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Jeong SY, Choi JH, Kim J, Woo JS, Lee EH. Tripartite Motif-Containing Protein 32 (TRIM32): What Does It Do for Skeletal Muscle? Cells 2023; 12:2104. [PMID: 37626915 PMCID: PMC10453674 DOI: 10.3390/cells12162104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 08/07/2023] [Accepted: 08/18/2023] [Indexed: 08/27/2023] Open
Abstract
Tripartite motif-containing protein 32 (TRIM32) is a member of the tripartite motif family and is highly conserved from flies to humans. Via its E3 ubiquitin ligase activity, TRIM32 mediates and regulates many physiological and pathophysiological processes, such as growth, differentiation, muscle regeneration, immunity, and carcinogenesis. TRIM32 plays multifunctional roles in the maintenance of skeletal muscle. Genetic variations in the TRIM32 gene are associated with skeletal muscular dystrophies in humans, including limb-girdle muscular dystrophy type 2H (LGMD2H). LGMD2H-causing genetic variations of TRIM32 occur most frequently in the C-terminal NHL (ncl-1, HT2A, and lin-41) repeats of TRIM32. LGMD2H is characterized by skeletal muscle dystrophy, myopathy, and atrophy. Surprisingly, most patients with LGMD2H show minimal or no dysfunction in other tissues or organs, despite the broad expression of TRIM32 in various tissues. This suggests more prominent roles for TRIM32 in skeletal muscle than in other tissues or organs. This review is focused on understanding the physiological roles of TRIM32 in skeletal muscle, the pathophysiological mechanisms mediated by TRIM32 genetic variants in LGMD2H patients, and the correlations between TRIM32 and Duchenne muscular dystrophy (DMD).
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Affiliation(s)
- Seung Yeon Jeong
- Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul 06591, Republic of Korea
- Department of Biomedicine & Health Sciences, Graduate School, The Catholic University of Korea, Seoul 06591, Republic of Korea
| | - Jun Hee Choi
- Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul 06591, Republic of Korea
- Department of Biomedicine & Health Sciences, Graduate School, The Catholic University of Korea, Seoul 06591, Republic of Korea
| | - Jooho Kim
- Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul 06591, Republic of Korea
- Department of Biomedicine & Health Sciences, Graduate School, The Catholic University of Korea, Seoul 06591, Republic of Korea
| | - Jin Seok Woo
- Department of Physiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 10833, USA
| | - Eun Hui Lee
- Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul 06591, Republic of Korea
- Department of Biomedicine & Health Sciences, Graduate School, The Catholic University of Korea, Seoul 06591, Republic of Korea
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2
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Garcia-Pelagio KP, Bloch RJ. Biomechanical Properties of the Sarcolemma and Costameres of Skeletal Muscle Lacking Desmin. Front Physiol 2021; 12:706806. [PMID: 34489727 PMCID: PMC8416993 DOI: 10.3389/fphys.2021.706806] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2021] [Accepted: 07/13/2021] [Indexed: 01/23/2023] Open
Abstract
Intermediate filaments (IFs), composed primarily by desmin and keratins, link the myofibrils to each other, to intracellular organelles, and to the sarcolemma. There they may play an important role in transfer of contractile force from the Z-disks and M-lines of neighboring myofibrils to costameres at the membrane, across the membrane to the extracellular matrix, and ultimately to the tendon (“lateral force transmission”). We measured the elasticity of the sarcolemma and the connections it makes at costameres with the underlying contractile apparatus of individual fast twitch muscle fibers of desmin-null mice. By positioning a suction pipet to the surface of the sarcolemma and applying increasing pressure, we determined the pressure at which the sarcolemma separated from nearby sarcomeres, Pseparation, and the pressure at which the isolated sarcolemma burst, Pbursting. We also examined the time required for the intact sarcolemma-costamere-sarcomere complex to reach equilibrium at lower pressures. All measurements showed the desmin-null fibers to have slower equilibrium times and lower Pseparation and Pbursting than controls, suggesting that the sarcolemma and its costameric links to nearby contractile structures were weaker in the absence of desmin. Comparisons to earlier values determined for muscles lacking dystrophin or synemin suggest that the desmin-null phenotype is more stable than the former and less stable than the latter. Our results are consistent with the moderate myopathy seen in desmin-null muscles and support the idea that desmin contributes significantly to sarcolemmal stability and lateral force transmission.
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Affiliation(s)
- Karla P Garcia-Pelagio
- Departamento de Fisica, Facultad de Ciencias, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Robert J Bloch
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, United States
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Oertzen-Hagemann V, Kirmse M, Eggers B, Pfeiffer K, Marcus K, de Marées M, Platen P. Effects of 12 Weeks of Hypertrophy Resistance Exercise Training Combined with Collagen Peptide Supplementation on the Skeletal Muscle Proteome in Recreationally Active Men. Nutrients 2019; 11:E1072. [PMID: 31091754 PMCID: PMC6566884 DOI: 10.3390/nu11051072] [Citation(s) in RCA: 30] [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: 04/10/2019] [Revised: 05/07/2019] [Accepted: 05/10/2019] [Indexed: 01/08/2023] Open
Abstract
Evidence has shown that protein supplementation following resistance exercise training (RET) helps to further enhance muscle mass and strength. Studies have demonstrated that collagen peptides containing mostly non-essential amino acids increase fat-free mass (FFM) and strength in sarcopenic men. The aim of this study was to investigate whether collagen peptide supplementation in combination with RET influences the protein composition of skeletal muscle. Twenty-five young men (age: 24.2 ± 2.6 years, body mass (BM): 79.6 ± 5.6 kg, height: 185.0 ± 5.0 cm, fat mass (FM): 11.5% ± 3.4%) completed body composition and strength measurements and vastus lateralis biopsies were taken before and after a 12-week training intervention. In a double-blind, randomized design, subjects consumed either 15 g of specific collagen peptides (COL) or a non-caloric placebo (PLA) every day within 60 min after their training session. A full-body hypertrophy workout was completed three times per week and included four exercises using barbells. Muscle proteome analysis was performed by liquid chromatography tandem mass spectrometry (LC-MS/MS). BM and FFM increased significantly in COL compared with PLA, whereas no differences in FM were detected between the two groups. Both groups improved in strength levels, with a slightly higher increase in COL compared with PLA. In COL, 221 higher abundant proteins were identified. In contrast, only 44 proteins were of higher abundance in PLA. In contrast to PLA, the upregulated proteins in COL were mostly associated with the protein metabolism of the contractile fibers. In conclusion, the use of RET in combination with collagen peptide supplementation results in a more pronounced increase in BM, FFM, and muscle strength than RET alone. More proteins were upregulated in the COL intervention most of which were associated with contractile fibers.
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Affiliation(s)
- Vanessa Oertzen-Hagemann
- Department of Sports Medicine and Sports Nutrition, Ruhr University Bochum, 44801 Bochum, Germany.
| | - Marius Kirmse
- Department of Sports Medicine and Sports Nutrition, Ruhr University Bochum, 44801 Bochum, Germany.
| | - Britta Eggers
- Medizinisches Proteom-Center, Medical Faculty, Ruhr University Bochum, 44801 Bochum, Germany.
| | - Kathy Pfeiffer
- Medizinisches Proteom-Center, Medical Faculty, Ruhr University Bochum, 44801 Bochum, Germany.
| | - Katrin Marcus
- Medizinisches Proteom-Center, Medical Faculty, Ruhr University Bochum, 44801 Bochum, Germany.
| | - Markus de Marées
- Department of Sports Medicine and Sports Nutrition, Ruhr University Bochum, 44801 Bochum, Germany.
| | - Petra Platen
- Department of Sports Medicine and Sports Nutrition, Ruhr University Bochum, 44801 Bochum, Germany.
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De La Mata A, Tajada S, O'Dwyer S, Matsumoto C, Dixon RE, Hariharan N, Moreno CM, Santana LF. BIN1 Induces the Formation of T-Tubules and Adult-Like Ca 2+ Release Units in Developing Cardiomyocytes. Stem Cells 2018; 37:54-64. [PMID: 30353632 PMCID: PMC6312737 DOI: 10.1002/stem.2927] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Revised: 08/29/2018] [Accepted: 09/22/2018] [Indexed: 12/26/2022]
Abstract
Human embryonic stem cell-derived cardiomyocytes (hESC-CMs) are at the center of new cell-based therapies for cardiac disease, but may also serve as a useful in vitro model for cardiac cell development. An intriguing feature of hESC-CMs is that although they express contractile proteins and have sarcomeres, they do not develop transverse-tubules (T-tubules) with adult-like Ca2+ release units (CRUs). We tested the hypothesis that expression of the protein BIN1 in hESC-CMs promotes T-tubules formation, facilitates CaV 1.2 channel clustering along the tubules, and results in the development of stable CRUs. Using electrophysiology, [Ca2+ ]i imaging, and super resolution microscopy, we found that BIN1 expression induced T-tubule development in hESC-CMs, while increasing differentiation toward a more ventricular-like phenotype. Voltage-gated CaV 1.2 channels clustered along the surface sarcolemma and T-tubules of hESC-CM. The length and width of the T-tubules as well as the expression and size of CaV 1.2 clusters grew, as BIN1 expression increased and cells matured. BIN1 expression increased CaV 1.2 channel activity and the probability of coupled gating within channel clusters. Interestingly, BIN1 clusters also served as sites for sarcoplasmic reticulum (SR) anchoring and stabilization. Accordingly, BIN1-expressing cells had more CaV 1.2-ryanodine receptor junctions than control cells. This was associated with larger [Ca2+ ]i transients during excitation-contraction coupling. Our data support the view that BIN1 is a key regulator of T-tubule formation and CaV 1.2 channel delivery. By studying the role of BIN1 during the differentiation of hESC-CMs, we show that BIN1 is also important for CaV 1.2 channel clustering, junctional SR organization, and the establishment of excitation-contraction coupling. Stem Cells 2019;37:54-64.
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Affiliation(s)
- Ana De La Mata
- Department of Physiology & Membrane Biology, University of California School of Medicine, Davis, California, USA
| | - Sendoa Tajada
- Department of Physiology & Membrane Biology, University of California School of Medicine, Davis, California, USA
| | - Samantha O'Dwyer
- Department of Physiology & Membrane Biology, University of California School of Medicine, Davis, California, USA
| | - Collin Matsumoto
- Department of Physiology & Membrane Biology, University of California School of Medicine, Davis, California, USA
| | - Rose E Dixon
- Department of Physiology & Membrane Biology, University of California School of Medicine, Davis, California, USA
| | - Nirmala Hariharan
- Department of Pharmacology, University of California School of Medicine, Davis, California, USA
| | - Claudia M Moreno
- Department of Physiology & Membrane Biology, University of California School of Medicine, Davis, California, USA
| | - Luis Fernando Santana
- Department of Physiology & Membrane Biology, University of California School of Medicine, Davis, California, USA
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Tsikitis M, Galata Z, Mavroidis M, Psarras S, Capetanaki Y. Intermediate filaments in cardiomyopathy. Biophys Rev 2018; 10:1007-1031. [PMID: 30027462 DOI: 10.1007/s12551-018-0443-2] [Citation(s) in RCA: 59] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Accepted: 07/05/2018] [Indexed: 12/20/2022] Open
Abstract
Intermediate filament (IF) proteins are critical regulators in health and disease. The discovery of hundreds of mutations in IF genes and posttranslational modifications has been linked to a plethora of human diseases, including, among others, cardiomyopathies, muscular dystrophies, progeria, blistering diseases of the epidermis, and neurodegenerative diseases. The major IF proteins that have been linked to cardiomyopathies and heart failure are the muscle-specific cytoskeletal IF protein desmin and the nuclear IF protein lamin, as a subgroup of the known desminopathies and laminopathies, respectively. The studies so far, both with healthy and diseased heart, have demonstrated the importance of these IF protein networks in intracellular and intercellular integration of structure and function, mechanotransduction and gene activation, cardiomyocyte differentiation and survival, mitochondrial homeostasis, and regulation of metabolism. The high coordination of all these processes is obviously of great importance for the maintenance of proper, life-lasting, and continuous contraction of this highly organized cardiac striated muscle and consequently a healthy heart. In this review, we will cover most known information on the role of IFs in the above processes and how their deficiency or disruption leads to cardiomyopathy and heart failure.
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Affiliation(s)
- Mary Tsikitis
- Center of Basic Research, Biomedical Research Foundation, Academy of Athens, 4 Soranou Ephesiou, 11527, Athens, Greece
| | - Zoi Galata
- Center of Basic Research, Biomedical Research Foundation, Academy of Athens, 4 Soranou Ephesiou, 11527, Athens, Greece
| | - Manolis Mavroidis
- Center of Basic Research, Biomedical Research Foundation, Academy of Athens, 4 Soranou Ephesiou, 11527, Athens, Greece
| | - Stelios Psarras
- Center of Basic Research, Biomedical Research Foundation, Academy of Athens, 4 Soranou Ephesiou, 11527, Athens, Greece
| | - Yassemi Capetanaki
- Center of Basic Research, Biomedical Research Foundation, Academy of Athens, 4 Soranou Ephesiou, 11527, Athens, Greece.
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Leyva-Leyva M, Sandoval A, Felix R, González-Ramírez R. Biochemical and Functional Interplay Between Ion Channels and the Components of the Dystrophin-Associated Glycoprotein Complex. J Membr Biol 2018; 251:535-550. [PMID: 29779049 DOI: 10.1007/s00232-018-0036-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Accepted: 05/09/2018] [Indexed: 12/19/2022]
Abstract
Dystrophin is a cytoskeleton-linked membrane protein that binds to a larger multiprotein assembly called the dystrophin-associated glycoprotein complex (DGC). The deficiency of dystrophin or the components of the DGC results in the loss of connection between the cytoskeleton and the extracellular matrix with significant pathophysiological implications in skeletal and cardiac muscle as well as in the nervous system. Although the DGC plays an important role in maintaining membrane stability, it can also be considered as a versatile and flexible molecular complex that contribute to the cellular organization and dynamics of a variety of proteins at specific locations in the plasma membrane. This review deals with the role of the DGC in transmembrane signaling by forming supramolecular assemblies for regulating ion channel localization and activity. These interactions are relevant for cell homeostasis, and its alterations may play a significant role in the etiology and pathogenesis of various disorders affecting muscle and nerve function.
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Affiliation(s)
- Margarita Leyva-Leyva
- Department of Molecular Biology and Histocompatibility, "Dr. Manuel Gea González" General Hospital, Mexico City, Mexico
| | - Alejandro Sandoval
- Faculty of Superior Studies Iztacala, National Autonomous University of Mexico (UNAM), Tlalnepantla, Mexico
| | - Ricardo Felix
- Department of Cell Biology, Center for Research and Advanced Studies of the National Polytechnic Institute (Cinvestav-IPN), Mexico City, Mexico.
| | - Ricardo González-Ramírez
- Department of Molecular Biology and Histocompatibility, "Dr. Manuel Gea González" General Hospital, Mexico City, Mexico.
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Cretoiu D, Pavelescu L, Duica F, Radu M, Suciu N, Cretoiu SM. Myofibers. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1088:23-46. [PMID: 30390246 DOI: 10.1007/978-981-13-1435-3_2] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Muscle tissue is a highly specialized type of tissue, made up of cells that have as their fundamental properties excitability and contractility. The cellular elements that make up this type of tissue are called muscle fibers, or myofibers, because of the elongated shape they have. Contractility is due to the presence of myofibrils in the muscle fiber cytoplasm, as large cellular assemblies. Also, myofibers are responsible for the force that the muscle generates which represents a countless aspect of human life. Movements due to muscles are based on the ability of muscle fibers to use the chemical energy procured in metabolic processes, to shorten and then to return to the original dimensions. We describe in detail the levels of organization for the myofiber, and we correlate the structural aspects with the functional ones, beginning with neuromuscular transmission down to the biochemical reactions achieved in the sarcoplasmic reticulum by the release of Ca2+ and the cycling of crossbridges. Furthermore, we are reviewing the types of muscle contractions and the fiber-type classification.
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Affiliation(s)
- Dragos Cretoiu
- Alessandrescu-Rusescu National Institute of Mother and Child Health, Fetal Medicine Excellence Research Center Bucharest, Bucharest, Romania.,Division of Cell and Molecular Biology and Histology, Carol Davila University of Medicine and Pharmacy, Bucharest, Romania
| | - Luciana Pavelescu
- Division of Cell and Molecular Biology and Histology, Carol Davila University of Medicine and Pharmacy, Bucharest, Romania
| | - Florentina Duica
- Alessandrescu-Rusescu National Institute of Mother and Child Health, Fetal Medicine Excellence Research Center Bucharest, Bucharest, Romania
| | - Mihaela Radu
- Alessandrescu-Rusescu National Institute of Mother and Child Health, Fetal Medicine Excellence Research Center Bucharest, Bucharest, Romania
| | - Nicolae Suciu
- Alessandrescu-Rusescu National Institute of Mother and Child Health, Fetal Medicine Excellence Research Center Bucharest, Bucharest, Romania
| | - Sanda Maria Cretoiu
- Division of Cell and Molecular Biology and Histology, Carol Davila University of Medicine and Pharmacy, Bucharest, Romania.
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8
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García-Pelagio KP, Chen L, Joca HC, Ward C, Jonathan Lederer W, Bloch RJ. Absence of synemin in mice causes structural and functional abnormalities in heart. J Mol Cell Cardiol 2018; 114:354-363. [PMID: 29247678 PMCID: PMC5850968 DOI: 10.1016/j.yjmcc.2017.12.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/07/2016] [Revised: 11/22/2017] [Accepted: 12/12/2017] [Indexed: 12/28/2022]
Abstract
Cardiomyopathies have been linked to changes in structural proteins, including intermediate filament (IF) proteins located in the cytoskeleton. IFs associate with the contractile machinery and costameres of striated muscle and with intercalated disks in the heart. Synemin is a large IF protein that mediates the association of desmin with Z-disks and stabilizes intercalated disks. It also acts as an A-kinase anchoring protein (AKAP). In murine skeletal muscle, the absence of synemin causes a mild myopathy. Here, we report that the genetic silencing of synemin in mice (synm -/-) causes left ventricular systolic dysfunction at 3months and 12-16months of age, and left ventricular hypertrophy and dilatation at 12-16months of age. Isolated cardiomyocytes showed alterations in calcium handling that indicate defects intrinsic to the heart. Although contractile and costameric proteins remained unchanged in the old synm -/- hearts, we identified alterations in several signaling proteins (PKA-RII, ERK and p70S6K) critical to cardiomyocyte function. Our data suggest that synemin plays an important regulatory role in the heart and that the consequences of its absence are profound.
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Affiliation(s)
- Karla P García-Pelagio
- Department of Physiology, School of Medicine, University of Maryland, 655 W. Baltimore St., Baltimore, MD 21201, USA; Department of Physics, School of Science, Universidad Nacional Autónoma de México, Av. Universidad 3000, Mexico City 04320, Mexico
| | - Ling Chen
- Department of Physiology, School of Medicine, University of Maryland, 655 W. Baltimore St., Baltimore, MD 21201, USA; Department of Medicine, School of Medicine, University of Maryland, 655 W. Baltimore St., Baltimore, MD 21201, USA
| | - Humberto C Joca
- BioMET, University of Maryland, 111 S Penn St, Baltimore, MD 21201, USA; Department of Biochemistry and Immunology, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Av Prof. Alfredo Balena, 190, Belo Horizonte, MG 30130, Brazil
| | - Christopher Ward
- School of Nursing and Department of Orthopedics, School of Medicine, University of Maryland,100 Penn St, Baltimore, MD 21201, USA
| | - W Jonathan Lederer
- Department of Physiology, School of Medicine, University of Maryland, 655 W. Baltimore St., Baltimore, MD 21201, USA; BioMET, University of Maryland, 111 S Penn St, Baltimore, MD 21201, USA
| | - Robert J Bloch
- Department of Physiology, School of Medicine, University of Maryland, 655 W. Baltimore St., Baltimore, MD 21201, USA.
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Zubac D, Šimunič B. Skeletal Muscle Contraction Time and Tone Decrease After 8 Weeks of Plyometric Training. J Strength Cond Res 2017; 31:1610-1619. [PMID: 28538312 DOI: 10.1519/jsc.0000000000001626] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The aim of the study was to examine whether an improvement in jumping performance after 8 weeks of plyometric training (PT) runs in parallel with changes in lower-limb skeletal muscle contractile properties. Using noninvasive tensiomyography (TMG), we assessed contraction time (Tc) and the maximal amplitude of radial displacement (Dm) in 20 subjects (50% men; age 22.4 ± 4.7 years of age), randomly divided in PT group (N = 10; PLYO) and a control group (N = 10; CTRL). The PLYO performed 8 weeks of PT. Tensiomyography was measured in 5 leg skeletal muscles: vastus lateralis (VL), biceps femoris (BF), tibialis anterior (TA), gastrocnemius medialis (GM), and gastrocnemius lateralis (GL). Additionally, we evaluated countermovement jump (CMJ) height improvement on a ground force plate. Assessments were repeated before and after PT. After 8 weeks of PT, CMJ height increased by 12.2% in PLYO (p = 0.015), but not in CRTL. Contraction time, which is related to myosin heavy-chain type 1 (MHC-1) proportion, decreased in VL (-8.7%; p < 0.001), BF (-26.7%; p = 0.032), TA (-32.9%; p = 0.004), and GL (-25.8%; p = 0.044), but not in GM (-8.1%; p = 0.158). The estimated VL MHC-1 proportion decreased by -8.2% (p = 0.041). The maximal amplitude of radial displacement, inversely related to muscle tone, decreased in BF (-26.5%; p = 0.032), GM (-14.9%; p = 0.017), GL (-31.5%; p = 0.017), but not in TA (-16.8%; p = 0.113) and VL (-6.0%; p = 0.654). After PT, jumping performance increased, which was paralleled by decreased Tc and decreased muscle tone. Additionally, adaptations to contractile properties were muscle specific, which is important for future studies. It seems that adjustments were dose dependent, being higher in muscles with lower habitual load.
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Affiliation(s)
- Damir Zubac
- 1Faculty of Kinesiology, University of Split, Split, Croatia; and 2Science and Research Center, Institute for Kinesiology Research, University of Primorska, Koper, Slovenia
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Relationship between proteolysis and water-holding of myofibrils. Meat Sci 2017; 131:48-55. [DOI: 10.1016/j.meatsci.2017.04.232] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Revised: 04/07/2017] [Accepted: 04/24/2017] [Indexed: 12/31/2022]
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11
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Manso AM, Okada H, Sakamoto FM, Moreno E, Monkley SJ, Li R, Critchley DR, Ross RS. Loss of mouse cardiomyocyte talin-1 and talin-2 leads to β-1 integrin reduction, costameric instability, and dilated cardiomyopathy. Proc Natl Acad Sci U S A 2017; 114:E6250-E6259. [PMID: 28698364 PMCID: PMC5544289 DOI: 10.1073/pnas.1701416114] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Continuous contraction-relaxation cycles of the heart require strong and stable connections of cardiac myocytes (CMs) with the extracellular matrix (ECM) to preserve sarcolemmal integrity. CM attachment to the ECM is mediated by integrin complexes localized at the muscle adhesion sites termed costameres. The ubiquitously expressed cytoskeletal protein talin (Tln) is a component of muscle costameres that links integrins ultimately to the sarcomere. There are two talin genes, Tln1 and Tln2. Here, we tested the function of these two Tln forms in myocardium where Tln2 is the dominant isoform in postnatal CMs. Surprisingly, global deletion of Tln2 in mice caused no structural or functional changes in heart, presumably because CM Tln1 became up-regulated. Tln2 loss increased integrin activation, although levels of the muscle-specific β1D-integrin isoform were reduced by 50%. With this result, we produced mice that had simultaneous loss of both CM Tln1 and Tln2 and found that cardiac dysfunction occurred by 4 wk with 100% mortality by 6 mo. β1D integrin and other costameric proteins were lost from the CMs, and membrane integrity was compromised. Given that integrin protein reduction occurred with Tln loss, rescue of the phenotype was attempted through transgenic integrin overexpression, but this could not restore WT CM integrin levels nor improve heart function. Our results show that CM Tln2 is essential for proper β1D-integrin expression and that Tln1 can substitute for Tln2 in preserving heart function, but that loss of all Tln forms from the heart-muscle cell leads to myocyte instability and a dilated cardiomyopathy.
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Affiliation(s)
- Ana Maria Manso
- Division of Cardiology, Department of Medicine, University of California at San Diego School of Medicine, La Jolla, CA 92093;
- Cardiology Section, Department of Medicine, Veterans Administration Healthcare, San Diego, CA 92161
| | - Hideshi Okada
- Division of Cardiology, Department of Medicine, University of California at San Diego School of Medicine, La Jolla, CA 92093
- Cardiology Section, Department of Medicine, Veterans Administration Healthcare, San Diego, CA 92161
| | - Francesca M Sakamoto
- Division of Cardiology, Department of Medicine, University of California at San Diego School of Medicine, La Jolla, CA 92093
| | - Emily Moreno
- Division of Cardiology, Department of Medicine, University of California at San Diego School of Medicine, La Jolla, CA 92093
| | - Susan J Monkley
- Department of Molecular Cell Biology, University of Leicester, Leicester LE1 9HN, United Kingdom
| | - Ruixia Li
- Division of Cardiology, Department of Medicine, University of California at San Diego School of Medicine, La Jolla, CA 92093
| | - David R Critchley
- Department of Molecular Cell Biology, University of Leicester, Leicester LE1 9HN, United Kingdom
| | - Robert S Ross
- Division of Cardiology, Department of Medicine, University of California at San Diego School of Medicine, La Jolla, CA 92093;
- Cardiology Section, Department of Medicine, Veterans Administration Healthcare, San Diego, CA 92161
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12
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Malis V, Sinha U, Csapo R, Narici M, Sinha S. Relationship of changes in strain rate indices estimated from velocity-encoded MR imaging to loss of muscle force following disuse atrophy. Magn Reson Med 2017; 79:912-922. [PMID: 28560822 DOI: 10.1002/mrm.26759] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Revised: 04/30/2017] [Accepted: 05/01/2017] [Indexed: 11/06/2022]
Abstract
PURPOSE This study explores changes in strain rate (SR) (rate of regional deformation) parameters extracted from velocity-encoded MRI and their relationship to muscle force loss following 4-week unilateral lower limb suspension in healthy humans. METHODS Two-dimensional SR maps were derived from three directional velocity-encoded MR phase-contrast images of the medial gastrocnemius in seven subjects. Atrophy-related and regional differences in the SR eigenvalues, angle between the SR and muscle fiber (SR-fiber angle), and strain rates in the fiber basis were statistically analyzed using analysis of variance and linear regression. RESULTS During isometric contraction, SR in the fiber cross section (SRin-plane ) was significantly lower, and the SR-fiber angle was significantly higher postsuspension (P < 0.05). On multiple variable regression analysis, the volume of medial gastrocnemius, SRin-plane , and SR-fiber angle were significantly associated with force and changes in the, and the SR eigenvalues and shear SR were significantly associated with change in force with disuse. CONCLUSIONS Changes in SR-fiber angle, SRin-plane , and shear SR as well as their ability to predict force and force changes may reflect the role of remodeling of the extracellular matrix in disuse atrophy and its functional consequence in reducing lateral transmission of force. Magn Reson Med 79:912-922, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Vadim Malis
- Muscle Imaging and Modeling Lab, Department of Radiology, University of California, San Diego, California, USA.,Physics, University of California, San Diego, California, USA
| | - Usha Sinha
- Physics, San Diego State University, San Diego, California, USA
| | - Robert Csapo
- Muscle Imaging and Modeling Lab, Department of Radiology, University of California, San Diego, California, USA
| | - Marco Narici
- School of Graduate Entry Medicine and Health University of Nottingham, Derby, UK
| | - Shantanu Sinha
- Muscle Imaging and Modeling Lab, Department of Radiology, University of California, San Diego, California, USA
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13
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Le Rumeur E. Dystrophin and the two related genetic diseases, Duchenne and Becker muscular dystrophies. Bosn J Basic Med Sci 2015; 15:14-20. [PMID: 26295289 DOI: 10.17305/bjbms.2015.636] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Accepted: 07/20/2015] [Indexed: 01/01/2023] Open
Abstract
Mutations of the dystrophin DMD gene, essentially deletions of one or several exons, are the cause of two devastating and to date incurable diseases, Duchenne (DMD) and Becker (BMD) muscular dystrophies. Depending upon the preservation or not of the reading frame, dystrophin is completely absent in DMD, or present in either a mutated or a truncated form in BMD. DMD is a severe disease which leads to a premature death of the patients. Therapy approaches are evolving with the aim to transform the severe DMD in the BMD form of the disease by restoring the expression of a mutated or truncated dystrophin. These therapies are based on the assumption that BMD is a mild disease. However, this is not completely true as BMD patients are more or less severely affected and no molecular basis of this heterogeneity of the BMD form of the disease is yet understood. The aim of this review is to report for the correlation between dystrophin structures in BMD deletions in view of this heterogeneity and to emphasize that examining BMD patients in details is highly relevant to anticipate for DMD therapy effects.
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Affiliation(s)
- Elisabeth Le Rumeur
- Institut de Génétique et Développement de Rennes (IGDR), Faculté de Médecine, Rennes Cedex.
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14
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Abstract
Muscle fibres are very specialised cells with a complex structure that requires a high level of organisation of the constituent proteins. For muscle contraction to function properly, there is a need for not only sarcomeres, the contractile structures of the muscle fibre, but also costameres. These are supramolecular structures associated with the sarcolemma that allow muscle adhesion to the extracellular matrix. They are composed of protein complexes that interact and whose functions include maintaining cell structure and signal transduction mediated by their constituent proteins. It is important to improve our understanding of these structures, as mutations in various genes that code for costamere proteins cause many types of muscular dystrophy. In this review, we provide a description of costameres detailing each of their constituent proteins, such as dystrophin, dystrobrevin, syntrophin, sarcoglycans, dystroglycans, vinculin, talin, integrins, desmin, plectin, etc. We describe as well the diseases associated with deficiency thereof, providing a general overview of their importance.
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15
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García-Pelagio KP, Muriel J, O'Neill A, Desmond PF, Lovering RM, Lund L, Bond M, Bloch RJ. Myopathic changes in murine skeletal muscle lacking synemin. Am J Physiol Cell Physiol 2015; 308:C448-62. [PMID: 25567810 DOI: 10.1152/ajpcell.00331.2014] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Diseases of striated muscle linked to intermediate filament (IF) proteins are associated with defects in the organization of the contractile apparatus and its links to costameres, which connect the sarcomeres to the cell membrane. Here we study the role in skeletal muscle of synemin, a type IV IF protein, by examining mice null for synemin (synm-null). Synm-null mice have a mild skeletal muscle phenotype. Tibialis anterior (TA) muscles show a significant decrease in mean fiber diameter, a decrease in twitch and tetanic force, and an increase in susceptibility to injury caused by lengthening contractions. Organization of proteins associated with the contractile apparatus and costameres is not significantly altered in the synm-null. Elastimetry of the sarcolemma and associated contractile apparatus in extensor digitorum longus myofibers reveals a reduction in tension consistent with an increase in sarcolemmal deformability. Although fatigue after repeated isometric contractions is more marked in TA muscles of synm-null mice, the ability of the mice to run uphill on a treadmill is similar to controls. Our results suggest that synemin contributes to linkage between costameres and the contractile apparatus and that the absence of synemin results in decreased fiber size and increased sarcolemmal deformability and susceptibility to injury. Thus synemin plays a moderate but distinct role in fast twitch skeletal muscle.
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Affiliation(s)
- Karla P García-Pelagio
- Department of Physiology, School of Medicine, University of Maryland, Baltimore, Maryland
| | - Joaquin Muriel
- Department of Physiology, School of Medicine, University of Maryland, Baltimore, Maryland
| | - Andrea O'Neill
- Department of Physiology, School of Medicine, University of Maryland, Baltimore, Maryland
| | - Patrick F Desmond
- Program in Biochemistry and Molecular Biology, School of Medicine, University of Maryland, Baltimore, Maryland
| | - Richard M Lovering
- Department of Orthopaedics, School of Medicine, University of Maryland, Baltimore, Maryland
| | - Linda Lund
- Merrick School of Business, University of Baltimore, Baltimore, Maryland; and
| | - Meredith Bond
- College of Sciences and Health Professions, Cleveland State University, Cleveland, Ohio
| | - Robert J Bloch
- Department of Physiology, School of Medicine, University of Maryland, Baltimore, Maryland;
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16
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mTOR and the health benefits of exercise. Semin Cell Dev Biol 2014; 36:130-9. [DOI: 10.1016/j.semcdb.2014.08.013] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Revised: 08/08/2014] [Accepted: 08/22/2014] [Indexed: 01/06/2023]
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17
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Abstract
Muscle cells have an elaborate plasma membrane and t-tubule system that has been evolutionarily refined to maximize electrical conductivity for synchronous muscle contraction. However, this elaborate plasma membrane network has intrinsic vulnerabilities to stretch-induced membrane injury, and thus requires ongoing maintenance and repair. Herein we discuss the types of membrane injuries encountered by myofibers in healthy muscle and in muscular dystrophy. We review the different mechanisms by which muscle fibers in patients with muscular dystrophy are rendered more susceptible to injury, and we summarize the latest developments in our understanding of how the muscular dystrophy protein dysferlin mediates satellite-cell independent membrane repair.
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Affiliation(s)
- Sandra T Cooper
- Institute for Neuroscience and Muscle Research, Kids Research Institute, The Children's Hospital at Westmead, Sydney, New South Wales, Australia Discipline of Paediatrics and Child Health, Faculty of Medicine, University of Sydney, New South Wales, Australia
| | - Stewart I Head
- School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia
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18
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Impaired functional communication between the L-type calcium channel and mitochondria contributes to metabolic inhibition in the mdx heart. Proc Natl Acad Sci U S A 2014; 111:E2905-14. [PMID: 24969422 DOI: 10.1073/pnas.1402544111] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Duchenne muscular dystrophy is a fatal X-linked disease characterized by the absence of dystrophin. Approximately 20% of boys will die of dilated cardiomyopathy that is associated with cytoskeletal protein disarray, contractile dysfunction, and reduced energy production. However, the mechanisms for altered energy metabolism are not yet fully clarified. Calcium influx through the L-type Ca(2+) channel is critical for maintaining cardiac excitation and contraction. The L-type Ca(2+) channel also regulates mitochondrial function and metabolic activity via transmission of movement of the auxiliary beta subunit through intermediate filament proteins. Here, we find that activation of the L-type Ca(2+) channel is unable to induce increases in mitochondrial membrane potential and metabolic activity in intact cardiac myocytes from the murine model of Duchenne muscular dystrophy (mdx) despite robust increases recorded in wt myocytes. Treatment of mdx mice with morpholino oligomers to induce exon skipping of dystrophin exon 23 (that results in functional dystrophin accumulation) or application of a peptide that resulted in block of voltage-dependent anion channel (VDAC) "rescued" mitochondrial membrane potential and metabolic activity in mdx myocytes. The mitochondrial VDAC coimmunoprecipitated with the L-type Ca(2+) channel. We conclude that the absence of dystrophin in the mdx ventricular myocyte leads to impaired functional communication between the L-type Ca(2+) channel and mitochondrial VDAC. This appears to contribute to metabolic inhibition. These findings provide new mechanistic and functional insight into cardiomyopathy associated with Duchenne muscular dystrophy.
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19
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Goodman CA, Bennie JA, Leikis MJ, McKenna MJ. Unaccustomed eccentric contractions impair plasma K+ regulation in the absence of changes in muscle Na+,K+-ATPase content. PLoS One 2014; 9:e101039. [PMID: 24959836 PMCID: PMC4069193 DOI: 10.1371/journal.pone.0101039] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Accepted: 06/02/2014] [Indexed: 12/31/2022] Open
Abstract
The Na+,K+-ATPase (NKA) plays a fundamental role in the regulation of skeletal muscle membrane Na+ and K+ gradients, excitability and fatigue during repeated intense contractions. Many studies have investigated the effects of acute concentric exercise on K+ regulation and skeletal muscle NKA, but almost nothing is known about the effects of repeated eccentric contractions. We therefore investigated the effects of unaccustomed maximal eccentric knee extensor contractions on K+ regulation during exercise, peak knee extensor muscle torque, and vastus lateralis muscle NKA content and 3-O-MFPase activity. Torque measurements, muscle biopsies, and venous blood samples were taken before, during and up to 7 days following the contractions in six healthy adults. Eccentric contractions reduced peak isometric muscle torque immediately post-exercise by 26±11% and serum creatine kinase concentration peaked 24 h post-exercise at 339±90 IU/L. During eccentric contractions, plasma [K+] rose during Set 1 and remained elevated at ∼4.9 mM during sets 4–10; this was despite a decline in work output by Set 4, which fell by 18.9% at set 10. The rise in plasma [K+].work−1 ratio was elevated over Set 2 from Set 4– Set 10. Eccentric contractions had no effect on muscle NKA content or maximal in-vitro 3-O-MFPase activity immediately post- or up to 7 d post-exercise. The sustained elevation in plasma [K+] despite a decrease in work performed by the knee extensor muscles suggests an impairment in K+ regulation during maximal eccentric contractions, possibly due to increased plasma membrane permeability or to excitation-contraction uncoupling.
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Affiliation(s)
- Craig A. Goodman
- Institute of Sport, Exercise and Active Living (ISEAL), Muscle, Ions and Exercise Group, Victoria University, Melbourne, Victoria, Australia
- Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Jason A. Bennie
- Institute of Sport, Exercise and Active Living (ISEAL), Muscle, Ions and Exercise Group, Victoria University, Melbourne, Victoria, Australia
| | - Murray J. Leikis
- Institute of Sport, Exercise and Active Living (ISEAL), Muscle, Ions and Exercise Group, Victoria University, Melbourne, Victoria, Australia
- Department of Nephrology, Royal Melbourne Hospital, Department of Medicine, University of Melbourne, Melbourne, Victoria, Australia
| | - Michael J. McKenna
- Institute of Sport, Exercise and Active Living (ISEAL), Muscle, Ions and Exercise Group, Victoria University, Melbourne, Victoria, Australia
- * E-mail:
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20
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Viola HM, Davies SMK, Filipovska A, Hool LC. L-type Ca(2+) channel contributes to alterations in mitochondrial calcium handling in the mdx ventricular myocyte. Am J Physiol Heart Circ Physiol 2013; 304:H767-75. [PMID: 23335798 DOI: 10.1152/ajpheart.00700.2012] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The L-type Ca(2+) channel is the main route for calcium entry into cardiac myocytes, and it is essential for contraction. Alterations in whole cell L-type Ca(2+) channel current and Ca(2+) homeostasis have been implicated in the development of cardiomyopathies. Cytoskeletal proteins can influence whole cell L-type Ca(2+) current and mitochondrial function. Duchenne muscular dystrophy is a fatal X-linked disease that leads to progressive muscle weakness due to the absence of cytoskeletal protein dystrophin. This includes dilated cardiomyopathy, but the mechanisms are not well understood. We sought to identify the effect of alterations in whole cell L-type Ca(2+) channel current on mitochondrial function in the murine model of Duchenne muscular dystrophy (mdx). Activation of the L-type Ca(2+) channel with the dihydropyridine agonist BayK(-) caused a significantly larger increase in cytosolic Ca(2+) in mdx vs. wild-type (wt) ventricular myocytes. Consistent with elevated cytosolic Ca(2+), resting mitochondrial Ca(2+), NADH, and mitochondrial superoxide were significantly greater in mdx vs. wt myocytes. Activation of the channel with BayK(-) caused a further increase in mitochondrial Ca(2+), NADH, and superoxide in mdx myocytes. The ratios of the increases were similar to the ratios recorded in wt myocytes. In mitochondria isolated from 8-wk-old mdx hearts, respiration and mitochondrial electron transport chain complex activity were similar to mitochondria isolated from wt hearts. We conclude that mitochondria function at a higher level of resting calcium in the intact mdx myocyte and activation of the L-type Ca(2+) channel contributes to alterations in calcium handling by the mitochondria. This perturbation may contribute to the development of cardiomyopathy.
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Affiliation(s)
- Helena M Viola
- School of Anatomy, Physiology and Human Biology, University of Western Australia, Crawley, Western Australia, Australia
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21
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Goodall MH, Ward CW, Pratt SJP, Bloch RJ, Lovering RM. Structural and functional evaluation of branched myofibers lacking intermediate filaments. Am J Physiol Cell Physiol 2012; 303:C224-32. [PMID: 22592402 DOI: 10.1152/ajpcell.00136.2012] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Intermediate filaments (IFs), composed of desmin and keratins, link myofibrils to each other and to the sarcolemma in skeletal muscle. Fast-twitch muscle of mice lacking the IF proteins, desmin and keratin 19 (K19), showed reduced specific force and increased susceptibility to injury in earlier studies. Here we tested the hypothesis that the number of malformed myofibers in mice lacking desmin (Des(-/-)), keratin 19 (K19(-/-)), or both IF proteins (double knockout, DKO) is increased and is coincident with altered excitation-contraction (EC) coupling Ca(2+) kinetics, as reported for mdx mice. We quantified the number of branched myofibers, characterized their organization with confocal and electron microscopy (EM), and compared the Ca(2+) kinetics of EC coupling in flexor digitorum brevis myofibers from adult Des(-/-), K19(-/-), or DKO mice and compared them to age-matched wild type (WT) and mdx myofibers. Consistent with our previous findings, 9.9% of mdx myofibers had visible malformations. Des(-/-) myofibers had more malformations (4.7%) than K19(-/-) (0.9%) or DKO (1.3%) myofibers. Confocal and EM imaging revealed no obvious changes in sarcomere misalignment at the branch points, and the neuromuscular junctions in the mutant mice, while more variably located, were limited to one per myofiber. Global, electrically evoked Ca(2+) signals showed a decrease in the rate of Ca(2+) uptake (decay rate) into the sarcoplasmic reticulum after Ca(2+) release, with the most profound effect in branched DKO myofibers (44% increase in uptake relative to WT). Although branched DKO myofibers showed significantly faster rates of Ca(2+) clearance, the milder branching phenotype observed in DKO muscle suggests that the absence of K19 corrects the defect created by the absence of desmin alone. Thus, there are complex roles for desmin-based and K19-based IFs in skeletal muscle, with the null and DKO mutations having different effects on Ca(2+) reuptake and myofiber branching.
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Affiliation(s)
- Mariah H Goodall
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, 21201, USA
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22
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Influences of desmin and keratin 19 on passive biomechanical properties of mouse skeletal muscle. J Biomed Biotechnol 2012; 2012:704061. [PMID: 22287836 PMCID: PMC3263816 DOI: 10.1155/2012/704061] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2011] [Accepted: 09/10/2011] [Indexed: 11/17/2022] Open
Abstract
In skeletal muscle fibers, forces must be transmitted between the plasma membrane and the intracellular contractile lattice, and within this lattice between adjacent myofibrils. Based on their prevalence, biomechanical properties and localization, desmin and keratin intermediate filaments (IFs) are likely to participate in structural connectivity and force transmission. We examined the passive load-bearing response of single fibers from the extensor digitorum longus (EDL) muscles of young (3 months) and aged (10 months) wild-type, desmin-null, K19-null, and desmin/K19 double-null mice. Though fibers are more compliant in all mutant genotypes compared to wild-type, the structural response of each genotype is distinct, suggesting multiple mechanisms by which desmin and keratin influence the biomechanical properties of myofibers. This work provides additional insight into the influences of IFs on structure-function relationships in skeletal muscle. It may also have implications for understanding the progression of desminopathies and other IF-related myopathies.
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23
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Obscurin depletion impairs organization of skeletal muscle in developing zebrafish embryos. J Biomed Biotechnol 2011; 2011:479135. [PMID: 22190853 PMCID: PMC3228690 DOI: 10.1155/2011/479135] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2011] [Revised: 07/10/2011] [Accepted: 07/27/2011] [Indexed: 12/20/2022] Open
Abstract
During development, skeletal myoblasts differentiate into myocytes and skeletal myotubes with mature contractile structures that are precisely oriented with respect to surrounding cells and tissues. Establishment of this highly ordered structure requires reciprocal interactions between the differentiating myocytes and the surrounding extracellular matrix to form correctly positioned and well-organized attachments from the skeletal muscle to the bony skeleton. Using the developing zebrafish embryo as a model, we examined the relationship between new myofibril assembly and the organization of the membrane domains involved in cell-extracellular matrix interactions. We determined that depletion of obscurin, a giant muscle protein, resulted in irregular cell morphology and disturbed extracellular matrix organization during skeletal muscle development. The resulting impairment of myocyte organization was associated with disturbance of the internal architecture of the myocyte suggesting that obscurin participates in organizing the internal structure of the myocyte and translating those structural cues to surrounding cells and tissues.
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24
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Biochemical and anisotropical properties of tendons. Micron 2011; 43:205-14. [PMID: 21890364 DOI: 10.1016/j.micron.2011.07.015] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2011] [Revised: 07/26/2011] [Accepted: 07/26/2011] [Indexed: 01/30/2023]
Abstract
Tendons are formed by dense connective tissue composed of an abundant extracellular matrix (ECM) that is constituted mainly of collagen molecules, which are organized into fibrils, fibers, fiber bundles and fascicles helicoidally arranged along the largest axis of the tendon. The biomechanical properties of tendons are directly related to the organization of the collagen molecules that aggregate to become a super-twisted cord. In addition to collagen, the ECM of tendons is composed of non-fibrillar components, such as proteoglycans and non-collagenous glycoproteins. The capacity of tendons to resist mechanical stress is directly related to the structural organization of the ECM. Collagen is a biopolymer and presents optical anisotropies, such as birefringence and linear dichroism, that are important optical properties in the characterization of the supramolecular organization of the fibers. The objective of this study was to present a review of the composition and organization of the ECM of tendons and to highlight the importance of the anisotropic optical properties in the study of alterations in the ECM.
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25
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Biomechanics of the sarcolemma and costameres in single skeletal muscle fibers from normal and dystrophin-null mice. J Muscle Res Cell Motil 2011; 31:323-36. [PMID: 21312057 DOI: 10.1007/s10974-011-9238-9] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2010] [Accepted: 01/11/2011] [Indexed: 01/01/2023]
Abstract
We studied the biomechanical properties of the sarcolemma and its links through costameres to the contractile apparatus in single mammalian myofibers of Extensor digitorum longus muscles isolated from wild (WT) and dystrophin-null (mdx) mice. Suction pressures (P) applied through a pipette to the sarcolemma generated a bleb, the height of which increased with increasing P. Larger increases in P broke the connections between the sarcolemma and myofibrils and eventually caused the sarcolemma to burst. We used the values of P at which these changes occurred to estimate the tensions and stiffness of the system and its individual elements. Tensions of the whole system and the sarcolemma, as well as the maximal tension sustained by the costameres, were all significantly lower (1.8-3.3 fold) in muscles of mdx mice compared to WT. Values of P at which separation and bursting occurred, as well as the stiffness of the whole system and of the isolated sarcolemma, were ~2-fold lower in mdx than in WT. Our results indicate that the absence of dystrophin reduces muscle stiffness, increases sarcolemmal deformability, and compromises the mechanical stability of costameres and their connections to nearby myofibrils.
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26
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Lovering RM, O'Neill A, Muriel JM, Prosser BL, Strong J, Bloch RJ. Physiology, structure, and susceptibility to injury of skeletal muscle in mice lacking keratin 19-based and desmin-based intermediate filaments. Am J Physiol Cell Physiol 2011; 300:C803-13. [PMID: 21209367 DOI: 10.1152/ajpcell.00394.2010] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Intermediate filaments, composed of desmin and of keratins, play important roles in linking contractile elements to each other and to the sarcolemma in striated muscle. Our previous results show that the tibialis anterior (TA) muscles of mice lacking keratin 19 (K19) lose costameres, accumulate mitochondria under the sarcolemma, and generate lower specific tension than controls. Here we compare the physiology and morphology of TA muscles of mice lacking K19 with muscles lacking desmin or both proteins [double knockout (DKO)]. K19-/- mice and DKO mice showed a threefold increase in the levels of creatine kinase (CK) in the serum. The absence of desmin caused a larger change in specific tension (-40%) than the absence of K19 (-19%) and played the predominant role in contractile function (-40%) and decreased tolerance to exercise in the DKO muscle. By contrast, the absence of both proteins was required to obtain a significantly greater loss of contractile torque after injury (-48%) compared with wild type (-39%), as well as near-complete disruption of costameres. The DKO muscle also showed a significantly greater misalignment of myofibrils than either mutant alone. In contrast, large subsarcolemmal gaps and extensive accumulation of mitochondria were only seen in K19-null TA muscles, and the absence of both K19 and desmin yielded milder phenotypes. Our results suggest that keratin filaments containing K19- and desmin-based intermediate filaments can play independent, complementary, or antagonistic roles in the physiology and morphology of fast-twitch skeletal muscle.
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Affiliation(s)
- Richard M Lovering
- Department of Physiology, University of Maryland, Baltimore, 21201, USA.
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27
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Kee AJ, Gunning PW, Hardeman EC. A cytoskeletal tropomyosin can compromise the structural integrity of skeletal muscle. ACTA ACUST UNITED AC 2009; 66:710-20. [PMID: 19530183 DOI: 10.1002/cm.20400] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
We have identified a number of extra-sarcomeric actin filaments defined by cytoskeletal tropomyosin (Tm) isoforms. Expression of a cytoskeletal Tm (Tm3) not normally present in skeletal muscle in a transgenic mouse resulted in muscular dystrophy. In the present report we show that muscle pathology in this mouse is late onset (between 2 and 6 months of age) and is predominately in the back and paraspinal muscles. In the Tm3 mice, Evans blue dye uptake in muscle and serum levels of creatine kinase were markedly increased following downhill exercise, and the force drop following a series of lengthening contractions in isolated muscles (extensor digitorum longus) was also significantly increased in these mice. These results demonstrate that expression of an inappropriate Tm in skeletal muscle results in increased susceptibility to contraction-induced damage. The extra-sarcomeric actin cytoskeleton therefore may have an important role in protecting the muscle from contractile stress.
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Affiliation(s)
- Anthony J Kee
- Department of Anatomy, School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia
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28
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Röder IV, Lissandron V, Martin J, Petersen Y, Di Benedetto G, Zaccolo M, Rudolf R. PKA microdomain organisation and cAMP handling in healthy and dystrophic muscle in vivo. Cell Signal 2009; 21:819-26. [PMID: 19263518 DOI: 10.1016/j.cellsig.2009.01.029] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Signalling through protein kinase A (PKA) triggers a multitude of intracellular effects in response to a variety of extracellular stimuli. To guarantee signal specificity, different PKA isoforms are compartmentalised by Akinase anchoring proteins (AKAPs) into functional microdomains. By using genetically encoded fluorescent reporters of cAMP concentration that are targeted to the intracellular sites where PKA type I and PKA type II isoforms normally reside, we directly show for the first time spatially and functionally separate PKA microdomains in mouse skeletal muscle in vivo. The reporters localised into clearly distinct patterns within sarcomers, from where they could be displaced by means of AKAP disruptor peptides indicating the presence of disparate PKA type I and PKA type II anchor sites within skeletal muscle fibres. The functional relevance of such differential localisation was underscored by the finding of mutually exclusive and AKAP-dependent increases in [cAMP] in the PKA type I and PKA type II microdomains upon application of different cAMP agonists. Specifically, the sensors targeted to the PKA type II compartment responded only to norepinephrine, whereas those targeted to the PKA type I compartment responded only to alpha-calcitonin gene-related peptide. Notably, in dystrophic mdx mice the localisation pattern of the reporters was altered and the functional separation of the cAMP microdomains was abolished. In summary, our data indicate that an efficient organisation in microdomains of the cAMP/PKA pathway exists in the healthy skeletal muscle and that such organisation is subverted in dystrophic skeletal muscle.
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Affiliation(s)
- Ira Verena Röder
- Institute of Toxicology and Genetics, Forschungszentrum Karlsruhe, 76344 Eggenstein-Leopoldshafen, Germany
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29
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Hirn C, Shapovalov G, Petermann O, Roulet E, Ruegg UT. Nav1.4 deregulation in dystrophic skeletal muscle leads to Na+ overload and enhanced cell death. ACTA ACUST UNITED AC 2008; 132:199-208. [PMID: 18625851 PMCID: PMC2483333 DOI: 10.1085/jgp.200810024] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Duchenne muscular dystrophy (DMD) is a hereditary degenerative disease manifested by the absence of dystrophin, a structural, cytoskeletal protein, leading to muscle degeneration and early death through respiratory and cardiac muscle failure. Whereas the rise of cytosolic Ca2+ concentrations in muscles of mdx mouse, an animal model of DMD, has been extensively documented, little is known about the mechanisms causing alterations in Na+ concentrations. Here we show that the skeletal muscle isoform of the voltage-gated sodium channel, Nav1.4, which represents over 90% of voltage-gated sodium channels in muscle, plays an important role in development of abnormally high Na+ concentrations found in muscle from mdx mice. The absence of dystrophin modifies the expression level and gating properties of Nav1.4, leading to an increased Na+ concentration under the sarcolemma. Moreover, the distribution of Nav1.4 is altered in mdx muscle while maintaining the colocalization with one of the dystrophin-associated proteins, syntrophin α-1, thus suggesting that syntrophin is an important linker between dystrophin and Nav1.4. Additionally, we show that these modifications of Nav1.4 gating properties and increased Na+ concentrations are strongly correlated with increased cell death in mdx fibers and that both cell death and Na+ overload can be reversed by 3 nM tetrodotoxin, a specific Nav1.4 blocker.
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Affiliation(s)
- Carole Hirn
- Laboratory of Pharmacology, Geneva-Lausanne School of Pharmaceutical Sciences, University of Geneva, CH 1211 Geneva 4, Switzerland
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Konieczny P, Fuchs P, Reipert S, Kunz WS, Zeöld A, Fischer I, Paulin D, Schröder R, Wiche G. Myofiber integrity depends on desmin network targeting to Z-disks and costameres via distinct plectin isoforms. ACTA ACUST UNITED AC 2008; 181:667-81. [PMID: 18490514 PMCID: PMC2386106 DOI: 10.1083/jcb.200711058] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Dysfunction of plectin, a 500-kD cytolinker protein, leads to skin blistering and muscular dystrophy. Using conditional gene targeting in mice, we show that plectin deficiency results in progressive degenerative alterations in striated muscle, including aggregation and partial loss of intermediate filament (IF) networks, detachment of the contractile apparatus from the sarcolemma, profound changes in myofiber costameric cytoarchitecture, and decreased mitochondrial number and function. Analysis of newly generated plectin isoform-specific knockout mouse models revealed that IF aggregates accumulate in distinct cytoplasmic compartments, depending on which isoform is missing. Our data show that two major plectin isoforms expressed in muscle, plectin 1d and 1f, integrate fibers by specifically targeting and linking desmin IFs to Z-disks and costameres, whereas plectin 1b establishes a linkage to mitochondria. Furthermore, disruption of Z-disk and costamere linkages leads to the pathological condition of epidermolysis bullosa with muscular dystrophy. Our findings establish plectin as the major organizer of desmin IFs in myofibers and provide new insights into plectin- and desmin-related muscular dystrophies.
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Affiliation(s)
- Patryk Konieczny
- Max F. Perutz Laboratories, Department of Molecular Cell Biology, University of Vienna, A-1030 Vienna, Austria
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Zhang M, Liu J, Cheng A, DeYoung SM, Saltiel AR. Identification of CAP as a costameric protein that interacts with filamin C. Mol Biol Cell 2007; 18:4731-40. [PMID: 17898075 PMCID: PMC2096606 DOI: 10.1091/mbc.e07-06-0628] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Cbl-associated protein (CAP) is an adaptor protein that interacts with both signaling and cytoskeletal proteins. Here, we characterize the expression, localization and potential function of CAP in striated muscle. CAP is markedly induced during myoblast differentiation, and colocalizes with vinculin during costamerogenesis. In adult mice, CAP is enriched in oxidative muscle fibers, and it is found in membrane anchorage complexes, including intercalated discs, costameres, and myotendinous junctions. Using both yeast two-hybrid and proteomic approaches, we identified the sarcomeric protein filamin C (FLNc) as a binding partner for CAP. When overexpressed, CAP recruits FLNc to cell-extracellular matrix adhesions, where the two proteins cooperatively regulate actin reorganization. Moreover, overexpression of CAP inhibits FLNc-induced cell spreading on fibronectin. In dystrophin-deficient mdx mice, the expression and membrane localization of CAP is increased, concomitant with the elevated plasma membrane content of FLNc, suggesting that CAP may compensate for the reduced membrane linkage of the myofibrils due to the loss of the dystroglycan-sarcoglycan complex in these mice. Thus, through its interaction with FLNc, CAP provides another link between the myofibril cytoskeleton and the plasma membrane of muscle cells, and it may play a dynamic role in the regulation and maintenance of muscle structural integrity.
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Affiliation(s)
- Mei Zhang
- Departments of Internal Medicine and Physiology, Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109
| | - Jun Liu
- Departments of Internal Medicine and Physiology, Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109
| | - Alan Cheng
- Departments of Internal Medicine and Physiology, Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109
| | - Stephanie M. DeYoung
- Departments of Internal Medicine and Physiology, Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109
| | - Alan R. Saltiel
- Departments of Internal Medicine and Physiology, Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109
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32
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Rezniczek GA, Konieczny P, Nikolic B, Reipert S, Schneller D, Abrahamsberg C, Davies KE, Winder SJ, Wiche G. Plectin 1f scaffolding at the sarcolemma of dystrophic (mdx) muscle fibers through multiple interactions with beta-dystroglycan. ACTA ACUST UNITED AC 2007; 176:965-77. [PMID: 17389230 PMCID: PMC2064082 DOI: 10.1083/jcb.200604179] [Citation(s) in RCA: 122] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In skeletal muscle, the cytolinker plectin is prominently expressed at Z-disks and the sarcolemma. Alternative splicing of plectin transcripts gives rise to more than eight protein isoforms differing only in small N-terminal sequences (5-180 residues), four of which (plectins 1, 1b, 1d, and 1f) are found at substantial levels in muscle tissue. Using plectin isoform-specific antibodies and isoform expression constructs, we show the differential regulation of plectin isoforms during myotube differentiation and their localization to different compartments of muscle fibers, identifying plectins 1 and 1f as sarcolemma-associated isoforms, whereas plectin 1d localizes exclusively to Z-disks. Coimmunoprecipitation and in vitro binding assays using recombinant protein fragments revealed the direct binding of plectin to dystrophin (utrophin) and beta-dystroglycan, the key components of the dystrophin-glycoprotein complex. We propose a model in which plectin acts as a universal mediator of desmin intermediate filament anchorage at the sarcolemma and Z-disks. It also explains the plectin phenotype observed in dystrophic skeletal muscle of mdx mice and Duchenne muscular dystrophy patients.
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MESH Headings
- Animals
- Cell Compartmentation/physiology
- Cell Differentiation/physiology
- Cells, Cultured
- Cytoskeleton/metabolism
- Cytoskeleton/ultrastructure
- Desmin/metabolism
- Dystroglycans/metabolism
- Humans
- Immunohistochemistry
- Intermediate Filaments/metabolism
- Intermediate Filaments/ultrastructure
- Mice
- Mice, Inbred C57BL
- Mice, Inbred mdx
- Models, Biological
- Muscle Fibers, Skeletal/metabolism
- Muscle Fibers, Skeletal/pathology
- Muscle Fibers, Skeletal/ultrastructure
- Muscle, Skeletal/metabolism
- Muscle, Skeletal/pathology
- Muscle, Skeletal/physiopathology
- Muscular Dystrophy, Animal/genetics
- Muscular Dystrophy, Animal/metabolism
- Muscular Dystrophy, Animal/physiopathology
- Plectin/immunology
- Plectin/metabolism
- Protein Isoforms/immunology
- Protein Isoforms/metabolism
- Rats
- Sarcolemma/metabolism
- Sarcolemma/pathology
- Sarcolemma/ultrastructure
- Utrophin/metabolism
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Affiliation(s)
- Günther A Rezniczek
- Max F. Perutz Laboratories, Department of Molecular Cell Biology, University of Vienna, A-1030 Vienna, Austria
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Senetar MA, Moncman CL, McCann RO. Talin2 is induced during striated muscle differentiation and is targeted to stable adhesion complexes in mature muscle. CELL MOTILITY AND THE CYTOSKELETON 2007; 64:157-73. [PMID: 17183545 DOI: 10.1002/cm.20173] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The cytoskeletal protein talin serves as an essential link between integrins and the actin cytoskeleton in several similar, but functionally distinct, adhesion complexes, including focal adhesions, costameres, and intercalated disks. Vertebrates contain two talin genes, TLN1 and TLN2, but the different roles of Talin1 and Talin2 in cell adhesion are unclear. In this report we have analyzed Talin1 and Talin2 in striated muscle. Using isoform-specific antibodies, we found that Talin2 is highly expressed in mature striated muscle. Using mouse C2C12 cells and primary human skeletal muscle myoblasts as models of muscle differentiation, we show that Talin1 is expressed in undifferentiated myoblasts and that Talin2 expression is upregulated during muscle differentiation at both the mRNA and protein levels. We have also identified regulatory sequences that may be responsible for the differential expression of Talin1 and Talin2. Using GFP-tagged Talin1 and Talin2 constructs, we found that GFP-Talin1 targets to focal adhesions while GFP-Talin2 targets to abnormally large adhesions in myoblasts. We also found that ectopic expression of Talin2 in myoblasts, which do not contain appreciable levels of Talin2, dysregulates the actin cytoskeleton. Finally we demonstrate that Talin2, but not Talin1, localizes to costameres and intercalated disks, which are stable adhesions required for the assembly of mature striated muscle. Our results suggest that Talin1 is the primary link between integrins and actin in dynamic focal adhesions in undifferentiated, motile cells, but that Talin2 may serve as the link between integrins and the sarcomeric cytoskeletonin stable adhesion complexes in mature striated muscle.
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Affiliation(s)
- Melissa A Senetar
- Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, Kentucky 40536-0509, USA
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Trimarchi F, Favaloro A, Fulle S, Magaudda L, Puglielli C, Di Mauro D. Culture of human skeletal muscle myoblasts: timing appearance and localization of dystrophin-glycoprotein complex and vinculin-talin-integrin complex. Cells Tissues Organs 2006; 183:87-98. [PMID: 17053325 DOI: 10.1159/000095513] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/19/2006] [Indexed: 11/19/2022] Open
Abstract
The dystrophin-glycoprotein complex together with the vinculin-talin-integrin complex plays an important role in muscle function; in fact the mutations of their elements lead to diverse forms of muscular dystrophies. The relationship between the elements of dystrophin-glycoprotein complex and vinculin-talin-integrin and the time course of their formation are still not known in detail. In order to better understand this relationship we studied their expression during development in normal human skeletal muscle culture. Using a standardized muscle cell culture procedure, this study was performed to analyze the timing, appearance and the localization of some proteins of the dystrophin-glycoprotein complex and vinculin-talin-integrin complex during cellular proliferation (myoblast) and differentiation (4, 7, 15 and 21 days). The indirect immunofluorescence technique was used and cells were examined using a Meta Zeiss LSM510 confocal laser scanning inverted microscope. We examined the progressive appearance of the following proteins: alpha, beta, gamma, delta-sarcoglycans, beta-dystroglycan, dystrophin, talin, vinculin and integrin isoform alpha7/beta1. Immunofluorescence of these proteins, in satellite cells entering myogenic differentiation, revealed different patterns of localization depending on the time of culture. We showed that nondifferentiated cultures of human myoblasts expressed a perinuclear distribution of all proteins tested. During myoblast differentiation into myotubes (4 days) immunofluorescence gradually increased and was located in the whole cytoplasm. Subsequently, at day 7, a strong and homogeneous cytoplasmic labelling of all proteins was seen. At 15 days the distribution of the proteins was on the membrane. At this time some myotubes displayed a significant degree of precostameric banding pattern. As fusion proceeded at 21 days, the cytodistribution progressively changed and appeared along fibrillar longitudinal structures, and myotubes showed a clear periodic distribution (costameres). In conclusion, in normal human muscle cultures DGC and vinculin-talin-integrin proteins are first localized in the perinuclear region, then they diffuse in the cytoplasm and finally form at the plasma membrane into typical rib-like structures that are sarcolemma-associated.
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Affiliation(s)
- F Trimarchi
- Department of Biomorphology and Biotechnologies, University of Messina, Messina, Italy.
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35
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Reed P, Porter NC, Strong J, Pumplin DW, Corse AM, Luther PW, Flanigan KM, Bloch RJ. Sarcolemmal reorganization in facioscapulohumeral muscular dystrophy. Ann Neurol 2006; 59:289-97. [PMID: 16437580 DOI: 10.1002/ana.20750] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
OBJECTIVE We examined the sarcolemma of skeletal muscle from patients with facioscapulohumeral muscular dystrophy (FSHD1A) to learn if, as in other murine and human muscular dystrophies, its organization and relationship to nearby contractile structures are altered. METHODS Unfixed biopsies of control and FSHD deltoid and biceps muscles, snap-frozen at resting length, were cryosectioned, indirectly immunolabeled with fluorescent antibodies to sarcolemmal and myofibrillar markers, and examined with confocal microscopy to localize the immunolabeled proteins. Glutaraldehyde-fixed samples were stained with heavy metals, embedded, thin-sectioned, and examined with electron microscopy to determine the relationship between the sarcolemma and the underlying myofibrils. RESULTS Confocal microscopy showed that some of the structures at the sarcolemma in FSHD samples were misaligned with respect to the underlying contractile apparatus. Electron microscopy showed a significant increase in the distance between the sarcolemma and the nearest myofibrils, from less than 100 nm in controls to values as high as 550 nm in FSHD. INTERPRETATION Our results show that the pathophysiology of FSHD includes novel changes in the organization of the sarcolemma and its association with nearby contractile structures and suggest that, as in other muscular dystrophies, the integrity of the sarcolemma may be compromised in FSHD.
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Affiliation(s)
- Patrick Reed
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
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36
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Abstract
Mechanical force is generated within skeletal muscle cells by contraction of specialized myofibrillar proteins. This paper explores how the contractile force generated at the sarcomeres within an individual muscle fiber is transferred through the connective tissue to move the bones. The initial key point for transfer of the contractile force is the muscle cell membrane (sarcolemma) where force is transferred laterally to the basement membrane (specialized extracellular matrix rich in laminins) to be integrated within the connective tissue (rich in collagens) before transmission to the tendons. Connections between (1) key molecules outside the myofiber in the basement membrane to (2) molecules within the sarcolemma of the myofiber and (3) the internal cytoplasmic structures of the cytoskeleton and sarcomeres are evaluated. Disturbances to many components of this complex interactive system adversely affect skeletal muscle strength and integrity, and can result in severe muscle diseases. The mechanical aspects of these crucial linkages are discussed, with particular reference to defects in laminin-alpha2 and integrin-alpha7. Novel interventions to potentially increase muscle strength and reduce myofiber damage are mentioned, and these are also highly relevant to muscle diseases and aging muscle.
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Affiliation(s)
- M D Grounds
- School of Anatomy and Human Biology, The University of Western Australia, Perth, WA, Australia.
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37
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Quach NL, Rando TA. Focal adhesion kinase is essential for costamerogenesis in cultured skeletal muscle cells. Dev Biol 2006; 293:38-52. [PMID: 16533505 DOI: 10.1016/j.ydbio.2005.12.040] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2005] [Revised: 12/12/2005] [Accepted: 12/14/2005] [Indexed: 02/03/2023]
Abstract
A central question in muscle biology is how costameres are formed and become aligned with underlying myofibrils in mature tissues. Costameres are composed of focal adhesion proteins, including vinculin and paxillin, and anchor myofibril Z-bands to the sarcolemma. In the present study, we investigated the process of costamere formation ("costamerogenesis") in differentiating primary mouse myoblasts. Using vinculin and paxillin as costameric markers, we found that two additional focal adhesion components, alpha5beta1 integrin and focal adhesion kinase (FAK), are associated with costameres. We have characterized costamerogenesis as occurring in three distinct stages based on the organizational pattern of these costameric proteins. We show that both costamerogenesis and myofibrillogenesis are initiated at sites of membrane contacts with the extracellular matrix and that their maturation is tightly coupled. To test the importance of FAK signaling in these processes, we analyzed cells expressing a dominant negative form of FAK (dnFAK). When cells expressing dnFAK were induced to differentiate, both costamerogenesis and myofibrillogenesis were disrupted although the expression of constituent proteins was not inhibited. Likewise, inhibiting FAK activity by reducing FAK levels using an siRNA approach also resulted in an inhibition of costamerogenesis and myofibrillogenesis. The relationship between costamere and myofibril formation was tested further by treating myotube cultures with potassium or tetrodotoxin to block contraction and disrupt myofibril organization. This also resulted in inhibition of costamere maturation. We present a model of costamerogenesis whereby signaling through FAK is essential for both normal costamerogenesis and normal myofibrillogenesis which are tightly coupled during skeletal myogenesis.
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Affiliation(s)
- Navaline L Quach
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305, USA
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38
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Raeker MO, Su F, Geisler SB, Borisov AB, Kontrogianni-Konstantopoulos A, Lyons SE, Russell MW. Obscurin is required for the lateral alignment of striated myofibrils in zebrafish. Dev Dyn 2006; 235:2018-29. [PMID: 16779859 DOI: 10.1002/dvdy.20812] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Obscurin/obscurin-MLCK is a giant sarcomere-associated protein with multiple isoforms whose interactions with titin and small ankyrin-1 suggest that it has an important role in myofibril assembly, structural support, and the sarcomeric alignment of the sarcoplasmic reticulum. In this study, we characterized the zebrafish orthologue of obscurin and examined its role in striated myofibril assembly. Zebrafish obscurin was expressed in the somites and central nervous system by 24 hours post-fertilization (hpf) and in the heart by 48 hpf. Depletion of obscurin using two independent morpholino antisense oligonucleotides resulted in diminished numbers and marked disarray of skeletal myofibrils, impaired lateral alignment of adjacent myofibrils, disorganization of the sarcoplasmic reticulum, somite segmentation defects, and abnormalities of cardiac structure and function. This is the first demonstration that obscurin is required for vertebrate cardiac and skeletal muscle development. The diminished capacity to generate and organize new myofibrils in response to obscurin depletion suggests that it may have a vital role in the causation of or adaptation to cardiac and skeletal myopathies.
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Affiliation(s)
- Maide O Raeker
- Department of Pediatrics and Communicable Diseases, University of Michigan, Ann Arbor, Michigan 48109, USA
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39
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Reed P, Bloch RJ. Postnatal changes in sarcolemmal organization in the mdx mouse. Neuromuscul Disord 2005; 15:552-61. [PMID: 16051092 DOI: 10.1016/j.nmd.2005.03.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2004] [Revised: 12/03/2004] [Accepted: 03/16/2005] [Indexed: 10/25/2022]
Abstract
The tibialis anterior muscles of mdx mice degenerate between 3 and 4 weeks after birth and then partially recover. We show that the membrane cytoskeleton at the mdx sarcolemma is disorganized at 18-days postnatal, and becomes more disorganized at 4 weeks compared to earlier or later times. Mdx muscle at 18 days have few central nuclei, suggesting that it has not yet sustained significant damage. The variance of myofiber diameter confirms that the mdx pathology is greatest at 4 weeks, when the sarcolemma is most disorganized. Sarcolemmal disorganization in the mdx does not involve contractile structures, nor is it seen in age-matched controls. In revertant mdx fibers expressing dystrophin, sarcolemmal organization is similar to controls. Our results suggest that the absence of dystrophin results in the disorganization of the sarcolemma, even in 18-day-old mice, and that the extent of disorganization is greater when the myopathy is most severe.
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Affiliation(s)
- Patrick Reed
- Department of Physiology, School of Medicine, University of Maryland, 655 W. Baltimore Steet, Baltimore, MD 21201, USA
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Bennett PM, Baines AJ, Lecomte MC, Maggs AM, Pinder JC. Not just a plasma membrane protein: in cardiac muscle cells alpha-II spectrin also shows a close association with myofibrils. J Muscle Res Cell Motil 2005; 25:119-26. [PMID: 15360127 DOI: 10.1023/b:jure.0000035892.77399.51] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Spectrin and its associated proteins are essential for the integrity of muscle cells and there is increasing evidence for their involvement in signalling pathways as well as having a structural function in mediating stress. Spectrin is a multigene family and it is essential to determine which isoforms are present and their location in the cell. In heart muscle, we have found that one spectrin isoform, alphaII-spectrin, is strongly represented and, using immunofluorescence, we show that it lies within the contractile fibres near the Z-disc as well as on the cardiomyocyte plasma membrane. Electron microscopy of immunogold-labelled cryosections reveals statistically significant clustering of gold particles near the Z-disc, within and close to the edge of myofibrils. betaII-spectrin and ankyrin-R and G are both known to occupy this region. We suggest that alphaIIbetaII spectrin tetramers with ankyrin organise and/or stabilise cardiac muscle cell membrane components relative to the contractile apparatus.
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Affiliation(s)
- Pauline M Bennett
- The Randall Centre for Molecular Mechanisms of Cell Function, New Hunt's House, King's College London, Guy's Campus, London SE1 1UL, UK.
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41
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Takamure M, Murata KY, Tamada Y, Azuma M, Ueno S. Calpain-dependent α-fodrin cleavage at the sarcolemma in muscle diseases. Muscle Nerve 2005; 32:303-9. [PMID: 15948206 DOI: 10.1002/mus.20362] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
To clarify the involvement of calpains in sarcolemmal remodeling, we examined the expression of calpains and their substrate, alpha-fodrin, in various disorders of muscle. Although immunohistological reactions for alpha-fodrin and calpains were weak in normal control muscles, intense immunoreactivity for alpha-fodrin at the sarcolemma and for calpains throughout the cytoplasm were detected in small muscle fibers from patients with inflammatory myositis (IM), rhabdomyolysis (Rhab), and Duchenne muscular dystrophy (DMD). Most of the calpain-alpha-fodrin double-positive muscle fibers in IM and Rhab also expressed the developmental form of myosin heavy chain. The sarcolemma of these small muscle fibers reacted with an antibody that specifically recognizes the 150-kDa fragments of alpha-fodrin (SBDP 150s) cleaved by calpain, but not caspase 3. Western blot analysis confirmed these results. These observations indicate that calpain is activated and reacts with alpha-fodrin as a substrate at the sarcolemma, and plays a key role in modulating sarcolemmal proteins to adapt to the specific conditions in each myopathy.
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Affiliation(s)
- Miwa Takamure
- Department of Neurology, Nara Medical University, Kashihara, Nara 634-8521, Japan
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Abstract
In the Large(myd) mouse, dystroglycan is incompletely glycosylated and thus cannot bind its extracellular ligands, causing a muscular dystrophy that is usually lethal in early adulthood. We show that the Large(myd) mutation alters the composition and organization of the sarcolemma of fast-twitch skeletal muscle fibers in young adult mice. Costameres at the sarcolemma of the tibialis anterior muscle of Large(myd) mice contain reduced levels of several membrane cytoskeletal proteins, including dystrophin and beta-spectrin. In the quadriceps, longitudinally oriented costameric structures tend to become thickened and branched. More strikingly, proteins of the dystrophin complex present between costameres in controls are absent from Large(myd) muscles. We propose that the absence of the dystrophin complex from these regions destabilizes the sarcolemma of the Large(myd) mouse and thereby contributes to the severity of its muscular dystrophy. Thus, the positioning of sarcolemmal proteins may have a profound effect on the health of skeletal muscle.
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Affiliation(s)
- Patrick W Reed
- Department of Physiology, University of Maryland School of Medicine, 660 West Redwood Street, Baltimore, Maryland 21201, USA
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Ursitti JA, Lee PC, Resneck WG, McNally MM, Bowman AL, O'Neill A, Stone MR, Bloch RJ. Cloning and characterization of cytokeratins 8 and 19 in adult rat striated muscle. Interaction with the dystrophin glycoprotein complex. J Biol Chem 2004; 279:41830-8. [PMID: 15247274 DOI: 10.1074/jbc.m400128200] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We used degenerate primers for the amino- and carboxyl-terminal ends of the rod domains of intermediate filament proteins in reverse transcriptase-PCR experiments to identify and clone cytokeratins 8 and 19 (K8 and K19) from cardiac muscle of the adult rat. Northern blots showed that K8 has a 2.2-kb transcript and K19 has a 1.9-kb transcript in both adult cardiac and skeletal muscles. Immunolocalization of the cytokeratins in adult cardiac muscle with isoform-specific antibodies for K8 and K19 showed labeling at Z-lines within the muscle fibers and at Z-line and M-line domains at costameres at the sarcolemmal membrane. Dystrophin and K19 could be co-immunoprecipitated and co-purified from extracts of cardiac muscle, suggesting a link between the cytokeratins and the dystrophin-based cytoskeleton at the sarcolemma. Furthermore, transfection experiments indicate that K8 and K19 may associate with dystrophin through a specific interaction with its actin-binding domain. Consistent with this observation, the cytokeratins are disrupted at the sarcolemmal membrane of skeletal muscle of the mdx mouse that lacks dystrophin. Together these results indicate that at least two cytokeratins are expressed in adult striated muscle, where they may contribute to the organization of both the myoplasm and sarcolemma.
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Affiliation(s)
- Jeanine A Ursitti
- University of Maryland Biotechnology Institute, University of Maryland School of Medicine, Baltimore, MD 21202, USA.
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44
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Kjaer M. Role of extracellular matrix in adaptation of tendon and skeletal muscle to mechanical loading. Physiol Rev 2004; 84:649-98. [PMID: 15044685 DOI: 10.1152/physrev.00031.2003] [Citation(s) in RCA: 943] [Impact Index Per Article: 47.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The extracellular matrix (ECM), and especially the connective tissue with its collagen, links tissues of the body together and plays an important role in the force transmission and tissue structure maintenance especially in tendons, ligaments, bone, and muscle. The ECM turnover is influenced by physical activity, and both collagen synthesis and degrading metalloprotease enzymes increase with mechanical loading. Both transcription and posttranslational modifications, as well as local and systemic release of growth factors, are enhanced following exercise. For tendons, metabolic activity, circulatory responses, and collagen turnover are demonstrated to be more pronounced in humans than hitherto thought. Conversely, inactivity markedly decreases collagen turnover in both tendon and muscle. Chronic loading in the form of physical training leads both to increased collagen turnover as well as, dependent on the type of collagen in question, some degree of net collagen synthesis. These changes will modify the mechanical properties and the viscoelastic characteristics of the tissue, decrease its stress, and likely make it more load resistant. Cross-linking in connective tissue involves an intimate, enzymatical interplay between collagen synthesis and ECM proteoglycan components during growth and maturation and influences the collagen-derived functional properties of the tissue. With aging, glycation contributes to additional cross-linking which modifies tissue stiffness. Physiological signaling pathways from mechanical loading to changes in ECM most likely involve feedback signaling that results in rapid alterations in the mechanical properties of the ECM. In developing skeletal muscle, an important interplay between muscle cells and the ECM is present, and some evidence from adult human muscle suggests common signaling pathways to stimulate contractile and ECM components. Unaccostumed overloading responses suggest an important role of ECM in the adaptation of myofibrillar structures in adult muscle. Development of overuse injury in tendons involve morphological and biochemical changes including altered collagen typing and fibril size, hypervascularization zones, accumulation of nociceptive substances, and impaired collagen degradation activity. Counteracting these phenomena requires adjusted loading rather than absence of loading in the form of immobilization. Full understanding of these physiological processes will provide the physiological basis for understanding of tissue overloading and injury seen in both tendons and muscle with repetitive work and leisure time physical activity.
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Affiliation(s)
- Michael Kjaer
- Sports Medicine Research Unit, Department of Rheumatology, Copenhagen University Hospital at Bispebjerg, 23 Bispebjerg Bakke, DK-2400 Copenhagen NV, Denmark.
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Yurchenco PD, Cheng YS, Campbell K, Li S. Loss of basement membrane, receptor and cytoskeletal lattices in a laminin-deficient muscular dystrophy. J Cell Sci 2004; 117:735-42. [PMID: 14734655 DOI: 10.1242/jcs.00911] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Basement membrane laminins bearing the α2-subunit interact with α-dystroglycan and β1-integrins, cell-surface receptors that are found within the rectilinear costameric lattices of skeletal muscle sarcolemma. Mutations of the α2 subunit are a major cause of congenital muscular dystrophy. To determine whether the costameres are altered as a result of laminin α2-mutations, the skeletal muscle surface of a dystrophic mouse (dy2J/dy2J) lacking the α2-LN domain was examined by confocal and widefield deconvolution immunomicroscopy. Although the dy2J dystrophic fibers possessed a normal-appearing distribution of α2-laminins and α-dystroglycan within a rectilinear costameric lattice at 6.5 weeks of age, by 11 weeks the surface architecture of these components were found to be disorganized, with frequent effacement of the circumferential and longitudinal lattice striations. The defect in the lattice organization was also noted to be a characteristic of type IV collagen, nidogen, perlecan, β1D-integrin, dystrophin and vinculin. The development of this pattern change occurring only after birth suggests that although α2-laminins are not essential for the initial assembly of the costameric framework, they play a role in maintaining the stability and organization of the framework.
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Affiliation(s)
- Peter D Yurchenco
- Department of Pathology & Laboratory Medicine, UMDNJ-Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA.
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Draeger A, Monastyrskaya K, Burkhard FC, Wobus AM, Moss SE, Babiychuk EB. Membrane segregation and downregulation of raft markers during sarcolemmal differentiation in skeletal muscle cells. Dev Biol 2003; 262:324-34. [PMID: 14550795 DOI: 10.1016/s0012-1606(03)00398-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Muscle contraction implies flexibility in combination with force resistance and requires a high degree of sarcolemmal organization. Smooth muscle cells differentiate largely from mesenchymal precursor cells and gradually assume a highly periodic sarcolemmal organization. Skeletal muscle undergoes an even more striking differentiation programme, leading to cell fusion and alignment into myofibrils. The lipid bilayer of each cell type is further segregated into raft and non-raft microdomains of distinct lipid composition. Considering the extent of developmental rearrangement in skeletal muscle, we investigated sarcolemmal microdomain organization in skeletal and smooth muscle cells. The rafts in both muscle types are characterized by marker proteins belonging to the annexin family which localize to the inner membrane leaflet, as well as glycosyl-phosphatidyl-inositol (GPI)-anchored enzymes attached to the outer leaflet. We demonstrate that the profound structural rearrangements that occur during skeletal muscle maturation coincide with a striking decrease in membrane lipid segregation, downregulation of annexins 2 and 6, and a significant decrease in raft-associated 5'-nucleotidase activity. The relative paucity of lipid rafts in mature skeletal in contrast to smooth muscle suggests that the organization of sarcolemmal microdomains contributes to the muscle-specific differences in stimulatory responses and contractile properties.
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Affiliation(s)
- A Draeger
- Department of Cell Biology, Institute of Anatomy, University of Bern, Switzerland.
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Lewis MK, Nahirney PC, Chen V, Adhikari BB, Wright J, Reedy MK, Bass AH, Wang K. Concentric intermediate filament lattice links to specialized Z-band junctional complexes in sonic muscle fibers of the type I male midshipman fish. J Struct Biol 2003; 143:56-71. [PMID: 12892726 DOI: 10.1016/s1047-8477(03)00121-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Type I male midshipman fish produce high-frequency hums for prolonged durations using sonic muscle fibers, each of which contains a hollow tube of radially oriented thin and flat myofibrils that display extraordinarily wide ( approximately 1.2 microm) Z bands. We have revealed an elaborate cytoskeletal network of desmin filaments associated with the contractile cylinder that form interconnected concentric ring structures in the core and periphery at the level of the Z bands. Stretch and release of single fibers revealed reversible length changes in the elastic desmin lattice. This lattice is linked to Z bands via novel intracellular desmosome-like junctional complexes that collectively form a ring, termed the "Z corset," around the periphery and within the core of the cylinder. The junctional complex consists of regularly spaced parallel approximately 900-nm-long cytoskeletal rods, or "Z bars," interconnected with slender (3-4 nm) plectin-positive filaments. Z bars are linked to the Z band by plectin filaments and on the opposite side to a dense mesh of desmin filaments. Adjacent Z bands are linked by slender filaments that appear to suspend sarcotubules. We propose that the highly reinforced elastic desmin cytoskeleton and the unique Z band junctions are structural adaptations that enable the muscles' high-frequency and high-endurance activity.
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Affiliation(s)
- Michael K Lewis
- Muscle Proteomics and Nanotechnology Section, Laboratory of Muscle Biology, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, DHHS, Bethesda, MD 20892, USA
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48
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Abstract
In skeletal muscle, contractile force can be transmitted laterally between the z-disks and M-lines of neighboring myofibrils, across the sarcolemma, and through the extracellular matrix to the tendon. Here we examine the data that support this model and the sarcolemmal properties and structures, termed "costameres," that are consistent with it.
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Affiliation(s)
- Robert J Bloch
- Department of Physiology, University of Maryland School of Medicine, Baltimore 21201, USA.
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Caiozzo VJ, Utkan A, Chou R, Khalafi A, Chandra H, Baker M, Rourke B, Adams G, Baldwin K, Green S. Effects of distraction on muscle length: mechanisms involved in sarcomerogenesis. Clin Orthop Relat Res 2002:S133-45. [PMID: 12394462 DOI: 10.1097/00003086-200210001-00016] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Although a great deal of interest has been given to understanding the mechanisms involved in regulating the radial growth that occurs because of resistance training, much less has been given to studying the longitudinal growth of skeletal muscle that occurs because of passive stretch. The current authors provide a brief overview of key issues relevant to the longitudinal growth of skeletal muscle that occurs during distraction osteogenesis. Specifically, five key issues are addressed: (1) the pattern of sarcomerogenesis during distraction; (2) sarcomerogenesis and altered expression of sarcomeric and nonsarcomeric genes; (3) the satellite cell hypothesis; (4) mitogenic factors; and (5) new approaches for studying the longitudinal growth of skeletal muscle. A discussion is provided that revolves around the concept of a negative feedback loop. One of the most interesting issues to be resolved in muscle biology is the role of satellite cells in regulating the growth of skeletal muscle. Currently, it is not known whether satellite cell activation is a prerequisite for the longitudinal growth of skeletal muscle. Gene chip analyses provide a paradoxical view, showing that distraction osteogenesis results in the upregulation of a gene, GADD45, involved with growth arrest and deoxyribonucleic acid destruction.
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Affiliation(s)
- Vincent J Caiozzo
- Medical Sciences I B-152, Department of Orthopaedics, College of Medicine, University of California, Irvine, CA 92627, USA
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