1
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Dystrophin missense mutations alter focal adhesion tension and mechanotransduction. Proc Natl Acad Sci U S A 2022; 119:e2205536119. [PMID: 35700360 PMCID: PMC9231619 DOI: 10.1073/pnas.2205536119] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Skeletal muscle is a mechanical organ that not only produces force but also uses mechanical stimuli as a signal to regulate cellular responses. Duchenne and Becker muscular dystrophy are lethal muscle wasting diseases that affect 1 in 3,500 boys and is caused by the absence or malfunction of dystrophin protein, respectively. There is a lack of understanding on how the integration of these mechanical signals is dysregulated in muscular dystrophy and how they may contribute to disease progression. In this study, we show that patient-relevant dystrophin mutations alter the mechanical signaling axis in muscle cells, leading to impaired migration. This work proposes dystrophin as a component of the cellular force-sensing machinery, furthering our knowledge in the pathomechanism of muscular dystrophy. Dystrophin is an essential muscle protein that contributes to cell membrane stability by mechanically linking the actin cytoskeleton to the extracellular matrix via an adhesion complex called the dystrophin–glycoprotein complex. The absence or impaired function of dystrophin causes muscular dystrophy. Focal adhesions (FAs) are also mechanosensitive adhesion complexes that connect the cytoskeleton to the extracellular matrix. However, the interplay between dystrophin and FA force transmission has not been investigated. Using a vinculin-based bioluminescent tension sensor, we measured FA tension in transgenic C2C12 myoblasts expressing wild-type (WT) dystrophin, a nonpathogenic single nucleotide polymorphism (SNP) (I232M), or two missense mutations associated with Duchenne (L54R), or Becker muscular dystrophy (L172H). Our data revealed cross talk between dystrophin and FAs, as the expression of WT or I232M dystrophin increased FA tension compared to dystrophin-less nontransgenic myoblasts. In contrast, the expression of L54R or L172H did not increase FA tension, indicating that these disease-causing mutations compromise the mechanical function of dystrophin as an FA allosteric regulator. Decreased FA tension caused by these mutations manifests as defective migration, as well as decreased Yes-associated protein 1 (YAP) activation, possibly by the disruption of the ability of FAs to transmit forces between the extracellular matrix and cytoskeleton. Our results indicate that dystrophin influences FA tension and suggest that dystrophin disease-causing missense mutations may disrupt a cellular tension-sensing pathway in dystrophic skeletal muscle.
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2
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Morris CE, Wheeler JJ, Joos B. The Donnan-dominated resting state of skeletal muscle fibers contributes to resilience and longevity in dystrophic fibers. J Gen Physiol 2022; 154:212743. [PMID: 34731883 PMCID: PMC8570295 DOI: 10.1085/jgp.202112914] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Accepted: 09/30/2021] [Indexed: 11/28/2022] Open
Abstract
Duchenne muscular dystrophy (DMD) is an X-linked dystrophin-minus muscle-wasting disease. Ion homeostasis in skeletal muscle fibers underperforms as DMD progresses. But though DMD renders these excitable cells intolerant of exertion, sodium overloaded, depolarized, and spontaneously contractile, they can survive for several decades. We show computationally that underpinning this longevity is a strikingly frugal, robust Pump-Leak/Donnan (P-L/D) ion homeostatic process. Unlike neurons, which operate with a costly “Pump-Leak–dominated” ion homeostatic steady state, skeletal muscle fibers operate with a low-cost “Donnan-dominated” ion homeostatic steady state that combines a large chloride permeability with an exceptionally small sodium permeability. Simultaneously, this combination keeps fiber excitability low and minimizes pump expenditures. As mechanically active, long-lived multinucleate cells, skeletal muscle fibers have evolved to handle overexertion, sarcolemmal tears, ischemic bouts, etc.; the frugality of their Donnan dominated steady state lets them maintain the outsized pump reserves that make them resilient during these inevitable transient emergencies. Here, P-L/D model variants challenged with DMD-type insult/injury (low pump-strength, overstimulation, leaky Nav and cation channels) show how chronic “nonosmotic” sodium overload (observed in DMD patients) develops. Profoundly severe DMD ion homeostatic insult/injury causes spontaneous firing (and, consequently, unwanted excitation–contraction coupling) that elicits cytotoxic swelling. Therefore, boosting operational pump-strength and/or diminishing sodium and cation channel leaks should help extend DMD fiber longevity.
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Affiliation(s)
- Catherine E Morris
- Neuroscience, Ottawa Hospital Research Institute, Ottawa, Canada.,Center for Neural Dynamics, University of Ottawa, Ottawa, Canada
| | | | - Béla Joos
- Center for Neural Dynamics, University of Ottawa, Ottawa, Canada.,Department of Physics, University of Ottawa, Ottawa, Canada
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3
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Banks GB, Chamberlain JS, Odom GL. Microutrophin expression in dystrophic mice displays myofiber type differences in therapeutic effects. PLoS Genet 2020; 16:e1009179. [PMID: 33175853 PMCID: PMC7682874 DOI: 10.1371/journal.pgen.1009179] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 11/23/2020] [Accepted: 10/06/2020] [Indexed: 12/28/2022] Open
Abstract
Gene therapy approaches for DMD using recombinant adeno-associated viral (rAAV) vectors to deliver miniaturized (or micro) dystrophin genes to striated muscles have shown significant progress. However, concerns remain about the potential for immune responses against dystrophin in some patients. Utrophin, a developmental paralogue of dystrophin, may provide a viable treatment option. Here we examine the functional capacity of an rAAV-mediated microutrophin (μUtrn) therapy in the mdx4cv mouse model of DMD. We found that rAAV-μUtrn led to improvement in dystrophic histopathology & mostly restored the architecture of the neuromuscular and myotendinous junctions. Physiological studies of tibialis anterior muscles indicated peak force maintenance, with partial improvement of specific force. A fundamental question for μUtrn therapeutics is not only can it replace critical functions of dystrophin, but whether full-length utrophin impacts the therapeutic efficacy of the smaller, highly expressed μUtrn. As such, we found that μUtrn significantly reduced the spacing of the costameric lattice relative to full-length utrophin. Further, immunostaining suggested the improvement in dystrophic pathophysiology was largely influenced by favored correction of fast 2b fibers. However, unlike μUtrn, μdystrophin (μDys) expression did not show this fiber type preference. Interestingly, μUtrn was better able to protect 2a and 2d fibers in mdx:utrn-/- mice than in mdx4cv mice where the endogenous full-length utrophin was most prevalent. Altogether, these data are consistent with the role of steric hindrance between full-length utrophin & μUtrn within the sarcolemma. Understanding the stoichiometry of this effect may be important for predicting clinical efficacy.
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MESH Headings
- Animals
- Dependovirus/genetics
- Disease Models, Animal
- Dystrophin/genetics
- Gene Transfer Techniques
- Genetic Therapy/methods
- Genetic Vectors/genetics
- HEK293 Cells
- Humans
- Mice
- Mice, Inbred mdx
- Microscopy, Electron
- Muscle Contraction
- Muscle Fibers, Skeletal/cytology
- Muscle Fibers, Skeletal/pathology
- Muscle Fibers, Skeletal/ultrastructure
- Muscle, Skeletal
- Muscular Dystrophy, Duchenne/genetics
- Muscular Dystrophy, Duchenne/pathology
- Muscular Dystrophy, Duchenne/therapy
- Neuromuscular Junction/pathology
- Neuromuscular Junction/ultrastructure
- Sarcolemma/pathology
- Sarcolemma/ultrastructure
- Utrophin/genetics
- Utrophin/therapeutic use
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Affiliation(s)
- Glen B. Banks
- Department of Neurology, University of Washington, Seattle, Washington, United States of America
- Department of Medicine, University of Washington, Seattle, Washington, United States of America
- Wellstone Muscular Dystrophy Specialized Research Center, University of Washington, Seattle, Washington, United States of America
| | - Jeffrey S. Chamberlain
- Department of Neurology, University of Washington, Seattle, Washington, United States of America
- Department of Medicine, University of Washington, Seattle, Washington, United States of America
- Wellstone Muscular Dystrophy Specialized Research Center, University of Washington, Seattle, Washington, United States of America
- Department of BioChemistry, University of Washington, Seattle, Washington, United States of America
| | - Guy L. Odom
- Department of Neurology, University of Washington, Seattle, Washington, United States of America
- Department of Medicine, University of Washington, Seattle, Washington, United States of America
- Wellstone Muscular Dystrophy Specialized Research Center, University of Washington, Seattle, Washington, United States of America
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4
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Danilov KA, Vassilieva SG, Polikarpova AV, Starikova AV, Shmidt AA, Galkin II, Tsitrina AA, Egorova TV, Orlov SN, Kotelevtsev YV. In vitro assay for the efficacy assessment of AAV vectors expressing microdystrophin. Exp Cell Res 2020; 392:112033. [PMID: 32360435 DOI: 10.1016/j.yexcr.2020.112033] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Revised: 03/23/2020] [Accepted: 04/21/2020] [Indexed: 12/26/2022]
Abstract
AAV-delivered microdystrophin genes hold great promise for Duchenne muscular dystrophy (DMD) treatment. It is anticipated that the optimization of engineered dystrophin genes will be required to increase the efficacy and reduce the immunogenicity of transgenic proteins. An in vitro system is required for the efficacy testing of genetically engineered dystrophin genes. We report here on the proof of concept for an in vitro assay based on the assessment of sarcolemma damage after repetitively applied electrical stimuli. The primary cell culture of myoblasts was established from wild-type C57BL/10ScSnJ and dystrophin-deficient mdx mice. The preparation parameters and the differentiation of contractile myotubes were optimized. DAPI and TO-PRO-3 dyes were used to assess myotubular membrane permeability in response to electrical pulse stimulation (EPS). Myotubes derived from mdx mice exhibited a greater increase in membrane damage, as assessed by TO-PRO-3-measured permeability after EPS, than was exhibited by the healthy control myotubes. AAV-DJ particles carrying the microdystrophin gene were used to transduce mdx-derived differentiated myotubes. Microdystrophin delivery ameliorated the disease phenotype and reduced the EPS-induced membrane damage to a level comparable to that of the healthy controls. Thus, the in vitro system was shown to be capable of supporting studies on DMD gene therapy.
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Affiliation(s)
- Kirill A Danilov
- Center of Life Sciences, Skolkovo Institute of Science and Technology, Moscow, 121205, Russia; Atlas Biomed Group Limited, Tintagel House, 92 Albert Embankment, Lambeth, SE1 7TY, London, United Kingdom.
| | - Svetlana G Vassilieva
- Laboratory of Modeling and Gene Therapy of Hereditary Diseases, Institute of Gene Biology, Russian Academy of Sciences, Moscow, 119334, Russia; Marlin Biotech LLC, Moscow, 143026, Russia.
| | - Anna V Polikarpova
- Laboratory of Modeling and Gene Therapy of Hereditary Diseases, Institute of Gene Biology, Russian Academy of Sciences, Moscow, 119334, Russia; Marlin Biotech LLC, Moscow, 143026, Russia.
| | - Anna V Starikova
- Laboratory of Modeling and Gene Therapy of Hereditary Diseases, Institute of Gene Biology, Russian Academy of Sciences, Moscow, 119334, Russia; Marlin Biotech LLC, Moscow, 143026, Russia.
| | - Anna A Shmidt
- Laboratory of Modeling and Gene Therapy of Hereditary Diseases, Institute of Gene Biology, Russian Academy of Sciences, Moscow, 119334, Russia; Marlin Biotech LLC, Moscow, 143026, Russia; Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Institute of Gene Biology, Russian Academy of Sciences, Moscow, 119334, Russia.
| | - Ivan I Galkin
- Marlin Biotech LLC, Moscow, 143026, Russia; A.N. Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119992, Moscow, Russia.
| | - Alexandra A Tsitrina
- Institute of Developmental Biology, Russian Academy of Sciences, Moscow, 119334, Russia.
| | - Tatiana V Egorova
- Laboratory of Modeling and Gene Therapy of Hereditary Diseases, Institute of Gene Biology, Russian Academy of Sciences, Moscow, 119334, Russia; Marlin Biotech LLC, Moscow, 143026, Russia.
| | - Sergei N Orlov
- M.V. Lomonosov Moscow State University, Moscow, 119234, Russia; National Research Tomsk State University, Tomsk, 634050, Russia.
| | - Yuri V Kotelevtsev
- Center for Neurobiology and Brain Restoration, Skolkovo Institute of Science and Technology, Moscow, 121205, Russia.
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5
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Abstract
Dystrophin is the largest protein isoform (427 kDa) expressed from the gene defective in Duchenne muscular dystrophy, a lethal muscle-wasting and genetically inherited disease. Dystrophin, localized within a cytoplasmic lattice termed costameres, connects the intracellular cytoskeleton of a myofiber through the cell membrane (sarcolemma) to the surrounding extracellular matrix. In spite of its mechanical regulation roles in stabilizing the sarcolemma during muscle contraction, the underlying molecular mechanism is still elusive. Here, we systematically investigated the mechanical stability and kinetics of the force-bearing central domain of human dystrophin that contains 24 spectrin repeats using magnetic tweezers. We show that the stochastic unfolding and refolding of central domain of dystrophin is able to keep the forces below 25 pN over a significant length change up to ∼800 nm in physiological level of pulling speeds. These results suggest that dystrophin may serve as a molecular shock absorber that defines the physiological level of force in the dystrophin-mediated force-transmission pathway during muscle contraction/stretch, thereby stabilizing the sarcolemma.
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Affiliation(s)
- Shimin Le
- Department of Physics, National University of Singapore, Singapore, 117551
| | - Miao Yu
- Mechanobiology Institute, National University of Singapore, Singapore, 117411
| | - Ladislav Hovan
- Mechanobiology Institute, National University of Singapore, Singapore, 117411
| | - Zhihai Zhao
- Department of Physics, National University of Singapore, Singapore, 117551
| | - James Ervasti
- College of Biological Sciences, University of Minnesota, MN, USA, 55455
| | - Jie Yan
- Department of Physics, National University of Singapore, Singapore, 117551
- Mechanobiology Institute, National University of Singapore, Singapore, 117411
- Centre for BioImaging Sciences, National University of Singapore, Singapore, 117546
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6
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Bhat HF, Mir SS, Dar KB, Bhat ZF, Shah RA, Ganai NA. ABC of multifaceted dystrophin glycoprotein complex (DGC). J Cell Physiol 2017; 233:5142-5159. [DOI: 10.1002/jcp.25982] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Accepted: 05/01/2017] [Indexed: 01/16/2023]
Affiliation(s)
- Hina F. Bhat
- Division of BiotechnologySher‐e‐Kashmir University of Agricultural Sciences and Technology of Kashmir SKUAST‐KShuhama, SrinagarJammu and KashmirIndia
| | - Saima S. Mir
- Department of BiotechnologyUniversity of KashmirHazratbal, SrinagarJammu and KashmirIndia
| | - Khalid B. Dar
- Department of BiochemistryUniversity of KashmirHazratbal, SrinagarJammu and KashmirIndia
| | - Zuhaib F. Bhat
- Division of Livestock Products and TechnologySher‐e‐Kashmir University of Agricultural Sciences and Technology of Jammu (SKUAST‐J), R.S. PoraJammuJammu and KashmirIndia
| | - Riaz A. Shah
- Division of BiotechnologySher‐e‐Kashmir University of Agricultural Sciences and Technology of Kashmir SKUAST‐KShuhama, SrinagarJammu and KashmirIndia
| | - Nazir A. Ganai
- Division of BiotechnologySher‐e‐Kashmir University of Agricultural Sciences and Technology of Kashmir SKUAST‐KShuhama, SrinagarJammu and KashmirIndia
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7
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Lansman JB. Utrophin suppresses low frequency oscillations and coupled gating of mechanosensitive ion channels in dystrophic skeletal muscle. Channels (Austin) 2015; 9:145-60. [PMID: 25941878 DOI: 10.1080/19336950.2015.1040211] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
An absence of utrophin in muscle from mdx mice prolongs the open time of single mechanosensitive channels. On a time scale much longer than the duration of individual channel activations, genetic depletion of utrophin produces low frequency oscillations of channel open probability. Oscillatory channel opening occurred in the dystrophin/utrophin mutants, but was absent in wild-type and mdx fibers. By contrast, small conductance channels showed random gating behavior when present in the same patch. Applying a negative pressure to a patch on a DKO fiber produced a burst of mode II activity, but channels subsequently closed and remained silent for tens of seconds during the maintained pressure stimulus. In addition, simultaneous opening of multiple MS channels could be frequently observed in recordings from patches on DKO fibers, but only rarely in wild-type and mdx muscle. A model which accounts for the single-channel data is proposed in which utrophin acts as gating spring which maintains the mechanical stability a caveolar-like compartment. The state of this compartment is suggested to be dynamic; its continuity with the extracellular surface varying over seconds to minutes. Loss of the mechanical stability of this compartment contributes to pathogenic Ca(2+) entry through MS channels in Duchenne dystrophy.
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Affiliation(s)
- Jeffry B Lansman
- a Department of Cellular and Molecular Pharmacology ; School of Medicine; University of California San Francisco; San Francisco , CA USA
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8
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Virgilio KM, Martin KS, Peirce SM, Blemker SS. Multiscale models of skeletal muscle reveal the complex effects of muscular dystrophy on tissue mechanics and damage susceptibility. Interface Focus 2015; 5:20140080. [PMID: 25844152 DOI: 10.1098/rsfs.2014.0080] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Computational models have been increasingly used to study the tissue-level constitutive properties of muscle microstructure; however, these models were not created to study or incorporate the influence of disease-associated modifications in muscle. The purpose of this paper was to develop a novel multiscale muscle modelling framework to elucidate the relationship between microstructural disease adaptations and modifications in both mechanical properties of muscle and strain in the cell membrane. We used an agent-based model to randomly generate new muscle fibre geometries and mapped them into a finite-element model representing a cross section of a muscle fascicle. The framework enabled us to explore variability in the shape and arrangement of fibres, as well as to incorporate disease-related changes. We applied this method to reveal the trade-offs between mechanical properties and damage susceptibility in Duchenne muscular dystrophy (DMD). DMD is a fatal genetic disease caused by a lack of the transmembrane protein dystrophin, leading to muscle wasting and death due to cardiac or pulmonary complications. The most prevalent microstructural variations in DMD include: lack of transmembrane proteins, fibrosis, fatty infiltration and variation in fibre cross-sectional area. A parameter analysis of these variations and case study of DMD revealed that the nature of fibrosis and density of transmembrane proteins strongly affected the stiffness of the muscle and susceptibility to membrane damage.
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Affiliation(s)
- Kelley M Virgilio
- Department of Biomedical Engineering , University of Virginia , Charlottesville, VA 22908 , USA
| | - Kyle S Martin
- Department of Biomedical Engineering , University of Virginia , Charlottesville, VA 22908 , USA
| | - Shayn M Peirce
- Department of Biomedical Engineering , University of Virginia , Charlottesville, VA 22908 , USA
| | - Silvia S Blemker
- Department of Biomedical Engineering , University of Virginia , Charlottesville, VA 22908 , USA ; Department of Orthopaedic Surgery , University of Virginia , Charlottesville, VA 22908 , USA ; Department of Mechanical and Aerospace Engineering , University of Virginia , Charlottesville, VA 22908 , USA
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9
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Tan N, Lansman JB. Utrophin regulates modal gating of mechanosensitive ion channels in dystrophic skeletal muscle. J Physiol 2014; 592:3303-23. [PMID: 24879867 DOI: 10.1113/jphysiol.2014.274332] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Dystrophin is a large, submembrane cytoskeletal protein, absence of which causes Duchenne muscular dystrophy. Utrophin is a dystrophin homologue found in both muscle and brain whose physiological function is unknown. Recordings of single-channel activity were made from membrane patches on skeletal muscle from mdx, mdx/utrn(+/-) heterozygotes and mdx/utrn(-/-) double knockout mice to investigate the role of these cytoskeletal proteins in mechanosensitive (MS) channel gating. We find complex, gene dose-dependent effects of utrophin depletion in dystrophin-deficient mdx muscle: (1) increased MS channel open probability, (2) a shift of MS channel gating to larger pressures, (3) appearance of modal gating of MS channels and small conductance channels and (4) expression of large conductance MS channels. We suggest a physical model in which utrophin acts as a scaffolding protein that stabilizes lipid microdomains and clusters MS channel subunits. Depletion of utrophin disrupts domain composition in a manner that favours open channel area expansion, as well as allowing diffusion and aggregation of additional MS channel subunits.
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Affiliation(s)
- Nhi Tan
- Department of Cellular and Molecular Pharmacology, School of Medicine, University of California, San Francisco, San Francisco, CA, 94143-0450, USA
| | - Jeffry B Lansman
- Department of Cellular and Molecular Pharmacology, School of Medicine, University of California, San Francisco, San Francisco, CA, 94143-0450, USA
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10
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Filamentous structures in skeletal muscle: anchors for the subsarcolemmal space. Med Mol Morphol 2014; 48:1-12. [PMID: 24519712 DOI: 10.1007/s00795-014-0070-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2013] [Accepted: 12/25/2013] [Indexed: 10/25/2022]
Abstract
In skeletal muscle fibers, intermediate filaments and actin filaments provide structural support to the myofibrils and the sarcolemma. For many years, it was poorly understood from ultrastructural observations that how these filamentous structures were kept anchored. The present study was conducted to determine the architecture of filamentous anchoring structures in the subsarcolemmal space and the intermyofibrils. The diaphragms (Dp) of adult wild type and mdx mice (mdx is a model for Duchenne muscular dystrophy) were subjected to tension applied perpendicular to the long axis of the muscle fibers, with or without treatment with 1% Triton X-100 or 0.03% saponin. These experiments were conducted to confirm the presence and integrity of the filamentous anchoring structures. Transmission electron microscopy revealed that these structures provide firm transverse connections between the sarcolemma and peripheral myofibrils. Most of the filamentous structures appeared to be inserted into subsarcolemmal densities, forming anchoring connections between the sarcolemma and peripheral myofibrils. In some cases, actin filaments were found to run longitudinally in the subsarcolemmal space to connect to the sarcolemma or in some cases to connect to the intermyofibrils as elongated thin filaments. These filamentous anchoring structures were less common in the mdx Dp. Our data suggest that the transverse and longitudinal filamentous structures form an anchoring system in the subsarcolemmal space and the intermyofibrils.
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11
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The bHLH transcription factor hand is required for proper wing heart formation in Drosophila. Dev Biol 2013; 381:446-59. [DOI: 10.1016/j.ydbio.2013.05.027] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Revised: 05/16/2013] [Accepted: 05/27/2013] [Indexed: 11/19/2022]
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12
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Duguez S, Duddy W, Johnston H, Lainé J, Le Bihan MC, Brown KJ, Bigot A, Hathout Y, Butler-Browne G, Partridge T. Dystrophin deficiency leads to disturbance of LAMP1-vesicle-associated protein secretion. Cell Mol Life Sci 2013; 70:2159-74. [PMID: 23344255 PMCID: PMC11113779 DOI: 10.1007/s00018-012-1248-2] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Revised: 12/13/2012] [Accepted: 12/17/2012] [Indexed: 01/06/2023]
Abstract
Duchenne muscular dystrophy results from loss of the protein dystrophin, which links the intracellular cytoskeletal network with the extracellular matrix, but deficiency in this function does not fully explain the onset or progression of the disease. While some intracellular events involved in the degeneration of dystrophin-deficient muscle fibers have been well characterized, changes in their secretory profile are undescribed. To analyze the secretome profile of mdx myotubes independently of myonecrosis, we labeled the proteins of mdx and wild-type myotubes with stable isotope-labeled amino acids (SILAC), finding marked enrichment of vesicular markers in the mdx secretome. These included the lysosomal-associated membrane protein, LAMP1, that co-localized in vesicles with an over-secreted cytoskeletal protein, myosin light chain 1. These LAMP1/MLC1-3-positive vesicles accumulated in the cytosol of mdx myotubes and were secreted into the culture medium in a range of abnormal densities. Restitution of dystrophin expression, by exon skipping, to some 30 % of the control value, partially normalized the secretome profile and the excess LAMP1 accumulation. Together, our results suggest that a lack of dystrophin leads to a general dysregulation of vesicle trafficking. We hypothesize that disturbance of the export of proteins through vesicles occurs before, and then concurrently with, the myonecrotic cascade and contributes chronically to the pathophysiology of DMD, thereby presenting us with a range of new potential therapeutic targets.
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Affiliation(s)
- Stephanie Duguez
- Center for Genetic Medicine, Children’s Research Institute, Children’s National Medical Center, 111 Michigan Avenue, Washington, DC USA
- Institut de Myologie, UM76, Inserm U974, CNRS, UMR7215, Université Pierre et Marie Curie-Paris 6, Paris, 75013 France
| | - William Duddy
- Center for Genetic Medicine, Children’s Research Institute, Children’s National Medical Center, 111 Michigan Avenue, Washington, DC USA
- Institut de Myologie, UM76, Inserm U974, CNRS, UMR7215, Université Pierre et Marie Curie-Paris 6, Paris, 75013 France
| | - Helen Johnston
- Center for Genetic Medicine, Children’s Research Institute, Children’s National Medical Center, 111 Michigan Avenue, Washington, DC USA
| | - Jeanne Lainé
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
- Département de Physiologie, Université Pierre Et Marie Curie-Paris 06, Site Pitié-Salpêtrière, Paris, 75013 France
| | - Marie Catherine Le Bihan
- Institut de Myologie, UM76, Inserm U974, CNRS, UMR7215, Université Pierre et Marie Curie-Paris 6, Paris, 75013 France
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
| | - Kristy J. Brown
- Center for Genetic Medicine, Children’s Research Institute, Children’s National Medical Center, 111 Michigan Avenue, Washington, DC USA
| | - Anne Bigot
- Institut de Myologie, UM76, Inserm U974, CNRS, UMR7215, Université Pierre et Marie Curie-Paris 6, Paris, 75013 France
| | - Yetrib Hathout
- Center for Genetic Medicine, Children’s Research Institute, Children’s National Medical Center, 111 Michigan Avenue, Washington, DC USA
| | - Gillian Butler-Browne
- Institut de Myologie, UM76, Inserm U974, CNRS, UMR7215, Université Pierre et Marie Curie-Paris 6, Paris, 75013 France
| | - Terence Partridge
- Center for Genetic Medicine, Children’s Research Institute, Children’s National Medical Center, 111 Michigan Avenue, Washington, DC USA
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13
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Randazzo D, Giacomello E, Lorenzini S, Rossi D, Pierantozzi E, Blaauw B, Reggiani C, Lange S, Peter AK, Chen J, Sorrentino V. Obscurin is required for ankyrinB-dependent dystrophin localization and sarcolemma integrity. ACTA ACUST UNITED AC 2013; 200:523-36. [PMID: 23420875 PMCID: PMC3575540 DOI: 10.1083/jcb.201205118] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Obscurin contributes to the organization of subsarcolemma microtubules, localization of dystrophin at costameres, and maintenance of sarcolemmal integrity in skeletal muscle fibers. Obscurin is a large myofibrillar protein that contains several interacting modules, one of which mediates binding to muscle-specific ankyrins. Interaction between obscurin and the muscle-specific ankyrin sAnk1.5 regulates the organization of the sarcoplasmic reticulum in striated muscles. Additional muscle-specific ankyrin isoforms, ankB and ankG, are localized at the subsarcolemma level, at which they contribute to the organization of dystrophin and β-dystroglycan at costameres. In this paper, we report that in mice deficient for obscurin, ankB was displaced from its localization at the M band, whereas localization of ankG at the Z disk was not affected. In obscurin KO mice, localization at costameres of dystrophin, but not of β-dystroglycan, was altered, and the subsarcolemma microtubule cytoskeleton was disrupted. In addition, these mutant mice displayed marked sarcolemmal fragility and reduced muscle exercise tolerance. Altogether, the results support a model in which obscurin, by targeting ankB at the M band, contributes to the organization of subsarcolemma microtubules, localization of dystrophin at costameres, and maintenance of sarcolemmal integrity.
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Affiliation(s)
- Davide Randazzo
- Molecular Medicine Section, Department of Molecular and Developmental Medicine, University of Siena, 53100 Siena, Italy
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14
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Oh HJ, Abraham LS, van Hengel J, Stove C, Proszynski TJ, Gevaert K, DiMario JX, Sanes JR, van Roy F, Kim H. Interaction of α-catulin with dystrobrevin contributes to integrity of dystrophin complex in muscle. J Biol Chem 2012; 287:21717-28. [PMID: 22577143 DOI: 10.1074/jbc.m112.369496] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The dystrophin complex is a multimolecular membrane-associated protein complex whose defects underlie many forms of muscular dystrophy. The dystrophin complex is postulated to function as a structural element that stabilizes the cell membrane by linking the contractile apparatus to the extracellular matrix. A better understanding of how this complex is organized and localized will improve our knowledge of the pathogenic mechanisms of diseases that involve the dystrophin complex. In a Caenorhabditis elegans genetic study, we demonstrate that CTN-1/α-catulin, a cytoskeletal protein, physically interacts with DYB-1/α-dystrobrevin (a component of the dystrophin complex) and that this interaction is critical for the localization of the dystrophin complex near dense bodies, structures analogous to mammalian costameres. We further show that in mouse α-catulin is localized at the sarcolemma and neuromuscular junctions and interacts with α-dystrobrevin and that the level of α-catulin is reduced in α-dystrobrevin-deficient mouse muscle. Intriguingly, in the skeletal muscle of mdx mice lacking dystrophin, we discover that the expression of α-catulin is increased, suggesting a compensatory role of α-catulin in dystrophic muscle. Together, our study demonstrates that the interaction between α-catulin and α-dystrobrevin is evolutionarily conserved in C. elegans and mammalian muscles and strongly suggests that this interaction contributes to the integrity of the dystrophin complex.
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Affiliation(s)
- Hyun J Oh
- Department of Cell Biology and Anatomy, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064, USA
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15
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Hakim CH, Grange RW, Duan D. The passive mechanical properties of the extensor digitorum longus muscle are compromised in 2- to 20-mo-old mdx mice. J Appl Physiol (1985) 2011; 110:1656-63. [PMID: 21415170 DOI: 10.1152/japplphysiol.01425.2010] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Muscle rigidity and myotendinous junction (MTJ) deficiency contribute to immobilization in Duchenne muscular dystrophy (DMD), a lethal disease caused by the absence of dystrophin. However, little is known about the muscle passive properties and MTJ strength in a diseased muscle. Here, we hypothesize that dystrophin-deficient muscle pathology renders skeletal muscle stiffer and MTJ weaker. To test our hypothesis, we examined the passive properties of an intact noncontracting muscle-tendon unit in mdx mice, a mouse model for DMD. The extensor digitorum longus (EDL) muscle-tendon preparations of 2-, 6-, 14-, and 20-mo-old mdx and normal control mice were strained stepwisely from 110% to 160% of the muscle optimal length. The stress-strain response and failure position were analyzed. In support of our hypothesis, the mdx EDL preparation consistently developed higher stress before muscle failure. Postfailure stresses decreased dramatically in mdx but not normal preparations. Further, mdx showed a significantly faster stress relaxation rate. Consistent with stress-strain assay results, we observed significantly higher fibrosis in mdx muscle. In 2- and 6-mo-old mdx and 20-mo-old BL10 mice failure occurred within the muscle (2- to 14-mo-old BL10 preparations did not fail). Interestingly, in ≥14-mo-old mdx mice the failure site shifted toward the MTJ. Electron microscopy revealed substantial MTJ degeneration in aged but not young mdx mice. In summary, our results suggest that the passive properties of the EDL muscle and the strength of MTJ are compromised in mdx in an age-dependent manner. These findings offer new insights in studying DMD pathogenesis and developing novel therapies.
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Affiliation(s)
- Chady H Hakim
- Dept. of Molecular Microbiology and Immunology, Univ. of Missouri, One Hospital Dr., Columbia, MO 65212, USA.
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16
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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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17
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Zhang Y, Resneck WG, Lee PC, Randall WR, Bloch RJ, Ursitti JA. Characterization and expression of a heart-selective alternatively spliced variant of alpha II-spectrin, cardi+, during development in the rat. J Mol Cell Cardiol 2010; 48:1050-9. [PMID: 20114050 DOI: 10.1016/j.yjmcc.2010.01.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2009] [Revised: 01/04/2010] [Accepted: 01/05/2010] [Indexed: 10/19/2022]
Abstract
Spectrin is a large, flexible protein that stabilizes membranes and organizes proteins and lipids into microdomains in intracellular organelles and at the plasma membrane. Alternative splicing occurs in spectrins, but it is not yet clear if these small variations in structure alter spectrin's functions. Three alternative splice sites have been identified previously for alpha II-spectrin. Here we describe a new alternative splice site, a 21-amino acid sequence in the 21st spectrin repeat that is only expressed in significant amounts in cardiac muscle (GenBank GQ502182). The insert, which we term alpha II-cardi+, results in an insertion within the high affinity nucleation site for binding of alpha-spectrins to beta-spectrins. To assess the developmental regulation of the alpha II-cardi+ isoform, we used qRT-PCR and quantitative immunoblotting methods to measure the levels of this form and the alpha II-cardi- form in the cardiac muscles of rats, from embryonic day 16 (E16) through adulthood. The alpha II-cardi+ isoform constituted approximately 26% of the total alpha II-spectrin in E16 hearts but decreased to approximately 6% of the total after 3 weeks of age. We used long-range RT-PCR and Southern blot hybridization to examine possible linkage of the alpha II-cardi+ alternatively spliced sequence with alternatively spliced sequences of alpha II-spectrin that had been previously reported. We identified two new isoforms of alpha II-spectrin containing the cardi+ insert. These were named alpha II Sigma 9 and alpha II Sigma 10 in accordance with the spectrin naming conventions. In vitro studies of recombinant alpha II-spectrin polypeptides representing the two splice variants of alpha II-spectrin, alpha II-cardi+ and alpha II-cardi-, revealed that the alpha II-cardi+ subunit has lower affinity for the complementary site in repeats 1-4 of betaII-spectrin, with a K(D) value of approximately 1 nM, as measured by surface plasmon resonance (SPR). In addition, the alpha II-cardi+ form showed 1.8-fold lower levels of binding to its site on beta II-spectrin than the alpha II-cardi- form, both by SPR and blot overlay. This suggests that the 21-amino acid insert prevented some of the alpha II-cardi+ form from interacting with beta II-spectrin. Fusion proteins expressing the alpha II-cardi+ sequence within the two terminal spectrin repeats of alpha II-spectrin were insoluble in solution and aggregated in neonatal myocytes, consistent with the possibility that this insert removes a significant portion of the protein from the population that can bind beta subunits. Neonatal rat cardiomyocytes infected with adenovirus encoding GFP-fusion proteins of repeats 18-21 of alpha II-spectrin with the cardi+ insert formed many new processes. These processes were only rarely seen in myocytes expressing the fusion protein lacking the insert or in controls expressing only GFP. Our results suggest that the embryonic mammalian heart expresses a significant amount of alpha II-spectrin with a reduced avidity for beta-spectrin and the ability to promote myocyte growth.
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Affiliation(s)
- Yinghua Zhang
- Department of Physiology, University of Maryland, School of Medicine, 655 W Baltimore Street, Baltimore, MD 21201, USA
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18
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Ziane R, Huang H, Moghadaszadeh B, Beggs AH, Levesque G, Chahine M. Cell membrane expression of cardiac sodium channel Na(v)1.5 is modulated by alpha-actinin-2 interaction. Biochemistry 2010; 49:166-78. [PMID: 19943616 DOI: 10.1021/bi901086v] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Cardiac sodium channel Na(v)1.5 plays a critical role in heart excitability and conduction. The molecular mechanism that underlies the expression of Na(v)1.5 at the cell membrane is poorly understood. Previous studies demonstrated that cytoskeleton proteins can be involved in the regulation of cell surface expression and localization of several ion channels. We performed a yeast two-hybrid screen to identify Na(v)1.5-associated proteins that may be involved in channel function and expression. We identified alpha-actinin-2 as an interacting partner of the cytoplasmic loop connecting domains III and IV of Na(v)1.5 (Na(v)1.5/LIII-IV). Co-immunoprecipitation and His(6) pull-down assays confirmed the physical association between Na(v)1.5 and alpha-actinin-2 and showed that the spectrin-like repeat domain is essential for binding of alpha-actinin-2 to Na(v)1.5. Patch-clamp studies revealed that the interaction with alpha-actinin-2 increases sodium channel density without changing their gating properties. Consistent with these findings, coexpression of alpha-actinin-2 and Na(v)1.5 in tsA201 cells led to an increase in the level of expression of Na(v)1.5 at the cell membrane as determined by cell surface biotinylation. Lastly, immunostaining experiments showed that alpha-actinin-2 was colocalized with Na(v)1.5 along the Z-lines and in the plasma membrane. Our data suggest that alpha-actinin-2, which is known to regulate the functional expression of the potassium channels, may play a role in anchoring Na(v)1.5 to the membrane by connecting the channel to the actin cytoskeleton network.
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Affiliation(s)
- Rahima Ziane
- Centre de Recherche Université Laval Robert-Giffard, Quebec City, QC, Canada
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19
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Wallace GQ, McNally EM. Mechanisms of muscle degeneration, regeneration, and repair in the muscular dystrophies. Annu Rev Physiol 2009; 71:37-57. [PMID: 18808326 DOI: 10.1146/annurev.physiol.010908.163216] [Citation(s) in RCA: 229] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
To withstand the rigors of contraction, muscle fibers have specialized protein complexes that buffer against mechanical stress and a multifaceted repair system that is rapidly activated after injury. Genetic studies first identified the mechanosensory signaling network that connects the structural elements of muscle and, more recently, have identified repair elements of muscle. Defects in the genes encoding the components of these systems lead to muscular dystrophy, a family of genetic disorders characterized by progressive muscle wasting. Although the age of onset, affected muscles, and severity vary considerably, all muscular dystrophies are characterized by muscle necrosis that overtakes the regenerative capacity of muscle. The resulting replacement of muscle by fatty and fibrous tissue leaves muscle increasingly weak and nonfunctional. This review discusses the cellular mechanisms that are primarily and secondarily disrupted in muscular dystrophy, focusing on membrane degeneration, muscle regeneration, and the repair of muscle.
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Affiliation(s)
- Gregory Q Wallace
- Department of Medicine, The University of Chicago, Chicago, Illinois 60637, USA
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20
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Ackermann MA, Hu LYR, Bowman AL, Bloch RJ, Kontrogianni-Konstantopoulos A. Obscurin interacts with a novel isoform of MyBP-C slow at the periphery of the sarcomeric M-band and regulates thick filament assembly. Mol Biol Cell 2009; 20:2963-78. [PMID: 19403693 DOI: 10.1091/mbc.e08-12-1251] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Obscurin is a multidomain protein composed of adhesion and signaling domains that plays key roles in the organization of contractile and membrane structures in striated muscles. Overexpression of the second immunoglobulin domain of obscurin (Ig2) in developing myotubes inhibits the assembly of A- and M-bands, but not Z-disks or I-bands. This effect is mediated by the direct interaction of the Ig2 domain of obscurin with a novel isoform of myosin binding protein-C slow (MyBP-C slow), corresponding to variant-1. Variant-1 contains all the structural motifs present in the known forms of MyBP-C slow, but it has a unique COOH terminus. Quantitative reverse transcription-polymerase chain reaction indicated that MyBP-C slow variant-1 is expressed in skeletal muscles both during development and at maturity. Immunolabeling of skeletal myofibers with antibodies to the unique COOH terminus of variant-1 demonstrated that, unlike other forms of MyBP-C slow that reside in the C-zones of A-bands, variant-1 preferentially concentrates around M-bands, where it codistributes with obscurin. Overexpression of the Ig2 domain of obscurin or reduction of expression of obscurin inhibited the integration of variant-1 into forming M-bands in skeletal myotubes. Collectively, our experiments identify a new ligand of obscurin at the M-band, MyBP-C slow variant-1 and suggest that their interaction contributes to the assembly of M- and A-bands.
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Affiliation(s)
- Maegen A Ackermann
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
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21
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Griffin JL, Des Rosiers C. Applications of metabolomics and proteomics to the mdx mouse model of Duchenne muscular dystrophy: lessons from downstream of the transcriptome. Genome Med 2009; 1:32. [PMID: 19341503 PMCID: PMC2664943 DOI: 10.1186/gm32] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Functional genomic studies are dominated by transcriptomic approaches, in part reflecting the vast amount of information that can be obtained, the ability to amplify mRNA and the availability of commercially standardized functional genomic DNA microarrays and related techniques. This can be contrasted with proteomics, metabolomics and metabolic flux analysis (fluxomics), which have all been much slower in development, despite these techniques each providing a unique viewpoint of what is happening in the overall biological system. Here, we give an overview of developments in these fields 'downstream' of the transcriptome by considering the characterization of one particular, but widely used, mouse model of human disease. The mdx mouse is a model of Duchenne muscular dystrophy (DMD) and has been widely used to understand the progressive skeletal muscle wasting that accompanies DMD, and more recently the associated cardiomyopathy, as well as to unravel the roles of the other isoforms of dystrophin, such as those found in the brain. Studies using proteomics, metabolomics and fluxomics have characterized perturbations in calcium homeostasis in dystrophic skeletal muscle, provided an understanding of the role of dystrophin in skeletal muscle regeneration, and defined the changes in substrate energy metabolism in the working heart. More importantly, they all point to perturbations in proteins, metabolites and metabolic fluxes reflecting mitochondrial energetic alterations, even in the early stage of the dystrophic pathology. Philosophically, these studies also illustrate an important lesson relevant to both functional genomics and the mouse phenotyping in that the knowledge generated has advanced our understanding of cell biology and physiological organization as much as it has advanced our understanding of the disease.
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Affiliation(s)
- Julian L Griffin
- Department of Biochemistry, Tennis Court Road, University of Cambridge, Cambridge, CB2 1QW, UK
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22
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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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23
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Papponen H, Kaisto T, Leinonen S, Kaakinen M, Metsikkö K. Evidence for γ-actin as a Z disc component in skeletal myofibers. Exp Cell Res 2009; 315:218-25. [DOI: 10.1016/j.yexcr.2008.10.021] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2008] [Revised: 09/22/2008] [Accepted: 10/11/2008] [Indexed: 11/16/2022]
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24
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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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25
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Bunnell TM, Jaeger MA, Fitzsimons DP, Prins KW, Ervasti JM. Destabilization of the dystrophin-glycoprotein complex without functional deficits in alpha-dystrobrevin null muscle. PLoS One 2008; 3:e2604. [PMID: 18596960 PMCID: PMC2432020 DOI: 10.1371/journal.pone.0002604] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2007] [Accepted: 06/03/2008] [Indexed: 11/20/2022] Open
Abstract
α-Dystrobrevin is a component of the dystrophin-glycoprotein complex (DGC) and is thought to have both structural and signaling roles in skeletal muscle. Mice deficient for α-dystrobrevin (adbn−/−) exhibit extensive myofiber degeneration and neuromuscular junction abnormalities. However, the biochemical stability of the DGC and the functional performance of adbn−/− muscle have not been characterized. Here we show that the biochemical association between dystrophin and β-dystroglycan is compromised in adbn−/− skeletal muscle, suggesting that α-dystrobrevin plays a structural role in stabilizing the DGC. However, despite muscle cell death and DGC destabilization, costamere organization and physiological performance is normal in adbn−/− skeletal muscle. Our results demonstrate that myofiber degeneration alone does not cause functional deficits and suggests that more complex pathological factors contribute to the development of muscle weakness in muscular dystrophy.
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Affiliation(s)
- Tina M. Bunnell
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Michele A. Jaeger
- Program in Cellular and Molecular Biology, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Daniel P. Fitzsimons
- Department of Physiology, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Kurt W. Prins
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - James M. Ervasti
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota, United States of America
- * E-mail:
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26
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Faulkner JA, Ng R, Davis CS, Li S, Chamberlain JS. Diaphragm muscle strip preparation for evaluation of gene therapies in mdx mice. Clin Exp Pharmacol Physiol 2008; 35:725-9. [PMID: 18215182 DOI: 10.1111/j.1440-1681.2007.04865.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
1. Duchenne muscular dystrophy (DMD), a severe muscle wasting disease of young boys with an incidence of one in every 3000, results from a mutation in the gene that encodes dystrophin. The absence of dystrophin expression in skeletal muscles and heart results in the degeneration of muscle fibres and, consequently, severe muscle weakness and wasting. The mdx mouse discovered in 1984, with some adjustments for differences, has proven to be an invaluable model for scientific investigations of dystrophy. 2. The development of the diaphagm strip preparation provided an ideal experimental model for investigations of skeletal muscle impairments in structure and function induced by interactions of disease- and age-related factors. Unlike the limb muscles of the mdx mouse, which show adaptive changes in structure and function, the diaphragm strip preparation reflects accurately the deterioration in muscle structure and function observed in boys with DMD. 3. The advent of sophisticated servo motors and force transducers interfaced with state-of-the-art software packages to drive complex experimental designs during the 1990s greatly enhanced the capability of the mdx mouse and the diaphragm strip preparation to evaluate more accurately the impact of the disease on the structure-function relationships throughout the life span of the mouse. 4. Finally, during the 1990s and through the early years of the 21st century, many promising, sophisticated genetic techniques have been designed to ameliorate the devastating impact of muscular dystrophy on the structure and function of skeletal muscles. During this period of rapid development of promising genetic therapies, the combination of the mdx mouse and the diaphragm strip preparation has provided an ideal model for the evaluation of the success, or failure, of these genetic techniques to improve dystrophic muscle structure, function or both. With the 2 year life span of the mdx mouse, the impact of age-related effects can be studied in this model.
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Affiliation(s)
- John A Faulkner
- Department of Molecular and Integrative Physiology, School of Medicine, University of Ann Arbor, Michigan 48109-2200, USA.
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27
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Ervasti JM, Sonnemann KJ. Biology of the striated muscle dystrophin-glycoprotein complex. INTERNATIONAL REVIEW OF CYTOLOGY 2008; 265:191-225. [PMID: 18275889 DOI: 10.1016/s0074-7696(07)65005-0] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
Since its first description in 1990, the dystrophin-glycoprotein complex has emerged as a critical nexus for human muscular dystrophies arising from defects in a variety of distinct genes. Studies in mammals widely support a primary role for the dystrophin-glycoprotein complex in mechanical stabilization of the plasma membrane in striated muscle and provide hints for secondary functions in organizing molecules involved in cellular signaling. Studies in model organisms confirm the importance of the dystrophin-glycoprotein complex for muscle cell viability and have provided new leads toward a full understanding of its secondary roles in muscle biology.
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Affiliation(s)
- James M Ervasti
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, USA
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28
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Lecroisey C, Martin E, Mariol MC, Granger L, Schwab Y, Labouesse M, Ségalat L, Gieseler K. DYC-1, a protein functionally linked to dystrophin in Caenorhabditis elegans is associated with the dense body, where it interacts with the muscle LIM domain protein ZYX-1. Mol Biol Cell 2007; 19:785-96. [PMID: 18094057 DOI: 10.1091/mbc.e07-05-0497] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
In Caenorhabditis elegans, mutations of the dystrophin homologue, dys-1, produce a peculiar behavioral phenotype (hyperactivity and a tendency to hypercontract). In a sensitized genetic background, dys-1 mutations also lead to muscle necrosis. The dyc-1 gene was previously identified in a genetic screen because its mutation leads to the same phenotype as dys-1, suggesting that the two genes are functionally linked. Here, we report the detailed characterization of the dyc-1 gene. dyc-1 encodes two isoforms, which are expressed in neurons and muscles. Isoform-specific RNAi experiments show that the absence of the muscle isoform, and not that of the neuronal isoform, is responsible for the dyc-1 mutant phenotype. In the sarcomere, the DYC-1 protein is localized at the edges of the dense body, the nematode muscle adhesion structure where actin filaments are anchored and linked to the sarcolemma. In yeast two-hybrid assays, DYC-1 interacts with ZYX-1, the homologue of the vertebrate focal adhesion LIM domain protein zyxin. ZYX-1 localizes at dense bodies and M-lines as well as in the nucleus of C. elegans striated muscles. The DYC-1 protein possesses a highly conserved 19 amino acid sequence, which is involved in the interaction with ZYX-1 and which is sufficient for addressing DYC-1 to the dense body. Altogether our findings indicate that DYC-1 may be involved in dense body function and stability. This, taken together with the functional link between the C. elegans DYC-1 and DYS-1 proteins, furthermore suggests a requirement of dystrophin function at this structure. As the dense body shares functional similarity with both the vertebrate Z-disk and the costamere, we therefore postulate that disruption of muscle cell adhesion structures might be the primary event of muscle degeneration occurring in the absence of dystrophin, in C. elegans as well as vertebrates.
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Affiliation(s)
- Claire Lecroisey
- Université Lyon 1, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5534, Centre de Génétique Moléculaire et Cellulaire, Bâtiment Mendel, Villeurbanne, F-69622, France
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Stone MR, O'Neill A, Lovering RM, Strong J, Resneck WG, Reed PW, Toivola DM, Ursitti JA, Omary MB, Bloch RJ. Absence of keratin 19 in mice causes skeletal myopathy with mitochondrial and sarcolemmal reorganization. J Cell Sci 2007; 120:3999-4008. [PMID: 17971417 DOI: 10.1242/jcs.009241] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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. We examined the contractile properties and morphology of fast-twitch skeletal muscle from mice lacking keratin 19. Tibialis anterior muscles of keratin-19-null mice showed a small but significant decrease in mean fiber diameter and in the specific force of tetanic contraction, as well as increased plasma creatine kinase levels. Costameres at the sarcolemma of keratin-19-null muscle, visualized with antibodies against spectrin or dystrophin, were disrupted and the sarcolemma was separated from adjacent myofibrils by a large gap in which mitochondria accumulated. The costameric dystrophin-dystroglycan complex, which co-purified with gamma-actin, keratin 8 and keratin 19 from striated muscles of wild-type mice, co-purified with gamma-actin but not keratin 8 in the mutant. Our results suggest that keratin 19 in fast-twitch skeletal muscle helps organize costameres and links them to the contractile apparatus, and that the absence of keratin 19 disrupts these structures, resulting in loss of contractile force, altered distribution of mitochondria and mild myopathy. This is the first demonstration of a mammalian phenotype associated with a genetic perturbation of keratin 19.
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Affiliation(s)
- Michele R Stone
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
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30
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Abstract
The dissection of mechanisms that regulate glucose transport by insulin has revealed an intricate network of signaling molecules scattered from the insulin receptor to the intracellular glucose transporter GLUT4. It is also appreciated that some insulin receptor signals jaunt in different directions to regulate events essential for the efficient redistribution of GLUT4 to the plasma membrane. Moreover key assists in the process appear to be arranged by membrane lipids and cytoskeletal proteins. Following current considerations of insulin signals regulating GLUT4, this review will focus on in vitro and in vivo evidence that supports an essential role for phosphoinositides and actin filaments in the control of glucose transport. The discussion will visit recent cell culture, whole animal, and human data highlighting membrane and cytoskeletal aspects of insulin resistance.
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Affiliation(s)
- Joseph T Brozinick
- Eli Lilly and Company, Lilly Corporate Center, Indianapolis, IN 46285, USA.
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Sonnemann KJ, Fitzsimons DP, Patel JR, Liu Y, Schneider MF, Moss RL, Ervasti JM. Cytoplasmic gamma-actin is not required for skeletal muscle development but its absence leads to a progressive myopathy. Dev Cell 2006; 11:387-97. [PMID: 16950128 DOI: 10.1016/j.devcel.2006.07.001] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2006] [Revised: 06/21/2006] [Accepted: 07/06/2006] [Indexed: 10/24/2022]
Abstract
Nonmuscle gamma(cyto)-actin is expressed at very low levels in skeletal muscle but uniquely localizes to costameres, the cytoskeletal networks that couple peripheral myofibrils to the sarcolemma. We generated and analyzed skeletal muscle-specific gamma(cyto)-actin knockout (Actg1-msKO) mice. Although muscle development proceeded normally, Actg1-msKO mice presented with overt muscle weakness accompanied by a progressive pattern of muscle fiber necrosis/regeneration. Functional deficits in whole-body tension and isometric twitch force were observed, consistent with defects in the connectivity between muscle fibers and/or myofibrils or at the myotendinous junctions. Surprisingly, gamma(cyto)-actin-deficient muscle did not demonstrate the fibrosis, inflammation, and membrane damage typical of several muscular dystrophies but rather presented with a novel progressive myopathy. Together, our data demonstrate an important role for minimally abundant but strategically localized gamma(cyto)-actin in adult skeletal muscle and describe a new mouse model to study the in vivo relevance of subcellular actin isoform sorting.
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Affiliation(s)
- Kevin J Sonnemann
- Program in Cellular and Molecular Biology, University of Wisconsin-Madison, 53706, USA
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33
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Schertzer JD, Ryall JG, Lynch GS. Systemic administration of IGF-I enhances oxidative status and reduces contraction-induced injury in skeletal muscles of mdx dystrophic mice. Am J Physiol Endocrinol Metab 2006; 291:E499-505. [PMID: 16621899 DOI: 10.1152/ajpendo.00101.2006] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The absence of dystrophin and resultant disruption of the dystrophin glycoprotein complex renders skeletal muscles of dystrophic patients and dystrophic mdx mice susceptible to contraction-induced injury. Strategies to reduce contraction-induced injury are of critical importance, because this mode of damage contributes to the etiology of myofiber breakdown in the dystrophic pathology. Transgenic overexpression of insulin-like growth factor-I (IGF-I) causes myofiber hypertrophy, increases force production, and can improve the dystrophic pathology in mdx mice. In contrast, the predominant effect of continuous exogenous administration of IGF-I to mdx mice at a low dose (1.0-1.5 mg.kg(-1).day(-1)) is a shift in muscle phenotype from fast glycolytic toward a more oxidative, fatigue-resistant, slow muscle without alterations in myofiber cross-sectional area, muscle mass, or maximum force-producing capacity. We found that exogenous administration of IGF-I to mdx mice increased myofiber succinate dehydrogenase activity, shifted the overall myosin heavy chain isoform composition toward a slower phenotype, and, most importantly, reduced contraction-induced damage in tibialis anterior muscles. The deficit in force-producing capacity after two damaging lengthening contractions was reduced significantly in tibialis anterior muscles of IGF-I-treated (53 +/- 4%) compared with untreated mdx mice (70 +/- 5%, P < 0.05). The results provide further evidence that IGF-I administration can enhance the functional properties of dystrophic skeletal muscle and, compared with results in transgenic mice or virus-mediated overexpression, highlight the disparities in different models of endocrine factor delivery.
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MESH Headings
- Animals
- Gene Expression/drug effects
- Insulin-Like Growth Factor I/pharmacology
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Inbred mdx
- Muscle Contraction/drug effects
- Muscle Contraction/physiology
- Muscle Fibers, Skeletal/drug effects
- Muscle Fibers, Skeletal/metabolism
- Muscle, Skeletal/drug effects
- Muscle, Skeletal/injuries
- Muscle, Skeletal/physiopathology
- Muscular Dystrophy, Animal/genetics
- Muscular Dystrophy, Animal/metabolism
- Muscular Dystrophy, Animal/physiopathology
- Myosin Heavy Chains/genetics
- Myosin Heavy Chains/metabolism
- Protein Isoforms/genetics
- Protein Isoforms/metabolism
- Succinate Dehydrogenase/metabolism
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Lansman JB, Franco-Obregón A. MECHANOSENSITIVE ION CHANNELS IN SKELETAL MUSCLE: A LINK IN THE MEMBRANE PATHOLOGY OF MUSCULAR DYSTROPHY. Clin Exp Pharmacol Physiol 2006; 33:649-56. [PMID: 16789935 DOI: 10.1111/j.1440-1681.2006.04393.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
1. Mechanosensitive (MS) channels are expressed abundantly in skeletal muscle at all stages of development. In recordings from membrane patches, MS channels are constitutively active at the resting potential. The channels are selective for cations and have a large single-channel conductance (approximately 25 pS in physiological saline) and a high Ca2+ permeability (relative permeability of Ca2+ to K+ (PCa/PK) = 7). 2. Mechanosensitive channel activity recorded from the surface of myotubes from dystrophic mdx mice was substantially greater than the activity recorded from wild-type myotubes. Increased channel activity in the mutant results from the induction in a subpopulation of channels of a novel MS gating mode characterized by markedly prolonged channel openings and inactivation in response to membrane stretch. 3. Membrane stretch or a strong depolarization causes an irreversible switch to the stretch-inactivated gating mode in mdx myotubes. A stretch-induced shift in MS channel gating mode may contribute to stretch-induced elevations in [Ca2+]i during the early stages of disease pathogenesis. 4. Abnormalities of MS channel behaviour are also detected in recordings from patches on flexor digitorum brevis fibres acutely isolated from mdx mice. Mechanosensitive channel opening probability is higher in mdx fibres at all developmental stages. In addition, channel numbers are persistently elevated during postnatal development, failing to undergo a normal process of downregulation during the first 3 postnatal weeks. 5. Two distinct mechanisms may contribute to elevations of [Ca2+]i in dystrophin-deficient skeletal muscle: (i) a membrane stress-dependent switch of MS channels into to a prolonged opening mode; and (ii) a loss of developmental downregulation leading to persistent MS channel expression during postnatal muscle development.
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Affiliation(s)
- Jeffry B Lansman
- Department of Cellular and Molecular Pharmacology, UCSF School of Medicine, San Francisco, California 94143-0450, USA.
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35
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Ervasti JM. Dystrophin, its interactions with other proteins, and implications for muscular dystrophy. Biochim Biophys Acta Mol Basis Dis 2006; 1772:108-17. [PMID: 16829057 DOI: 10.1016/j.bbadis.2006.05.010] [Citation(s) in RCA: 220] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2006] [Revised: 05/31/2006] [Accepted: 05/31/2006] [Indexed: 11/27/2022]
Abstract
Duchenne muscular dystrophy is the most prevalent and severe form of human muscular dystrophy. Investigations into the molecular basis for Duchenne muscular dystrophy were greatly facilitated by seminal studies in the 1980s that identified the defective gene and its major protein product, dystrophin. Biochemical studies revealed its tight association with a multi-subunit complex, the so-named dystrophin-glycoprotein complex. Since its description, the dystrophin-glycoprotein complex has emerged as an important structural unit of muscle and also as a critical nexus for understanding a diverse array of muscular dystrophies arising from defects in several distinct genes. The dystrophin homologue utrophin can compensate at the cell/tissue level for dystrophin deficiency, but functions through distinct molecular mechanisms of protein-protein interaction.
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Affiliation(s)
- James M Ervasti
- Department of Physiology, 127 Service Memorial Institute, University of Wisconsin Medical School, 1300 University Avenue, Madison, WI 53706, USA.
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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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37
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Halayko AJ, Stelmack GL. The association of caveolae, actin, and the dystrophin-glycoprotein complex: a role in smooth muscle phenotype and function? Can J Physiol Pharmacol 2006; 83:877-91. [PMID: 16333360 DOI: 10.1139/y05-107] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Smooth muscle cells exhibit phenotypic and mechanical plasticity. During maturation, signalling pathways controlling actin dynamics modulate contractile apparatus-associated gene transcription and contractile apparatus remodelling resulting from length change. Differentiated myocytes accumulate abundant caveolae that evolve from the structural association of lipid rafts with caveolin-1, a protein with domains that confer unique functional properties. Caveolae and caveolin-1 modulate and participate in receptor-mediated signalling, and thus contribute to functional diversity of phenotypically similar myocytes. In mature smooth muscle, caveolae are partitioned into discrete linear domains aligned with structural proteins that tether actin to the extracellular matrix. Caveolin-1 binds with beta-dystroglycan, a subunit of the dystrophin glycoprotein complex (DGC), and with filamin, an actin binding protein that organizes cortical actin, to which integrins and focal adhesion complexes are anchored. The DGC is linked to the actin cytoskeleton by a dystrophin subunit and is a receptor for extracellular laminin. Thus, caveolae and caveolin-associated signalling proteins and receptors are linked via structural proteins to a dynamic filamentous actin network. Despite development of transgenic models to investigate caveolins and membrane-associated actin-linking proteins in skeletal and cardiac muscle function, only superficial understanding of this association in smooth muscle phenotype and function has emerged.
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Affiliation(s)
- Andrew J Halayko
- Department of Physiology, University of Manitoba, Winnipeg, Canada.
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38
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Affiliation(s)
- Y Capetanaki
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas 77030, 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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40
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Stone MR, O'Neill A, Catino D, Bloch RJ. Specific interaction of the actin-binding domain of dystrophin with intermediate filaments containing keratin 19. Mol Biol Cell 2005; 16:4280-93. [PMID: 16000376 PMCID: PMC1196337 DOI: 10.1091/mbc.e05-02-0112] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Cytokeratins 8 and 19 concentrate at costameres of striated muscle and copurify with the dystrophin-glycoprotein complex, perhaps through the interaction of the cytokeratins with the actin-binding domain of dystrophin. We overexpressed dystrophin's actin-binding domain (Dys-ABD), K8 and K19, as well as closely related proteins, in COS-7 cells to assess the basis and specificity of their interaction. Dys-ABD alone associated with actin microfilaments. Expressed with K8 and K19, which form filaments, Dys-ABD associated preferentially with the cytokeratins. This interaction was specific, as the homologous ABD of betaI-spectrin failed to interact with K8/K19 filaments, and Dys-ABD did not associate with desmin or K8/K18 filaments. Studies in COS-7 cells and in vitro showed that Dys-ABD binds directly and specifically to K19. Expressed in muscle fibers in vivo, K19 accumulated in the myoplasm in structures that contained dystrophin and spectrin and disrupted the organization of the sarcolemma. K8 incorporated into sarcomeres, with no effect on the sarcolemma. Our results show that dystrophin interacts through its ABD with K19 specifically and are consistent with the idea that cytokeratins associate with dystrophin at the sarcolemma of striated muscle.
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Affiliation(s)
- Michele R Stone
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
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41
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Delhommeau F, Dalla Venezia N, Morinière M, Collin H, Maillet P, Guerfali I, Leclerc P, Fardeau M, Delaunay J, Baklouti F. Protein 4.1R expression in normal and dystrophic skeletal muscle. C R Biol 2005; 328:43-56. [PMID: 15714879 DOI: 10.1016/j.crvi.2004.11.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
4.1R pre-mRNA alternative splicing results in multiple mRNA and protein isoforms that are expressed in virtually all tissues. More specifically, isoforms containing the alternative exon 17a, are exclusively expressed in muscle tissues. In this report, we show that these isoforms are preferentially present in the myoplasm of fast myofibres. 4.1R epitopes are also found at the sarcolemma of both slow and fast myofibres in normal muscle. Interestingly, they are absent from dystrophin-deficient sarcolemma of DMD muscle, and colocalize with partially expressed dystrophin in BMD muscle. We also show that alternative splicing of exons 16 and 17a is regulated during muscle differentiation in an asynchronous fashion, with an early inclusion of exon 16 in forming myotubes, and a late inclusion of exon 17a. Consistently, Western blot analysis led to characterize mainly an approximately 96/98-kDa doublet bearing exons 16-17a-encoding peptide, exclusively occurring in the differentiated muscle.
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Affiliation(s)
- François Delhommeau
- Inserm U473 & Service d'hématologie, hôpital de Bicêtre and faculté de médecine Paris-Sud, 63, rue Gabriel-Péri, 94270 Le Kremlin-Bicêtre cedex, France
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42
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Johnson BD, Scheuer T, Catterall WA. Convergent regulation of skeletal muscle Ca2+ channels by dystrophin, the actin cytoskeleton, and cAMP-dependent protein kinase. Proc Natl Acad Sci U S A 2005; 102:4191-6. [PMID: 15753322 PMCID: PMC554817 DOI: 10.1073/pnas.0409695102] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The skeletal muscle L-type Ca2+ channel (Ca(V)1.1), which is responsible for initiating muscle contraction, is regulated by phosphorylation by cAMP-dependent protein kinase (PKA) in a voltage-dependent manner that requires direct physical association between the channel and the kinase mediated through A-kinase anchoring proteins (AKAPs). The role of the actin cytoskeleton in channel regulation was investigated in skeletal myocytes cultured from wild-type mice, mdx mice that lack the cytoskeletal linkage protein dystrophin, and a skeletal muscle cell line, 129 CB3. Voltage dependence of channel activation was shifted positively, and potentiation was greatly diminished in mdx myocytes and in 129 CB3 cells treated with the microfilament stabilizer phalloidin. Voltage-dependent potentiation by strong depolarizing prepulses was reduced in mdx myocytes but could be restored by positively shifting the stimulus potentials to compensate for the positive shift in the voltage dependence of gating. Inclusion of PKA in the pipette caused a negative shift in the voltage dependence of activation and restored voltage-dependent potentiation in mdx myocytes. These results show that skeletal muscle Ca2+ channel activity and voltage-dependent potentiation are controlled by PKA and microfilaments in a convergent manner. Regulation of Ca2+ channel activity by hormones and neurotransmitters that use the PKA signal transduction pathway may interact in a critical way with the cytoskeleton and may be impaired by deletion of dystrophin, contributing to abnormal regulation of intracellular calcium concentrations in dystrophic muscle.
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Affiliation(s)
- Barry D Johnson
- Department of Pharmacology, University of Washington, Box 357280, Seattle, WA 98195-7280, USA
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43
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Lynch GS. Role of contraction-induced injury in the mechanisms of muscle damage in muscular dystrophy. Clin Exp Pharmacol Physiol 2005; 31:557-61. [PMID: 15298551 DOI: 10.1111/j.1440-1681.2004.04026.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
1. Duchenne muscular dystrophy (DMD) is a severe disease of skeletal muscle, characterized by an X-linked recessive inheritance and a lack of dystrophin in muscle fibres. It is associated with progressive and severe wasting and weakness of nearly all muscles and premature death by cardiorespiratory failure. 2. Studies investigating the susceptibility of dystrophic skeletal muscles to contraction-mediated damage, especially after lengthening actions where activated muscles are stretched forcibly, have concluded that dystrophin may confer protection to muscle fibres by providing a mechanical link between the contractile apparatus and the plasma membrane. In the absence of dystrophin, there is disruption to normal force transmission and greater stress placed upon myofibrillar and membrane proteins, leading to muscle damage. 3. Contraction protocols (involving activation and stretch of isolated muscles or muscle fibres) have been developed to assess the relative susceptibility of dystrophic (and otherwise healthy) muscles to contraction-induced injury. These protocols have been used successfully to determine the relative efficacy of different (gene, cell or pharmacological) interventions designed to ameliorate or cure the dystrophic pathology. More research is needed to develop specific 'contraction assays' that will assist in the evaluation of the clinical significance of different therapeutic strategies for muscular dystrophy.
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Affiliation(s)
- Gordon S Lynch
- Department of Physiology, The University of Melbourne, Parkville, Victoria, Australia.
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Papponen H, Kaisto T, Myllylä VV, Myllylä R, Metsikkö K. Regulated sarcolemmal localization of the muscle-specific ClC-1 chloride channel. Exp Neurol 2005; 191:163-73. [PMID: 15589523 DOI: 10.1016/j.expneurol.2004.07.018] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2004] [Revised: 07/08/2004] [Accepted: 07/12/2004] [Indexed: 12/01/2022]
Abstract
The skeletal muscle-specific ClC-1 is a voltage-gated chloride channel protein. Specific antibodies against ClC-1 revealed in muscle sections a sarcolemmal staining that was absent in the myotonic arrested development of righting response (ADR) mouse muscle. The intensity of the sarcolemmal staining varied from one type of muscle to another and in lateral sections showed a typical mosaic pattern that colocalized with beta-dystroglycan and left the transverse tubule openings clear. Surprisingly, in isolated myofibers, the ClC-1 protein was absent from the sarcolemma. Instead, it localized to intracellular I band areas as soon as the myofibers were isolated. When the isolated myofibers were incubated with the kinase inhibitor staurosporine, the ClC-1 protein shifted back to the sarcolemma. Electric stimulation of the cultivated fibers had a similar effect. Also, myofibers infected with a recombinant Semliki Forest virus (SFV) expressing myc-tagged ClC-1 showed intracellular localization of the protein. The virally expressed mycClC-1 reached the Golgi apparatus but sarcolemmal staining remained nondetectable, and addition of staurosporine into the growth medium recruited the mycClC-1 to the sarcolemma. These data indicate that sarcolemmal targeting of the ClC-1 requires specific signals that are provided by the physiological environment.
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Affiliation(s)
- H Papponen
- Department of Anatomy and Cell Biology, University of Oulu, PO Box 5000, FIN-90014, Finland
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45
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Abstract
Spectrin family proteins represent an important group of actin-bundling and membrane-anchoring proteins found in diverse structures from yeast to man. Arising from a common ancestral alpha-actinin gene through duplications and rearrangements, the family has increased to include the spectrins and dystrophin/utrophin. The spectrin family is characterized by the presence of spectrin repeats, actin binding domains, and EF hands. With increasing divergence, new domains and functions have been added such that spectrin and dystrophin also contain specialized protein-protein interaction motifs and regions for interaction with membranes and phospholipids. The acquisition of new domains also increased the functional complexity of the family such that the proteins perform a range of tasks way beyond the simple bundling of actin filaments by alpha-actinin in S. pombe. We discuss the evolutionary, structural, functional, and regulatory roles of the spectrin family of proteins and describe some of the disease traits associated with loss of spectrin family protein function.
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Affiliation(s)
- M J F Broderick
- Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, United Kingdom
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46
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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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47
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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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Consolino CM, Brooks SV. Susceptibility to sarcomere injury induced by single stretches of maximally activated muscles of mdx mice. J Appl Physiol (1985) 2004; 96:633-8. [PMID: 14715682 DOI: 10.1152/japplphysiol.00587.2003] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The purpose was to investigate the contribution of mechanical damage to sarcomeres to the greater susceptibility of dystrophic muscle fibers to contraction-induced injury. Single stretches provide an effective method for studying mechanical factors that contribute to the initiation of contraction-induced injury. We hypothesized that, after single stretches, the deficits in isometric force would be greater for muscles of mdx than C57BL/10 mice, whereas membrane damage would be minimal for all muscles. Extensor digitorum longus (EDL) and soleus muscles of mice were removed under anesthesia with Avertin (tribromoethanol). During the plateau of a maximum isometric contraction in vitro, muscles were stretched through single strains of 20-60% fiber length. Isometric force was remeasured 1 min later, and muscles were then incubated in procion orange dye to identify fibers with membrane damage. Force deficits at 1 min were two- to threefold greater for EDL muscles of mdx compared with C57BL/10 mice, whereas no significant differences were observed between soleus muscles of mdx and C57BL/10 mice. For all muscles, membrane damage was minimal and not significantly increased by single stretches for either strain of mice. These data support a critical role of dystrophin maintaining sarcomere stability in EDL muscles, whereas soleus muscles retain abilities, in the absence of dystrophin, not different from control muscles to resist sarcomere damage.
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Affiliation(s)
- Christina M Consolino
- Institute of Gerontology, University of Michigan, Ann Arbor, Michigan 48109-2007, 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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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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