used for patch-clamp recording, intracellular Ca(2+) measurements, and immunocytochemistry/confocal microscopy. LV tissues adjacent to the area of myocyte isolation were used for the immunoblot quantification of protein expression. RESULTS In the PVC group, LV ejection fraction decreased from 57.6% ± 1.5% to 30.4% ± 3.1% after ≥4 months of ventricular bigeminy. Compared to control myocytes, PVC myocytes had decreased densities of both outward (transient outward current [Ito] and inward rectifier current [IK1]) and inward (L-type Ca current [ICaL]) currents, but no consistent changes in rapid or slow delayed rectifier currents. The reduction in Ito, IK1, and ICaL was accompanied by decreased protein levels of their channel subunits. The extent of reduction in Ito, IK1, and ICaL varied among PVC myocytes, creating marked heterogeneity in action potential configurations and durations. PVC myocytes showed impaired Ca-induced Ca release from the sarcoplasmic reticulum (SR), without increase in SR Ca leak or decrease in SR Ca store. This was accompanied by a decrease in dyad scaffolding protein, junctophilin-2, and loss of Cav1.2 registry with Ca-releasing channels (ryanodine receptor 2). CONCLUSION PVCs increase dispersion of action potential configuration/duration, a risk factor for sudden cardiac death, because of the heterogeneous reduction in Ito, IK1, and ICaL. The excitation-contraction coupling is impaired because of the decrease in ICaL and Cav1.2 misalignment with respect to ryanodine receptor 2.
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Affiliation(s)
- Yuhong Wang
- Department of Physiology and Biophysics, Virginia Commonwealth University
| | - Jose M Eltit
- Department of Physiology and Biophysics, Virginia Commonwealth University
| | - Karoly Kaszala
- Department of Physiology and Biophysics, Virginia Commonwealth University; McGuire VA Medical Center
| | - Alex Tan
- Department of Physiology and Biophysics, Virginia Commonwealth University; McGuire VA Medical Center
| | - Min Jiang
- Department of Physiology and Biophysics, Virginia Commonwealth University
| | - Mei Zhang
- Department of Physiology and Biophysics, Virginia Commonwealth University
| | - Gea-Ny Tseng
- Department of Physiology and Biophysics, Virginia Commonwealth University.
| | - Jose F Huizar
- Department of Physiology and Biophysics, Virginia Commonwealth University; McGuire VA Medical Center; Pauley Heart Center of Virginia Commonwealth University, Richmond, Virginia
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25
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KCNE2 modulates cardiac L-type Ca2+ channel. J Mol Cell Cardiol 2014; 72:208-18. [DOI: 10.1016/j.yjmcc.2014.03.013] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/22/2013] [Revised: 03/05/2014] [Accepted: 03/18/2014] [Indexed: 11/19/2022]
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