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Grogan A, Huang W, Brong A, Kane MA, Kontrogianni-Konstantopoulos A. Alterations in cytoskeletal and Ca 2+ cycling regulators in atria lacking the obscurin Ig58/59 module. Front Cardiovasc Med 2023; 10:1085840. [PMID: 37304957 PMCID: PMC10251194 DOI: 10.3389/fcvm.2023.1085840] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Accepted: 01/26/2023] [Indexed: 06/13/2023] Open
Abstract
Introduction Obscurin (720-870 kDa) is a giant cytoskeletal and signaling protein that possesses both structural and regulatory functions in striated muscles. Immunoglobulin domains 58/59 (Ig58/59) of obscurin bind to a diverse set of proteins that are essential for the proper structure and function of the heart, including giant titin, novex-3, and phospholamban (PLN). Importantly, the pathophysiological significance of the Ig58/59 module has been further underscored by the discovery of several mutations within Ig58/59 that are linked to various forms of myopathy in humans. We previously generated a constitutive deletion mouse model, Obscn-ΔIg58/59, that expresses obscurin lacking Ig58/59, and characterized the effects of this deletion on cardiac morphology and function through aging. Our findings demonstrated that Obscn-ΔIg58/59 male animals develop severe arrhythmia, primarily manifesting as episodes of junctional escape and spontaneous loss of regular p-waves, reminiscent of human atrial fibrillation, accompanied by significant atrial enlargement that progresses in severity with aging. Methods and Results To comprehensively characterize the molecular alterations responsible for these pathologies, we performed proteomic and phospho-proteomic analyses in aging Obscn-ΔIg58/59 atria. Our studies revealed extensive and novel alterations in the expression and phosphorylation profile of major cytoskeletal proteins, Ca2+ regulators, and Z-disk associated protein complexes in the Obscn-ΔIg58/59 atria through aging. Discussion These studies implicate obscurin, particularly the Ig58/59 module, as an essential regulator of the Z-disk associated cytoskeleton and Ca2+ cycling in the atria and provide new molecular insights into the development of atrial fibrillation and remodeling.
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Affiliation(s)
- Alyssa Grogan
- Department of Biochemistry and Molecular Biology, University of Maryland, Baltimore, MD, United States
| | - Weiliang Huang
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD, United States
| | - Annie Brong
- Department of Biochemistry and Molecular Biology, University of Maryland, Baltimore, MD, United States
| | - Maureen A. Kane
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD, United States
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Wang BX, Kane C, Nicastro L, King O, Kit-Anan W, Downing B, Deidda G, Couch LS, Pinali C, Mitraki A, MacLeod KT, Terracciano CM. Integrins Increase Sarcoplasmic Reticulum Activity for Excitation-Contraction Coupling in Human Stem Cell-Derived Cardiomyocytes. Int J Mol Sci 2022; 23:10940. [PMID: 36142853 PMCID: PMC9504605 DOI: 10.3390/ijms231810940] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Revised: 09/10/2022] [Accepted: 09/14/2022] [Indexed: 11/16/2022] Open
Abstract
Engagement of the sarcoplasmic reticulum (SR) Ca2+ stores for excitation-contraction (EC)-coupling is a fundamental feature of cardiac muscle cells. Extracellular matrix (ECM) proteins that form the extracellular scaffolding supporting cardiac contractile activity are thought to play an integral role in the modulation of EC-coupling. At baseline, human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) show poor utilisation of SR Ca2+ stores, leading to inefficient EC-coupling, like developing or human CMs in cardiac diseases such as heart failure. We hypothesised that integrin ligand-receptor interactions between ECM proteins and CMs recruit the SR to Ca2+ cycling during EC-coupling. hiPSC-CM monolayers were cultured on fibronectin-coated glass before 24 h treatment with fibril-forming peptides containing the integrin-binding tripeptide sequence arginine-glycine-aspartic acid (2 mM). Micropipette application of 40 mM caffeine in standard or Na+/Ca2+-free Tyrode's solutions was used to assess the Ca2+ removal mechanisms. Microelectrode recordings were conducted to analyse action potentials in current-clamp. Confocal images of labelled hiPSC-CMs were analysed to investigate hiPSC-CM morphology and ultrastructural arrangements in Ca2+ release units. This study demonstrates that peptides containing the integrin-binding sequence arginine-glycine-aspartic acid (1) abbreviate hiPSC-CM Ca2+ transient and action potential duration, (2) increase co-localisation between L-type Ca2+ channels and ryanodine receptors involved in EC-coupling, and (3) increase the rate of SR-mediated Ca2+ cycling. We conclude that integrin-binding peptides induce recruitment of the SR for Ca2+ cycling in EC-coupling through functional and structural improvements and demonstrate the importance of the ECM in modulating cardiomyocyte function in physiology.
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Affiliation(s)
- Brian X. Wang
- National Heart & Lung Institute, Imperial College London, London SW7 2AZ, UK
- Department of Metabolism, Digestion and Reproduction, Imperial College London, London SW7 2AZ, UK
| | - Christopher Kane
- National Heart & Lung Institute, Imperial College London, London SW7 2AZ, UK
| | - Laura Nicastro
- National Heart & Lung Institute, Imperial College London, London SW7 2AZ, UK
| | - Oisín King
- National Heart & Lung Institute, Imperial College London, London SW7 2AZ, UK
- Human Safety, Bayer Crop Science, 06903 Sophia-Antipolis, France
| | - Worrapong Kit-Anan
- National Heart & Lung Institute, Imperial College London, London SW7 2AZ, UK
| | - Barrett Downing
- National Heart & Lung Institute, Imperial College London, London SW7 2AZ, UK
| | - Graziano Deidda
- Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology−Hellas (FORTH), 700 13 Heraklion, Greece
- Department of Materials Science and Technology, University of Crete, 700 13 Heraklion, Greece
| | - Liam S. Couch
- National Heart & Lung Institute, Imperial College London, London SW7 2AZ, UK
| | - Christian Pinali
- Division of Cardiovascular Sciences, University of Manchester, Manchester M13 9NT, UK
| | - Anna Mitraki
- Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology−Hellas (FORTH), 700 13 Heraklion, Greece
- Department of Materials Science and Technology, University of Crete, 700 13 Heraklion, Greece
| | - Kenneth T. MacLeod
- National Heart & Lung Institute, Imperial College London, London SW7 2AZ, UK
| | - Cesare M. Terracciano
- National Heart & Lung Institute, Imperial College London, London SW7 2AZ, UK
- Laboratory of Myocardial Electrophysiology, 4th Floor, Imperial Centre for Translational and Experimental Medicine, Imperial College London, Du Cane Road, London W12 0NN, UK
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Martinez‐Hernandez E, Blatter LA, Kanaporis G. L-type Ca 2+ channel recovery from inactivation in rabbit atrial myocytes. Physiol Rep 2022; 10:e15222. [PMID: 35274829 PMCID: PMC8915713 DOI: 10.14814/phy2.15222] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Revised: 02/07/2022] [Accepted: 02/16/2022] [Indexed: 01/27/2023]
Abstract
Adaptation of the myocardium to varying workloads critically depends on the recovery from inactivation (RFI) of L-type Ca2+ channels (LCCs) which provide the trigger for cardiac contraction. The goal of the present study was a comprehensive investigation of LCC RFI in atrial myocytes. The study was performed on voltage-clamped rabbit atrial myocytes using a double pulse protocol with variable diastolic intervals in cells held at physiological holding potentials, with intact intracellular Ca2+ release, and preserved Na+ current and Na+ /Ca2+ exchanger (NCX) activity. We demonstrate that the kinetics of RFI of LCCs are co-regulated by several factors including resting membrane potential, [Ca2+ ]i , Na+ influx, and activity of CaMKII. In addition, activation of CaMKII resulted in increased ICa amplitude at higher pacing rates. Pharmacological inhibition of NCX failed to have any significant effect on RFI, indicating that impaired removal of Ca2+ by NCX has little effect on LCC recovery. Finally, RFI of intracellular Ca2+ release was substantially slower than LCC RFI, suggesting that inactivation kinetics of LCC do not significantly contribute to the beat-to-beat refractoriness of SR Ca2+ release. The study demonstrates that CaMKII and intracellular Ca2+ dynamics play a central role in modulation of LCC activity in atrial myocytes during increased workloads that could have important consequences under pathological conditions such as atrial fibrillations, where Ca2+ cycling and CaMKII activity are altered.
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Affiliation(s)
| | - Lothar A. Blatter
- Department of Physiology & BiophysicsRush University Medical CenterChicagoIllinoisUSA
| | - Giedrius Kanaporis
- Department of Physiology & BiophysicsRush University Medical CenterChicagoIllinoisUSA
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4
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Ernst P, Chen K, Tang Y, Kim S, Guan J, He J, Xie M, Zhang JJ, Liu XM, Zhou L. Investigation into the difference in mitochondrial-cytosolic calcium coupling between adult cardiomyocyte and hiPSC-CM using a novel multifunctional genetic probe. Pflugers Arch 2021; 473:447-459. [PMID: 33587181 PMCID: PMC8100988 DOI: 10.1007/s00424-021-02524-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 01/24/2021] [Accepted: 01/26/2021] [Indexed: 10/22/2022]
Abstract
Ca2+ cycling plays a critical role in regulating cardiomyocyte (CM) function under both physiological and pathological conditions. Mitochondria have been implicated in Ca2+ handling in adult cardiomyocytes (ACMs). However, little is known about their role in the regulation of Ca2+ dynamics in human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). In the present study, we developed a multifunctional genetically encoded Ca2+ probe capable of simultaneously measuring cytosolic and mitochondrial Ca2+ in real time. Using this novel probe, we determined and compared mitochondrial Ca2+ activity and the coupling with cytosolic Ca2+ dynamics in hiPSC-CMs and ACMs. Our data showed that while ACMs displayed a highly coordinated beat-by-beat response in mitochondrial Ca2+ in sync with cytosolic Ca2+, hiPSC-CMs showed high cell-wide variability in mitochondrial Ca2+ activity that is poorly coordinated with cytosolic Ca2+. We then revealed that mitochondrial-sarcoplasmic reticulum (SR) tethering, as well as the inter-mitochondrial network connection, is underdeveloped in hiPSC-CM compared to ACM, which may underlie the observed spatiotemporal decoupling between cytosolic and mitochondrial Ca2+ dynamics. Finally, we showed that knockdown of mitofusin-2 (Mfn2), a protein tethering mitochondria and SR, led to reduced cytosolic-mitochondrial Ca2+ coupling in ACMs, albeit to a lesser degree compared to hiPSC-CMs, suggesting that Mfn2 is a potential engineering target for improving mitochondrial-cytosolic Ca2+ coupling in hiPSC-CMs. Physiological relevance: The present study will advance our understanding of the role of mitochondria in Ca2+ handling and cycling in CMs, and guide the development of hiPSC-CMs for healing injured hearts.
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Affiliation(s)
- Patrick Ernst
- Department of Medicine, The University of Alabama at Birmingham, Birmingham, AL, 35294, USA
- Department of Biomedical Engineering, The University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Kai Chen
- Department of Medicine, The University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Yawen Tang
- Department of Biomedical Engineering, The University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Seulhee Kim
- Department of Medicine, The University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Jiashiung Guan
- Department of Medicine, The University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Jin He
- Department of Medicine, The University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Min Xie
- Department of Medicine, The University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Jianyi Jay Zhang
- Department of Biomedical Engineering, The University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Xiaoguang Margaret Liu
- Department of Biomedical Engineering, The University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Lufang Zhou
- Department of Medicine, The University of Alabama at Birmingham, Birmingham, AL, 35294, USA.
- Department of Biomedical Engineering, The University of Alabama at Birmingham, Birmingham, AL, 35294, USA.
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Kuo MW, Tsai HH, Wang SH, Chen YY, Yu AL, Yu J. Yulink, predicted from evolutionary analysis, is involved in cardiac function. J Biomed Sci 2021; 28:7. [PMID: 33423678 PMCID: PMC7798328 DOI: 10.1186/s12929-020-00701-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Accepted: 12/21/2020] [Indexed: 11/11/2022] Open
Abstract
Background The comparative evolutionary genomics analysis was used to study the functions of novel Ka/Ks-predicted human exons in a zebrafish model. The Yulink (MIOS, Entrez Gene: 54,468), a conserved gene from zebrafish to human with WD40 repeats at N-terminus, was identified and found to encode an 875 amino acid in human. The biological function of this Yulink gene in cardiomyocytes remains unexplored. The purpose of this study is to determine the involvement of Yulink in the functions of cardiomyocytes and to investigate its molecular regulatory mechanism. Methods Knockdown of Yulink was performed using morpholino or shRNA in zebrafish, mouse HL-1 cardiomyocytes, and human iPSC-derived cardiomyocytes. The expression levels of mRNA and protein were quantified by qPCR and western blots. Other methods including DNA binding, ligand uptake, agonists treatment and Ca2+ imaging assays were used to study the molecular regulatory mechanism by Yulink. Statistical data were shown as mean ± SD or mean ± standard error. Results The knockdown of yulink with three specific morpholinos in zebrafish resulted in cardiac dysfunctions with pericardial edema, decreased heart beats and cardiac output. The Yulink knockdown in mouse HL-1 cardiomyocytes disrupted Ca2+ cycling, reduced DNA binding activity of PPARγ (peroxisome proliferator-activated receptor gamma) and resulted in a reduction of Serca2 (sarcoplasmic reticulum Ca2+ ATPase 2) expression. Expression of Serca2 was up-regulated by PPARγ agonists and down-regulated by PPARγ-shRNA knockdown, suggesting that Yulink regulates SERCA2 expression through PPARγ in mouse HL-1 cardiomyocytes. On the other hand, YULINK, PPARγ or SERCA2 over-expression rescued the phenotypes of Yulink KD cells. In addition, knockdown of YULINK in human iPSC-derived cardiomyocytes also disrupted Ca2+ cycling via decreased SERCA2 expression. Conclusions Overall, our data showed that Yulink is an evolutionarily conserved gene from zebrafish to human. Mechanistically Yulink regulated Serca2 expression in cardiomyocytes, presumably mediated through PPARγ nuclear entry. Deficiency of Yulink in mouse and human cardiomyocytes resulted in irregular Ca2+ cycling, which may contribute to arrhythmogenesis.
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Affiliation(s)
- Ming-Wei Kuo
- Institute of Stem Cell and Translational Cancer Research, Chang Gung Memorial Hospital at Linkou, Taoyuan, 333, Taiwan
| | - Hsiu-Hui Tsai
- Institute of Stem Cell and Translational Cancer Research, Chang Gung Memorial Hospital at Linkou, Taoyuan, 333, Taiwan
| | - Sheng-Hung Wang
- Institute of Stem Cell and Translational Cancer Research, Chang Gung Memorial Hospital at Linkou, Taoyuan, 333, Taiwan
| | - Yi-Yin Chen
- Institute of Stem Cell and Translational Cancer Research, Chang Gung Memorial Hospital at Linkou, Taoyuan, 333, Taiwan
| | - Alice L Yu
- Institute of Stem Cell and Translational Cancer Research, Chang Gung Memorial Hospital at Linkou, Taoyuan, 333, Taiwan.,Department of Pediatrics, University of California, San Diego, CA, USA
| | - John Yu
- Institute of Stem Cell and Translational Cancer Research, Chang Gung Memorial Hospital at Linkou, Taoyuan, 333, Taiwan. .,Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan.
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6
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Grogan A, Coleman A, Joca H, Granzier H, Russel MW, Ward CW, Kontrogianni-Konstantopoulos A. Deletion of obscurin immunoglobulin domains Ig58/59 leads to age-dependent cardiac remodeling and arrhythmia. Basic Res Cardiol 2020; 115:60. [PMID: 32910221 PMCID: PMC9302192 DOI: 10.1007/s00395-020-00818-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Accepted: 08/06/2020] [Indexed: 12/23/2022]
Abstract
Obscurin comprises a family of giant modular proteins that play key structural and regulatory roles in striated muscles. Immunoglobulin domains 58/59 (Ig58/59) of obscurin mediate binding to essential modulators of muscle structure and function, including canonical titin, a smaller splice variant of titin, termed novex-3, and phospholamban (PLN). Importantly, missense mutations localized within the obscurin-Ig58/59 region that affect binding to titins and/or PLN have been linked to the development of myopathy in humans. To elucidate the pathophysiological role of this region, we generated a constitutive deletion mouse model, Obscn-ΔIg58/59, that expresses obscurin lacking Ig58/59, and determined the consequences of this manipulation on cardiac morphology and function under conditions of acute stress and through the physiological process of aging. Our studies show that young Obscn-ΔIg58/59 mice are susceptible to acute β-adrenergic stress. Moreover, sedentary Obscn-ΔIg58/59 mice develop left ventricular hypertrophy that progresses to dilation, contractile impairment, atrial enlargement, and arrhythmia as a function of aging with males being more affected than females. Experiments in ventricular cardiomyocytes revealed altered Ca2+ cycling associated with changes in the expression and/or phosphorylation levels of major Ca2+ cycling proteins, including PLN, SERCA2, and RyR2. Taken together, our work demonstrates that obscurin-Ig58/59 is an essential regulatory module in the heart and its deletion leads to age- and sex-dependent cardiac remodeling, ventricular dilation, and arrhythmia due to deregulated Ca2+ cycling.
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MESH Headings
- Action Potentials
- Age Factors
- Animals
- Arrhythmias, Cardiac/enzymology
- Arrhythmias, Cardiac/genetics
- Arrhythmias, Cardiac/pathology
- Arrhythmias, Cardiac/physiopathology
- Calcium Signaling
- Calcium-Binding Proteins/metabolism
- Female
- Gene Deletion
- Heart Rate
- Hypertrophy, Left Ventricular/enzymology
- Hypertrophy, Left Ventricular/genetics
- Hypertrophy, Left Ventricular/pathology
- Hypertrophy, Left Ventricular/physiopathology
- Immunoglobulin Domains
- Male
- Mice, Inbred C57BL
- Mice, Knockout
- Myocytes, Cardiac/enzymology
- Myocytes, Cardiac/pathology
- Phosphorylation
- Protein Serine-Threonine Kinases/deficiency
- Protein Serine-Threonine Kinases/genetics
- Rho Guanine Nucleotide Exchange Factors/deficiency
- Rho Guanine Nucleotide Exchange Factors/genetics
- Ryanodine Receptor Calcium Release Channel/metabolism
- Sarcoplasmic Reticulum Calcium-Transporting ATPases/metabolism
- Sedentary Behavior
- Sex Factors
- Ventricular Dysfunction, Left/enzymology
- Ventricular Dysfunction, Left/genetics
- Ventricular Dysfunction, Left/pathology
- Ventricular Dysfunction, Left/physiopathology
- Ventricular Function, Left
- Ventricular Remodeling
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Affiliation(s)
- Alyssa Grogan
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD, 21201, USA
| | - Andrew Coleman
- Department of Orthopedics, University of Maryland School of Medicine, Baltimore, MD, 21201, USA
| | - Humberto Joca
- Department of Orthopedics, University of Maryland School of Medicine, Baltimore, MD, 21201, USA
| | - Henk Granzier
- Department of Physiology, University of Arizona College of Medicine, Tucson, AZ, 85724, USA
| | - Mark W Russel
- Department of Pediatrics and Communicable Diseases, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
| | - Christopher W Ward
- Department of Orthopedics, University of Maryland School of Medicine, Baltimore, MD, 21201, USA
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Hu LYR, Kontrogianni-Konstantopoulos A. Proteomic Analysis of Myocardia Containing the Obscurin R4344Q Mutation Linked to Hypertrophic Cardiomyopathy. Front Physiol 2020; 11:478. [PMID: 32528308 PMCID: PMC7247546 DOI: 10.3389/fphys.2020.00478] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Accepted: 04/20/2020] [Indexed: 12/25/2022] Open
Abstract
Obscurin is a giant cytoskeletal protein with structural and regulatory roles encoded by the OBSCN gene. Recently, mutations in OBSCN were associated with the development of different forms of cardiomyopathies, including hypertrophic cardiomyopathy (HCM). We previously reported that homozygous mice carrying the HCM-linked R4344Q obscurin mutation develop arrhythmia by 1-year of age under sedentary conditions characterized by increased heart rate, frequent incidents of premature ventricular contractions, and episodes of spontaneous ventricular tachycardia. In an effort to delineate the molecular mechanisms that contribute to the observed arrhythmic phenotype, we subjected protein lysates prepared from left ventricles of 1-year old R4344Q and wild-type mice to comparative proteomics analysis using tandem mass spectrometry; raw data are available via ProteomeXchange with identifier PXD017314. We found that the expression levels of proteins involved in cardiac function and disease, cytoskeletal organization, electropotential regulation, molecular transport and metabolism were significantly altered. Moreover, phospho-proteomic evaluation revealed changes in the phosphorylation profile of Ca2+ cycling proteins, including sAnk1.5, a major binding partner of obscurin localized in the sarcoplasmic reticulum; notably, this is the first report indicating that sAnk1 undergoes phosphorylation. Taken together, our findings implicate obscurin in diverse cellular processes within the myocardium, which is consistent with its multiple binding partners, localization in different subcellular compartments, and disease association.
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Affiliation(s)
- Li-Yen R Hu
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD, United States
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8
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Abstract
Endotherms defend their body temperature in the cold by employing shivering (ST) and/or non-shivering thermogenesis (NST). Although NST is well documented in mammals, its importance to avian heat generation is unclear. Recent work points to a prominent role for the sarco/endoplasmic reticulum Ca2+ ATPase (SERCA) in muscular NST. SERCA's involvement in both ST and NST, however, posits a tradeoff between these two heat-generating mechanisms. To explore this tradeoff, we assayed pectoralis gene expression of adult songbirds exposed to chronic temperature acclimations. Counter to mammal models, we found that cold-acclimated birds downregulated the expression of sarcolipin (SLN), a gene coding for a peptide that promotes heat generation by uncoupling SERCA Ca2+ transport from ATP hydrolysis, indicating a reduced potential for muscular NST. We also found differential expression of many genes involved in Ca2+ cycling and muscle contraction and propose that decreased SLN could promote increased pectoralis contractility for ST. Moreover, SLN transcript abundance negatively correlated with peak oxygen consumption under cold exposure (a proxy for ST) across individuals, and higher SLN transcript abundance escalated an individual's risk of hypothermia in acute cold. Our results therefore suggest that SLN-mediated NST may not be an important mechanism of-and could be a hindrance to-avian thermoregulation in extreme cold.
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Affiliation(s)
- Maria Stager
- Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA
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Fischer TH, Eiringhaus J, Dybkova N, Saadatmand A, Pabel S, Weber S, Wang Y, Köhn M, Tirilomis T, Ljubojevic S, Renner A, Gummert J, Maier LS, Hasenfuß G, El-Armouche A, Sossalla S. Activation of protein phosphatase 1 by a selective phosphatase disrupting peptide reduces sarcoplasmic reticulum Ca 2+ leak in human heart failure. Eur J Heart Fail 2018; 20:1673-1685. [PMID: 30191648 DOI: 10.1002/ejhf.1297] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Revised: 07/11/2018] [Accepted: 07/14/2018] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND Disruption of Ca2+ homeostasis is a key pathomechanism in heart failure. CaMKII-dependent hyperphosphorylation of ryanodine receptors in the sarcoplasmic reticulum (SR) increases the arrhythmogenic SR Ca2+ leak and depletes SR Ca2+ stores. The contribution of conversely acting serine/threonine phosphatases [protein phosphatase 1 (PP1) and 2A (PP2A)] is largely unknown. METHODS AND RESULTS Human myocardium from three groups of patients was investigated: (i) healthy controls (non-failing, NF, n = 8), (ii) compensated hypertrophy (Hy, n = 16), and (iii) end-stage heart failure (HF, n = 52). Expression of PP1 was unchanged in Hy but greater in HF compared to NF while its endogenous inhibitor-1 (I-1) was markedly lower expressed in both compared to NF, suggesting increased total PP1 activity. In contrast, PP2A expression was lower in Hy and HF compared to NF. Ca2+ homeostasis was severely disturbed in HF compared to Hy signified by a higher SR Ca2+ leak, lower systolic Ca2+ transients as well as a decreased SR Ca2+ load. Inhibition of PP1/PP2A by okadaic acid increased SR Ca2+ load and systolic Ca2+ transients but severely aggravated diastolic SR Ca2+ leak and cellular arrhythmias in Hy. Conversely, selective activation of PP1 by a PP1-disrupting peptide (PDP3) in HF potently reduced SR Ca2+ leak as well as cellular arrhythmias and, importantly, did not compromise systolic Ca2+ release and SR Ca2+ load. CONCLUSION This study is the first to functionally investigate the role of PP1/PP2A for Ca2+ homeostasis in diseased human myocardium. Our data indicate that a modulation of phosphatase activity potently impacts Ca2+ cycling properties. An activation of PP1 counteracts increased kinase activity in heart failure and successfully seals the arrhythmogenic SR Ca2+ leak. It may thus represent a promising future antiarrhythmic therapeutic approach.
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Affiliation(s)
- Thomas H Fischer
- Klinik für Kardiologie und Pneumologie, Georg-August-Universität Göttingen, Germany.,Medizinische Klinik II, Kardiologie, Angiologie, Pneumologie, Klinikum Coburg, Germany.,Deutsches Zentrum für Herz-Kreislauf Forschung (DZHK), Standort Göttingen, Germany
| | - Jörg Eiringhaus
- Klinik für Kardiologie und Pneumologie, Georg-August-Universität Göttingen, Germany.,Deutsches Zentrum für Herz-Kreislauf Forschung (DZHK), Standort Göttingen, Germany
| | - Nataliya Dybkova
- Klinik für Kardiologie und Pneumologie, Georg-August-Universität Göttingen, Germany.,Deutsches Zentrum für Herz-Kreislauf Forschung (DZHK), Standort Göttingen, Germany
| | - Alireza Saadatmand
- Abt. Molekulare Kardiologie und Epigenetik, Universitätsklinikum Heidelberg, Germany
| | - Steffen Pabel
- Deutsches Zentrum für Herz-Kreislauf Forschung (DZHK), Standort Göttingen, Germany.,Klinik und Poliklinik für Innere Medizin II, Universitätsklinikum Regensburg, Germany
| | - Silvio Weber
- Institut für Pharmakologie, Technische Universität Dresden, Germany
| | - Yansong Wang
- European Molecular Biology Laboratory, Genome Biology Unit, Heidelberg, Germany
| | - Maja Köhn
- European Molecular Biology Laboratory, Genome Biology Unit, Heidelberg, Germany.,Centre for Biological Signalling Studies (BIOSS) and Faculty of Biology, University of Freiburg, Germany
| | - Theodor Tirilomis
- Klinik für Thorax-, Herz-, Gefäßchirurgie, Georg-August-Universität Göttingen, Germany
| | - Senka Ljubojevic
- Abteilung für Kardiologie, Medizinische Universität Graz, Austria
| | - André Renner
- Abteilung für Herz- und Transplantationschirurgie, Herz- und Diabeteszentrum, Bad Oeynhausen, Germany
| | - Jan Gummert
- Abteilung für Herz- und Transplantationschirurgie, Herz- und Diabeteszentrum, Bad Oeynhausen, Germany
| | - Lars S Maier
- Klinik und Poliklinik für Innere Medizin II, Universitätsklinikum Regensburg, Germany
| | - Gerd Hasenfuß
- Klinik für Kardiologie und Pneumologie, Georg-August-Universität Göttingen, Germany.,Deutsches Zentrum für Herz-Kreislauf Forschung (DZHK), Standort Göttingen, Germany
| | - Ali El-Armouche
- Institut für Pharmakologie, Technische Universität Dresden, Germany
| | - Samuel Sossalla
- Klinik für Kardiologie und Pneumologie, Georg-August-Universität Göttingen, Germany.,Deutsches Zentrum für Herz-Kreislauf Forschung (DZHK), Standort Göttingen, Germany.,Klinik und Poliklinik für Innere Medizin II, Universitätsklinikum Regensburg, Germany
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10
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Bögeholz N, Schulte JS, Kaese S, Bauer BK, Pauls P, Dechering DG, Frommeyer G, Goldhaber JI, Kirchhefer U, Eckardt L, Pott C, Müller FU. The Effects of SEA0400 on Ca 2+ Transient Amplitude and Proarrhythmia Depend on the Na +/Ca 2+ Exchanger Expression Level in Murine Models. Front Pharmacol 2017; 8:649. [PMID: 28983248 PMCID: PMC5613119 DOI: 10.3389/fphar.2017.00649] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Accepted: 09/01/2017] [Indexed: 11/13/2022] Open
Abstract
Background/Objective: The cardiac Na+/Ca2+ exchanger (NCX) has been identified as a promising target to counter arrhythmia in previous studies investigating the benefit of NCX inhibition. However, the consequences of NCX inhibition have not been investigated in the setting of altered NCX expression and function, which is essential, since major cardiac diseases (heart failure/atrial fibrillation) exhibit NCX upregulation. Thus, we here investigated the effects of the NCX inhibitor SEA0400 on the Ca2+ transient amplitude and on proarrhythmia in homozygous NCX overexpressor (OE) and heterozygous NCX knockout (hetKO) mice compared to corresponding wild-types (WTOE/WThetKO). Methods/Results: Ca2+ transients of field-stimulated isolated ventricular cardiomyocytes were recorded with fluo-4-AM or indo-1-AM. SEA0400 (1 μM) significantly reduced NCX forward mode function in all mouse lines. SEA0400 (1 μM) significantly increased the amplitude of field-stimulated Ca2+ transients in WTOE, WThetKO, and hetKO, but not in OE (% of basal; OE = 98.7 ± 5.0; WTOE = 137.8 ± 5.2*; WThetKO = 126.3 ± 6.0*; hetKO = 140.6 ± 12.8*; *p < 0.05 vs. basal). SEA0400 (1 μM) significantly reduced the number of proarrhythmic spontaneous Ca2+ transients (sCR) in OE, but increased it in WTOE, WThetKO and hetKO (sCR per cell; basal/+SEA0400; OE = 12.5/3.7; WTOE = 0.2/2.4; WThetKO = 1.3/8.8; hetKO = 0.2/5.5) and induced Ca2+ overload with subsequent cell death in hetKO. Conclusion: The effects of SEA0400 on Ca2+ transient amplitude and the occurrence of spontaneous Ca2+ transients as a proxy measure for inotropy and cellular proarrhythmia depend on the NCX expression level. The antiarrhythmic effect of SEA0400 in conditions of increased NCX expression promotes the therapeutic concept of NCX inhibition in heart failure/atrial fibrillation. Conversely, in conditions of reduced NCX expression, SEA0400 suppressed the NCX function below a critical level leading to adverse Ca2+ accumulation as reflected by an increase in Ca2+ transient amplitude, proarrhythmia and cell death. Thus, the remaining NCX function under inhibition may be a critical factor determining the inotropic and antiarrhythmic efficacy of SEA0400.
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Affiliation(s)
- Nils Bögeholz
- Division of Electrophysiology, Department of Cardiovascular Medicine, University Hospital MünsterMünster, Germany
| | - Jan S Schulte
- Institute of Pharmacology and Toxicology, University of MünsterMünster, Germany
| | - Sven Kaese
- Division of Electrophysiology, Department of Cardiovascular Medicine, University Hospital MünsterMünster, Germany
| | - B Klemens Bauer
- Division of Electrophysiology, Department of Cardiovascular Medicine, University Hospital MünsterMünster, Germany.,Institute of Pharmacology and Toxicology, University of MünsterMünster, Germany
| | - Paul Pauls
- Division of Electrophysiology, Department of Cardiovascular Medicine, University Hospital MünsterMünster, Germany.,Institute of Pharmacology and Toxicology, University of MünsterMünster, Germany
| | - Dirk G Dechering
- Division of Electrophysiology, Department of Cardiovascular Medicine, University Hospital MünsterMünster, Germany
| | - Gerrit Frommeyer
- Division of Electrophysiology, Department of Cardiovascular Medicine, University Hospital MünsterMünster, Germany
| | - Joshua I Goldhaber
- Cedars-Sinai Medical Center, Heart InstituteLos Angeles, CA, United States
| | - Uwe Kirchhefer
- Institute of Pharmacology and Toxicology, University of MünsterMünster, Germany
| | - Lars Eckardt
- Division of Electrophysiology, Department of Cardiovascular Medicine, University Hospital MünsterMünster, Germany
| | - Christian Pott
- Division of Electrophysiology, Department of Cardiovascular Medicine, University Hospital MünsterMünster, Germany
| | - Frank U Müller
- Institute of Pharmacology and Toxicology, University of MünsterMünster, Germany
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11
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Behar J, Yaniv Y. Dynamics of PKA phosphorylation and gain of function in cardiac pacemaker cells: a computational model analysis. Am J Physiol Heart Circ Physiol 2016; 310:H1259-66. [PMID: 26945074 DOI: 10.1152/ajpheart.00076.2016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Accepted: 03/02/2016] [Indexed: 11/22/2022]
Abstract
Cardiac pacemaker cell function is regulated by a coupled-clock system that integrates molecular cues on the cell-membrane surface (i.e., membrane clock) and on the sarcoplasmic reticulum (SR) (i.e., Ca(2+) clock). A recent study has shown that cotransfection of spontaneous beating cells (HEK293 cells and neonatal rat myocytes) with R524Q-mutant human hyperpolarization-activated cyclic nucleotide-gated molecules (the dominant component of funny channels) increases the funny channel's sensitivity to cAMP and leads to a decrease in spontaneous action potential (AP) cycle length (i.e., tachycardia). We hypothesize that in rabbit pacemaker cells, the same behavior is expected, and because of the coupled-clock system, the resultant steady-state decrease in AP cycle length will embody contributions from both clocks: the initial decrease in the spontaneous AP beating interval, arising from increased sensitivity of the f-channel to cAMP, will be accompanied by an increase in the adenylyl cyclase (AC)-cAMP-PKA-dependent phosphorylation activity, which will further decrease this interval. To test our hypothesis, we used the recently developed Yaniv-Lakatta pacemaker cell numerical model. This model predicts the cAMP signaling dynamics, as well as the kinetics and magnitude of protein phosphorylation in both normal and mutant pacemaker cells. We found that R524Q-mutant pacemaker cells have a shorter AP firing rate than that of wild-type cells and that gain in pacemaker function is the net effect of the R514Q mutation on the functioning of the coupled-clock system. Specifically, our results directly support the hypothesis that changes in Ca(2+)-activated AC-cAMP-PKA signaling are involved in the development of tachycardia in R524Q-mutant pacemaker cells.
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Affiliation(s)
- Joachim Behar
- Laboratory of Bioenergetic and Bioelectric Systems, Biomedical Engineering Faculty, Technion-IIT, Haifa, Israel
| | - Yael Yaniv
- Laboratory of Bioenergetic and Bioelectric Systems, Biomedical Engineering Faculty, Technion-IIT, Haifa, Israel
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