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Kuo CW, Pratiwi FW, Liu YT, Chueh DY, Chen P. Revealing the nanometric structural changes in myocardial infarction models by time-lapse intravital imaging. Front Bioeng Biotechnol 2022; 10:935415. [PMID: 36051583 PMCID: PMC9424828 DOI: 10.3389/fbioe.2022.935415] [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] [Received: 05/05/2022] [Accepted: 07/25/2022] [Indexed: 11/13/2022] Open
Abstract
In the development of bioinspired nanomaterials for therapeutic applications, it is very important to validate the design of nanomaterials in the disease models. Therefore, it is desirable to visualize the change of the cells in the diseased site at the nanoscale. Heart diseases often start with structural, morphological, and functional alterations of cardiomyocyte components at the subcellular level. Here, we developed straightforward technique for long-term real-time intravital imaging of contracting hearts without the need of cardiac pacing and complex post processing images to understand the subcellular structural and dynamic changes in the myocardial infarction model. A two-photon microscope synchronized with electrocardiogram signals was used for long-term in vivo imaging of a contracting heart with subcellular resolution. We found that the structural and dynamic behaviors of organelles in cardiomyocytes closely correlated with heart function. In the myocardial infarction model, sarcomere shortening decreased from ∼15% (healthy) to ∼8% (diseased) as a result of impaired cardiac function, whereas the distances between sarcomeres increased by 100 nm (from 2.11 to 2.21 μm) in the diastolic state. In addition, T-tubule system regularity analysis revealed that T-tubule structures that were initially highly organized underwent significant remodeling. Morphological remodeling and changes in dynamic activity at the subcellular level are essential to maintain heart function after infarction in a heart disease model.
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Affiliation(s)
- Chiung Wen Kuo
- Research Center for Applied Science, Academia Sinica, Taipei, Taiwan
| | | | - Yen-Ting Liu
- Research Center for Applied Science, Academia Sinica, Taipei, Taiwan
| | - Di-Yen Chueh
- Research Center for Applied Science, Academia Sinica, Taipei, Taiwan
| | - Peilin Chen
- Research Center for Applied Science, Academia Sinica, Taipei, Taiwan
- Institute of Physics, Academia Sinica, Taipei, Taiwan
- *Correspondence: Peilin Chen,
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2
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Lombardo ME, Carraro E, Sancricca C, Armando M, Catteruccia M, Mazzone E, Ricci G, Salamino F, Santorelli FM, Filosto M. Management of motor rehabilitation in individuals with muscular dystrophies. 1 st Consensus Conference report from UILDM - Italian Muscular Dystrophy Association (Rome, January 25-26, 2019). ACTA MYOLOGICA : MYOPATHIES AND CARDIOMYOPATHIES : OFFICIAL JOURNAL OF THE MEDITERRANEAN SOCIETY OF MYOLOGY 2021; 40:72-87. [PMID: 34355124 PMCID: PMC8290512 DOI: 10.36185/2532-1900-046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Accepted: 06/09/2021] [Indexed: 11/03/2022]
Abstract
Muscular dystrophy (MD) is a group of neuromuscular diseases characterized by progressive muscle weakness due to various mutations in several genes involved in muscle structure and function. The age at onset, evolution and severity of the different forms of MD can vary and there is often impairment of motor function and activities of daily living. Although there have been important scientific advances with regard to pharmacological therapies for many forms of MD, rehabilitation management remains central to ensuring the patient's psychophysical well-being. Here we report the results of an Italian consensus conference promoted by UILDM (Unione Italiana Lotta alla Distrofia Muscolare, the Italian Muscular Dystrophy Association) in order to establish general indications and agreed protocols for motor rehabilitation of the different forms of MD.
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Affiliation(s)
| | - Elena Carraro
- Neuromuscular Omnicentre, Fondazione Serena Onlus, Milan, Italy
| | - Cristina Sancricca
- Centro di Riabilitazione UILDM Lazio ONLUS, Rome, Italy
- UOC Neurofisiopatologia, Dipartimento Scienze dell’Invecchiamento, Neurologiche, Ortopediche e della Testa-Collo, Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy
| | - Michela Armando
- Department of Rehabilitation, Bambino Gesù Children’s Hospital, IRCCS, Rome, Italy
| | - Michela Catteruccia
- Unit of Neuromuscular and Neurodegenerative Disorders, Laboratory of Molecular Medicine, Department of Neurosciences, Bambino Gesù Children’s Hospital, IRCCS, Rome, Italy
| | - Elena Mazzone
- Physioterapist and international trainer for therapeutic trials, Rome, Italy
| | - Giulia Ricci
- Neurology Unit, Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy
| | | | | | - Massimiliano Filosto
- Department of Clinical and Experimental Sciences, University of Brescia; NeMO-Brescia Clinical Center for Neuromuscular Diseases, Brescia, Italy
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Kaya-Çopur A, Marchiano F, Hein MY, Alpern D, Russeil J, Luis NM, Mann M, Deplancke B, Habermann BH, Schnorrer F. The Hippo pathway controls myofibril assembly and muscle fiber growth by regulating sarcomeric gene expression. eLife 2021; 10:e63726. [PMID: 33404503 PMCID: PMC7815313 DOI: 10.7554/elife.63726] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Accepted: 01/05/2021] [Indexed: 12/30/2022] Open
Abstract
Skeletal muscles are composed of gigantic cells called muscle fibers, packed with force-producing myofibrils. During development, the size of individual muscle fibers must dramatically enlarge to match with skeletal growth. How muscle growth is coordinated with growth of the contractile apparatus is not understood. Here, we use the large Drosophila flight muscles to mechanistically decipher how muscle fiber growth is controlled. We find that regulated activity of core members of the Hippo pathway is required to support flight muscle growth. Interestingly, we identify Dlg5 and Slmap as regulators of the STRIPAK phosphatase, which negatively regulates Hippo to enable post-mitotic muscle growth. Mechanistically, we show that the Hippo pathway controls timing and levels of sarcomeric gene expression during development and thus regulates the key components that physically mediate muscle growth. Since Dlg5, STRIPAK and the Hippo pathway are conserved a similar mechanism may contribute to muscle or cardiomyocyte growth in humans.
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Affiliation(s)
- Aynur Kaya-Çopur
- Aix Marseille University, CNRS, IBDM, Turing Center for Living SystemsMarseilleFrance
- Max Planck Institute of BiochemistryMartinsriedGermany
| | - Fabio Marchiano
- Aix Marseille University, CNRS, IBDM, Turing Center for Living SystemsMarseilleFrance
| | - Marco Y Hein
- Max Planck Institute of BiochemistryMartinsriedGermany
| | - Daniel Alpern
- Institute of Bioengineering, School of Life Sciences, École Polytechnique Fédérale de Lausanne (EPFL)LausanneSwitzerland
| | - Julie Russeil
- Institute of Bioengineering, School of Life Sciences, École Polytechnique Fédérale de Lausanne (EPFL)LausanneSwitzerland
| | - Nuno Miguel Luis
- Aix Marseille University, CNRS, IBDM, Turing Center for Living SystemsMarseilleFrance
| | - Matthias Mann
- Max Planck Institute of BiochemistryMartinsriedGermany
| | - Bart Deplancke
- Institute of Bioengineering, School of Life Sciences, École Polytechnique Fédérale de Lausanne (EPFL)LausanneSwitzerland
| | - Bianca H Habermann
- Aix Marseille University, CNRS, IBDM, Turing Center for Living SystemsMarseilleFrance
| | - Frank Schnorrer
- Aix Marseille University, CNRS, IBDM, Turing Center for Living SystemsMarseilleFrance
- Max Planck Institute of BiochemistryMartinsriedGermany
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4
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Estimation of Forces on Actin Filaments in Living Muscle from X-ray Diffraction Patterns and Mechanical Data. Int J Mol Sci 2019; 20:ijms20236044. [PMID: 31801239 PMCID: PMC6928692 DOI: 10.3390/ijms20236044] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2019] [Revised: 11/12/2019] [Accepted: 11/26/2019] [Indexed: 11/17/2022] Open
Abstract
Many biological processes are triggered or driven by mechanical forces in the cytoskeletal network, but these transducing forces have rarely been assessed. Striated muscle, with its well-organized structure provides an opportunity to assess intracellular forces using small-angle X-ray fiber diffraction. We present a new methodology using Monte Carlo simulations of muscle contraction in an explicit 3D sarcomere lattice to predict the fiber deformations and length changes along thin filaments during contraction. Comparison of predicted diffraction patterns to experimental meridional X-ray reflection profiles allows assessment of the stepwise changes in intermonomer spacings and forces in the myofilaments within living muscle cells. These changes along the filament length reflect the effect of forces from randomly attached crossbridges. This approach enables correlation of the molecular events, such as the current number of attached crossbridges and the distributions of crossbridge forces to macroscopic measurements of force and length changes during muscle contraction. In addition, assessments of fluctuations in local forces in the myofilaments may reveal how variations in the filament forces acting on signaling proteins in the sarcomere M-bands and Z-discs modulate gene expression, protein synthesis and degradation, and as well to mechanisms of adaptation of muscle in response to changes in mechanical loading.
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5
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Ovchinnikova E, Hoes M, Ustyantsev K, Bomer N, de Jong TV, van der Mei H, Berezikov E, van der Meer P. Modeling Human Cardiac Hypertrophy in Stem Cell-Derived Cardiomyocytes. Stem Cell Reports 2018; 10:794-807. [PMID: 29456183 PMCID: PMC5918264 DOI: 10.1016/j.stemcr.2018.01.016] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2017] [Revised: 01/15/2018] [Accepted: 01/15/2018] [Indexed: 12/17/2022] Open
Abstract
Cardiac hypertrophy accompanies many forms of cardiovascular diseases. The mechanisms behind the development and regulation of cardiac hypertrophy in the human setting are poorly understood, which can be partially attributed to the lack of a human cardiomyocyte-based preclinical test system recapitulating features of diseased myocardium. The objective of our study is to determine whether human embryonic stem cell-derived cardiomyocytes (hESC-CMs) subjected to mechanical stretch can be used as an adequate in vitro model for studying molecular mechanisms of cardiac hypertrophy. We show that hESC-CMs subjected to cyclic stretch, which mimics mechanical overload, exhibit essential features of a hypertrophic state on structural, functional, and gene expression levels. The presented hESC-CM stretch approach provides insight into molecular mechanisms behind mechanotransduction and cardiac hypertrophy and lays groundwork for the development of pharmacological approaches as well as for discovering potential circulating biomarkers of cardiac dysfunction.
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Affiliation(s)
- Ekaterina Ovchinnikova
- Department of Cardiology, University Medical Center Groningen, University of Groningen, Hanzeplein 1, PO Box 30.001, Groningen, the Netherlands; European Research Institute for the Biology of Ageing, University of Groningen, University Medical Center Groningen, Antonius Deusinglaan, 1, PO Box 196, Groningen, the Netherlands
| | - Martijn Hoes
- Department of Cardiology, University Medical Center Groningen, University of Groningen, Hanzeplein 1, PO Box 30.001, Groningen, the Netherlands
| | - Kirill Ustyantsev
- Laboratory of Molecular Genetic Systems, Institute of Cytology and Genetics, Novosibirsk, 630090, Russia
| | - Nils Bomer
- Department of Cardiology, University Medical Center Groningen, University of Groningen, Hanzeplein 1, PO Box 30.001, Groningen, the Netherlands
| | - Tristan V de Jong
- European Research Institute for the Biology of Ageing, University of Groningen, University Medical Center Groningen, Antonius Deusinglaan, 1, PO Box 196, Groningen, the Netherlands
| | - Henny van der Mei
- University of Groningen, University Medical Center Groningen, Biomedical Engineering Department, Groningen, 9713AV, the Netherlands
| | - Eugene Berezikov
- European Research Institute for the Biology of Ageing, University of Groningen, University Medical Center Groningen, Antonius Deusinglaan, 1, PO Box 196, Groningen, the Netherlands.
| | - Peter van der Meer
- Department of Cardiology, University Medical Center Groningen, University of Groningen, Hanzeplein 1, PO Box 30.001, Groningen, the Netherlands.
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Lang F, Aravamudhan S, Nolte H, Türk C, Hölper S, Müller S, Günther S, Blaauw B, Braun T, Krüger M. Dynamic changes in the mouse skeletal muscle proteome during denervation-induced atrophy. Dis Model Mech 2017; 10:881-896. [PMID: 28546288 PMCID: PMC5536905 DOI: 10.1242/dmm.028910] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Accepted: 05/16/2017] [Indexed: 01/07/2023] Open
Abstract
Loss of neuronal stimulation enhances protein breakdown and reduces protein synthesis, causing rapid loss of muscle mass. To elucidate the pathophysiological adaptations that occur in atrophying muscles, we used stable isotope labelling and mass spectrometry to quantify protein expression changes accurately during denervation-induced atrophy after sciatic nerve section in the mouse gastrocnemius muscle. Additionally, mice were fed a stable isotope labelling of amino acids in cell culture (SILAC) diet containing 13C6-lysine for 4, 7 or 11 days to calculate relative levels of protein synthesis in denervated and control muscles. Ubiquitin remnant peptides (K-ε-GG) were profiled by immunoaffinity enrichment to identify potential substrates of the ubiquitin-proteasomal pathway. Of the 4279 skeletal muscle proteins quantified, 850 were differentially expressed significantly within 2 weeks after denervation compared with control muscles. Moreover, pulse labelling identified Lys6 incorporation in 4786 proteins, of which 43 had differential Lys6 incorporation between control and denervated muscle. Enrichment of diglycine remnants identified 2100 endogenous ubiquitination sites and revealed a metabolic and myofibrillar protein diglycine signature, including myosin heavy chains, myomesins and titin, during denervation. Comparative analysis of these proteomic data sets with known atrogenes using a random forest approach identified 92 proteins subject to atrogene-like regulation that have not previously been associated directly with denervation-induced atrophy. Comparison of protein synthesis and proteomic data indicated that upregulation of specific proteins in response to denervation is mainly achieved by protein stabilization. This study provides the first integrated analysis of protein expression, synthesis and ubiquitin signatures during muscular atrophy in a living animal. Summary: Comprehensive proteomic profiling of protein expression, synthesis and ubiquitination during skeletal muscle atrophy reveals that complex regulatory networks are activated during muscle wasting.
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Affiliation(s)
- Franziska Lang
- Institute for Genetics, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), 50931 Cologne, Germany
| | - Sriram Aravamudhan
- Max Planck Institute for Heart and Lung Research, 61231 Bad Nauheim, Germany
| | - Hendrik Nolte
- Institute for Genetics, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), 50931 Cologne, Germany
| | - Clara Türk
- Institute for Genetics, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), 50931 Cologne, Germany
| | - Soraya Hölper
- Institute of Biochemistry II, Goethe University Medical School, 60590 Frankfurt, Germany
| | - Stefan Müller
- Center for Molecular Medicine (CMMC), University of Cologne, 50931 Cologne, Germany
| | - Stefan Günther
- Max Planck Institute for Heart and Lung Research, 61231 Bad Nauheim, Germany
| | - Bert Blaauw
- Venetian Institute of Molecular Medicine (VIMM), Department of Biomedical Sciences Padova, University of Padova, 35137 Padova, Italy
| | - Thomas Braun
- Max Planck Institute for Heart and Lung Research, 61231 Bad Nauheim, Germany
| | - Marcus Krüger
- Institute for Genetics, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), 50931 Cologne, Germany .,Center for Molecular Medicine (CMMC), University of Cologne, 50931 Cologne, Germany
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7
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Lindqvist J, Levy Y, Pati-Alam A, Hardeman EC, Gregorevic P, Ochala J. Modulating myosin restores muscle function in a mouse model of nemaline myopathy. Ann Neurol 2016; 79:717-725. [PMID: 26891371 PMCID: PMC4950341 DOI: 10.1002/ana.24619] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Revised: 02/16/2016] [Accepted: 02/16/2016] [Indexed: 12/18/2022]
Abstract
OBJECTIVE Nemaline myopathy, one of the most common congenital myopathies, is associated with mutations in various genes including ACTA1. This disease is also characterized by various forms/degrees of muscle weakness, with most cases being severe and resulting in death in infancy. Recent findings have provided valuable insight into the underlying pathophysiological mechanisms. Mutations in ACTA1 directly disrupt binding interactions between actin and myosin, and consequently the intrinsic force-generating capacity of muscle fibers. ACTA1 mutations are also associated with variations in myofiber size, the mechanisms of which have been unclear. In the present study, we sought to test the hypotheses that the compromised functional and morphological attributes of skeletal muscles bearing ACTA1 mutations (1) would be directly due to the inefficient actomyosin complex and (2) could be restored by manipulating myosin expression. METHODS We used a knockin mouse model expressing the ACTA1 His40Tyr actin mutation found in human patients. We then performed in vivo intramuscular injections of recombinant adeno-associated viral vectors harboring a myosin transgene known to facilitate muscle contraction. RESULTS We observed that in the presence of the transgene, the intrinsic force-generating capacity was restored and myofiber size was normal. INTERPRETATION This demonstrates a direct link between disrupted attachment of myosin molecules to actin monomers and muscle fiber atrophy. These data also suggest that further therapeutic interventions should primarily target myosin dysfunction to alleviate the pathology of ACTA1-related nemaline myopathy. Ann Neurol 2016;79:717-725.
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Affiliation(s)
- Johan Lindqvist
- Department of Neuroscience, Uppsala University, Uppsala, Sweden
| | - Yotam Levy
- Centre of Human and Aerospace Physiological Sciences, Faculty of Life Sciences & Medicine, King's College London, London, United Kingdom
| | - Alisha Pati-Alam
- Centre of Human and Aerospace Physiological Sciences, Faculty of Life Sciences & Medicine, King's College London, London, United Kingdom
| | - Edna C Hardeman
- Neuromuscular and Regenerative Medicine Unit, School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Paul Gregorevic
- Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia
- Department of Biochemistry and Molecular Biology, Monash University, Melbourne, Victoria, Australia
- Department of Physiology, University of Melbourne, Melbourne, Victoria, Australia
- Department of Neurology, University of Washington School of Medicine, Seattle, WA
| | - Julien Ochala
- Centre of Human and Aerospace Physiological Sciences, Faculty of Life Sciences & Medicine, King's College London, London, United Kingdom
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8
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Wallace MA, Della Gatta PA, Ahmad Mir B, Kowalski GM, Kloehn J, McConville MJ, Russell AP, Lamon S. Overexpression of Striated Muscle Activator of Rho Signaling (STARS) Increases C2C12 Skeletal Muscle Cell Differentiation. Front Physiol 2016; 7:7. [PMID: 26903873 PMCID: PMC4745265 DOI: 10.3389/fphys.2016.00007] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Accepted: 01/11/2016] [Indexed: 01/10/2023] Open
Abstract
Background: Skeletal muscle growth and regeneration depend on the activation of satellite cells, which leads to myocyte proliferation, differentiation and fusion with existing muscle fibers. Skeletal muscle cell proliferation and differentiation are tightly coordinated by a continuum of molecular signaling pathways. The striated muscle activator of Rho signaling (STARS) is an actin binding protein that regulates the transcription of genes involved in muscle cell growth, structure and function via the stimulation of actin polymerization and activation of serum-response factor (SRF) signaling. STARS mediates cell proliferation in smooth and cardiac muscle models; however, whether STARS overexpression enhances cell proliferation and differentiation has not been investigated in skeletal muscle cells. Results: We demonstrate for the first time that STARS overexpression enhances differentiation but not proliferation in C2C12 mouse skeletal muscle cells. Increased differentiation was associated with an increase in the gene levels of the myogenic differentiation markers Ckm, Ckmt2 and Myh4, the differentiation factor Igf2 and the myogenic regulatory factors (MRFs) Myf5 and Myf6. Exposing C2C12 cells to CCG-1423, a pharmacological inhibitor of SRF preventing the nuclear translocation of its co-factor MRTF-A, had no effect on myotube differentiation rate, suggesting that STARS regulates differentiation via a MRTF-A independent mechanism. Conclusion: These findings position STARS as an important regulator of skeletal muscle growth and regeneration.
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Affiliation(s)
- Marita A Wallace
- Centre for Physical Activity and Nutrition Research, School of Exercise and Nutrition Sciences, Deakin University Burwood, VIC, Australia
| | - Paul A Della Gatta
- Centre for Physical Activity and Nutrition Research, School of Exercise and Nutrition Sciences, Deakin University Burwood, VIC, Australia
| | - Bilal Ahmad Mir
- Centre for Physical Activity and Nutrition Research, School of Exercise and Nutrition Sciences, Deakin University Burwood, VIC, Australia
| | - Greg M Kowalski
- Centre for Physical Activity and Nutrition Research, School of Exercise and Nutrition Sciences, Deakin University Burwood, VIC, Australia
| | - Joachim Kloehn
- Department of Biochemistry and Molecular Biology, Bio21 Institute of Molecular Science and Biotechnology, University of Melbourne Parkville, VIC, Australia
| | - Malcom J McConville
- Department of Biochemistry and Molecular Biology, Bio21 Institute of Molecular Science and Biotechnology, University of Melbourne Parkville, VIC, Australia
| | - Aaron P Russell
- Centre for Physical Activity and Nutrition Research, School of Exercise and Nutrition Sciences, Deakin University Burwood, VIC, Australia
| | - Séverine Lamon
- Centre for Physical Activity and Nutrition Research, School of Exercise and Nutrition Sciences, Deakin University Burwood, VIC, Australia
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9
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Kalamgi RC, Larsson L. Mechanical Signaling in the Pathophysiology of Critical Illness Myopathy. Front Physiol 2016; 7:23. [PMID: 26869939 PMCID: PMC4740381 DOI: 10.3389/fphys.2016.00023] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 01/18/2016] [Indexed: 12/14/2022] Open
Abstract
The complete loss of mechanical stimuli of skeletal muscles, i.e., the loss of external strain, related to weight bearing, and internal strain, related to the contraction of muscle cells, is uniquely observed in pharmacologically paralyzed or deeply sedated mechanically ventilated intensive care unit (ICU) patients. The preferential loss of myosin and myosin associated proteins in limb and trunk muscles is a significant characteristic of critical illness myopathy (CIM) which separates CIM from other types of acquired muscle weaknesses in ICU patients. Mechanical silencing is an important factor triggering CIM. Microgravity or ground based microgravity models form the basis of research on the effect of muscle unloading-reloading, but the mechanisms and effects may differ from the ICU conditions. In order to understand how mechanical tension regulates muscle mass, it is critical to know how muscles sense mechanical information and convert stimulus to intracellular biochemical actions and changes in gene expression, a process called cellular mechanotransduction. In adult skeletal muscles and muscle fibers, this process may differ, the same stimulus can cause divergent response and the same fiber type may undergo opposite changes in different muscles. Skeletal muscle contains multiple types of mechano-sensors and numerous structures that can be affected differently and hence respond differently in distinct muscles.
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Affiliation(s)
- Rebeca C Kalamgi
- Basic and Clinical Muscle Biology, Department of Physiology and Pharmacology, Karolinska Institutet Stockholm, Sweden
| | - Lars Larsson
- Basic and Clinical Muscle Biology, Department of Physiology and Pharmacology, Karolinska InstitutetStockholm, Sweden; Department of Clinical Neuroscience, Clinical Neurophysiology, Karolinska InstitutetStockholm, Sweden
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10
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Lamon S, Wallace MA, Russell AP. The STARS signaling pathway: a key regulator of skeletal muscle function. Pflugers Arch 2014; 466:1659-71. [DOI: 10.1007/s00424-014-1475-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2013] [Revised: 02/04/2014] [Accepted: 02/05/2014] [Indexed: 01/08/2023]
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Abstract
In this review, we present an overview of the role of exercise in neuromuscular disease (NMD). We demonstrate that despite the different pathologies in NMDs, exercise is beneficial, whether aerobic/endurance or strength/resistive training, and we explore whether this benefit has a similar mechanism to that of healthy subjects. We discuss further areas for study, incorporating imaginative and novel approaches to training and its assessment in NMD. We conclude by suggesting ways to improve future trials by avoiding previous methodological flaws and drawbacks in this field.
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Affiliation(s)
- Yaacov Anziska
- Department of Neurology, SUNY-Downstate Medical Center, 450 Clarkson Avenue, Box 1213, Brooklyn, New York, 11203, USA.
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12
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Abresch RT, Carter GT, Han JJ, McDonald CM. Exercise in neuromuscular diseases. Phys Med Rehabil Clin N Am 2013; 23:653-73. [PMID: 22938880 DOI: 10.1016/j.pmr.2012.06.001] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
This article reviews the current knowledge regarding the benefits and contraindications of exercise on individuals with neuromuscular diseases (NMDs). Specific exercise prescriptions for individuals with NMDs do not exist because the evidence base is limited. Understanding the effect of exercise on individuals with NMDs requires the implementation of a series of multicenter, randomized controlled trials that are sufficiently powered and use reliable and valid outcome measures to assess the effect of exercise interventions-a major effort for each NMD. In addition to traditional measures of exercise efficacy, outcome variables should include measures of functional status and health-related quality of life.
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Affiliation(s)
- R Ted Abresch
- Department of Rehabilitation Medicine, University of California, Davis, 4860 Y Street Suite, 3850, Sacramento, CA 95817, USA.
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13
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Mizukoshi K, Suzuki K, Yoneyama K, Kamijima R, Kou S, Takai M, Izumo M, Hayashi A, Ohtaki E, Akashi YJ, Osada N, Omiya K, Harada T, Nobuoka S, Miyake F. Early diastolic function during exertion influences exercise intolerance in patients with hypertrophic cardiomyopathy. J Echocardiogr 2012; 11:9-17. [PMID: 27278427 DOI: 10.1007/s12574-012-0150-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Revised: 09/23/2012] [Accepted: 10/04/2012] [Indexed: 01/19/2023]
Abstract
BACKGROUND Hypertrophic cardiomyopathy (HCM) patients with preserved left ventricular ejection fraction (LVEF) often develop dyspnea and exercise intolerance. Diastolic dysfunction may contribute to exercise intolerance in these patients. This study aimed to clarify our hypothesis as to whether diastolic function rather than systolic function would be associated with exercise intolerance in HCM using two-dimensional (2D) speckle tracking echocardiography during exercise. METHODS Thirty-three HCM patients (mean age 59.3 ± 15.7 years) underwent 2D speckle tracking echocardiography at rest and during submaximal semi-supine bicycle exercise. Global longitudinal strain (LS), LS rate during systole (LSRs), early diastole (LSRe), and late diastole (LSRa) were measured. The symptom-limited cardiopulmonary exercise testing was performed using a cycle ergometer for measuring the peak oxygen consumption (peak [Formula: see text]). RESULTS In the multivariate linear regression analysis, peak [Formula: see text] did not associate with strain or strain rate at rest. However, peak [Formula: see text] correlated with LS (β = -0.403, p = 0.007), LSRe (β = 6.041, p = 0.001), and LSRa (β = 5.117, p = 0.021) during exercise after adjustment for age, gender, and heart rate. The first quartile peak [Formula: see text] (14.2 mL/min/kg) was assessed to predict exercise intolerance. The C-statistic of delta LSRe was 0.74, which was relatively greater than that of delta LS (0.70) and delta LSRa (0.58), indicating that early diastolic function rather than systolic and late diastolic function affects exercise intolerance. CONCLUSIONS LSRe during exercise is closely associated with the peak [Formula: see text]. Early diastolic function during exercise is an important determinant of exercise capacity in patients with HCM.
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Affiliation(s)
- Kei Mizukoshi
- Division of Cardiology, Department of Internal Medicine, St. Marianna University School of Medicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki, Kanagawa, 216-8511, Japan
| | - Kengo Suzuki
- Division of Cardiology, Department of Internal Medicine, St. Marianna University School of Medicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki, Kanagawa, 216-8511, Japan.
| | - Kihei Yoneyama
- Division of Cardiology, Department of Internal Medicine, St. Marianna University School of Medicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki, Kanagawa, 216-8511, Japan
| | - Ryo Kamijima
- Division of Cardiology, Department of Internal Medicine, St. Marianna University School of Medicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki, Kanagawa, 216-8511, Japan
| | - Seisyou Kou
- Division of Cardiology, Department of Internal Medicine, St. Marianna University School of Medicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki, Kanagawa, 216-8511, Japan
| | - Manabu Takai
- Division of Cardiology, Department of Internal Medicine, St. Marianna University School of Medicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki, Kanagawa, 216-8511, Japan
| | - Masaki Izumo
- Division of Cardiology, Department of Internal Medicine, St. Marianna University School of Medicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki, Kanagawa, 216-8511, Japan
| | - Akio Hayashi
- Division of Cardiology, Department of Internal Medicine, St. Marianna University School of Medicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki, Kanagawa, 216-8511, Japan
| | | | - Yoshihiro J Akashi
- Division of Cardiology, Department of Internal Medicine, St. Marianna University School of Medicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki, Kanagawa, 216-8511, Japan
| | - Naohiko Osada
- Division of Cardiology, Department of Internal Medicine, St. Marianna University School of Medicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki, Kanagawa, 216-8511, Japan
| | - Kazuto Omiya
- Division of Cardiology, Department of Internal Medicine, St. Marianna University School of Medicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki, Kanagawa, 216-8511, Japan
| | - Tomoo Harada
- Division of Cardiology, Department of Internal Medicine, St. Marianna University School of Medicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki, Kanagawa, 216-8511, Japan
| | - Sachihiko Nobuoka
- Department of Laboratory Medicine, St. Marianna University School of Medicine, Kawasaki, Japan
| | - Fumihiko Miyake
- Division of Cardiology, Department of Internal Medicine, St. Marianna University School of Medicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki, Kanagawa, 216-8511, Japan
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Ruggiero A, Chen SN, Lombardi R, Rodriguez G, Marian AJ. Pathogenesis of hypertrophic cardiomyopathy caused by myozenin 2 mutations is independent of calcineurin activity. Cardiovasc Res 2012; 97:44-54. [PMID: 22987565 DOI: 10.1093/cvr/cvs294] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
AIMS The role of calcineurin protein phosphatase 2B (PP2B) in the pathogenesis of human hypertrophic cardiomyopathy (HCM) remains unsettled. We determined potential involvement of calcineurin in the pathogenesis of HCM caused by mutations in myozenin 2 (MYOZ2), an inhibitor of calcineurin. METHODS AND RESULTS We generated multiple lines of transgenic mice expressing either Flag-tagged wild-type (WT) (MYOZ2(WT)) or mutant MYOZ2(S48P) and MYOZ2(I246M), identified in families with HCM, in the heart. To mimic the human genotype, we generated bigenic mice expressing WT and mutant MYOZ2 in the background of hemizygous endogenous MYOZ2 (Myoz2(+/-)). Transgene proteins constituted 15-48% of the total MYOZ2 protein in the heart. Mutant MYOZ2 mice showed molecular, cellular, and gross cardiac hypertrophy, preserved systolic function, and interstitial fibrosis. Immunofluorescence staining showed co-localization of WT and mutant MYOZ2 proteins with α-actinin at the Z disks. Electron microscopy showed disrupted and mal-aligned Z disks in the mutant mice. Cardiac calcineurin activity, determined by quantifying Rcan1.4 mRNA and protein levels, luciferase activity in triple transgenic Myoz2(+/-):NFATc-Luc:MYOZ2(I246M) and Myoz2(+/-):NFATc-Luc:MYOZ2(WT) mice, and NFATc transcriptional activity assay, was unchanged in the mutant transgenic mice. However, levels of phospho-ERK1/2 and JNK54/46 were altered in the transgenic mice. Likewise, lentiviral-mediated expression of the MYOZ2(I246M) did not affect RCAN1.4 and calcineurin (PPP3CB) protein levels. CONCLUSIONS Thus, the cardiac phenotype in HCM caused by MYOZ2 mutations might be independent of calcineurin activity in the heart. Z disk abnormalities might provide the stimulus for the induction of cardiac hypertrophy caused by MYOZ2 mutations.
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Affiliation(s)
- Alessandra Ruggiero
- Center for Cardiovascular Genetics, The Brown Foundation Institute of Molecular Medicine, The University of Texas Health Science Center and Texas Heart Institute, 6770 Bertner Street, Suite C900A, Houston, TX 77030, USA
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15
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Developmental regulation of MURF E3 ubiquitin ligases in skeletal muscle. J Muscle Res Cell Motil 2012; 33:107-22. [PMID: 22426552 PMCID: PMC3353113 DOI: 10.1007/s10974-012-9288-7] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2011] [Accepted: 03/01/2012] [Indexed: 12/23/2022]
Abstract
The striated muscle-specific tripartite motif (TRIM) proteins TRIM63/MURF1, TRIM55/MURF2 and TRIM54/MURF3 can function as E3 ubiquitin ligases in ubiquitin-mediated muscle protein turnover. Despite the well-characterised role of MURF1 in skeletal muscle atrophy, the dynamics of MURF isogene expression in the development and early postnatal adaptation of skeletal muscle is unknown. Here, we show that MURF2 is the isogene most highly expressed in embryonic skeletal muscle at E15.5, with the 50 kDa A isoform predominantly expressed. MURF1 and MURF3 are upregulated only postnatally. Knockdown of MURF2 p50A by isoform-specific siRNA results in delayed myogenic differentiation and myotube formation in vitro, with perturbation of the stable, glutamylated microtubule population. This underscores that MURF2 plays an important role in the earliest stages of skeletal muscle differentiation and myofibrillogenesis. During further development, there is a shift towards the 60 kDa A isoform, which dominates postnatally. Analysis of the fibre-type expression shows that MURF2 A isoforms are predominantly slow-fibre associated, whilst MURF1 is largely excluded from these fibres, and MURF3 is ubiquitously distributed in both type I and II fibres.
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16
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Abstract
Hypertrophic cardiomyopathy (HCM) is the most-common monogenically inherited form of heart disease, characterized by thickening of the left ventricular wall, contractile dysfunction, and potentially fatal arrhythmias. HCM is also the most-common cause of sudden cardiac death in individuals younger than 35 years of age. Much progress has been made in the elucidation of the genetic basis of HCM, resulting in the identification of more than 900 individual mutations in over 20 genes. Interestingly, most of these genes encode sarcomeric proteins, such as myosin-7 (also known as cardiac muscle β-myosin heavy chain; MYH7), cardiac myosin-binding protein C (MYBPC3), and cardiac muscle troponin T (TNNT2). However, the molecular events that ultimately lead to the clinical phenotype of HCM are still unclear. We discuss several potential pathways, which include altered calcium cycling and sarcomeric calcium sensitivity, increased fibrosis, disturbed biomechanical stress sensing, and impaired cardiac energy homeostasis. An improved understanding of the pathological mechanisms involved will result in greater specificity and success of therapies for patients with HCM.
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Affiliation(s)
- Norbert Frey
- Department of Cardiology and Angiology, University of Kiel, Schittenhelmstrasse 12, 24105 Kiel, Germany
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17
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Abstract
Chronic heart failure continues to impose a substantial health-care burden, despite recent treatment advances. The key pathophysiological process that ultimately leads to chronic heart failure is cardiac remodelling in response to chronic disease stresses. Here, we review recent advances in our understanding of molecular and cellular mechanisms that play a part in the complex remodelling process, with a focus on key molecules and pathways that might be suitable targets for therapeutic manipulation. Such pathways include those that regulate cardiac myocyte hypertrophy, calcium homoeostasis, energetics, and cell survival, and processes that take place outside the cardiac myocyte--eg, in the myocardial vasculature and extracellular matrix. We also discuss major gaps in our current understanding, take a critical look at conventional approaches to target discovery that have been used to date, and consider new investigational avenues that might accelerate clinically relevant discovery.
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Affiliation(s)
- Ajay M Shah
- King's College London British Heart Foundation Centre of Excellence, London, UK.
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18
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Braun T, Gautel M. Transcriptional mechanisms regulating skeletal muscle differentiation, growth and homeostasis. Nat Rev Mol Cell Biol 2011; 12:349-61. [PMID: 21602905 DOI: 10.1038/nrm3118] [Citation(s) in RCA: 469] [Impact Index Per Article: 36.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Skeletal muscle is the dominant organ system in locomotion and energy metabolism. Postnatal muscle grows and adapts largely by remodelling pre-existing fibres, whereas embryonic muscle grows by the proliferation of myogenic cells. Recently, the genetic hierarchies of the myogenic transcription factors that control vertebrate muscle development - by myoblast proliferation, migration, fusion and functional adaptation into fast-twitch and slow-twitch fibres - have become clearer. The transcriptional mechanisms controlling postnatal hypertrophic growth, remodelling and functional differentiation redeploy myogenic factors in concert with serum response factor (SRF), JUNB and forkhead box protein O3A (FOXO3A). It has also emerged that there is extensive post-transcriptional regulation by microRNAs in development and postnatal remodelling.
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Affiliation(s)
- Thomas Braun
- Max-Planck-Institute for Heart and Lung Research, Department for Cardiac Development and Remodelling, Benekestrasse, Bad Nauheim, Germany. thomas.braun@ mpi-bn.mpg.de
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19
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Gautel M. Cytoskeletal protein kinases: titin and its relations in mechanosensing. Pflugers Arch 2011; 462:119-34. [PMID: 21416260 PMCID: PMC3114093 DOI: 10.1007/s00424-011-0946-1] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2011] [Revised: 02/15/2011] [Accepted: 02/18/2011] [Indexed: 12/22/2022]
Abstract
Titin, the giant elastic ruler protein of striated muscle sarcomeres, contains a catalytic kinase domain related to a family of intrasterically regulated protein kinases. The most extensively studied member of this branch of the human kinome is the Ca2+–calmodulin (CaM)-regulated myosin light-chain kinases (MLCK). However, not all kinases of the MLCK branch are functional MLCKs, and about half lack a CaM binding site in their C-terminal autoinhibitory tail (AI). A unifying feature is their association with the cytoskeleton, mostly via actin and myosin filaments. Titin kinase, similar to its invertebrate analogue twitchin kinase and likely other “MLCKs”, is not Ca2+–calmodulin-activated. Recently, local protein unfolding of the C-terminal AI has emerged as a common mechanism in the activation of CaM kinases. Single-molecule data suggested that opening of the TK active site could also be achieved by mechanical unfolding of the AI. Mechanical modulation of catalytic activity might thus allow cytoskeletal signalling proteins to act as mechanosensors, creating feedback mechanisms between cytoskeletal tension and tension generation or cellular remodelling. Similar to other MLCK-like kinases like DRAK2 and DAPK1, TK is linked to protein turnover regulation via the autophagy/lysosomal system, suggesting the MLCK-like kinases have common functions beyond contraction regulation.
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Affiliation(s)
- Mathias Gautel
- King's College London BHF Centre of Research Excellence, Cardiovascular Division, London, SE1 1UL, UK.
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20
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Iskratsch T, Lange S, Dwyer J, Kho AL, dos Remedios C, Ehler E. Formin follows function: a muscle-specific isoform of FHOD3 is regulated by CK2 phosphorylation and promotes myofibril maintenance. ACTA ACUST UNITED AC 2011; 191:1159-72. [PMID: 21149568 PMCID: PMC3002041 DOI: 10.1083/jcb.201005060] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Phosphorylation of the muscle-specific formin splice variant FHOD3 by CK2 regulates its stability, myofibril targeting, and myofibril integrity. Members of the formin family are important for actin filament nucleation and elongation. We have identified a novel striated muscle–specific splice variant of the formin FHOD3 that introduces a casein kinase 2 (CK2) phosphorylation site. The specific targeting of muscle FHOD3 to the myofibrils in cardiomyocytes is abolished in phosphomutants or by the inhibition of CK2. Phosphorylation of muscle FHOD3 also prevents its interaction with p62/sequestosome 1 and its recruitment to autophagosomes. Furthermore, we show that muscle FHOD3 efficiently promotes the polymerization of actin filaments in cardiomyocytes and that the down-regulation of its expression severely affects myofibril integrity. In murine and human cardiomyopathy, we observe reduced FHOD3 expression with a concomitant isoform switch and change of subcellular targeting. Collectively, our data suggest that a muscle-specific isoform of FHOD3 is required for the maintenance of the contractile structures in heart muscle and that its function is regulated by posttranslational modification.
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Affiliation(s)
- Thomas Iskratsch
- The Muscle Cell Biology Section, Randall Division of Cell and Molecular Biophysics, British Heart Foundation Research Excellence Centre, King's College London, London SE1 1UL, England, UK
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21
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Krüger M, Linke WA. The giant protein titin: a regulatory node that integrates myocyte signaling pathways. J Biol Chem 2011; 286:9905-12. [PMID: 21257761 DOI: 10.1074/jbc.r110.173260] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Titin, the largest protein in the human body, is well known as a molecular spring in muscle cells and scaffold protein aiding myofibrillar assembly. However, recent evidence has established another important role for titin: that of a regulatory node integrating, and perhaps coordinating, diverse signaling pathways, particularly in cardiomyocytes. We review key findings within this emerging field, including those related to phosphorylation of the titin springs, and also discuss how titin participates in hypertrophic gene regulation and protein quality control.
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Affiliation(s)
- Martina Krüger
- Department of Cardiovascular Physiology, Ruhr University Bochum, D-44780 Bochum, Germany.
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22
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Gautel M. The sarcomeric cytoskeleton: who picks up the strain? Curr Opin Cell Biol 2010; 23:39-46. [PMID: 21190822 DOI: 10.1016/j.ceb.2010.12.001] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2010] [Revised: 12/01/2010] [Accepted: 12/02/2010] [Indexed: 01/01/2023]
Abstract
In striated muscle sarcomeres, the contractile actin and myosin filaments are organised by a subset of specialised cytoskeletal proteins, the sarcomeric cytoskeleton. They include α-actinin, myomesin, and the giant proteins titin, obscurin and nebulin, which combine architectural, mechanical and signalling functions. Mechanics and signalling in the sarcomere appear tightly interdependent, but the exact contributions of the various sarcomeric cytoskeleton proteins to strain handling or signalling are only just emerging. General mechanisms of cytoskeletal mechanics and signalling may be gleaned from the sarcomere as a specialised actomyosin system. Recent work has led to insight into the interactions, structure, and mechanical stability of sarcomeric protein complexes that fulfil both structural and signalling roles.
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Affiliation(s)
- Mathias Gautel
- King's College London BHF Centre of Research Excellence, Cardiovascular Division and Randall Division for Cell and Molecular Biophysics, London SE1 1UL, United Kingdom.
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23
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Perera S, Holt MR, Mankoo BS, Gautel M. Developmental regulation of MURF ubiquitin ligases and autophagy proteins nbr1, p62/SQSTM1 and LC3 during cardiac myofibril assembly and turnover. Dev Biol 2010; 351:46-61. [PMID: 21185285 PMCID: PMC3047806 DOI: 10.1016/j.ydbio.2010.12.024] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2010] [Revised: 12/14/2010] [Accepted: 12/15/2010] [Indexed: 02/07/2023]
Abstract
The striated muscle-specific tripartite motif (TRIM) proteins TRIM63/MURF1, TRIM55/MURF2 and TRIM54/MURF3 can function as ubiquitin E3 ligases in ubiquitin-mediated muscle protein turnover. Despite their well-characterised roles in muscle atrophy, the dynamics of MURF expression in the development and early postnatal adaptation of striated muscle is largely unknown. Here, we show that MURF2 is expressed at the very onset of mouse cardiac differentiation at embryonic day 8.5, and represents a sensitive marker for differentiating myocardium. During cardiac development, expression shifts from the 50 kDa to the 60 kDa A-isoform, which dominates postnatally. In contrast, MURF1 shows strong postnatal upregulation and MURF3 is not significantly expressed before birth. MURF2 expression parallels that of the autophagy-associated proteins LC3, p62/SQSTM1 and nbr1. SiRNA knockdown of MURF2 in neonatal rat cardiomyocytes disrupts posttranslational microtubule modification and myofibril assembly, and is only partly compensated by upregulation of MURF3 but not MURF1. Knockdown of both MURF2 and MURF3 severely disrupts the formation of ordered Z- and M-bands, likely by perturbed tubulin dynamics. These results suggest that ubiquitin-mediated protein turnover and MURF2 in particular play an unrecognised role in the earliest steps of heart muscle differentiation, and that partial complementation of MURF2 deficiency is afforded by MURF3.
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Affiliation(s)
- Sue Perera
- King's College London BHF Centre of Research Excellence, Randall Division for Cell and Molecular Biophysics and Cardiovascular Division, New Hunt's House, Guy's Campus, London SE1 1UL, UK
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24
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Ram R, Blaxall BC. Nebulette mutations in cardiac remodeling: big effects from a small mechanosensor. J Am Coll Cardiol 2010; 56:1503-5. [PMID: 20951327 DOI: 10.1016/j.jacc.2010.06.031] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/24/2010] [Accepted: 06/01/2010] [Indexed: 01/13/2023]
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Abstract
Major advances in the fields of medical science and physiology, molecular genetics, biomedical engineering, and computer science have provided individuals with muscular dystrophy (MD) with more functional equipment, allowing better strategies for improvement of quality of life. These advances have also allowed a significant number of these patients to live much longer. As progress continues to change management, it also changes patients' expectations. A comprehensive medical and rehabilitative approach to management of aging MD patients can often fulfill expectations and help them enjoy an enhanced quality of life.
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26
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Molecular structure of sarcomere-to-membrane attachment at M-Lines in C. elegans muscle. J Biomed Biotechnol 2010; 2010:864749. [PMID: 20414365 PMCID: PMC2857872 DOI: 10.1155/2010/864749] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2009] [Accepted: 01/30/2010] [Indexed: 01/09/2023] Open
Abstract
C. elegans is an excellent model for studying nonmuscle cell focal adhesions and the analogous muscle cell attachment structures. In the major striated muscle of this nematode, all of the M-lines and the Z-disk analogs (dense bodies) are attached to the muscle cell membrane and underlying extracellular matrix. Accumulating at these sites are many proteins associated with integrin. We have found that nematode M-lines contain a set of protein complexes that link integrin-associated proteins to myosin thick filaments. We have also obtained evidence for intriguing additional functions for these muscle cell attachment proteins.
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27
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Abstract
BACKGROUND Hypertrophic cardiomyopathy (HCM) is the prototypic form of pathological cardiac hypertrophy. HCM is an important cause of sudden cardiac death in the young and a major cause of morbidity in the elderly. DESIGN We discuss the clinical implications of recent advances in the molecular genetics of HCM. RESULTS The current diagnosis of HCM is neither adequately sensitive nor specific. Partial elucidation of the molecular genetic basis of HCM has raised interest in genetic-based diagnosis and management. Over a dozen causal genes have been identified. MYH7 and MYBPC3 mutations account for about 50% of cases. The remaining known causal genes are uncommon and some are rare. Advances in DNA sequencing techniques have made genetic screening practical. The difficulty, particularly in the sporadic cases and in small families, is to discern the causal from the non-causal variants. Overall, the causal mutations alone have limited implications in risk stratification and prognostication, as the clinical phenotype arises from complex and often non-linear interactions between various determinants. CONCLUSIONS The clinical phenotype of 'HCM' results from mutations in sarcomeric proteins and subsequent activation of multiple cellular constituents including signal transducers. We advocate that HCM, despite its current recognition and management as a single disease entity, involves multiple partially independent mechanisms, despite similarity in the ensuing phenotype. To treat HCM effectively, it is necessary to delineate the underlying fundamental mechanisms that govern the pathogenesis of the phenotype and apply these principles to the treatment of each subset of clinically recognized HCM.
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Affiliation(s)
- Ali J Marian
- Center for Cardiovascular Genetics, The Brown Foundation Institute of Molecular Medicine, The University of Texas Health Science Center and Texas Heart Institute at St. Luke's Episcopal Hospital, 6770 Bertner Street, Suite C900A, Houston, TX 77030, USA.
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28
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Mechanical stress-induced sarcomere assembly for cardiac muscle growth in length and width. J Mol Cell Cardiol 2010; 48:817-23. [PMID: 20188736 DOI: 10.1016/j.yjmcc.2010.02.016] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/30/2009] [Revised: 02/15/2010] [Accepted: 02/17/2010] [Indexed: 12/27/2022]
Abstract
A ventricular myocyte experiences changes in length and load during every beat of the heart and has the ability to remodel cell shape to maintain cardiac performance. Specifically, myocytes elongate in response to increased diastolic strain by adding sarcomeres in series, and they thicken in response to continued systolic stress by adding filaments in parallel. Myocytes do this while still keeping the resting sarcomere length close to its optimal value at the peak of the length-tension curve. This review focuses on the little understood mechanisms by which direction of growth is matched in a physiologically appropriate direction. We propose that the direction of strain is detected by differential phosphorylation of proteins in the costamere, which then transmit signaling to the Z-disc for parallel or series addition of thin filaments regulated via the actin capping processes. In this review, we link mechanotransduction to the molecular mechanisms for regulation of myocyte length and width.
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Abstract
PURPOSE OF REVIEW Highly prevalent in the population older than 65 years and leading to poor outcomes (functional decline and its related consequences), sarcopenia does not benefit yet either of a clear understanding of its pathophysiology or of precise clinical or biological markers allowing its identification. RECENT FINDINGS The new scientific definition of 'geriatric syndromes' challenges the authors to review the current sarcopenia literature, allowing them to affirm that sarcopenia cannot be considered as an age-related disease but as a true 'geriatric syndrome'. More than 50% of the population older than 80 years suffer from this medical condition, which is linked to multiple causations: the ageing process itself, genetic susceptibility, certain life habits, changes in living conditions and a number of chronic diseases. Moreover, sarcopenia favours poor outcomes such as mobility disorders, disability, poor quality of life and death. SUMMARY Considering sarcopenia as a geriatric syndrome allows us to request its recognition and assess its multiple risk factors, to implement a clinical and public health approach to the management of sarcopenic patients and population at risk and to disentangle the links among sarcopenia, frailty, disability and mortality.
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Abresch RT, Han JJ, Carter GT. Rehabilitation management of neuromuscular disease: the role of exercise training. J Clin Neuromuscul Dis 2009; 11:7-21. [PMID: 19730017 DOI: 10.1097/cnd.0b013e3181a8d36b] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
This paper summarizes the current state of knowledge regarding exercise and neuromuscular diseases/disorders (NMDs) and reviews salient studies in the literature. Unfortunately, there is inadequate evidence in much of the NMDs to make specific recommendations regarding exercise prescriptions. This review focuses on the role of exercise in a few of the specific NMDs where most research has taken place and recommends future research directions.
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Affiliation(s)
- R Ted Abresch
- Department of Physical Medicine and Rehabilitation, University of California, Davis, Davis, CA, USA
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