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Gregorich ZR, Yanghai Z, Kamp TJ, Granzier H, Guo W. Mechanisms of RBM20 Cardiomyopathy: Insights From Model Systems. CIRCULATION. GENOMIC AND PRECISION MEDICINE 2024; 17:e004355. [PMID: 38288598 PMCID: PMC10923161 DOI: 10.1161/circgen.123.004355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2024]
Abstract
RBM20 (RNA-binding motif protein 20) is a vertebrate- and muscle-specific RNA-binding protein that belongs to the serine-arginine-rich family of splicing factors. The RBM20 gene was first identified as a dilated cardiomyopathy-linked gene over a decade ago. Early studies in Rbm20 knockout rodents implicated disrupted splicing of RBM20 target genes as a causative mechanism. Clinical studies show that pathogenic variants in RBM20 are linked to aggressive dilated cardiomyopathy with early onset heart failure and high mortality. Subsequent studies employing pathogenic variant knock-in animal models revealed that variants in a specific portion of the arginine-serine-rich domain in RBM20 not only disrupt splicing but also hinder nucleocytoplasmic transport and lead to the formation of RBM20 biomolecular condensates in the sarcoplasm. Conversely, mice harboring a disease-associated variant in the RRM (RNA recognition motif) do not show evidence of adverse remodeling or exhibit sudden death despite disrupted splicing of RBM20 target genes. Thus, whether disrupted splicing, biomolecular condensates, or both contribute to dilated cardiomyopathy is under debate. Beyond this, additional questions remain, such as whether there is sexual dimorphism in the presentation of RBM20 cardiomyopathy. What are the clinical features of RBM20 cardiomyopathy and why do some individuals develop more severe disease than others? In this review, we summarize the reported observations and discuss potential mechanisms of RBM20 cardiomyopathy derived from studies employing in vivo animal models and in vitro human-induced pluripotent stem cell-derived cardiomyocytes. Potential therapeutic strategies to treat RBM20 cardiomyopathy are also discussed.
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Affiliation(s)
- Zachery R. Gregorich
- Department of Animal and Dairy Sciences, University of Wisconsin-Madison, Madison, WI
| | - Zhang Yanghai
- Department of Animal and Dairy Sciences, University of Wisconsin-Madison, Madison, WI
| | - Timothy J. Kamp
- Cellular and Molecular Arrhythmia Research Program, University of Wisconsin-Madison, Madison, WI
- Department of Medicine, University of Wisconsin-Madison, Madison, WI
- Cardiovascular Research Center, University of Wisconsin-Madison, Madison, WI
| | - Henk Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ
| | - Wei Guo
- Department of Animal and Dairy Sciences, University of Wisconsin-Madison, Madison, WI
- Cardiovascular Research Center, University of Wisconsin-Madison, Madison, WI
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2
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Linke WA. Stretching the story of titin and muscle function. J Biomech 2023; 152:111553. [PMID: 36989971 DOI: 10.1016/j.jbiomech.2023.111553] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Accepted: 03/14/2023] [Indexed: 03/29/2023]
Abstract
The discovery of the giant protein titin, also known as connectin, dates almost half a century back. In this review, I recapitulate major advances in the discovery of the titin filaments and the recognition of their properties and function until today. I briefly discuss how our understanding of the layout and interactions of titin in muscle sarcomeres has evolved and review key facts about the titin sequence at the gene (TTN) and protein levels. I also touch upon properties of titin important for the stability of the contractile units and the assembly and maintenance of sarcomeric proteins. The greater part of my discussion centers around the mechanical function of titin in skeletal muscle. I cover milestones of research on titin's role in stretch-dependent passive tension development, recollect the reasons behind the enormous elastic diversity of titin, and provide an update on the molecular mechanisms of titin elasticity, details of which are emerging even now. I reflect on current knowledge of how muscle fibers behave mechanically if titin stiffness is removed and how titin stiffness can be dynamically regulated, such as by posttranslational modifications or calcium binding. Finally, I highlight novel and exciting, but still controversially discussed, insight into the role titin plays in active tension development, such as length-dependent activation and contraction from longer muscle lengths.
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Affiliation(s)
- Wolfgang A Linke
- Institute of Physiology II, University of Münster, Germany; Clinic for Cardiology and Pneumology, University Medical Center Göttingen, Germany; German Centre for Cardiovascular Research, Berlin, Germany.
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3
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Han SW, Boldt K, Joumaa V, Herzog W. Characterizing residual and passive force enhancements in cardiac myofibrils. Biophys J 2023; 122:1538-1547. [PMID: 36932677 PMCID: PMC10147830 DOI: 10.1016/j.bpj.2023.03.022] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2022] [Revised: 11/07/2022] [Accepted: 03/14/2023] [Indexed: 03/19/2023] Open
Abstract
Residual force enhancement (RFE), an increase in isometric force after active stretching of a muscle compared with the purely isometric force at the corresponding length, has been consistently observed throughout the structural hierarchy of skeletal muscle. Similar to RFE, passive force enhancement (PFE) is also observable in skeletal muscle and is defined as an increase in passive force when a muscle is deactivated after it has been actively stretched compared with the passive force following deactivation of a purely isometric contraction. These history-dependent properties have been investigated abundantly in skeletal muscle, but their presence in cardiac muscle remains unresolved and controversial. The purpose of this study was to investigate whether RFE and PFE exist in cardiac myofibrils and whether the magnitudes of RFE and PFE increase with increasing stretch magnitudes. Cardiac myofibrils were prepared from the left ventricles of New Zealand White rabbits, and the history-dependent properties were tested at three different final average sarcomere lengths (n = 8 for each), 1.8, 2, and 2.2 μm, while the stretch magnitude was kept at 0.2 μm/sarcomere. The same experiment was repeated with a final average sarcomere length of 2.2 μm and a stretching magnitude of 0.4 μm/sarcomere (n = 8). All 32 cardiac myofibrils exhibited increased forces after active stretching compared with the corresponding purely isometric reference conditions (p < 0.05). Furthermore, the magnitude of RFE was greater when myofibrils were stretched by 0.4 compared with 0.2 μm/sarcomere (p < 0.05). We conclude that, like in skeletal muscle, RFE and PFE are properties of cardiac myofibrils and are dependent on stretch magnitude.
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Affiliation(s)
- Seong-Won Han
- Institute of Physiology II, Faculty of Medicine, University of Münster, Münster, Germany; Faculty of Kinesiology, University of Calgary, Calgary, Canada.
| | - Kevin Boldt
- Faculty of Kinesiology, University of Calgary, Calgary, Canada; Kinesiology Program, Trent University, Peterborough, ON, Canada; Department of Human Health and Nutritional Science, University of Guelph, Guelph, ON, Canada
| | - Venus Joumaa
- Faculty of Kinesiology, University of Calgary, Calgary, Canada
| | - Walter Herzog
- Faculty of Kinesiology, University of Calgary, Calgary, Canada
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4
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Tanner BCW, Awinda PO, Agonias KB, Attili S, Blair CA, Thompson MS, Walker LA, Kampourakis T, Campbell KS. Sarcomere length affects Ca2+ sensitivity of contraction in ischemic but not non-ischemic myocardium. J Gen Physiol 2023; 155:213800. [PMID: 36633584 PMCID: PMC9859763 DOI: 10.1085/jgp.202213200] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Revised: 11/18/2022] [Accepted: 12/22/2022] [Indexed: 01/13/2023] Open
Abstract
In healthy hearts, myofilaments become more sensitive to Ca2+ as the myocardium is stretched. This effect is known as length-dependent activation and is an important cellular-level component of the Frank-Starling mechanism. Few studies have measured length-dependent activation in the myocardium from failing human hearts. We investigated whether ischemic and non-ischemic heart failure results in different length-dependent activation responses at physiological temperature (37°C). Myocardial strips from the left ventricular free wall were chemically permeabilized and Ca2+-activated at sarcomere lengths (SLs) of 1.9 and 2.3 µm. Data were acquired from 12 hearts that were explanted from patients receiving cardiac transplants; 6 had ischemic heart failure and 6 had non-ischemic heart failure. Another 6 hearts were obtained from organ donors. Maximal Ca2+-activated force increased at longer SL for all groups. Ca2+ sensitivity increased with SL in samples from donors (P < 0.001) and patients with ischemic heart failure (P = 0.003) but did not change with SL in samples from patients with non-ischemic heart failure. Compared with donors, troponin I phosphorylation decreased in ischemic samples and even more so in non-ischemic samples; cardiac myosin binding protein-C (cMyBP-C) phosphorylation also decreased with heart failure. These findings support the idea that troponin I and cMyBP-C phosphorylation promote length-dependent activation and show that length-dependent activation of contraction is blunted, yet extant, in the myocardium from patients with ischemic heart failure and further reduced in the myocardium from patients with non-ischemic heart failure. Patients who have a non-ischemic disease may exhibit a diminished contractile response to increased ventricular filling.
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Affiliation(s)
- Bertrand C W Tanner
- Department of Integrative Physiology and Neuroscience, Washington State University , Pullman, WA, USA
| | - Peter O Awinda
- Department of Integrative Physiology and Neuroscience, Washington State University , Pullman, WA, USA
| | - Keinan B Agonias
- Department of Integrative Physiology and Neuroscience, Washington State University , Pullman, WA, USA
| | - Seetharamaiah Attili
- Randall Centre for Cell and Molecular Biophysics, King's College London , London, UK
| | - Cheavar A Blair
- Department of Physiology, University of Kentucky , Lexington, KY, USA
| | - Mindy S Thompson
- Department of Physiology, University of Kentucky , Lexington, KY, USA
| | - Lori A Walker
- Division of Cardiology, Department of Medicine, University of Colorado Anschutz Medical Campus , Aurora, CO, USA
| | - Thomas Kampourakis
- Randall Centre for Cell and Molecular Biophysics, King's College London , London, UK
| | - Kenneth S Campbell
- Department of Physiology, University of Kentucky , Lexington, KY, USA.,Division of Cardiovascular Medicine, University of Kentucky , Lexington, KY, USA
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5
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Hu H, Geng Z, Zhang S, Xu Y, Wang Q, Chen S, Zhang B, Sun K, Lu Y. Rare copy number variation analysis identifies disease-related variants in atrioventricular septal defect patients. Front Genet 2023; 14:1075349. [PMID: 36816019 PMCID: PMC9936062 DOI: 10.3389/fgene.2023.1075349] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Accepted: 01/25/2023] [Indexed: 02/05/2023] Open
Abstract
Atrioventricular septal defect (AVSD) is a deleterious subtype of congenital heart diseases (CHD) characterized by atrioventricular canal defect. The pathogenic genetic changes of AVSD remain elusive, particularly for copy number variation (CNV), a large segment variation of the genome, which is one of the major forms of genetic variants resulting in congenital heart diseases. In the present study, we recruited 150 AVSD cases and 100 healthy subjects as controls for whole exome sequencing (WES). We identified total 4255 rare CNVs using exon Hidden Markov model (XHMM) and screened rare CNVs by eliminating common CNVs based on controls and Database of Genomic Variants (DGV). Each patient contained at least 9 CNVs, and the CNV burden was prominently presented in chromosomes 19,22,21&16. Small CNVs (<500 kb) were frequently observed. By leveraging gene-based burden test, we further identified 20 candidate AVSD-risk genes. Among them, DYRK1A, OBSCN and TTN were presented in the core disease network of CHD and highly and dynamically expressed in the heart during the development, which indicated they possessed the high potency to be AVSD-susceptible genes. These findings not only provided a roadmap for finally unveiling the genetic cause of AVSD, but also provided more resources and proofs for clinical genetics.
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Affiliation(s)
- Huan Hu
- Department of Pediatric Cardiology, Xin Hua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Zilong Geng
- Key Laboratory of Systems Biomedicine, Shanghai Center for Systems Biomedicine, Shanghai Jiao Tong University, Shanghai, China
| | - Shasha Zhang
- Key Laboratory of Systems Biomedicine, Shanghai Center for Systems Biomedicine, Shanghai Jiao Tong University, Shanghai, China
| | - Yuejuan Xu
- Department of Pediatric Cardiology, Xin Hua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Qingjie Wang
- Department of Pediatric Cardiology, Xin Hua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Sun Chen
- Department of Pediatric Cardiology, Xin Hua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Bing Zhang
- Key Laboratory of Systems Biomedicine, Shanghai Center for Systems Biomedicine, Shanghai Jiao Tong University, Shanghai, China,*Correspondence: Bing Zhang, ; Kun Sun, ; Yanan Lu,
| | - Kun Sun
- Department of Pediatric Cardiology, Xin Hua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China,*Correspondence: Bing Zhang, ; Kun Sun, ; Yanan Lu,
| | - Yanan Lu
- Department of Pediatric Cardiology, Xin Hua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China,*Correspondence: Bing Zhang, ; Kun Sun, ; Yanan Lu,
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6
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Zheng Y, Chan WX, Charles CJ, Richards AM, Lee LC, Leo HL, Yap CH. Morphological, functional, and biomechanical progression of LV remodelling in a porcine model of HFpEF. J Biomech 2022; 144:111348. [DOI: 10.1016/j.jbiomech.2022.111348] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Revised: 08/24/2022] [Accepted: 10/03/2022] [Indexed: 10/31/2022]
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7
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Contini M, Altman D, Cornachione A, Rassier DE, Bagni MA. An increase in force after stretch of diaphragm fibers and myofibrils is accompanied by an increase in sarcomere length non-uniformities and Ca 2+ sensitivity. Am J Physiol Cell Physiol 2022; 323:C14-C28. [PMID: 35613356 DOI: 10.1152/ajpcell.00394.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
When muscle fibers from limb muscles are stretched while activated, the force increases to a steady-state level that is higher than that produced during isometric contractions at a corresponding sarcomere length, a phenomenon known as residual force enhancement (RFE). The mechanisms responsible for the RFE are an increased stiffness of titin molecules which may lead to an increased Ca2+ sensitivity of the contractile apparatus,and the development of sarcomere length non-uniformities. RFE is not observed in cardiac muscles, which makes this phenomenon specific to certain preparations. The aim of this study was to investigate if the RFE is present in the diaphragm, and its potential association with an increased Ca2+ sensitivity and the development of sarcomere length non-uniformities. We used two preparations: single intact fibers and myofibrils isolated from the diaphragm from mice. We investigated RFE in a variety of lengths across the force-length relationship. RFE was observed in both preparations at all lengths investigated, and was larger with increasing magnitudes of stretch. RFE was accompanied by an increased Ca2+ sensitivity as shown by a change in the force-pCa2+-curve, and increased sarcomere length non-uniformities. Therefore, RFE is a phenomenon commonly observed in skeletal muscles, with mechanisms that are similar across preparations.
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Affiliation(s)
- Massimo Contini
- Department of Experimental and Clinical Medicine, University of Florence, Italy
| | - David Altman
- Department of Physics, Willamette University, Salem, OR, United States
| | - Anabelle Cornachione
- Department of Physiological Sciences, Federal University of São Carlos, São Paulo, Brazil
| | | | - Maria Angela Bagni
- Department of Experimental and Clinical Medicine, University of Florence, Italy
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8
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Lin YH, Major JL, Liebner T, Hourani Z, Travers JG, Wennersten SA, Haefner KR, Cavasin MA, Wilson CE, Jeong MY, Han Y, Gotthardt M, Ferguson SK, Ambardekar AV, Lam MP, Choudhary C, Granzier HL, Woulfe KC, McKinsey TA. HDAC6 modulates myofibril stiffness and diastolic function of the heart. J Clin Invest 2022; 132:e148333. [PMID: 35575093 PMCID: PMC9106344 DOI: 10.1172/jci148333] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Accepted: 04/05/2022] [Indexed: 01/26/2023] Open
Abstract
Passive stiffness of the heart is determined largely by extracellular matrix and titin, which functions as a molecular spring within sarcomeres. Titin stiffening is associated with the development of diastolic dysfunction (DD), while augmented titin compliance appears to impair systolic performance in dilated cardiomyopathy. We found that myofibril stiffness was elevated in mice lacking histone deacetylase 6 (HDAC6). Cultured adult murine ventricular myocytes treated with a selective HDAC6 inhibitor also exhibited increased myofibril stiffness. Conversely, HDAC6 overexpression in cardiomyocytes led to decreased myofibril stiffness, as did ex vivo treatment of mouse, rat, and human myofibrils with recombinant HDAC6. Modulation of myofibril stiffness by HDAC6 was dependent on 282 amino acids encompassing a portion of the PEVK element of titin. HDAC6 colocalized with Z-disks, and proteomics analysis suggested that HDAC6 functions as a sarcomeric protein deacetylase. Finally, increased myofibril stiffness in HDAC6-deficient mice was associated with exacerbated DD in response to hypertension or aging. These findings define a role for a deacetylase in the control of myofibril function and myocardial passive stiffness, suggest that reversible acetylation alters titin compliance, and reveal the potential of targeting HDAC6 to manipulate the elastic properties of the heart to treat cardiac diseases.
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Affiliation(s)
- Ying-Hsi Lin
- Department of Medicine, Division of Cardiology, and
- Consortium for Fibrosis Research & Translation, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Jennifer L. Major
- Department of Medicine, Division of Cardiology, and
- Consortium for Fibrosis Research & Translation, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Tim Liebner
- Department of Proteomics, Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Zaynab Hourani
- Department of Cellular and Molecular Medicine and Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, Arizona, USA
| | - Joshua G. Travers
- Department of Medicine, Division of Cardiology, and
- Consortium for Fibrosis Research & Translation, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Sara A. Wennersten
- Department of Medicine, Division of Cardiology, and
- Consortium for Fibrosis Research & Translation, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Korey R. Haefner
- Department of Medicine, Division of Cardiology, and
- Consortium for Fibrosis Research & Translation, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Maria A. Cavasin
- Department of Medicine, Division of Cardiology, and
- Consortium for Fibrosis Research & Translation, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | | | | | - Yu Han
- Department of Medicine, Division of Cardiology, and
- Consortium for Fibrosis Research & Translation, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Michael Gotthardt
- Neuromuscular and Cardiovascular Cell Biology, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
- Charité–Universitätsmedizin Berlin, Berlin, Germany
| | - Scott K. Ferguson
- Cardiovascular and Pulmonary Research Laboratory, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Amrut V. Ambardekar
- Department of Medicine, Division of Cardiology, and
- Consortium for Fibrosis Research & Translation, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Maggie P.Y. Lam
- Department of Medicine, Division of Cardiology, and
- Consortium for Fibrosis Research & Translation, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Chunaram Choudhary
- Department of Proteomics, Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Henk L. Granzier
- Department of Cellular and Molecular Medicine and Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, Arizona, USA
| | | | - Timothy A. McKinsey
- Department of Medicine, Division of Cardiology, and
- Consortium for Fibrosis Research & Translation, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
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9
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Stachowski-Doll MJ, Papadaki M, Martin TG, Ma W, Gong HM, Shao S, Shen S, Muntu NA, Kumar M, Perez E, Martin JL, Moravec CS, Sadayappan S, Campbell SG, Irving T, Kirk JA. GSK-3β Localizes to the Cardiac Z-Disc to Maintain Length Dependent Activation. Circ Res 2022; 130:871-886. [PMID: 35168370 PMCID: PMC8930626 DOI: 10.1161/circresaha.121.319491] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Altered kinase localization is gaining appreciation as a mechanism of cardiovascular disease. Previous work suggests GSK-3β (glycogen synthase kinase 3β) localizes to and regulates contractile function of the myofilament. We aimed to discover GSK-3β's in vivo role in regulating myofilament function, the mechanisms involved, and the translational relevance. METHODS Inducible cardiomyocyte-specific GSK-3β knockout mice and left ventricular myocardium from nonfailing and failing human hearts were studied. RESULTS Skinned cardiomyocytes from knockout mice failed to exhibit calcium sensitization with stretch indicating a loss of length-dependent activation (LDA), the mechanism underlying the Frank-Starling Law. Titin acts as a length sensor for LDA, and knockout mice had decreased titin stiffness compared with control mice, explaining the lack of LDA. Knockout mice exhibited no changes in titin isoforms, titin phosphorylation, or other thin filament phosphorylation sites known to affect passive tension or LDA. Mass spectrometry identified several z-disc proteins as myofilament phospho-substrates of GSK-3β. Agreeing with the localization of its targets, GSK-3β that is phosphorylated at Y216 binds to the z-disc. We showed pY216 was necessary and sufficient for z-disc binding using adenoviruses for wild-type, Y216F, and Y216E GSK-3β in neonatal rat ventricular cardiomyocytes. One of GSK-3β's z-disc targets, abLIM-1 (actin-binding LIM protein 1), binds to the z-disc domains of titin that are important for maintaining passive tension. Genetic knockdown of abLIM-1 via siRNA in human engineered heart tissues resulted in enhancement of LDA, indicating abLIM-1 may act as a negative regulator that is modulated by GSK-3β. Last, GSK-3β myofilament localization was reduced in left ventricular myocardium from failing human hearts, which correlated with depressed LDA. CONCLUSIONS We identified a novel mechanism by which GSK-3β localizes to the myofilament to modulate LDA. Importantly, z-disc GSK-3β levels were reduced in patients with heart failure, indicating z-disc localized GSK-3β is a possible therapeutic target to restore the Frank-Starling mechanism in patients with heart failure.
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Affiliation(s)
- Marisa J Stachowski-Doll
- Department of Cell and Molecular Physiology, Loyola University Stritch School of Medicine, Maywood, IL (M.J.S.-D., M.P., T.G.M., N.A.M., E.P., J.A.K.)
| | - Maria Papadaki
- Department of Cell and Molecular Physiology, Loyola University Stritch School of Medicine, Maywood, IL (M.J.S.-D., M.P., T.G.M., N.A.M., E.P., J.A.K.)
| | - Thomas G Martin
- Department of Cell and Molecular Physiology, Loyola University Stritch School of Medicine, Maywood, IL (M.J.S.-D., M.P., T.G.M., N.A.M., E.P., J.A.K.)
| | - Weikang Ma
- Center for Synchrotron Radiation Research and Instrumentation and Department of Biological Sciences, Illinois Institute of Technology, Chicago (W.M., H.M.G., T.I.)
| | - Henry M Gong
- Center for Synchrotron Radiation Research and Instrumentation and Department of Biological Sciences, Illinois Institute of Technology, Chicago (W.M., H.M.G., T.I.)
| | - Stephanie Shao
- Department of Bioengineering, Yale University, New Haven, CT (S. Shao, S. Shen, S.G.C.)
| | - Shi Shen
- Department of Bioengineering, Yale University, New Haven, CT (S. Shao, S. Shen, S.G.C.)
| | - Nitha Aima Muntu
- Department of Cell and Molecular Physiology, Loyola University Stritch School of Medicine, Maywood, IL (M.J.S.-D., M.P., T.G.M., N.A.M., E.P., J.A.K.)
| | - Mohit Kumar
- Division of Cardiovascular Health and Disease, Department of Internal Medicine, Heart, Lung, and Vascular Institute, University of Cincinnati, OH (M.K., S. Sadayappan)
| | - Edith Perez
- Department of Cell and Molecular Physiology, Loyola University Stritch School of Medicine, Maywood, IL (M.J.S.-D., M.P., T.G.M., N.A.M., E.P., J.A.K.)
| | - Jody L Martin
- Department of Pharmacology, Cardiovascular Research Institute, UC Davis School of Medicine, CA (J.L.M.)
| | - Christine S Moravec
- Department of Cardiovascular and Metabolic Sciences, Cleveland Clinic, OH (C.S.M.)
| | - Sakthivel Sadayappan
- Division of Cardiovascular Health and Disease, Department of Internal Medicine, Heart, Lung, and Vascular Institute, University of Cincinnati, OH (M.K., S. Sadayappan)
| | - Stuart G Campbell
- Department of Bioengineering, Yale University, New Haven, CT (S. Shao, S. Shen, S.G.C.).,Department of Cellular and Molecular Physiology, Yale School of Medicine, New Haven, CT (S.G.C.)
| | - Thomas Irving
- Center for Synchrotron Radiation Research and Instrumentation and Department of Biological Sciences, Illinois Institute of Technology, Chicago (W.M., H.M.G., T.I.)
| | - Jonathan A Kirk
- Department of Cell and Molecular Physiology, Loyola University Stritch School of Medicine, Maywood, IL (M.J.S.-D., M.P., T.G.M., N.A.M., E.P., J.A.K.)
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10
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Lewalle A, Campbell KS, Campbell SG, Milburn GN, Niederer SA. Functional and structural differences between skinned and intact muscle preparations. J Gen Physiol 2022; 154:e202112990. [PMID: 35045156 PMCID: PMC8929306 DOI: 10.1085/jgp.202112990] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2021] [Accepted: 12/16/2021] [Indexed: 11/20/2022] Open
Abstract
Myofilaments and their associated proteins, which together constitute the sarcomeres, provide the molecular-level basis for contractile function in all muscle types. In intact muscle, sarcomere-level contraction is strongly coupled to other cellular subsystems, in particular the sarcolemmal membrane. Skinned muscle preparations (where the sarcolemma has been removed or permeabilized) are an experimental system designed to probe contractile mechanisms independently of the sarcolemma. Over the last few decades, experiments performed using permeabilized preparations have been invaluable for clarifying the understanding of contractile mechanisms in both skeletal and cardiac muscle. Today, the technique is increasingly harnessed for preclinical and/or pharmacological studies that seek to understand how interventions will impact intact muscle contraction. In this context, intrinsic functional and structural differences between skinned and intact muscle pose a major interpretational challenge. This review first surveys measurements that highlight these differences in terms of the sarcomere structure, passive and active tension generation, and calcium dependence. We then highlight the main practical challenges and caveats faced by experimentalists seeking to emulate the physiological conditions of intact muscle. Gaining an awareness of these complexities is essential for putting experiments in due perspective.
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Affiliation(s)
- Alex Lewalle
- Department of Biomedical Engineering, School of Biomedical Engineering and Imaging Sciences, King’s College London, London, UK
| | - Kenneth S. Campbell
- Department of Physiology and Division of Cardiovascular Medicine, University of Kentucky, Lexington, KY
| | - Stuart G. Campbell
- Departments of Biomedical Engineering and Cellular and Molecular Physiology, Yale University, New Haven, CT
| | - Gregory N. Milburn
- Department of Physiology and Division of Cardiovascular Medicine, University of Kentucky, Lexington, KY
| | - Steven A. Niederer
- Department of Biomedical Engineering, School of Biomedical Engineering and Imaging Sciences, King’s College London, London, UK
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11
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Pezhouman A, Nguyen NB, Sercel AJ, Nguyen TL, Daraei A, Sabri S, Chapski DJ, Zheng M, Patananan AN, Ernst J, Plath K, Vondriska TM, Teitell MA, Ardehali R. Transcriptional, Electrophysiological, and Metabolic Characterizations of hESC-Derived First and Second Heart Fields Demonstrate a Potential Role of TBX5 in Cardiomyocyte Maturation. Front Cell Dev Biol 2021; 9:787684. [PMID: 34988079 PMCID: PMC8722677 DOI: 10.3389/fcell.2021.787684] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 11/25/2021] [Indexed: 12/03/2022] Open
Abstract
Background: Human embryonic stem cell-derived cardiomyocytes (hESC-CMs) can be used as a source for cell delivery to remuscularize the heart after myocardial infarction. Despite their therapeutic potential, the emergence of ventricular arrhythmias has limited their application. We previously developed a double reporter hESC line to isolate first heart field (FHF: TBX5+NKX2-5+) and second heart field (SHF: TBX5-NKX2-5+) CMs. Herein, we explore the role of TBX5 and its effects on underlying gene regulatory networks driving phenotypical and functional differences between these two populations. Methods: We used a combination of tools and techniques for rapid and unsupervised profiling of FHF and SHF populations at the transcriptional, translational, and functional level including single cell RNA (scRNA) and bulk RNA sequencing, atomic force and quantitative phase microscopy, respirometry, and electrophysiology. Results: Gene ontology analysis revealed three biological processes attributed to TBX5 expression: sarcomeric structure, oxidative phosphorylation, and calcium ion handling. Interestingly, migratory pathways were enriched in SHF population. SHF-like CMs display less sarcomeric organization compared to FHF-like CMs, despite prolonged in vitro culture. Atomic force and quantitative phase microscopy showed increased cellular stiffness and decreased mass distribution over time in FHF compared to SHF populations, respectively. Electrophysiological studies showed longer plateau in action potentials recorded from FHF-like CMs, consistent with their increased expression of calcium handling genes. Interestingly, both populations showed nearly identical respiratory profiles with the only significant functional difference being higher ATP generation-linked oxygen consumption rate in FHF-like CMs. Our findings suggest that FHF-like CMs display more mature features given their enhanced sarcomeric alignment, calcium handling, and decreased migratory characteristics. Finally, pseudotime analyses revealed a closer association of the FHF population to human fetal CMs along the developmental trajectory. Conclusion: Our studies reveal that distinguishing FHF and SHF populations based on TBX5 expression leads to a significant impact on their downstream functional properties. FHF CMs display more mature characteristics such as enhanced sarcomeric organization and improved calcium handling, with closer positioning along the differentiation trajectory to human fetal hearts. These data suggest that the FHF CMs may be a more suitable candidate for cardiac regeneration.
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Affiliation(s)
- Arash Pezhouman
- Division of Cardiology, Department of Internal Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
- Eli and Edythe Broad Stem Cell Research Center, University of California, Los Angeles, Los Angeles, CA, United States
| | - Ngoc B. Nguyen
- Division of Cardiology, Department of Internal Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
- Eli and Edythe Broad Stem Cell Research Center, University of California, Los Angeles, Los Angeles, CA, United States
- Molecular, Cellular and Integrative Physiology Graduate Program, University of California, Los Angeles, Los Angeles, CA, United States
| | - Alexander J. Sercel
- Molecular Biology Interdepartmental Doctoral Program, University of California, Los Angeles, Los Angeles, CA, United States
| | - Thang L. Nguyen
- Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA, United States
| | - Ali Daraei
- Division of Cardiology, Department of Internal Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
| | - Shan Sabri
- Department of Biological Chemistry, University of California, Los Angeles, Los Angeles, CA, United States
| | - Douglas J. Chapski
- Department of Anesthesiology and Perioperative Medicine, University of California, Los Angeles, Los Angeles, CA, United States
| | - Melton Zheng
- Division of Cardiology, Department of Internal Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
| | - Alexander N. Patananan
- Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA, United States
| | - Jason Ernst
- Eli and Edythe Broad Stem Cell Research Center, University of California, Los Angeles, Los Angeles, CA, United States
- Department of Biological Chemistry, University of California, Los Angeles, Los Angeles, CA, United States
- Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA, United States
- Jonsson Comprehensive Cancer Center, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
| | - Kathrin Plath
- Eli and Edythe Broad Stem Cell Research Center, University of California, Los Angeles, Los Angeles, CA, United States
- Department of Biological Chemistry, University of California, Los Angeles, Los Angeles, CA, United States
- Jonsson Comprehensive Cancer Center, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
| | - Thomas M. Vondriska
- Department of Anesthesiology and Perioperative Medicine, University of California, Los Angeles, Los Angeles, CA, United States
- Department of Physiology, University of California, Los Angeles, Los Angeles, CA, United States
- Department of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
| | - Michael A. Teitell
- Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA, United States
- Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA, United States
- Jonsson Comprehensive Cancer Center, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
- Department of Pediatrics, University of California, Los Angeles, Los Angeles, CA, United States
| | - Reza Ardehali
- Division of Cardiology, Department of Internal Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
- Eli and Edythe Broad Stem Cell Research Center, University of California, Los Angeles, Los Angeles, CA, United States
- Molecular, Cellular and Integrative Physiology Graduate Program, University of California, Los Angeles, Los Angeles, CA, United States
- Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA, United States
- *Correspondence: Reza Ardehali,
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12
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Shi J, Watanabe D, Wada M. Effects of vigorous isometric muscle contraction on titin stiffness-related contractile properties in rat fast-twitch muscles. Am J Physiol Regul Integr Comp Physiol 2021; 321:R858-R868. [PMID: 34668430 DOI: 10.1152/ajpregu.00189.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Accepted: 10/13/2021] [Indexed: 12/30/2022]
Abstract
This study was conducted to examine the effects of an acute bout of vigorous isometric contractions on titin stiffness-related contractile properties in rat fast-twitch skeletal muscles. Intact gastrocnemius muscles were electrically stimulated in situ until the force was reduced to ∼50% of the initial force. Immediately after cessation of the stimulation, the superficial regions of the muscles were dissected and subjected to biochemical and skinned fiber analyses. The stimulation resulted in a decrease in the titin-based passive force. The amounts of fragmented titin were unchanged by the stimulation. Protein kinase Cα-treatment increased the passive force in stimulated fibers to resting levels. The stimulation had no effect on the maximum Ca2+-activated force (max Ca2+ force) at a sarcomere length (SL) of 2.4 μm and decreased myofibrillar (my)-Ca2+ sensitivity at 2.6-μm SL. Stretching the SL to 3.0 μm led to the augmentation of the max Ca2+ force and my-Ca2+ sensitivity in both rested and stimulated fibers. For the max Ca2+ force, the extent of the increase was smaller in stimulated than in rested fibers, whereas for my-Ca2+ sensitivity, it was higher in stimulated than in rested fibers. These results suggest that vigorous isometric contractions decrease the titin-based passive force, possibly because of a reduction in phosphorylation by protein kinase Cα, and that the decreased titin stiffness may contribute, at least in part, to muscle fatigue.
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Affiliation(s)
- Jiayu Shi
- Graduate School of Integrated Arts and Sciences, Hiroshima University, Higashihiroshima-shi, Japan
| | - Daiki Watanabe
- Graduate School of Humanities and Social Sciences, Hiroshima University, Higashihiroshima-shi, Japan
| | - Masanobu Wada
- Graduate School of Integrated Arts and Sciences, Hiroshima University, Higashihiroshima-shi, Japan
- Graduate School of Humanities and Social Sciences, Hiroshima University, Higashihiroshima-shi, Japan
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13
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Solís C, Russell B. Striated muscle proteins are regulated both by mechanical deformation and by chemical post-translational modification. Biophys Rev 2021; 13:679-695. [PMID: 34777614 DOI: 10.1007/s12551-021-00835-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Accepted: 08/23/2021] [Indexed: 01/09/2023] Open
Abstract
All cells sense force and build their cytoskeleton to optimize function. How is this achieved? Two major systems are involved. The first is that load deforms specific protein structures in a proportional and orientation-dependent manner. The second is post-translational modification of proteins as a consequence of signaling pathway activation. These two processes work together in a complex way so that local subcellular assembly as well as overall cell function are controlled. This review discusses many cell types but focuses on striated muscle. Detailed information is provided on how load deforms the structure of proteins in the focal adhesions and filaments, using α-actinin, vinculin, talin, focal adhesion kinase, LIM domain-containing proteins, filamin, myosin, titin, and telethonin as examples. Second messenger signals arising from external triggers are distributed throughout the cell causing post-translational or chemical modifications of protein structures, with the actin capping protein CapZ and troponin as examples. There are numerous unanswered questions of how mechanical and chemical signals are integrated by muscle proteins to regulate sarcomere structure and function yet to be studied. Therefore, more research is needed to see how external triggers are integrated with local tension generated within the cell. Nonetheless, maintenance of tension in the sarcomere is the essential and dominant mechanism, leading to the well-known phrase in exercise physiology: "use it or lose it."
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Affiliation(s)
- Christopher Solís
- Department of Physiology and Biophysics, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612 USA
| | - Brenda Russell
- Department of Physiology and Biophysics, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612 USA
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14
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Kobirumaki-Shimozawa F, Shimozawa T, Oyama K, Baba S, Li J, Nakanishi T, Terui T, Louch WE, Ishiwata S, Fukuda N. Synchrony of sarcomeric movement regulates left ventricular pump function in the in vivo beating mouse heart. J Gen Physiol 2021; 153:212675. [PMID: 34605861 PMCID: PMC8493835 DOI: 10.1085/jgp.202012860] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2021] [Accepted: 09/03/2021] [Indexed: 11/20/2022] Open
Abstract
Sarcomeric contraction in cardiomyocytes serves as the basis for the heart's pump functions. It has generally been considered that in cardiac muscle as well as in skeletal muscle, sarcomeres equally contribute to myofibrillar dynamics in myocytes at varying loads by producing similar levels of active and passive force. In the present study, we expressed α-actinin-AcGFP in Z-disks to analyze dynamic behaviors of sequentially connected individual sarcomeres along a myofibril in a left ventricular (LV) myocyte of the in vivo beating mouse heart. To quantify the magnitude of the contribution of individual sarcomeres to myofibrillar dynamics, we introduced the novel parameter "contribution index" (CI) to measure the synchrony in movements between a sarcomere and a myofibril (from -1 [complete asynchrony] to 1 [complete synchrony]). First, CI varied markedly between sarcomeres, with an average value of ∼0.3 during normal systole. Second, when the movements between adjacent sarcomeres were asynchronous (CI < 0), a sarcomere and the ones next to the adjacent sarcomeres and farther away moved in synchrony (CI > 0) along a myofibril. Third, when difference in LV pressure in diastole and systole (ΔLVP) was lowered to <10 mm Hg, diastolic sarcomere length increased. Under depressed conditions, the movements between adjacent sarcomeres were in marked asynchrony (CI, -0.3 to -0.4), and, as a result, average CI was linearly decreased in association with a decrease in ΔLVP. These findings suggest that in the left ventricle of the in vivo beating mouse heart, (1) sarcomeres heterogeneously contribute to myofibrillar dynamics due to an imbalance of active and passive force between neighboring sarcomeres, (2) the force imbalance is pronounced under depressed conditions coupled with a marked increase in passive force and the ensuing tug-of-war between sarcomeres, and (3) sarcomere synchrony via the distal intersarcomere interaction regulates the heart's pump function in coordination with myofibrillar contractility.
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Affiliation(s)
| | - Togo Shimozawa
- Technical Division, School of Science, The University of Tokyo, Tokyo, Japan
| | - Kotaro Oyama
- Department of Cell Physiology, The Jikei University School of Medicine, Tokyo, Japan.,Quantum Beam Science Research Directorate, National Institutes for Quantum and Radiological Science and Technology, Gunma, Japan
| | - Shunsuke Baba
- Department of Pediatrics, The Jikei University School of Medicine, Tokyo, Japan
| | - Jia Li
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
| | - Tomohiro Nakanishi
- Department of Cell Physiology, The Jikei University School of Medicine, Tokyo, Japan
| | - Takako Terui
- Department of Anesthesiology, The Jikei University School of Medicine, Tokyo, Japan
| | - William E Louch
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,K.G. Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
| | - Shin'ichi Ishiwata
- Department of Physics, Faculty of Science and Engineering, Waseda University, Tokyo, Japan
| | - Norio Fukuda
- Department of Cell Physiology, The Jikei University School of Medicine, Tokyo, Japan
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15
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Müller E, Salcan S, Bongardt S, Barbosa DM, Krüger M, Kötter S. E3-ligase knock down revealed differential titin degradation by autopagy and the ubiquitin proteasome system. Sci Rep 2021; 11:21134. [PMID: 34702928 PMCID: PMC8548520 DOI: 10.1038/s41598-021-00618-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Accepted: 09/30/2021] [Indexed: 01/09/2023] Open
Abstract
The sarcomere protein titin is a major determinant of cardiomyocyte stiffness and ventricular distensibility. The constant mechanical stress on titin requires well-controlled protein quality control, the exact mechanisms of which have not yet been fully elucidated. Here, we analyzed E3-ligases potentially responsible for cardiac titin ubiquitination and specifically studied the involvement of the autophagosomal system in titin degradation. Pharmacological inhibition of autophagy and the proteasome in cultured primary rat cardiomyocytes significantly elevated titin ubiquitination and increased titin degradation. Using in-vitro pull down assays we identified binding of E3-ligases MuRF1-3, CHIP and Fbx32 to several titin domains. Immunofluorescence analysis showed sarcomeric localization of the E3-ligases. siRNA-mediated knock-down of the E3-ligases MuRF-1, -3 and a combination of CHIP/Fbx32 significantly reduced autophagy-related titin ubiquitination, whereas knock-down of MuRF-2 and -3 reduced proteasome-related titin ubiquitination. We demonstrated that the proteasomal and the autophagosomal-lysosomal system participate in degradation of the titin filament. We found that ubiquitination and degradation of titin are partially regulated by E3-ligases of the MuRF family. We further identified CHIP and Fbx32 as E3-ligases involved in titin ubiquitination.
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Affiliation(s)
- Erik Müller
- Department of Cardiovascular Physiology, Medical Faculty and University Hospital Düsseldorf, Heinrich-Heine-University Düsseldorf, Universitätsstr. 1, 22.03 02, 40225, Düsseldorf, Germany
| | - Senem Salcan
- Department of Cardiovascular Physiology, Medical Faculty and University Hospital Düsseldorf, Heinrich-Heine-University Düsseldorf, Universitätsstr. 1, 22.03 02, 40225, Düsseldorf, Germany
| | - Sabine Bongardt
- Department of Cardiovascular Physiology, Medical Faculty and University Hospital Düsseldorf, Heinrich-Heine-University Düsseldorf, Universitätsstr. 1, 22.03 02, 40225, Düsseldorf, Germany
| | - David Monteiro Barbosa
- Department of Cardiovascular Physiology, Medical Faculty and University Hospital Düsseldorf, Heinrich-Heine-University Düsseldorf, Universitätsstr. 1, 22.03 02, 40225, Düsseldorf, Germany
| | - Martina Krüger
- Department of Cardiovascular Physiology, Medical Faculty and University Hospital Düsseldorf, Heinrich-Heine-University Düsseldorf, Universitätsstr. 1, 22.03 02, 40225, Düsseldorf, Germany
| | - Sebastian Kötter
- Department of Cardiovascular Physiology, Medical Faculty and University Hospital Düsseldorf, Heinrich-Heine-University Düsseldorf, Universitätsstr. 1, 22.03 02, 40225, Düsseldorf, Germany.
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16
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Loescher CM, Hobbach AJ, Linke WA. Titin (TTN): from molecule to modifications, mechanics and medical significance. Cardiovasc Res 2021; 118:2903-2918. [PMID: 34662387 PMCID: PMC9648829 DOI: 10.1093/cvr/cvab328] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Accepted: 10/13/2021] [Indexed: 12/19/2022] Open
Abstract
The giant sarcomere protein titin is a major determinant of cardiomyocyte stiffness and contributor to cardiac strain sensing. Titin-based forces are highly regulated in health and disease, which aids in the regulation of myocardial function, including cardiac filling and output. Due to the enormous size, complexity, and malleability of the titin molecule, titin properties are also vulnerable to dysregulation, as observed in various cardiac disorders. This review provides an overview of how cardiac titin properties can be changed at a molecular level, including the role isoform diversity and post-translational modifications (acetylation, oxidation, and phosphorylation) play in regulating myocardial stiffness and contractility. We then consider how this regulation becomes unbalanced in heart disease, with an emphasis on changes in titin stiffness and protein quality control. In this context, new insights into the key pathomechanisms of human cardiomyopathy due to a truncation in the titin gene (TTN) are discussed. Along the way, we touch on the potential for titin to be therapeutically targeted to treat acquired or inherited cardiac conditions, such as HFpEF or TTN-truncation cardiomyopathy.
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Affiliation(s)
- Christine M Loescher
- Institute of Physiology II, University Hospital Münster, Robert-Koch-Str. 27B, Münster, 48149 Germany
| | - Anastasia J Hobbach
- Department of Cardiology I, Coronary, Peripheral Vascular Disease and Heart Failure, University Hospital Münster, Münster, Germany
| | - Wolfgang A Linke
- Institute of Physiology II, University Hospital Münster, Robert-Koch-Str. 27B, Münster, 48149 Germany
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17
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Effect of Active Lengthening and Shortening on Small-Angle X-ray Reflections in Skinned Skeletal Muscle Fibres. Int J Mol Sci 2021; 22:ijms22168526. [PMID: 34445232 PMCID: PMC8395229 DOI: 10.3390/ijms22168526] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 07/30/2021] [Accepted: 08/03/2021] [Indexed: 01/04/2023] Open
Abstract
Our purpose was to use small-angle X-ray diffraction to investigate the structural changes within sarcomeres at steady-state isometric contraction following active lengthening and shortening, compared to purely isometric contractions performed at the same final lengths. We examined force, stiffness, and the 1,0 and 1,1 equatorial and M3 and M6 meridional reflections in skinned rabbit psoas bundles, at steady-state isometric contraction following active lengthening to a sarcomere length of 3.0 µm (15.4% initial bundle length at 7.7% bundle length/s), and active shortening to a sarcomere length of 2.6 µm (15.4% bundle length at 7.7% bundle length/s), and during purely isometric reference contractions at the corresponding sarcomere lengths. Compared to the reference contraction, the isometric contraction after active lengthening was associated with an increase in force (i.e., residual force enhancement) and M3 spacing, no change in stiffness and the intensity ratio I1,1/I1,0, and decreased lattice spacing and M3 intensity. Compared to the reference contraction, the isometric contraction after active shortening resulted in decreased force, stiffness, I1,1/I1,0, M3 and M6 spacings, and M3 intensity. This suggests that residual force enhancement is achieved without an increase in the proportion of attached cross-bridges, and that force depression is accompanied by a decrease in the proportion of attached cross-bridges. Furthermore, the steady-state isometric contraction following active lengthening and shortening is accompanied by an increase in cross-bridge dispersion and/or a change in the cross-bridge conformation compared to the reference contractions.
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18
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Hanft LM, Fitzsimons DP, Hacker TA, Moss RL, McDonald KS. Cardiac MyBP-C phosphorylation regulates the Frank-Starling relationship in murine hearts. J Gen Physiol 2021; 153:e202012770. [PMID: 33646280 PMCID: PMC7927661 DOI: 10.1085/jgp.202012770] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 01/04/2021] [Accepted: 01/26/2021] [Indexed: 01/08/2023] Open
Abstract
The Frank-Starling relationship establishes that elevated end-diastolic volume progressively increases ventricular pressure and stroke volume in healthy hearts. The relationship is modulated by a number of physiological inputs and is often depressed in human heart failure. Emerging evidence suggests that cardiac myosin-binding protein-C (cMyBP-C) contributes to the Frank-Starling relationship. We measured contractile properties at multiple levels of structural organization to determine the role of cMyBP-C and its phosphorylation in regulating (1) the sarcomere length dependence of power in cardiac myofilaments and (2) the Frank-Starling relationship in vivo. We compared transgenic mice expressing wild-type cMyBP-C on the null background, which have ∼50% phosphorylated cMyBP-C (Controls), to transgenic mice lacking cMyBP-C (KO) and to mice expressing cMyBP-C that have serine-273, -282, and -302 mutated to aspartate (cMyBP-C t3SD) or alanine (cMyBP-C t3SA) on the null background to mimic either constitutive PKA phosphorylation or nonphosphorylated cMyBP-C, respectively. We observed a continuum of length dependence of power output in myocyte preparations. Sarcomere length dependence of power progressively increased with a rank ordering of cMyBP-C KO = cMyBP-C t3SA < Control < cMyBP-C t3SD. Length dependence of myofilament power translated, at least in part, to hearts, whereby Frank-Starling relationships were steepest in cMyBP-C t3SD mice. The results support the hypothesis that cMyBP-C and its phosphorylation state tune sarcomere length dependence of myofibrillar power, and these regulatory processes translate across spatial levels of myocardial organization to control beat-to-beat ventricular performance.
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Affiliation(s)
- Laurin M. Hanft
- Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO
| | - Daniel P. Fitzsimons
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI
| | - Timothy A. Hacker
- Department of Medicine, University of Wisconsin-Madison, Madison, WI
| | - Richard L. Moss
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI
| | - Kerry S. McDonald
- Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO
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19
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Stronczek C, Lange S, Bullard B, Wolniak S, Börgeson E, Mayans O, Fleming JR. The N2A region of titin has a unique structural configuration. J Gen Physiol 2021; 153:211969. [PMID: 33836065 PMCID: PMC8042602 DOI: 10.1085/jgp.202012766] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Accepted: 03/09/2021] [Indexed: 01/04/2023] Open
Abstract
The N2A segment of titin is a main signaling hub in the sarcomeric I-band that recruits various signaling factors and processing enzymes. It has also been proposed to play a role in force production through its Ca2+-regulated association with actin. However, the molecular basis by which N2A performs these functions selectively within the repetitive and extensive titin chain remains poorly understood. Here, we analyze the structure of N2A components and their association with F-actin. Specifically, we characterized the structure of its Ig domains by elucidating the atomic structure of the I81-I83 tandem using x-ray crystallography and computing a homology model for I80. Structural data revealed these domains to present heterogeneous and divergent Ig folds, where I81 and I83 have unique loop structures. Notably, the I81-I83 tandem has a distinct rotational chain arrangement that confers it a unique multi-domain topography. However, we could not identify specific Ca2+-binding sites in these Ig domains, nor evidence of the association of titin N2A components with F-actin in transfected C2C12 myoblasts or C2C12-derived myotubes. In addition, F-actin cosedimentation assays failed to reveal binding to N2A. We conclude that N2A has a unique architecture that predictably supports its selective recruitment of binding partners in signaling, but that its mechanical role through interaction with F-actin awaits validation.
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Affiliation(s)
- Chiara Stronczek
- Department of Biology, University of Konstanz, Konstanz, Germany
| | - Stephan Lange
- Division of Cardiology, School of Medicine, University of California, San Diego, San Diego, CA.,Wallenberg Laboratory, Department of Molecular and Clinical Medicine, Institute of Medicine, University of Gothenburg, Gothenburg, Sweden
| | | | | | - Emma Börgeson
- Wallenberg Laboratory, Department of Molecular and Clinical Medicine, Institute of Medicine, University of Gothenburg, Gothenburg, Sweden
| | - Olga Mayans
- Department of Biology, University of Konstanz, Konstanz, Germany
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20
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Fenwick AJ, Wood AM, Tanner BCW. The spatial distribution of thin filament activation influences force development and myosin activity in computational models of muscle contraction. Arch Biochem Biophys 2021; 703:108855. [PMID: 33781771 DOI: 10.1016/j.abb.2021.108855] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 03/03/2021] [Accepted: 03/18/2021] [Indexed: 01/22/2023]
Abstract
Striated muscle contraction is initiated by Ca2+ binding to, and activating, thin filament regulatory units (RU) within the sarcomere, which then allows myosin cross-bridges from the opposing thick filament to bind actin and generate force. The amount of overlap between the filaments dictates how many potential cross-bridges are capable of binding, and thus how force is generated by the sarcomere. Myopathies and atrophy can impair muscle function by limiting cross-bridge interactions between the filaments, which can occur when the length of the thin filament is reduced or when RU function is disrupted. To investigate how variations in thin filament length and RU density affect ensemble cross-bridge behavior and force production, we simulated muscle contraction using a spatially explicit computational model of the half-sarcomere. Thin filament RUs were disabled either uniformly from the pointed end of the filament (to model shorter thin filament length) or randomly throughout the length of the half-sarcomere. Both uniform and random RU 'knockout' schemes decreased overall force generation during maximal and submaximal activation. The random knockout scheme also led to decreased calcium sensitivity and cooperativity of the force-pCa relationship. We also found that the rate of force development slowed with the random RU knockout, compared to the uniform RU knockout or conditions of normal RU activation. These findings imply that the relationship between RU density and force production within the sarcomere involves more complex coordination than simply the raw number of RUs available for myosin cross-bridge binding, and that the spatial pattern in which activatable RU are distributed throughout the sarcomere influences the dynamics of force production.
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Affiliation(s)
- Axel J Fenwick
- Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, WA, 99164, USA
| | - Alexander M Wood
- Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, WA, 99164, USA
| | - Bertrand C W Tanner
- Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, WA, 99164, USA.
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21
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Solís C, Solaro RJ. Novel insights into sarcomere regulatory systems control of cardiac thin filament activation. J Gen Physiol 2021; 153:211903. [PMID: 33740037 PMCID: PMC7988513 DOI: 10.1085/jgp.202012777] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 02/23/2021] [Indexed: 12/11/2022] Open
Abstract
Our review focuses on sarcomere regulatory mechanisms with a discussion of cardiac-specific modifications to the three-state model of thin filament activation from a blocked to closed to open state. We discuss modulation of these thin filament transitions by Ca2+, by crossbridge interactions, and by thick filament–associated proteins, cardiac myosin–binding protein C (cMyBP-C), cardiac regulatory light chain (cRLC), and titin. Emerging evidence supports the idea that the cooperative activation of the thin filaments despite a single Ca2+ triggering regulatory site on troponin C (cTnC) cannot be considered in isolation of other functional domains of the sarcomere. We discuss long- and short-range interactions among these domains with the regulatory units of thin filaments, including proteins at the barbed end at the Z-disc and the pointed end near the M-band. Important to these discussions is the ever-increasing understanding of the role of cMyBP-C, cRLC, and titin filaments. Detailed knowledge of these control processes is critical to the understanding of mechanisms sustaining physiological cardiac state with varying hemodynamic load, to better defining genetic and acquired cardiac disorders, and to developing targets for therapies at the level of the sarcomeres.
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Affiliation(s)
- Christopher Solís
- University of Illinois at Chicago, College of Medicine, Department of Physiology and Biophysics and Center for Cardiovascular Research, Chicago, IL
| | - R John Solaro
- University of Illinois at Chicago, College of Medicine, Department of Physiology and Biophysics and Center for Cardiovascular Research, Chicago, IL
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22
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Mijailovich SM, Prodanovic M, Poggesi C, Geeves MA, Regnier M. Multiscale modeling of twitch contractions in cardiac trabeculae. J Gen Physiol 2021; 153:e202012604. [PMID: 33512405 PMCID: PMC7852458 DOI: 10.1085/jgp.202012604] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Revised: 08/31/2020] [Accepted: 11/20/2020] [Indexed: 12/23/2022] Open
Abstract
Understanding the dynamics of a cardiac muscle twitch contraction is complex because it requires a detailed understanding of the kinetic processes of the Ca2+ transient, thin-filament activation, and the myosin-actin cross-bridge chemomechanical cycle. Each of these steps has been well defined individually, but understanding how all three of the processes operate in combination is a far more complex problem. Computational modeling has the potential to provide detailed insight into each of these processes, how the dynamics of each process affect the complexity of contractile behavior, and how perturbations such as mutations in sarcomere proteins affect the complex interactions of all of these processes. The mechanisms involved in relaxation of tension during a cardiac twitch have been particularly difficult to discern due to nonhomogeneous sarcomere lengthening during relaxation. Here we use the multiscale MUSICO platform to model rat trabecular twitches. Validation of computational models is dependent on being able to simulate different experimental datasets, but there has been a paucity of data that can provide all of the required parameters in a single experiment, such as simultaneous measurements of force, intracellular Ca2+ transients, and sarcomere length dynamics. In this study, we used data from different studies collected under similar experimental conditions to provide information for all the required parameters. Our simulations established that twitches either in an isometric sarcomere or in fixed-length, multiple-sarcomere trabeculae replicate the experimental observations if models incorporate a length-tension relationship for the nonlinear series elasticity of muscle preparations and a scheme for thick-filament regulation. The thick-filament regulation assumes an off state in which myosin heads are parked onto the thick-filament backbone and are unable to interact with actin, a state analogous to the super-relaxed state. Including these two mechanisms provided simulations that accurately predict twitch contractions over a range of different conditions.
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Affiliation(s)
| | - Momcilo Prodanovic
- Bioengineering Research and Development Center, Kragujevac, Serbia
- Faculty of Engineering, University of Kragujevac, Kragujevac, Serbia
| | - Corrado Poggesi
- Department of Experimental & Clinical Medicine, University of Florence, Florence, Italy
| | | | - Michael Regnier
- Department of Bioengineering, University of Washington, Seattle, WA
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23
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Hypertrophic Cardiomyopathy: Diverse Pathophysiology Revealed by Genetic Research, Toward Future Therapy. Keio J Med 2020; 69:77-87. [PMID: 32224552 DOI: 10.2302/kjm.2019-0012-oa] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Hypertrophic cardiomyopathy (HCM) is an intractable disease that causes heart failure mainly due to unexplained severe cardiac hypertrophy and diastolic dysfunction. HCM, which occurs in 0.2% of the general population, is the most common cause of sudden cardiac death in young people. HCM has been studied extensively using molecular genetic approaches. Genes encoding cardiac β-myosin heavy chain, cardiac myosin-binding protein C, and troponin complex, which were originally identified as causative genes, were subsequently reported to be frequently implicated in HCM. Indeed, HCM has been considered a disease of sarcomere gene mutations. However, fewer than half of patients with HCM have mutations in sarcomere genes. The others have been documented to have mutations in cardiac proteins in various other locations, including the Z disc, sarcoplasmic reticulum, plasma membrane, nucleus, and mitochondria. Next-generation sequencing makes it possible to detect mutations at high throughput, and it has become increasingly common to identify multiple cardiomyopathy-causing gene mutations in a single HCM patient. Elucidating how mutations in different genes contribute to the disease pathophysiology will be a challenge. In studies using animal models, sarcomere mutations generally tend to increase myocardial Ca2+ sensitivity, and some mutations increase the activity of myosin ATPase. Clinical trials of drugs to treat HCM are ongoing, and further new therapies based on pathophysiological analyses of the causative genes are eagerly anticipated.
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24
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Abstract
Muscle stiffness, muscle elasticity and explosive strength are the main components of athletes' performance and they show a sex-based as well as ethnicity variation. Muscle stiffness is thought to be one of the risk factors associated with sports injuries and is less common in females than in males. These observations may be explained by circulating levels of sex hormones and their specific receptors. It has been shown that higher levels of estrogen are associated with lower muscle stiffness responsible for suppression of collagen synthesis. It is thought that these properties, at least in part, depend on genetic factors. Particularly, the gene encoding estrogen receptor 1 (ESR1) is one of the candidates that may be associated with muscle stiffness. Muscle elasticity increases with aging and there is evidence suggesting that titin (encoded by the TTN gene), a protein that is expressed in cardiac and skeletal muscles, is one of the factors responsible for elastic properties of the muscles. Mutations in the TTN gene result in some types of muscular dystrophy or cardiomyopathy. In this context, TTN may be regarded as a promising candidate for studying the elastic properties of muscles in athletes. The physiological background of explosive strength depends not only on the muscle architecture and muscle fiber composition, but also on the central nervous system and functionality of neuromuscular units. These properties are, at least partly, genetically determined. In this context, the ACTN3 gene code for α-actinin 3 has been widely researched.
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25
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McDonald KS, Hanft LM, Robinett JC, Guglin M, Campbell KS. Regulation of Myofilament Contractile Function in Human Donor and Failing Hearts. Front Physiol 2020; 11:468. [PMID: 32523542 PMCID: PMC7261867 DOI: 10.3389/fphys.2020.00468] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Accepted: 04/16/2020] [Indexed: 01/14/2023] Open
Abstract
Heart failure (HF) often includes changes in myocardial contractile function. This study addressed the myofibrillar basis for contractile dysfunction in failing human myocardium. Regulation of contractile properties was measured in cardiac myocyte preparations isolated from frozen, left ventricular mid-wall biopsies of donor (n = 7) and failing human hearts (n = 8). Permeabilized cardiac myocyte preparations were attached between a force transducer and a position motor, and both the Ca2+ dependence and sarcomere length (SL) dependence of force, rate of force, loaded shortening, and power output were measured at 15 ± 1°C. The myocyte preparation size was similar between groups (donor: length 148 ± 10 μm, width 21 ± 2 μm, n = 13; HF: length 131 ± 9 μm, width 23 ± 1 μm, n = 16). The maximal Ca2+-activated isometric force was also similar between groups (donor: 47 ± 4 kN⋅m-2; HF: 44 ± 5 kN⋅m-2), which implicates that previously reported force declines in multi-cellular preparations reflect, at least in part, tissue remodeling. Maximal force development rates were also similar between groups (donor: k tr = 0.60 ± 0.05 s-1; HF: k tr = 0.55 ± 0.04 s-1), and both groups exhibited similar Ca2+ activation dependence of k tr values. Human cardiac myocyte preparations exhibited a Ca2+ activation dependence of loaded shortening and power output. The peak power output normalized to isometric force (PNPO) decreased by ∼12% from maximal Ca2+ to half-maximal Ca2+ activations in both groups. Interestingly, the SL dependence of PNPO was diminished in failing myocyte preparations. During sub-maximal Ca2+ activation, a reduction in SL from ∼2.25 to ∼1.95 μm caused a ∼26% decline in PNPO in donor myocytes but only an ∼11% change in failing myocytes. These results suggest that altered length-dependent regulation of myofilament function impairs ventricular performance in failing human hearts.
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Affiliation(s)
- Kerry S. McDonald
- Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO, United States
| | - Laurin M. Hanft
- Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO, United States
| | - Joel C. Robinett
- Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO, United States
| | - Maya Guglin
- Division of Cardiovascular Medicine, University of Kentucky, Lexington, KY, United States
| | - Kenneth S. Campbell
- Division of Cardiovascular Medicine, University of Kentucky, Lexington, KY, United States
- Department of Physiology, University of Kentucky, Lexington, KY, United States
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26
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Tune TC, Ma W, Irving T, Sponberg S. Nanometer-scale structure differences in the myofilament lattice spacing of two cockroach leg muscles correspond to their different functions. J Exp Biol 2020; 223:jeb212829. [PMID: 32205362 PMCID: PMC7225125 DOI: 10.1242/jeb.212829] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Accepted: 03/09/2020] [Indexed: 01/21/2023]
Abstract
Muscle is highly organized across multiple length scales. Consequently, small changes in the arrangement of myofilaments can influence macroscopic mechanical function. Two leg muscles of a cockroach have identical innervation, mass, twitch responses, length-tension curves and force-velocity relationships. However, during running, one muscle is dissipative (a 'brake'), while the other dissipates and produces significant positive mechanical work (bifunctional). Using time-resolved X-ray diffraction in intact, contracting muscle, we simultaneously measured the myofilament lattice spacing, packing structure and macroscopic force production of these muscles to test whether structural differences in the myofilament lattice might correspond to the muscles' different mechanical functions. While the packing patterns are the same, one muscle has 1 nm smaller lattice spacing at rest. Under isometric stimulation, the difference in lattice spacing disappeared, consistent with the two muscles' identical steady-state behavior. During periodic contractions, one muscle undergoes a 1 nm greater change in lattice spacing, which correlates with force. This is the first identified structural feature in the myofilament lattice of these two muscles that shares their whole-muscle dynamic differences and quasi-static similarities.
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Affiliation(s)
- Travis Carver Tune
- School of Physics, Georgia Institute of Technology, Atlanta, GA, 30332 USA
| | - Weikang Ma
- Biophysics Collaborative Access Team and CSRRI, Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL, 60616 USA
| | - Thomas Irving
- Biophysics Collaborative Access Team and CSRRI, Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL, 60616 USA
| | - Simon Sponberg
- School of Physics, Georgia Institute of Technology, Atlanta, GA, 30332 USA
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, 30332 USA
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27
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Abstract
Muscle has conventionally been viewed as a motor that converts chemical to kinetic energy in series with a passive spring, but new insights emerge when muscle is viewed as a composite material whose elastic elements are tuned by activation. New evidence demonstrates that calcium-dependent binding of N2A titin to actin increases titin stiffness in active skeletal muscles, which explains many long-standing enigmas of muscle physiology.
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Affiliation(s)
- Kiisa Nishikawa
- Department of Biological Sciences, Northern Arizona University, Flagstaff, Arizona
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28
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Lookin O, Protsenko Y. Length-Dependent Activation of Contractility and Ca-Transient Kinetics in Auxotonically Contracting Isolated Rat Ventricular Cardiomyocytes. Front Physiol 2019; 10:1473. [PMID: 31920687 PMCID: PMC6917588 DOI: 10.3389/fphys.2019.01473] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Accepted: 11/14/2019] [Indexed: 11/13/2022] Open
Abstract
Length-dependent activation (LDA) of contraction is an important mechanism of proper myocardial function that is often blunted in diseases accompanied by deficient contractility and impaired calcium homeostasis. We evaluated how the extent of LDA is related to the decreased force in healthy rat myocardium under negative inotropic conditions that affect the calcium cycle. The length-dependent effects on auxotonic twitch and Ca-transient were compared in isolated rat ventricular cardiomyocytes at room temperature (“25C”) and near-physiological temperature (“35C”) in normal Tyrode and at 25°C with thapsigargin-depleted sarcoplasmic reticulum (“25C + Thap”). At the slack length, a similar negative inotropy in “35C” and “25C + Thap” was accompanied by totally different changes in Ca-transient amplitude, time-to-peak, and time-to-decline from peak to 50% amplitude. End-systolic/end-diastolic tension-sarcomere length relationships were obtained for each individual cell, and the ratio of their slopes, the dimensionless Frank-Starling Gain index, was 2.32 ± 0.16, 1.78 ± 0.09, and 1.37 ± 0.06 in “25C,” “35C” and “25C + Thap,” respectively (mean ± S.E.M.). Ca-transient diastolic level and amplitude did not differ between “25C” and “35C” at any SL, but in “35C” it developed and declined significantly faster. In contrast, thapsigargin-induced depletion of SERCA2a significantly attenuated and retarded Ca-transient. The relative amount of Ca2+ utilized by troponin C, evaluated by the integral magnitude of a short-lived component of Ca-transient decline (“bump”), increased by ~25% per each 0.05 μm increase in SL in all groups. The kinetics of the Ca-TnC dissociation, evaluated by the bump time-to-peak, was significantly faster in “35C” and slower in “25C + Thap” vs. “25C” (respectively, 63.7 ± 5.3 and 253.6 ± 8.3% of the value in “25C,” mean ± S.E.M.). In conclusion, a similar inotropic effect can be observed in rat ventricular myocardium under totally different kinetics of free cytosolic calcium. The extent of LDA is not determined by actual peak systolic tension but is regulated by the level of peak systolic calcium and the kinetics of Ca-transient decline which, in turn, are governed by Ca-TnC dissociation and Ca2+ reuptake by the sarcoplasmic reticulum. Altogether, these findings constitute new evidence about the role of the length-dependent modulation of Ca2+ homeostasis in the mechanisms of calcium regulation of contraction and mechano-calcium feedback in the myocardium.
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Affiliation(s)
- Oleg Lookin
- Laboratory of Biological Motility, Institute of Immunology and Physiology, Ural Branch of Russian Academy of Sciences, Yekaterinburg, Russia.,Center for Fundamental Biotechnology and Bioengineering, Institute of Natural Sciences and Mathematics, Ural Federal University, Yekaterinburg, Russia
| | - Yuri Protsenko
- Laboratory of Biological Motility, Institute of Immunology and Physiology, Ural Branch of Russian Academy of Sciences, Yekaterinburg, Russia
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29
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Abstract
See Article by Shijie Li et al.
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30
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Najafi A, van de Locht M, Schuldt M, Schönleitner P, van Willigenburg M, Bollen I, Goebel M, Ottenheijm CAC, van der Velden J, Helmes M, Kuster DWD. End-diastolic force pre-activates cardiomyocytes and determines contractile force: role of titin and calcium. J Physiol 2019; 597:4521-4531. [PMID: 31314138 PMCID: PMC6852589 DOI: 10.1113/jp277985] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Accepted: 07/10/2019] [Indexed: 12/22/2022] Open
Abstract
Titin functions as a molecular spring, and cardiomyocytes are able, through splicing, to control the length of titin. We hypothesized that together with diastolic [Ca2+], titin‐based stretch pre‐activates cardiomyocytes during diastole and is a major determinant of force production in the subsequent contraction. Through this mechanism titin would play an important role in active force development and length‐dependent activation. Mutations in the splicing factor RNA binding motif protein 20 (RBM20) result in expression of large, highly compliant titin isoforms. We measured single cardiomyocyte work loops that mimic the cardiac cycle in wild‐type (WT) and heterozygous (HET) RBM20‐deficient rats. In addition, we studied the role of diastolic [Ca2+] in membrane‐permeabilized WT and HET cardiomyocytes. Intact cardiomyocytes isolated from HET left ventricles were unable to produce normal levels of work (55% of WT) at low pacing frequencies, but this difference disappeared at high pacing frequencies. Length‐dependent activation (force–sarcomere length relationship) was blunted in HET cardiomyocytes, but the force–end‐diastolic force relationship was not different between HET and WT cardiomyocytes. To delineate the effects of diastolic [Ca2+] and titin pre‐activation on force generation, measurements were performed in detergent‐permeabilized cardiomyocytes. Cardiac twitches were simulated by transiently exposing permeabilized cardiomyocytes to 2 µm Ca2+. Increasing diastolic [Ca2+] from 1 to 80 nm increased force development twofold in WT. Higher diastolic [Ca2+] was needed in HET. These findings are consistent with our hypothesis that pre‐activation increases active force development. Highly compliant titin allows cells to function at higher diastolic [Ca2+].
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Affiliation(s)
- Aref Najafi
- Amsterdam UMC, Vrije Universiteit Amsterdam, Physiology, Amsterdam Cardiovascular Sciences, de Boelelaan 1117, 1081 HZ, Amsterdam, the Netherlands.,Netherlands Heart Institute, PO box 19258, 3501 DG, Utrecht, the Netherlands
| | - Martijn van de Locht
- Amsterdam UMC, Vrije Universiteit Amsterdam, Physiology, Amsterdam Cardiovascular Sciences, de Boelelaan 1117, 1081 HZ, Amsterdam, the Netherlands
| | - Maike Schuldt
- Amsterdam UMC, Vrije Universiteit Amsterdam, Physiology, Amsterdam Cardiovascular Sciences, de Boelelaan 1117, 1081 HZ, Amsterdam, the Netherlands
| | | | | | - Ilse Bollen
- Amsterdam UMC, Vrije Universiteit Amsterdam, Physiology, Amsterdam Cardiovascular Sciences, de Boelelaan 1117, 1081 HZ, Amsterdam, the Netherlands
| | - Max Goebel
- Amsterdam UMC, Vrije Universiteit Amsterdam, Physiology, Amsterdam Cardiovascular Sciences, de Boelelaan 1117, 1081 HZ, Amsterdam, the Netherlands
| | - Coen A C Ottenheijm
- Amsterdam UMC, Vrije Universiteit Amsterdam, Physiology, Amsterdam Cardiovascular Sciences, de Boelelaan 1117, 1081 HZ, Amsterdam, the Netherlands
| | - Jolanda van der Velden
- Amsterdam UMC, Vrije Universiteit Amsterdam, Physiology, Amsterdam Cardiovascular Sciences, de Boelelaan 1117, 1081 HZ, Amsterdam, the Netherlands.,Netherlands Heart Institute, PO box 19258, 3501 DG, Utrecht, the Netherlands
| | - Michiel Helmes
- Amsterdam UMC, Vrije Universiteit Amsterdam, Physiology, Amsterdam Cardiovascular Sciences, de Boelelaan 1117, 1081 HZ, Amsterdam, the Netherlands.,Ionoptix, de Boelelaan 1108, 1081 HV, Amsterdam, the Netherlands.,CytoCypher, de Boelelaan 1108, 1081 HV, Amsterdam, the Netherlands
| | - Diederik W D Kuster
- Amsterdam UMC, Vrije Universiteit Amsterdam, Physiology, Amsterdam Cardiovascular Sciences, de Boelelaan 1117, 1081 HZ, Amsterdam, the Netherlands
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31
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Abstract
Irving and Craig reflect on new work showing that thick filament activation involves myosin motors returning to their OFF state during diastole.
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Affiliation(s)
- Thomas C Irving
- Center for Synchrotron Radiation Research and Instrumentation and Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL
| | - Roger Craig
- Division of Cell Biology and Imaging, Department of Radiology, University of Massachusetts Medical School, Worcester, MA
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32
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Chase PB. Elastic domains of giant proteins in striated muscle: Modeling compliance with rulers. J Gen Physiol 2019; 151:619-622. [PMID: 30975697 PMCID: PMC6504283 DOI: 10.1085/jgp.201912345] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Chase examines a study using the MUSICO model of striated muscle to evaluate the function of giant elastic proteins titin and nebulin.
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Affiliation(s)
- P. Bryant Chase
- Department of Biological Science, Florida State University, Tallahassee, FL
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33
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Koser F, Loescher C, Linke WA. Posttranslational modifications of titin from cardiac muscle: how, where, and what for? FEBS J 2019; 286:2240-2260. [PMID: 30989819 PMCID: PMC6850032 DOI: 10.1111/febs.14854] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Revised: 02/27/2019] [Accepted: 04/13/2019] [Indexed: 12/11/2022]
Abstract
Titin is a giant elastic protein expressed in the contractile units of striated muscle cells, including the sarcomeres of cardiomyocytes. The last decade has seen enormous progress in our understanding of how titin molecular elasticity is modulated in a dynamic manner to help cardiac sarcomeres adjust to the varying hemodynamic demands on the heart. Crucial events mediating the rapid modulation of cardiac titin stiffness are post‐translational modifications (PTMs) of titin. In this review, we first recollect what is known from earlier and recent work on the molecular mechanisms of titin extensibility and force generation. The main goal then is to provide a comprehensive overview of current insight into the relationship between titin PTMs and cardiomyocyte stiffness, notably the effect of oxidation and phosphorylation of titin spring segments on titin stiffness. A synopsis is given of which type of oxidative titin modification can cause which effect on titin stiffness. A large part of the review then covers the mechanically relevant phosphorylation sites in titin, their location along the elastic segment, and the protein kinases and phosphatases known to target these sites. We also include a detailed coverage of the complex changes in phosphorylation at specific titin residues, which have been reported in both animal models of heart disease and in human heart failure, and their correlation with titin‐based stiffness alterations. Knowledge of the relationship between titin PTMs and titin elasticity can be exploited in the search for therapeutic approaches aimed at softening the pathologically stiffened myocardium in heart failure patients.
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34
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Clinical and genetic insights into non-compaction: a meta-analysis and systematic review on 7598 individuals. Clin Res Cardiol 2019; 108:1297-1308. [PMID: 30980206 DOI: 10.1007/s00392-019-01465-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Accepted: 03/19/2019] [Indexed: 10/27/2022]
Abstract
BACKGROUND Left ventricular non-compaction has been increasingly diagnosed in recent years. However, it is still debated whether non-compaction is a pathological condition or a physiological trait. In this meta-analysis and systematic review, we compare studies, which investigated these two different perspectives. Furthermore, we provide a comprehensive overview on the clinical outcome as well as genetic background of left ventricular non-compaction cardiomyopathy in adult patients. METHODS AND RESULTS We retrieved PubMed/Medline literatures in English language from 2000 to 19/09/2018 on clinical outcome and genotype of patients with non-compaction. We summarized and extensively reviewed all studies that passed selection criteria and performed a meta-analysis on key phenotypic parameters. Altogether, 35 studies with 2271 non-compaction patients were included in our meta-analysis. The mean age at diagnosis was the mid of their fifth decade. Two-thirds of patients were male. Congenital heart diseases including atrial or ventricular septum defect or Ebstein anomaly were reported in 7% of patients. Twenty-four percent presented with family history of cardiomyopathy. The mean frequency of neuromuscular diseases was 5%. Heart rhythm abnormalities were reported frequently: conduction disease in 26%, supraventricular tachycardia in 17%, and sustained or non-sustained ventricular tachycardia in 18% of patients. Three important outcome measures were reported including systemic thromboembolic events with a mean frequency of 9%, heart transplantation with 4%, and adequate ICD therapy with 15%. Nine studies investigated the genetics of non-compaction cardiomyopathy. The most frequently mutated gene was TTN with a pooled frequency of 11%. The average frequency of MYH7 mutations was 9%, for MYBPC3 mutations 5%, and for CASQ2 and LDB3 3% each. TPM1, MIB1, ACTC1, and LMNA mutations had an average frequency of 2% each. Mutations in PLN, HCN4, TAZ, DTNA, TNNT2, and RBM20 were reported with a frequency of 1% each. We also summarized the results of eight studies investigating the non-compaction in altogether 5327 athletes, pregnant women, patients with sickle cell disease, as well as individuals from population-based cohorts, in which the presence of left ventricular hypertrabeculation ranged from 1.3 to 37%. CONCLUSION The summarized data indicate that non-compaction may lead to unfavorable outcome in different cardiomyopathy entities. The presence of key features in a multimodal diagnostic approach could distinguish between benign morphological trait and manifest cardiomyopathy.
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35
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Mijailovich SM, Stojanovic B, Nedic D, Svicevic M, Geeves MA, Irving TC, Granzier HL. Nebulin and titin modulate cross-bridge cycling and length-dependent calcium sensitivity. J Gen Physiol 2019; 151:680-704. [PMID: 30948421 PMCID: PMC6504291 DOI: 10.1085/jgp.201812165] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 01/15/2019] [Accepted: 03/03/2019] [Indexed: 12/13/2022] Open
Abstract
Various mutations in the structural proteins nebulin and titin that are present in human disease are known to affect the contractility of striated muscle. Loss of nebulin is associated with reduced actin filament length and impairment of myosin binding to actin, whereas titin is thought to regulate muscle passive elasticity and is likely involved in length-dependent activation. Here, we sought to assess the modulation of muscle function by these sarcomeric proteins by using the computational platform muscle simulation code (MUSICO) to quantitatively separate the effects of structural changes, kinetics of cross-bridge cycling, and calcium sensitivity of the thin filaments. The simulations show that variation in thin filament length cannot by itself account for experimental observations of the contractility in nebulin-deficient muscle, but instead must be accompanied by a decreased myosin binding rate. Additionally, to match the observed calcium sensitivity, the rate of TnI detachment from actin needed to be increased. Simulations for cardiac muscle provided quantitative estimates of the effects of different titin-based passive elasticities on muscle force and activation in response to changes in sarcomere length and interfilament lattice spacing. Predicted force-pCa relations showed a decrease in both active tension and sensitivity to calcium with a decrease in passive tension and sarcomere length. We conclude that this behavior is caused by partial redistribution of the muscle load between active muscle force and titin-dependent passive force, and also by redistribution of stretch along the thin filament, which together modulate the release of TnI from actin. These data help advance understanding of how nebulin and titin mutations affect muscle function.
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Affiliation(s)
- Srboljub M Mijailovich
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, MA .,Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL
| | - Boban Stojanovic
- University of Kragujevac, Faculty of Science, Kragujevac, Serbia
| | - Djordje Nedic
- University of Kragujevac, Faculty of Science, Kragujevac, Serbia
| | - Marina Svicevic
- University of Kragujevac, Faculty of Science, Kragujevac, Serbia
| | - Michael A Geeves
- Department of Biosciences, University of Kent, Canterbury, Kent, UK
| | - Thomas C Irving
- Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL
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36
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Kellermayer D, Smith JE, Granzier H. Titin mutations and muscle disease. Pflugers Arch 2019; 471:673-682. [PMID: 30919088 DOI: 10.1007/s00424-019-02272-5] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Accepted: 03/11/2019] [Indexed: 12/12/2022]
Abstract
The introduction of next-generation sequencing technology has revealed that mutations in the gene that encodes titin (TTN) are linked to multiple skeletal and cardiac myopathies. The most prominent of these myopathies is dilated cardiomyopathy (DCM). Over 60 genes are linked to the etiology of DCM, but by far, the leading cause of DCM is mutations in TTN with truncating variants in TTN (TTNtvs) associated with familial DCM in ∼ 20% of the cases. Titin is a large (3-4 MDa) and abundant protein that forms the third myofilament type of striated muscle where it spans half the sarcomere, from the Z-disk to the M-line. The underlying mechanisms by which titin mutations induce disease are poorly understood and targeted therapies are not available. Here, we review what is known about TTN mutations in muscle disease, with a major focus on DCM. We highlight that exon skipping might provide a possible therapeutic avenue to address diseases that arise from TTNtvs.
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Affiliation(s)
- Dalma Kellermayer
- Department of Cellular and Molecular Medicine, University of Arizona, MRB 325. 1656 E Mabel Street, Tucson, AZ, 85724-5217, USA.,Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, AZ, 85721, USA
| | - John E Smith
- Department of Cellular and Molecular Medicine, University of Arizona, MRB 325. 1656 E Mabel Street, Tucson, AZ, 85724-5217, USA.,Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, AZ, 85721, USA
| | - Henk Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, MRB 325. 1656 E Mabel Street, Tucson, AZ, 85724-5217, USA. .,Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, AZ, 85721, USA.
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37
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Murphy S, Dowling P, Zweyer M, Swandulla D, Ohlendieck K. Proteomic profiling of giant skeletal muscle proteins. Expert Rev Proteomics 2019; 16:241-256. [DOI: 10.1080/14789450.2019.1575205] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- Sandra Murphy
- Department of Biology, Maynooth University, National University of Ireland, Maynooth, Ireland
- Newcastle Fibrosis Research Group, Institute of Cellular Medicine, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
| | - Paul Dowling
- Department of Biology, Maynooth University, National University of Ireland, Maynooth, Ireland
| | - Margit Zweyer
- Institute of Physiology II, University of Bonn, Bonn, Germany
| | | | - Kay Ohlendieck
- Department of Biology, Maynooth University, National University of Ireland, Maynooth, Ireland
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38
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How myofilament strain and strain rate lead the dance of the cardiac cycle. Arch Biochem Biophys 2019; 664:62-67. [PMID: 30710504 PMCID: PMC6589344 DOI: 10.1016/j.abb.2019.01.034] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Revised: 01/21/2019] [Accepted: 01/28/2019] [Indexed: 12/20/2022]
Abstract
Movement of the myocardium can modify organ-level cardiac function and its molecular (crossbridge) mechanisms. This motion, which is defined by myocardial strain and strain rate (muscle shortening, lengthening, and the speed of these movements), occurs throughout the cardiac cycle, including during isovolumic periods. This review highlights how the left ventricular myocardium moves throughout the cardiac cycle, how muscle mechanics experiments provide insight into the regulation of forces used to move blood in and out of the left ventricle, and its impact on (and regulation by) crossbridge and sarcomere kinetics. We specifically highlight how muscle mechanics experiments explain how myocardial relaxation is accelerated by lengthening (strain rate) during late systole and isovolumic relaxation, a lengthening which has been measured in human hearts. Advancing and refining both in vivo measurement and ex vivo protocols with physiologic strain and strain rates could reveal important insights into molecular (crossbridge) kinetics. These advances could provide an improvement in both diagnosis and precise treatment of cardiac dysfunction.
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39
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Rouhana S, Farah C, Roy J, Finan A, Rodrigues de Araujo G, Bideaux P, Scheuermann V, Saliba Y, Reboul C, Cazorla O, Aimond F, Richard S, Thireau J, Fares N. Early calcium handling imbalance in pressure overload-induced heart failure with nearly normal left ventricular ejection fraction. Biochim Biophys Acta Mol Basis Dis 2019; 1865:230-242. [DOI: 10.1016/j.bbadis.2018.08.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Revised: 07/13/2018] [Accepted: 08/02/2018] [Indexed: 02/07/2023]
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40
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Li KL, Methawasin M, Tanner BCW, Granzier HL, Solaro RJ, Dong WJ. Sarcomere length-dependent effects on Ca 2+-troponin regulation in myocardium expressing compliant titin. J Gen Physiol 2018; 151:30-41. [PMID: 30523116 PMCID: PMC6314383 DOI: 10.1085/jgp.201812218] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Accepted: 11/01/2018] [Indexed: 11/20/2022] Open
Abstract
Increases in sarcomere length cause enhanced force generation in cardiomyocytes by an unknown mechanism. Li et al. reveal that titin-based passive tension contributes to length-dependent activation of myofilaments and that tightly bound myosin–actin cross-bridges are associated with this effect. Cardiac performance is tightly regulated at the cardiomyocyte level by sarcomere length, such that increases in sarcomere length lead to sharply enhanced force generation at the same Ca2+ concentration. Length-dependent activation of myofilaments involves dynamic and complex interactions between a multitude of thick- and thin-filament components. Among these components, troponin, myosin, and the giant protein titin are likely to be key players, but the mechanism by which these proteins are functionally linked has been elusive. Here, we investigate this link in the mouse myocardium using in situ FRET techniques. Our objective was to monitor how length-dependent Ca2+-induced conformational changes in the N domain of cardiac troponin C (cTnC) are modulated by myosin–actin cross-bridge (XB) interactions and increased titin compliance. We reconstitute FRET donor- and acceptor-modified cTnC(13C/51C)AEDANS-DDPM into chemically skinned myocardial fibers from wild-type and RBM20-deletion mice. The Ca2+-induced conformational changes in cTnC are quantified and characterized using time-resolved FRET measurements as XB state and sarcomere length are varied. The RBM20-deficient mouse expresses a more compliant N2BA titin isoform, leading to reduced passive tension in the myocardium. This provides a molecular tool to investigate how altered titin-based passive tension affects Ca2+-troponin regulation in response to mechanical stretch. In wild-type myocardium, we observe a direct association of sarcomere length–dependent enhancement of troponin regulation with both Ca2+ activation and strongly bound XB states. In comparison, measurements from titin RBM20-deficient animals show blunted sarcomere length–dependent effects. These results suggest that titin-based passive tension contributes to sarcomere length–dependent Ca2+-troponin regulation. We also conclude that strong XB binding plays an important role in linking the modulatory effect of titin compliance to Ca2+-troponin regulation of the myocardium.
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Affiliation(s)
- King-Lun Li
- Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA
| | - Mei Methawasin
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ
| | - Bertrand C W Tanner
- Integrative Physiology and Neuroscience, Washington State University, Pullman, WA
| | - Henk L Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ
| | - R John Solaro
- The Department of Physiology and Biophysics, Center for Cardiovascular Research, College of Medicine, University of Illinois at Chicago, Chicago, IL
| | - Wen-Ji Dong
- Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA .,Integrative Physiology and Neuroscience, Washington State University, Pullman, WA
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Caremani M, Pinzauti F, Powers JD, Governali S, Narayanan T, Stienen GJM, Reconditi M, Linari M, Lombardi V, Piazzesi G. Inotropic interventions do not change the resting state of myosin motors during cardiac diastole. J Gen Physiol 2018; 151:53-65. [PMID: 30510036 PMCID: PMC6314382 DOI: 10.1085/jgp.201812196] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Accepted: 10/26/2018] [Indexed: 11/20/2022] Open
Abstract
When striated (skeletal and cardiac) muscle is in its relaxed state, myosin motors are packed in helical tracks on the surface of the thick filament, folded toward the center of the sarcomere, and unable to bind actin or hydrolyze ATP (OFF state). This raises the question of whatthe mechanism is that integrates the Ca2+-dependent thin filament activation, making myosin heads available for interaction with actin. Here we test the interdependency of the thin and thick filament regulatory mechanisms in intact trabeculae from the rat heart. We record the x-ray diffraction signals that mark the state of the thick filament during inotropic interventions (increase in sarcomere length from 1.95 to 2.25 µm and addition of 10-7 M isoprenaline), which potentiate the twitch force developed by an electrically paced trabecula by up to twofold. During diastole, none of the signals related to the OFF state of the thick filament are significantly affected by these interventions, except the intensity of both myosin-binding protein C- and troponin-related meridional reflections, which reduce by 20% in the presence of isoprenaline. These results indicate that recruitment of myosin motors from their OFF state occurs independently and downstream from thin filament activation. This is in agreement with the recently discovered mechanism based on thick filament mechanosensing in which the number of motors available for interaction with actin rapidly adapts to the stress on the thick filament and thus to the loading conditions of the contraction. The gain of this positive feedback may be modulated by both sarcomere length and the degree of phosphorylation of myosin-binding protein C.
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Affiliation(s)
| | | | | | | | | | - Ger J M Stienen
- Department of Physiology, VU University Medical Center, Amsterdam, The Netherlands
| | | | - Marco Linari
- PhysioLab, University of Florence, Firenze, Italy
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Chakouri N, Reboul C, Boulghobra D, Kleindienst A, Nottin S, Gayrard S, Roubille F, Matecki S, Lacampagne A, Cazorla O. Stress-induced protein S-glutathionylation and phosphorylation crosstalk in cardiac sarcomeric proteins - Impact on heart function. Int J Cardiol 2018; 258:207-216. [PMID: 29544934 DOI: 10.1016/j.ijcard.2017.12.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Revised: 11/16/2017] [Accepted: 12/01/2017] [Indexed: 11/25/2022]
Abstract
BACKGROUND The interplay between oxidative stress and other signaling pathways in the contractile machinery regulation during cardiac stress and its consequences on cardiac function remains poorly understood. We evaluated the effect of the crosstalk between β-adrenergic and redox signaling on post-translational modifications of sarcomeric regulatory proteins, Myosin Binding Protein-C (MyBP-C) and Troponin I (TnI). METHODS AND RESULTS We mimicked in vitro high level of physiological cardiac stress by forcing rat hearts to produce high levels of oxidized glutathione. This led to MyBP-C S-glutathionylation associated with lower protein kinase A (PKA) dependent phosphorylations of MyBP-C and TnI, increased myofilament Ca2+ sensitivity, and decreased systolic and diastolic properties of the isolated perfused heart. Moderate physiological cardiac stress achieved in vivo with a single 35 min exercise (Low stress induced by exercise, LSE) increased TnI and cMyBP-C phosphorylations and improved cardiac function in vivo (echocardiography) and ex-vivo (isolated perfused heart). High stress induced by exercise (HSE) altered strongly oxidative stress markers and phosphorylations were unchanged despite increased PKA activity. HSE led to in vivo intrinsic cardiac dysfunction associated with myofilament Ca2+ sensitivity defects. To limit protein S-glutathionylation after HSE, we treated rats with N-acetylcysteine (NAC). NAC restored the ability of PKA to modulate myofilament Ca2+ sensitivity and prevented cardiac dysfunction observed in HSE animals. CONCLUSION Under cardiac stress, adrenergic and oxidative signaling pathways work in concert to alter myofilament properties and are key regulators of cardiac function.
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Affiliation(s)
- Nourdine Chakouri
- PHYMEDEXP, INSERM U1046, CNRS UMR9214, Université de Montpellier, CHRU Montpellier, Montpellier, France
| | - Cyril Reboul
- EA 4278, Laboratoire de Pharm-Ecologie Cardiovasculaire, Avignon University, Avignon, France
| | - Doria Boulghobra
- EA 4278, Laboratoire de Pharm-Ecologie Cardiovasculaire, Avignon University, Avignon, France
| | - Adrien Kleindienst
- EA 4278, Laboratoire de Pharm-Ecologie Cardiovasculaire, Avignon University, Avignon, France
| | - Stéphane Nottin
- EA 4278, Laboratoire de Pharm-Ecologie Cardiovasculaire, Avignon University, Avignon, France
| | - Sandrine Gayrard
- EA 4278, Laboratoire de Pharm-Ecologie Cardiovasculaire, Avignon University, Avignon, France
| | - François Roubille
- PHYMEDEXP, INSERM U1046, CNRS UMR9214, Université de Montpellier, CHRU Montpellier, Montpellier, France
| | - Stefan Matecki
- PHYMEDEXP, INSERM U1046, CNRS UMR9214, Université de Montpellier, CHRU Montpellier, Montpellier, France
| | - Alain Lacampagne
- PHYMEDEXP, INSERM U1046, CNRS UMR9214, Université de Montpellier, CHRU Montpellier, Montpellier, France
| | - Olivier Cazorla
- PHYMEDEXP, INSERM U1046, CNRS UMR9214, Université de Montpellier, CHRU Montpellier, Montpellier, France.
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43
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Sedaghat-Hamedani F, Haas J, Zhu F, Geier C, Kayvanpour E, Liss M, Lai A, Frese K, Pribe-Wolferts R, Amr A, Li DT, Samani OS, Carstensen A, Bordalo DM, Müller M, Fischer C, Shao J, Wang J, Nie M, Yuan L, Haßfeld S, Schwartz C, Zhou M, Zhou Z, Shu Y, Wang M, Huang K, Zeng Q, Cheng L, Fehlmann T, Ehlermann P, Keller A, Dieterich C, Streckfuß-Bömeke K, Liao Y, Gotthardt M, Katus HA, Meder B. Clinical genetics and outcome of left ventricular non-compaction cardiomyopathy. Eur Heart J 2018; 38:3449-3460. [PMID: 29029073 DOI: 10.1093/eurheartj/ehx545] [Citation(s) in RCA: 139] [Impact Index Per Article: 23.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Accepted: 09/20/2017] [Indexed: 12/30/2022] Open
Abstract
Aims In this study, we aimed to clinically and genetically characterize LVNC patients and investigate the prevalence of variants in known and novel LVNC disease genes. Introduction Left ventricular non-compaction cardiomyopathy (LVNC) is an increasingly recognized cause of heart failure, arrhythmia, thromboembolism, and sudden cardiac death. We sought here to dissect its genetic causes, phenotypic presentation and outcome. Methods and results In our registry with follow-up of in the median 61 months, we analysed 95 LVNC patients (68 unrelated index patients and 27 affected relatives; definite familial LVNC = 23.5%) by cardiac phenotyping, molecular biomarkers and exome sequencing. Cardiovascular events were significantly more frequent in LVNC patients compared with an age-matched group of patients with non-ischaemic dilated cardiomyopathy (hazard ratio = 2.481, P = 0.002). Stringent genetic classification according to ACMG guidelines revealed that TTN, LMNA, and MYBPC3 are the most prevalent disease genes (13 patients are carrying a pathogenic truncating TTN variant, odds ratio = 40.7, Confidence interval = 21.6-76.6, P < 0.0001, percent spliced in 76-100%). We also identified novel candidate genes for LVNC. For RBM20, we were able to perform detailed familial, molecular and functional studies. We show that the novel variant p.R634L in the RS domain of RBM20 co-segregates with LVNC, leading to titin mis-splicing as revealed by RNA sequencing of heart tissue in mutation carriers, protein analysis, and functional splice-reporter assays. Conclusion Our data demonstrate that the clinical course of symptomatic LVNC can be severe. The identified pathogenic variants and distribution of disease genes-a titin-related pathomechanism is found in every fourth patient-should be considered in genetic counselling of patients. Pathogenic variants in the nuclear proteins Lamin A/C and RBM20 were associated with worse outcome.
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Affiliation(s)
- Farbod Sedaghat-Hamedani
- Department of Medicine III, Institute for Cardiomyopathies Heidelberg (ICH), University of Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), Heidelberg, Germany
| | - Jan Haas
- Department of Medicine III, Institute for Cardiomyopathies Heidelberg (ICH), University of Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), Heidelberg, Germany
| | - Feng Zhu
- Department of Medicine III, Institute for Cardiomyopathies Heidelberg (ICH), University of Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany.,Department of Cardiology, Institute of Cardiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, 430022 Wuhan, China
| | - Christian Geier
- Experimental and Clinical Research Center (ECRC), A Joint Cooperation of Charité Medical Faculty and Max Delbrück Center for Molecular Medicine (MDC), Augustenburger Platz 1, 13353 Berlin, Germany.,DZHK (German Centre for Cardiovascular Research), Berlin, Germany
| | - Elham Kayvanpour
- Department of Medicine III, Institute for Cardiomyopathies Heidelberg (ICH), University of Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), Heidelberg, Germany
| | - Martin Liss
- DZHK (German Centre for Cardiovascular Research), Berlin, Germany.,Neuromuscular and Cardiovascular Cell Biology, Max Delbrück Center for Molecular Medicine, Robert-Rössle-Str. 10, 13092 Berlin, Germany
| | - Alan Lai
- Department of Medicine III, Institute for Cardiomyopathies Heidelberg (ICH), University of Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), Heidelberg, Germany
| | - Karen Frese
- Department of Medicine III, Institute for Cardiomyopathies Heidelberg (ICH), University of Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), Heidelberg, Germany
| | - Regina Pribe-Wolferts
- Department of Medicine III, Institute for Cardiomyopathies Heidelberg (ICH), University of Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany
| | - Ali Amr
- Department of Medicine III, Institute for Cardiomyopathies Heidelberg (ICH), University of Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), Heidelberg, Germany
| | - Daniel Tian Li
- Department of Medicine III, Institute for Cardiomyopathies Heidelberg (ICH), University of Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), Heidelberg, Germany
| | - Omid Shirvani Samani
- Department of Medicine III, Institute for Cardiomyopathies Heidelberg (ICH), University of Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), Heidelberg, Germany
| | - Avisha Carstensen
- Department of Medicine III, Institute for Cardiomyopathies Heidelberg (ICH), University of Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany
| | - Diana Martins Bordalo
- Department of Medicine III, Institute for Cardiomyopathies Heidelberg (ICH), University of Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), Heidelberg, Germany
| | - Marion Müller
- Department of Medicine III, Institute for Cardiomyopathies Heidelberg (ICH), University of Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), Heidelberg, Germany
| | - Christine Fischer
- Department of Human Genetics, University of Heidelberg, Im Neuenheimer Feld 366, 69120 Heidelberg, Germany
| | - Jing Shao
- Department of Cardiology, Institute of Cardiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, 430022 Wuhan, China
| | - Jing Wang
- Department of Radiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, 430022 Wuhan, China
| | - Ming Nie
- Department of Cardiology, Institute of Cardiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, 430022 Wuhan, China
| | - Li Yuan
- Department of Ultrasound, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, 430022 Wuhan, China
| | - Sabine Haßfeld
- Department of Cardiology, Virchow Klinikum, Charité University Medicine Berlin, Augustenburger Platz 1, 13353 Berlin, Germany
| | - Christine Schwartz
- Experimental and Clinical Research Center (ECRC), A Joint Cooperation of Charité Medical Faculty and Max Delbrück Center for Molecular Medicine (MDC), Augustenburger Platz 1, 13353 Berlin, Germany
| | - Min Zhou
- Department of Internal Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Zihua Zhou
- Department of Cardiology, Institute of Cardiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, 430022 Wuhan, China
| | - Yanwen Shu
- Department of Cardiology, Institute of Cardiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, 430022 Wuhan, China
| | - Min Wang
- Department of Cardiology, Institute of Cardiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, 430022 Wuhan, China
| | - Kai Huang
- Department of Cardiology, Institute of Cardiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, 430022 Wuhan, China
| | - Qiutang Zeng
- Department of Cardiology, Institute of Cardiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, 430022 Wuhan, China
| | - Longxian Cheng
- Department of Cardiology, Institute of Cardiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, 430022 Wuhan, China
| | - Tobias Fehlmann
- Department of Bioinformatics, University of Saarland, Building E2.1, 66123 Saarbrücken, Germany
| | - Philipp Ehlermann
- Department of Medicine III, Institute for Cardiomyopathies Heidelberg (ICH), University of Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany
| | - Andreas Keller
- Department of Bioinformatics, University of Saarland, Building E2.1, 66123 Saarbrücken, Germany
| | - Christoph Dieterich
- DZHK (German Centre for Cardiovascular Research), Heidelberg, Germany.,Department of Medicine III, Klaus Tschira Institute for Computational Cardiology, University of Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany
| | - Katrin Streckfuß-Bömeke
- Department of Cardiology and Pneumology, Georg-August-University Göttingen, Robert-Koch-Str. 40, 37075 Göttingen, Germany.,DZHK (German Centre for Cardiovascular Research), Göttingen, Germany
| | - Yuhua Liao
- Department of Cardiology, Institute of Cardiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, 430022 Wuhan, China
| | - Michael Gotthardt
- DZHK (German Centre for Cardiovascular Research), Berlin, Germany.,Neuromuscular and Cardiovascular Cell Biology, Max Delbrück Center for Molecular Medicine, Robert-Rössle-Str. 10, 13092 Berlin, Germany
| | - Hugo A Katus
- Department of Medicine III, Institute for Cardiomyopathies Heidelberg (ICH), University of Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), Heidelberg, Germany
| | - Benjamin Meder
- Department of Medicine III, Institute for Cardiomyopathies Heidelberg (ICH), University of Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), Heidelberg, Germany
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Joumaa V, Bertrand F, Liu S, Poscente S, Herzog W. Does partial titin degradation affect sarcomere length nonuniformities and force in active and passive myofibrils? Am J Physiol Cell Physiol 2018; 315:C310-C318. [PMID: 29768046 DOI: 10.1152/ajpcell.00183.2017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The aim of this study was to determine the role of titin in preventing the development of sarcomere length nonuniformities following activation and after active and passive stretch by determining the effect of partial titin degradation on sarcomere length nonuniformities and force in passive and active myofibrils. Selective partial titin degradation was performed using a low dose of trypsin. Myofibrils were set at a sarcomere length of 2.4 µm and then passively stretched to sarcomere lengths of 3.4 and 4.4 µm. In the active condition, myofibrils were set at a sarcomere length of 2.8 µm, activated, and actively stretched by 1 µm/sarcomere. The extent of sarcomere length nonuniformities was calculated for each sarcomere as the absolute difference between sarcomere length and the mean sarcomere length of the myofibril. Our main finding is that partial titin degradation does not increase sarcomere length nonuniformities after passive stretch and activation compared with when titin is intact but increases the extent of sarcomere length nonuniformities after active stretch. Furthermore, when titin was partially degraded, active and passive stresses were substantially reduced. These results suggest that titin plays a crucial role in actively stretched myofibrils and is likely involved in active and passive force production.
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Affiliation(s)
- V Joumaa
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, AB, Canada
| | - F Bertrand
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, AB, Canada
| | - S Liu
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, AB, Canada
| | - S Poscente
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, AB, Canada
| | - W Herzog
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, AB, Canada
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Bohlooli Ghashghaee N, Li KL, Solaro RJ, Dong WJ. Role of the C-terminus mobile domain of cardiac troponin I in the regulation of thin filament activation in skinned papillary muscle strips. Arch Biochem Biophys 2018; 648:27-35. [PMID: 29704484 DOI: 10.1016/j.abb.2018.04.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Revised: 04/18/2018] [Accepted: 04/21/2018] [Indexed: 11/19/2022]
Abstract
The C-terminus mobile domain of cTnI (cTnI-MD) is a highly conserved region which stabilizes the actin-cTnI interaction during the diastole. Upon Ca2+-binding to cTnC, cTnI-MD participates in a regulatory switching that involves cTnI to switch from interacting with actin toward interacting with the Ca2+-regulatory domain of cTnC. Despite many studies targeting the cTnI-MD, the role of this region in the length-dependent activation of cardiac contractility is yet to be determined. The present study investigated the functional consequences of losing the entire cTnI-MD in cTnI(1-167) truncation mutant, as it was exchanged for endogenous cTnI in skinned rat papillary muscle fibers. The influence of cTnI-MD truncation on the extent of the N-domain of cTnC hydrophobic cleft opening and the steady-state force as a function of sarcomere length (SL), cross-bridge state, and [Ca2+] was assessed using the simultaneous in situ time-resolved FRET and force measurements at short (1.8 μm) and long (2.2 μm) SLs. Our results show the significant role of cTnI-MD in the length dependent thin filament activation and the coupling between thin and thick filament regulations affected by SL. Our results also suggest that cTnI-MD transmits the effects of SL change to the core of troponin complex.
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Affiliation(s)
- Nazanin Bohlooli Ghashghaee
- The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA 99164, USA
| | - King-Lun Li
- The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA 99164, USA
| | - R John Solaro
- The Department of Physiology and Biophysics, Center for Cardiovascular Research, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Wen-Ji Dong
- The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA 99164, USA; The Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, WA 99164, USA.
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Affiliation(s)
- Wolfgang A. Linke
- Institute of Physiology II, University of Münster, 48149 Münster, Germany
- Deutsches Zentrum für Herz-Kreislaufforschung, Partner Site Göttingen, 37073 Göttingen, Germany
- Cardiac Mechanotransduction Group, Clinic for Cardiology and Pneumology, University Medical Center, 37073 Göttingen, Germany
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Protein phosphatase 5 regulates titin phosphorylation and function at a sarcomere-associated mechanosensor complex in cardiomyocytes. Nat Commun 2018; 9:262. [PMID: 29343782 PMCID: PMC5772059 DOI: 10.1038/s41467-017-02483-3] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Accepted: 12/04/2017] [Indexed: 12/14/2022] Open
Abstract
Serine/threonine protein phosphatase 5 (PP5) is ubiquitously expressed in eukaryotic cells; however, its function in cardiomyocytes is unknown. Under basal conditions, PP5 is autoinhibited, but enzymatic activity rises upon binding of specific factors, such as the chaperone Hsp90. Here we show that PP5 binds and dephosphorylates the elastic N2B-unique sequence (N2Bus) of titin in cardiomyocytes. Using various binding and phosphorylation tests, cell-culture manipulation, and transgenic mouse hearts, we demonstrate that PP5 associates with N2Bus in vitro and in sarcomeres and is antagonistic to several protein kinases, which phosphorylate N2Bus and lower titin-based passive tension. PP5 is pathologically elevated and likely contributes to hypo-phosphorylation of N2Bus in failing human hearts. Furthermore, Hsp90-activated PP5 interacts with components of a sarcomeric, N2Bus-associated, mechanosensor complex, and blocks mitogen-activated protein-kinase signaling in this complex. Our work establishes PP5 as a compartmentalized, well-controlled phosphatase in cardiomyocytes, which regulates titin properties and kinase signaling at the myofilaments. Protein phosphatase 5 (PP5) is expressed in many cell types but its role in cardiomyocytes is unknown. Here the authors show that PP5 binds and dephosphorylates elastic titin in cardiac sarcomeres, and that PP5 is increased in heart failure, reducing cardiomyocyte compliance.
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Ait Mou Y, Lacampagne A, Irving T, Scheuermann V, Blot S, Ghaleh B, de Tombe PP, Cazorla O. Altered myofilament structure and function in dogs with Duchenne muscular dystrophy cardiomyopathy. J Mol Cell Cardiol 2017; 114:345-353. [PMID: 29275006 DOI: 10.1016/j.yjmcc.2017.12.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 11/28/2017] [Accepted: 12/20/2017] [Indexed: 11/16/2022]
Abstract
AIM Duchenne Muscular Dystrophy (DMD) is associated with progressive depressed left ventricular (LV) function. However, DMD effects on myofilament structure and function are poorly understood. Golden Retriever Muscular Dystrophy (GRMD) is a dog model of DMD recapitulating the human form of DMD. OBJECTIVE The objective of this study is to evaluate myofilament structure and function alterations in GRMD model with spontaneous cardiac failure. METHODS AND RESULTS We have employed synchrotron X-rays diffraction to evaluate myofilament lattice spacing at various sarcomere lengths (SL) on permeabilized LV myocardium. We found a negative correlation between SL and lattice spacing in both sub-epicardium (EPI) and sub-endocardium (ENDO) LV layers in control dog hearts. In the ENDO of GRMD hearts this correlation is steeper due to higher lattice spacing at short SL (1.9μm). Furthermore, cross-bridge cycling indexed by the kinetics of tension redevelopment (ktr) was faster in ENDO GRMD myofilaments at short SL. We measured post-translational modifications of key regulatory contractile proteins. S-glutathionylation of cardiac Myosin Binding Protein-C (cMyBP-C) was unchanged and PKA dependent phosphorylation of the cMyBP-C was significantly reduced in GRMD ENDO tissue and more modestly in EPI tissue. CONCLUSIONS We found a gradient of contractility in control dogs' myocardium that spreads across the LV wall, negatively correlated with myofilament lattice spacing. Chronic stress induced by dystrophin deficiency leads to heart failure that is tightly associated with regional structural changes indexed by increased myofilament lattice spacing, reduced phosphorylation of regulatory proteins and altered myofilament contractile properties in GRMD dogs.
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Affiliation(s)
- Younss Ait Mou
- College of Science and Engineering, Hamad Bin Khalifa University, Doha, Qatar; Department of Cell and Molecular Physiology, Heath Science Division, Loyola University Chicago, Maywood, IL 60153, USA
| | - Alain Lacampagne
- INSERM U1046, CNRS UMR 9214, Université de Montpellier, Physiologie et Médecine Expérimentale du cœur et des muscles - PHYMEDEXP, CHU Arnaud de Villeneuve, 34295 Montpellier cedex 05, France
| | - Thomas Irving
- Department of Cell and Molecular Physiology, Heath Science Division, Loyola University Chicago, Maywood, IL 60153, USA; Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Valérie Scheuermann
- INSERM U1046, CNRS UMR 9214, Université de Montpellier, Physiologie et Médecine Expérimentale du cœur et des muscles - PHYMEDEXP, CHU Arnaud de Villeneuve, 34295 Montpellier cedex 05, France
| | - Stéphane Blot
- Inserm U955-E10, IMRB, Université Paris Est, Ecole nationale vétérinaire d'Alfort, Maisons-Alfort 94700, France
| | | | - Pieter P de Tombe
- Department of Cell and Molecular Physiology, Heath Science Division, Loyola University Chicago, Maywood, IL 60153, USA
| | - Olivier Cazorla
- INSERM U1046, CNRS UMR 9214, Université de Montpellier, Physiologie et Médecine Expérimentale du cœur et des muscles - PHYMEDEXP, CHU Arnaud de Villeneuve, 34295 Montpellier cedex 05, France..
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Bohlooli Ghashghaee N, Tanner BCW, Dong WJ. Functional significance of C-terminal mobile domain of cardiac troponin I. Arch Biochem Biophys 2017; 634:38-46. [PMID: 28958680 DOI: 10.1016/j.abb.2017.09.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Revised: 09/08/2017] [Accepted: 09/24/2017] [Indexed: 01/22/2023]
Abstract
Ca2+-regulation of cardiac contractility is mediated through the troponin complex, which comprises three subunits: cTnC, cTnI, and cTnT. As intracellular [Ca2+] increases, cTnI reduces its binding interactions with actin to primarily interact with cTnC, thereby enabling contraction. A portion of this regulatory switching involves the mobile domain of cTnI (cTnI-MD), the role of which in muscle contractility is still elusive. To study the functional significance of cTnI-MD, we engineered two cTnI constructs in which the MD was truncated to various extents: cTnI(1-167) and cTnI(1-193). These truncations were exchanged for endogenous cTnI in skinned rat papillary muscle fibers, and their influence on Ca2+-activated contraction and cross-bridge cycling kinetics was assessed at short (1.9 μm) and long (2.2 μm) sarcomere lengths (SLs). Our results show that the cTnI(1-167) truncation diminished the SL-induced increase in Ca2+-sensitivity of contraction, but not the SL-dependent increase in maximal tension, suggesting an uncoupling between the thin and thick filament contributions to length dependent activation. Compared to cTnI(WT), both truncations displayed greater Ca2+-sensitivity and faster cross-bridge attachment rates at both SLs. Furthermore, cTnI(1-167) slowed MgADP release rate and enhanced cross-bridge binding. Our findings imply that cTnI-MD truncations affect the blocked-to closed-state transition(s) and destabilize the closed-state position of tropomyosin.
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Affiliation(s)
- Nazanin Bohlooli Ghashghaee
- The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA 99164, USA
| | - Bertrand C W Tanner
- The Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, WA 99164, USA
| | - Wen-Ji Dong
- The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA 99164, USA; The Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, WA 99164, USA.
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Titin-mediated thick filament activation, through a mechanosensing mechanism, introduces sarcomere-length dependencies in mathematical models of rat trabecula and whole ventricle. Sci Rep 2017; 7:5546. [PMID: 28717163 PMCID: PMC5514028 DOI: 10.1038/s41598-017-05999-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Accepted: 06/08/2017] [Indexed: 11/08/2022] Open
Abstract
Recent experimental evidence in skeletal muscle demonstrated the existence of a thick-filament mechanosensing mechanism, acting as a second regulatory system for muscle contraction, in addition to calcium-mediated thin filament regulation. These two systems cooperate to generate force, but the extent to which their interaction is relevant in physiologically contracting muscle was not yet assessed experimentally. Therefore, we included both regulatory mechanisms in a mathematical model of rat trabecula and whole ventricle. No additional regulatory mechanisms were considered in our model. Our simulations suggested that mechanosensing regulation is not limited to the initial phases of contraction but, instead, is crucial during physiological contraction. An important consequence of this finding is that titin mediated thick filament activation can account for several sarcomere length dependencies observed in contracting muscle. Under the hypothesis that a similar mechanism is acting on cardiac muscle, and within the limits of a finite element left ventricle model, we predict that these two regulatory mechanisms are crucial for the molecular basis of the Frank-Starling law of the heart.
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