251
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Reynolds JG, McCalmon SA, Tomczyk T, Naya FJ. Identification and mapping of protein kinase A binding sites in the costameric protein myospryn. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2007; 1773:891-902. [PMID: 17499862 PMCID: PMC1955755 DOI: 10.1016/j.bbamcr.2007.04.004] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2006] [Revised: 03/30/2007] [Accepted: 04/05/2007] [Indexed: 01/08/2023]
Abstract
Recently we identified a novel target gene of MEF2A named myospryn that encodes a large, muscle-specific, costamere-restricted alpha-actinin binding protein. Myospryn belongs to the tripartite motif (TRIM) superfamily of proteins and was independently identified as a dysbindin-interacting protein. Dysbindin is associated with alpha-dystrobrevin, a component of the dystrophin-glycoprotein complex (DGC) in muscle. Apart from these initial findings little else is known regarding the potential function of myospryn in striated muscle. Here we reveal that myospryn is an anchoring protein for protein kinase A (PKA) (or AKAP) whose closest homolog is AKAP12, also known as gravin/AKAP250/SSeCKS. We demonstrate that myospryn co-localizes with RII alpha, a type II regulatory subunit of PKA, at the peripheral Z-disc/costameric region in striated muscle. Myospryn interacts with RII alpha and this scaffolding function has been evolutionarily conserved as the zebrafish ortholog also interacts with PKA. Moreover, myospryn serves as a substrate for PKA. These findings point to localized PKA signaling at the muscle costamere.
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Affiliation(s)
- Joseph G Reynolds
- Department of Biology, Program in Cell and Molecular Biology, Boston University, 24 Cummington Street, Boston, MA 02215, USA
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252
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Paxillin and ponsin interact in nascent costameres of muscle cells. J Mol Biol 2007; 369:665-82. [PMID: 17462669 DOI: 10.1016/j.jmb.2007.03.050] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2006] [Revised: 03/13/2007] [Accepted: 03/13/2007] [Indexed: 11/30/2022]
Abstract
Muscle differentiation requires the transition from motile myoblasts to sessile myotubes and the assembly of a highly regular contractile apparatus. This striking cytoskeletal remodelling is coordinated with a transformation of focal adhesion-like cell-matrix contacts into costameres. To assess mechanisms underlying this differentiation process, we searched for muscle specific-binding partners of paxillin. We identified an interaction of paxillin with the vinexin adaptor protein family member ponsin in nascent costameres during muscle differentiation, which is mediated by an interaction of the second src homology domain 3 (SH3) domain of ponsin with the proline-rich region of paxillin. To understand the molecular basis of this interaction, we determined the structure of this SH3 domain at 0.83 A resolution, as well as its complex with the paxillin binding peptide at 1.63 A resolution. Upon binding, the paxillin peptide adopts a polyproline-II helix conformation in the complex. Contrary to the charged SH3 binding interface, the peptide contains only non-polar residues and for the first time such an interaction was observed structurally in SH3 domains. Fluorescence titration confirmed the ponsin/paxillin interaction, characterising it further by a weak binding affinity. Transfection experiments revealed further characteristics of ponsin functions in muscle cells: All three SH3 domains in the C terminus of ponsin appeared to synergise in targeting the protein to force-transducing structures. The overexpression of ponsin resulted in altered muscle cell-matrix contact morphology, suggesting its involvement in the establishment of mature costameres. Further evidence for the role of ponsin in the maintenance of mature mechanotransduction sites in cardiomyocytes comes from the observation that ponsin expression was down-regulated in end-stage failing hearts, and that this effect was reverted upon mechanical unloading. These results provide new insights in how low affinity protein-protein interactions may contribute to a fine tuning of cytoskeletal remodelling processes during muscle differentiation and in adult cardiomyocytes.
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253
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Senetar MA, Moncman CL, McCann RO. Talin2 is induced during striated muscle differentiation and is targeted to stable adhesion complexes in mature muscle. CELL MOTILITY AND THE CYTOSKELETON 2007; 64:157-73. [PMID: 17183545 DOI: 10.1002/cm.20173] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The cytoskeletal protein talin serves as an essential link between integrins and the actin cytoskeleton in several similar, but functionally distinct, adhesion complexes, including focal adhesions, costameres, and intercalated disks. Vertebrates contain two talin genes, TLN1 and TLN2, but the different roles of Talin1 and Talin2 in cell adhesion are unclear. In this report we have analyzed Talin1 and Talin2 in striated muscle. Using isoform-specific antibodies, we found that Talin2 is highly expressed in mature striated muscle. Using mouse C2C12 cells and primary human skeletal muscle myoblasts as models of muscle differentiation, we show that Talin1 is expressed in undifferentiated myoblasts and that Talin2 expression is upregulated during muscle differentiation at both the mRNA and protein levels. We have also identified regulatory sequences that may be responsible for the differential expression of Talin1 and Talin2. Using GFP-tagged Talin1 and Talin2 constructs, we found that GFP-Talin1 targets to focal adhesions while GFP-Talin2 targets to abnormally large adhesions in myoblasts. We also found that ectopic expression of Talin2 in myoblasts, which do not contain appreciable levels of Talin2, dysregulates the actin cytoskeleton. Finally we demonstrate that Talin2, but not Talin1, localizes to costameres and intercalated disks, which are stable adhesions required for the assembly of mature striated muscle. Our results suggest that Talin1 is the primary link between integrins and actin in dynamic focal adhesions in undifferentiated, motile cells, but that Talin2 may serve as the link between integrins and the sarcomeric cytoskeletonin stable adhesion complexes in mature striated muscle.
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Affiliation(s)
- Melissa A Senetar
- Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, Kentucky 40536-0509, USA
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254
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Sanger JW, Kang S, Siebrands CC, Freeman N, Du A, Wang J, Stout AL, Sanger JM. How to build a myofibril. J Muscle Res Cell Motil 2007; 26:343-54. [PMID: 16465476 DOI: 10.1007/s10974-005-9016-7] [Citation(s) in RCA: 128] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Building a myofibril from its component proteins requires the interactions of many different proteins in a process whose details are not understood. Several models have been proposed to provide a framework for understanding the increasing data on new myofibrillar proteins and their localizations during muscle development. In this article we discuss four current models that seek to explain how the assembly occurs in vertebrate cross-striated muscles. The models hypothesize: (a) stress fiber-like structures as templates for the assembly of myofibrils, (b) assembly in which the actin filaments and Z-bands form subunits independently from A-band subunits, with the two subsequently joined together to form a myofibril, (c) premyofibrils as precursors of myofibrils, or (d) assembly occurring without any intermediary structures. The premyofibril model, proposed by the authors, is discussed in more detail as it could explain myofibrillogenesis under a variety of different conditions: in ovo, in explants, and in tissue culture studies on cardiac and skeletal muscles.
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Affiliation(s)
- Joseph W Sanger
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6058, USA.
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255
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NAKAGAMI H, KIKUCHI Y, KATSUYA T, MORISHITA R, AKASAKA H, SAITOH S, RAKUGI H, KANEDA Y, SHIMAMOTO K, OGIHARA T. Gene Polymorphism of Myospryn (Cardiomyopathy-Associated 5) Is Associated with Left Ventricular Wall Thickness in Patients with Hypertension. Hypertens Res 2007; 30:1239-46. [DOI: 10.1291/hypres.30.1239] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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256
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Vlahovich N, Schevzov G, Nair-Shaliker V, Ilkovski B, Artap ST, Joya JE, Kee AJ, North KN, Gunning PW, Hardeman EC. Tropomyosin 4 defines novel filaments in skeletal muscle associated with muscle remodelling/regeneration in normal and diseased muscle. ACTA ACUST UNITED AC 2007; 65:73-85. [PMID: 17968984 DOI: 10.1002/cm.20245] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- Nicole Vlahovich
- Muscle Development Unit, Children's Medical Research Institute, Locked Bag 23, Wentworthville, New South Wales 2145, Australia
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257
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Miller RK, Qadota H, Landsverk ML, Mercer KB, Epstein HF, Benian GM. UNC-98 links an integrin-associated complex to thick filaments in Caenorhabditis elegans muscle. J Cell Biol 2006; 175:853-9. [PMID: 17158957 PMCID: PMC2064695 DOI: 10.1083/jcb.200608043] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2006] [Accepted: 11/15/2006] [Indexed: 11/30/2022] Open
Abstract
Focal adhesions are multiprotein assemblages that link cells to the extracellular matrix. The transmembrane protein, integrin, is a key component of these structures. In vertebrate muscle, focal adhesion-like structures called costameres attach myofibrils at the periphery of muscle cells to the cell membrane. In Caenorhabditis elegans muscle, all the myofibrils are attached to the cell membrane at both dense bodies (Z-disks) and M-lines. Clustered at the base of dense bodies and M-lines, and associated with the cytoplasmic tail of beta-integrin, is a complex of many proteins, including UNC-97 (vertebrate PINCH). Previously, we showed that UNC-97 interacts with UNC-98, a 37-kD protein, containing four C2H2 Zn fingers, that localizes to M-lines. We report that UNC-98 also interacts with the C-terminal portion of a myosin heavy chain. Multiple lines of evidence support a model in which UNC-98 links integrin-associated proteins to myosin in thick filaments at M-lines.
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Affiliation(s)
- Rachel K Miller
- Department of Pathology and 2Graduate Division of Biological and Biomedical Sciences, Emory University, Atlanta, GA 30322, USA
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258
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Lluri G, Langlois GD, McClellan B, Soloway PD, Jaworski DM. Tissue inhibitor of metalloproteinase-2 (TIMP-2) regulates neuromuscular junction development via a beta1 integrin-mediated mechanism. ACTA ACUST UNITED AC 2006; 66:1365-77. [PMID: 16967503 PMCID: PMC2982212 DOI: 10.1002/neu.20315] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Extracellular matrix (ECM) molecules play critical roles in muscle function by participating in neuromuscular junction (NMJ) development and the establishment of stable, cytoskeleton-associated adhesions required for muscle contraction. Matrix metalloproteinases (MMPs) are neutral endopeptidases that degrade all ECM components. While the role of MMPs and their inhibitors, the tissue inhibitor of metalloproteinases (TIMPs), has been investigated in many tissues, little is known about their role in muscle development and mature function. TIMP-2 -/- mice display signs of muscle weakness. Here, we report that TIMP-2 is expressed at the NMJ and its expression is greater in fast-twitch (extensor digitorum longus, EDL) than slow-twitch (soleus) muscle. EDL muscle mass is reduced in TIMP-2-/- mice without a concomitant change in fiber diameter or number. The TIMP-2-/- phenotype is not likely due to increased ECM proteolysis because net MMP activity is actually reduced in TIMP-2-/- muscle. Most strikingly, TIMP-2 colocalizes with beta1 integrin at costameres in the wild-type EDL and beta1 integrin expression is significantly reduced in TIMP-2-/- EDL. We propose that reduced beta1 integrin in fast-twitch muscle may be associated with destabilized ECM-cytoskeletal interactions required for muscle contraction in TIMP-2-/- muscle; thus, explaining the muscle weakness. Given that fast-twitch fibers are lost in muscular dystrophies and age-related sarcopenia, if TIMP-2 regulates mechanotransduction in an MMP-independent manner it opens new potential therapeutic avenues.
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Affiliation(s)
- Gentian Lluri
- Department of Anatomy and Neurobiology, University of Vermont College of Medicine, Burlington VT 05405
| | - Garret D. Langlois
- Department of Anatomy and Neurobiology, University of Vermont College of Medicine, Burlington VT 05405
| | - Brian McClellan
- Department of Anatomy and Neurobiology, University of Vermont College of Medicine, Burlington VT 05405
| | - Paul D. Soloway
- Division of Nutritional Sciences, Cornell University, Ithaca NY 14853
| | - Diane M. Jaworski
- Department of Anatomy and Neurobiology, University of Vermont College of Medicine, Burlington VT 05405
- Correspondence to: Dr. Diane M. Jaworski, Dept. of Anatomy & Neurobiology, Univ. of Vermont College of Medicine, 149 Beaumont Ave., HSRF 418, Burlington, VT 05405, Phone: (802) 656-0538, Fax: (802) 656-4674,
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259
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Abstract
The assembly, processing and translocation of proteins occur constantly in all cells, and these processes also take place during the genesis, maintenance and repair of skeletal muscle. Skeletal muscle fibers are composed of myofibrils and are surrounded by a muscle plasma membrane, the sarcolemma. The sarcolemma serves as a docking location for many proteins. These proteins are important for establishing the physical connection between the extracellular matrix and the cytoskeleton and play a role in transmitting force related to muscle contraction. This physical connection is maintained through a myriad of proteins including the dystrophin glycoprotein complex (DGC). Normal sarcolemmal function requires proper DGC synthesis and positioning, and perturbation of the DGC leads to muscle membrane instability and disease.
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Affiliation(s)
- Michael J Allikian
- Department of Medicine, Section of Cardiology, The University of Chicago, 5841 S. Maryland, MC6088, Chicago, IL 60637, USA.
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260
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Duan D. Challenges and opportunities in dystrophin-deficient cardiomyopathy gene therapy. Hum Mol Genet 2006; 15 Spec No 2:R253-61. [PMID: 16987891 PMCID: PMC2581718 DOI: 10.1093/hmg/ddl180] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The last decade has evidenced unprecedented progress in gene therapy of Duchenne and Becker muscular dystrophy (DMD and BMD) skeletal muscle disease. Cardiomyopathy is a leading cause of morbidity and mortality in both patients and carriers of DMD, BMD and X-linked dilated cardiomyopathy. However, there is little advance in heart gene therapy. The gene, the vector, vector delivery, the target tissue and animal models are five fundamental components in developing an effective gene therapy. Intensive effort has been made in optimizing gene transfer vectors and methods. Systemic and/or local delivery of recombinant adeno-associated viral vector have resulted in widespread transduction in the rodent heart. The current challenge is to define other parameters that are essential for a successful gene therapy such as the best candidate gene(s), the optimal expression level and the target tissue. This review focuses on these long-ignored aspects and points out future research directions. In particular, we need to address whether all or only some of the recently developed mini- and microgenes are protective in the heart, whether partial correction can lead to whole heart function improvement, whether over-expression is hazardous and whether correcting skeletal muscle disease can slow down or stop the progression of cardiomyopathy. Discussion is also made on whether the current mouse models can meet these research needs.
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Affiliation(s)
- Dongsheng Duan
- Department of Molecular Microbiology and Immunology, The University of Missouri School of Medicine, One Hospital Dr., Room M610G, MSB Columbia, MO 65212, USA.
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261
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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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262
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Huang HT, Brand OM, Mathew M, Ignatiou C, Ewen EP, McCalmon SA, Naya FJ. Myomaxin is a novel transcriptional target of MEF2A that encodes a Xin-related alpha-actinin-interacting protein. J Biol Chem 2006; 281:39370-9. [PMID: 17046827 DOI: 10.1074/jbc.m603244200] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The physiological targets regulated by MEF2 in striated muscle are not completely known. Several recent studies have identified novel downstream target genes and shed light on the global transcriptional network regulated by MEF2 in muscle. In our continuing effort to identify novel, downstream pathways controlled by MEF2, we have used mef2a knock-out mice to find those genes dependent on MEF2A transcriptional activity. Here, we describe the characterization of a direct, downstream target gene for the MEF2A transcription factor encoding a large, muscle-specific protein that localizes to the Z-disc/costameric region in striated muscle. This gene, called myomaxin, was identified as a gene markedly down-regulated in MEF2A knock-out hearts. Myomaxin is the mouse ortholog of a partial human cDNA of unknown function named cardiomyopathy associated gene 3 (CMYA3). Myomaxin is expressed as a single, large transcript of approximately 11 kilobases in adult heart and skeletal muscle with an open reading frame of 3,283 amino acids. The protein encoded by the myomaxin gene is related to the actin-binding protein Xin and interacts with the sarcomeric Z-disc protein, alpha-actinin-2. Our findings demonstrate that Myomaxin functions directly downstream of MEF2A at the peripheral Z-disc complex in striated muscle potentially playing a role in regulating cytoarchitectural integrity.
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Affiliation(s)
- Hsuan-Ting Huang
- Department of Biology, Program in Cell and Molecular Biology, Boston University, Boston, Massachusetts 02215, USA
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263
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Wolff AV, Niday AK, Voelker KA, Call JA, Evans NP, Granata KP, Grange RW. Passive mechanical properties of maturing extensor digitorum longus are not affected by lack of dystrophin. Muscle Nerve 2006; 34:304-12. [PMID: 16770793 DOI: 10.1002/mus.20588] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Mechanical weakness of skeletal muscle is thought to contribute to onset and early progression of Duchenne muscular dystrophy, but this has not been systematically assessed. The purpose of this study was to determine in mice: (1) whether the passive mechanical properties of maturing dystrophic (mdx) muscles were different from control; and (2) if different, the time during maturation when these properties change. Prior to and following the overt onset of the dystrophic process (14-35 days), control and dystrophic extensor digitorum longus (EDL) muscles were subjected to two passive stretch protocols in vitro (5% strain at instantaneous and 1.5 L(0)/s strain rates). Force profiles were fit to a viscoelastic muscle model to determine stiffness and damping. The mdx and control EDL muscles exhibited similar passive mechanical properties at each age, suggesting a functional threshold for dystrophic muscle below which damage may be minimized. Determining this threshold may have important clinical implications for treatments of muscular dystrophy involving physical activity.
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Affiliation(s)
- Andrew V Wolff
- Department of Mechanical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA.
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264
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Bhosle RC, Michele DE, Campbell KP, Li Z, Robson RM. Interactions of intermediate filament protein synemin with dystrophin and utrophin. Biochem Biophys Res Commun 2006; 346:768-77. [PMID: 16777071 DOI: 10.1016/j.bbrc.2006.05.192] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2006] [Accepted: 05/25/2006] [Indexed: 01/06/2023]
Abstract
Synemin is a unique, very large intermediate filament (IF) protein present in all types of muscle cells, which forms heteropolymeric intermediate filaments (IFs) with the major IF proteins desmin and/or vimentin. We show herein that tissue-purified avian synemin directly interacts with both dystrophin and utrophin, and that specific expressed regions of both of the mammalian (human) synemin isoforms (alpha-synemin and beta-synemin) directly interact with specific expressed domains/regions of the dystrophin and utrophin molecules. Mammalian synemin is also shown to colocalize with dystrophin within muscle cell cultures. These results indicate that synemin is an important IF protein in muscle cells that helps fortify the linkage between the peripheral layer of cellular myofibrils and the costameric regions located along the sarcolemma and the sarcolemma region located within the neuromuscular and myotendinous junctions (NMJs and MTJs).
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Affiliation(s)
- Rahul C Bhosle
- Muscle Biology Group, Department of Biochemistry, Iowa State University, Ames, IA 50011-3260, USA
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265
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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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266
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Hoshijima M. Mechanical stress-strain sensors embedded in cardiac cytoskeleton: Z disk, titin, and associated structures. Am J Physiol Heart Circ Physiol 2006; 290:H1313-25. [PMID: 16537787 PMCID: PMC3241960 DOI: 10.1152/ajpheart.00816.2005] [Citation(s) in RCA: 188] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Cardiac muscle is equipped with intricate intrinsic mechanisms to regulate adaptive remodeling. Recent and extensive experimental findings powered by novel strategies for screening protein-protein interactions, improved imaging technologies, and versatile transgenic mouse methodologies reveal that Z disks and titin filaments possess unexpectedly complicated sensory and modulatory mechanisms for signal reception and transduction. These mechanisms employ molecules such as muscle-enriched LIM domain proteins, PDZ-LIM domain proteins, myozenin gene family members, titin-associated ankyrin repeat family proteins, and muscle-specific ring finger proteins, which have been identified as potential molecular sensor components. Moreover, classic transmembrane signaling processes, including mitogen-activated kinase, protein kinase C, and calcium signaling, also involve novel interactions with the Z disk/titin network. This compartmentalization of signaling complexes permits alteration of receptor-dependent transcriptional regulation by direct sensing of intrinsic stress. Newly identified mechanical stress sensors are not limited to Z-disk region and to I-band and M-band regions of titin but are also embedded in muscle-specific membrane systems such as the costamere, intercalated disks, and caveolae-like microdomains. This review summarizes current knowledge of this rapidly developing area with focus on how the heart adjusts physiological remodeling process to meet with mechanical demands and how this process fails in cardiac pathologies.
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Affiliation(s)
- Masahiko Hoshijima
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093-0734, USA.
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267
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Judge LM, Haraguchiln M, Chamberlain JS. Dissecting the signaling and mechanical functions of the dystrophin-glycoprotein complex. J Cell Sci 2006; 119:1537-46. [PMID: 16569668 DOI: 10.1242/jcs.02857] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Duchenne muscular dystrophy is a severe disorder caused by mutations in the dystrophin gene. Dystrophin is required for assembly of the dystrophin-glycoprotein complex and provides a mechanically strong link between the cytoskeleton and the extracellular matrix. Several proteins in the complex also participate in signaling cascades, but the relationship between these signaling and mechanical functions in the development of muscular dystrophy is unclear. To explore the mechanisms of myofiber necrosis in dystrophin-deficient muscle, we tested the hypothesis that restoration of this complex without a link to the cytoskeleton ameliorates dystrophic pathology. Transgenic mice were generated that express Dp116, a non-muscle isoform of dystrophin that assembles the dystrophin-glycoprotein complex, in muscles of dystrophin-deficient mdx4cv mice. However, the phenotype of these mice was more severe than in controls. Displacement of utrophin by Dp116 correlated with the severity of dystrophy in different muscle groups. Comparison with other transgenic lines demonstrated that parts of the dystrophin central rod domain were required to localize neuronal nitric oxide synthase to the sarcolemma, but this was not correlated with presence or extent of dystrophy. Our results suggest that mechanical destabilization, rather than signaling dysfunction, is the primary cause of myofiber necrosis in dystrophin-deficient muscle.
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Affiliation(s)
- Luke M Judge
- University of Washington School of Medicine, Department of Neurology Box 357720, Seattle, WA 98195-7720, USA
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268
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Hanft LM, Rybakova IN, Patel JR, Rafael-Fortney JA, Ervasti JM. Cytoplasmic gamma-actin contributes to a compensatory remodeling response in dystrophin-deficient muscle. Proc Natl Acad Sci U S A 2006; 103:5385-90. [PMID: 16565216 PMCID: PMC1459364 DOI: 10.1073/pnas.0600980103] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Dystrophin mechanically links the costameric cytoskeleton and sarcolemma, yet dystrophin-deficient muscle exhibits abnormalities in cell signaling, gene expression, and contractile function that are not clearly understood. We generated new antibodies specific for cytoplasmic gamma-actin and confirmed that gamma-actin most predominantly localized to the sarcolemma and in a faint reticular lattice within normal muscle cells. However, we observed that gamma-actin levels were increased 10-fold at the sarcolemma and within the cytoplasm of striated muscle cells from dystrophin-deficient mdx mice. Transgenic overexpression of the dystrophin homologue utrophin, or functional dystrophin constructs in mdx muscle, restored gamma-actin to normal levels, whereas gamma-actin remained elevated in mdx muscle expressing nonfunctional dystrophin constructs. We conclude that increased cytoplasmic gamma-actin in dystrophin-deficient muscle may be a compensatory response to fortify the weakened costameric lattice through recruitment of parallel mechanical linkages. However, the presence of excessive myoplasmic gamma-actin may also contribute to altered cell signaling or gene expression in dystrophin-deficient muscle.
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Affiliation(s)
- Laurin M. Hanft
- *Department of Physiology, University of Wisconsin, Madison, WI 53706; and
| | - Inna N. Rybakova
- *Department of Physiology, University of Wisconsin, Madison, WI 53706; and
| | | | - Jill A. Rafael-Fortney
- Department of Molecular and Cellular Biochemistry, Ohio State University, Columbus, OH 43210
| | - James M. Ervasti
- *Department of Physiology, University of Wisconsin, Madison, WI 53706; and
- To whom correspondence should be addressed at:
Department of Physiology, University of Wisconsin, 127 Service Memorial Institute, 1300 University Avenue, Madison, WI 53706. E-mail:
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269
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Quach NL, Rando TA. Focal adhesion kinase is essential for costamerogenesis in cultured skeletal muscle cells. Dev Biol 2006; 293:38-52. [PMID: 16533505 DOI: 10.1016/j.ydbio.2005.12.040] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2005] [Revised: 12/12/2005] [Accepted: 12/14/2005] [Indexed: 02/03/2023]
Abstract
A central question in muscle biology is how costameres are formed and become aligned with underlying myofibrils in mature tissues. Costameres are composed of focal adhesion proteins, including vinculin and paxillin, and anchor myofibril Z-bands to the sarcolemma. In the present study, we investigated the process of costamere formation ("costamerogenesis") in differentiating primary mouse myoblasts. Using vinculin and paxillin as costameric markers, we found that two additional focal adhesion components, alpha5beta1 integrin and focal adhesion kinase (FAK), are associated with costameres. We have characterized costamerogenesis as occurring in three distinct stages based on the organizational pattern of these costameric proteins. We show that both costamerogenesis and myofibrillogenesis are initiated at sites of membrane contacts with the extracellular matrix and that their maturation is tightly coupled. To test the importance of FAK signaling in these processes, we analyzed cells expressing a dominant negative form of FAK (dnFAK). When cells expressing dnFAK were induced to differentiate, both costamerogenesis and myofibrillogenesis were disrupted although the expression of constituent proteins was not inhibited. Likewise, inhibiting FAK activity by reducing FAK levels using an siRNA approach also resulted in an inhibition of costamerogenesis and myofibrillogenesis. The relationship between costamere and myofibril formation was tested further by treating myotube cultures with potassium or tetrodotoxin to block contraction and disrupt myofibril organization. This also resulted in inhibition of costamere maturation. We present a model of costamerogenesis whereby signaling through FAK is essential for both normal costamerogenesis and normal myofibrillogenesis which are tightly coupled during skeletal myogenesis.
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Affiliation(s)
- Navaline L Quach
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305, USA
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270
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Durham JT, Brand OM, Arnold M, Reynolds JG, Muthukumar L, Weiler H, Richardson JA, Naya FJ. Myospryn Is a Direct Transcriptional Target for MEF2A That Encodes a Striated Muscle, α-Actinin-interacting, Costamere-localized Protein. J Biol Chem 2006; 281:6841-9. [PMID: 16407236 DOI: 10.1074/jbc.m510499200] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The full repertoire of proteins that comprise the striated muscle Z-disc and peripheral structures, such as the costamere, have yet to be discovered. Recent studies suggest that this elaborate protein network, which acts as a structural and signaling center for striated muscle, harbors factors that function as mechanosensors to ensure coordinated contractile activity. Mutations in genes whose products reside in this region often result in skeletal and cardio myopathies, demonstrating the importance of this macromolecular complex in muscle structure and function. Here, we describe the characterization of a direct, downstream target gene for the MEF2A transcription factor encoding a large, muscle-specific protein that localizes to the costamere in striated muscle. This gene, called myospryn, was identified by microarray analysis as a transcript down-regulated in MEF2A knock-out mice. MEF2A knock-out mice develop cardiac failure during the perinatal period with mutant hearts exhibiting several cardiac abnormalities including myofibrillar disarray. Myospryn is the mouse ortholog of a partial human cDNA of unknown function named cardiomyopathy-associated gene 5 (CMYA5). Myospryn is expressed as a single, large transcript of approximately 12 kilobases in adult heart and skeletal muscle with an open reading frame of 3739 amino acids. This protein, belonging to the tripartite motif superfamily of proteins, contains a B-box coiled-coil (BBC), two fibronectin type III (FN3) repeats, and SPRY domains and interacts with the sarcomeric Z-disc protein, alpha-actinin-2. Our findings demonstrate that myospryn functions directly downstream of MEF2A at the costamere in striated muscle potentially playing a role in myofibrillogenesis.
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Affiliation(s)
- Jennifer T Durham
- Department of Biology, Program in Cell and Molecular Biology, Boston University, Boston, Massachusetts 02215, USA
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271
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Ojima K, Ono Y, Hata S, Koyama S, Doi N, Sorimachi H. Possible functions of p94 in connectin-mediated signaling pathways in skeletal muscle cells. J Muscle Res Cell Motil 2006; 26:409-17. [PMID: 16453164 DOI: 10.1007/s10974-005-9023-8] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Calpains are intracellular Ca2+ -requiring 'modulator proteases', which modulate cellular functions by limited and specific proteolysis. p94/calpain3, a skeletal-muscle specific calpain, has been one of the representative calpain species which indicates physiological importance of calpain proteolytic system; a defect of proteolytic activity of p94 causes limb girdle muscular dystrophy type2A (LGMD2A, also called 'calpainopathy'). Immunohistochemical studies on myofibrils showed that p94 localizes at the Z- and N2-line regions of sarcomeres. It was also identified by the yeast two hybrid studies that p94 binds to the N2A and M-line regions of connectin. Furthermore, genetic studies indicate that p94 is indispensable for skeletal muscles, although its precise functions are still unclear. Interestingly, connectin provides sarcomere not only with elasticity but also with binding sites to various multi-functional proteins such as muscle ankyrin repeat proteins (MARPs), muscle RING finger proteins (MURFs), titin-capping protein (T-cap/telethonin), sarcomeric-alpha-actinin, p94 etc. Binding sites for these proteins are not randomly placed along connectin but rather accumulated in the Z-, N2-, and/or M-line regions, indicating the existence of 'signal complexes' unique to each regions. The concept of these complexes are strongly supported by the facts that mutations of connectin or its binding proteins in these regions severely perturb muscle functions, as in the case of LGMD2A caused by mutations in the p94 gene. Therefore, it is hypothesized that the 'signal complexes' in the Z-, N2-, and M-lines modulate muscle cell homeostasis by transducing signals of external stimulations/stresses to trigger appropriate response at various different cellular events such as protein modification and gene expressions. In this article, we performed detailed immunohistochemical analyses of p94 on isolated single myofibers. Together with recent findings about p94, it is suggested that sarcomeric localization of p94, especially its M-line localization, is affected by the combination of cellular contexts such as contractile status of myofibrils, fiber type compositions, sarcomeric maturation, and the composition of the 'signal complexes' in each region.
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Affiliation(s)
- Koichi Ojima
- Department of Enzymatic Regulation for Cell Function, The Metropolitan Institute of Medical Science (Rinshoken), 3-18-22 Honkomagome, 113-8613, Bunkyo-ku, Tokyo, Japan
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272
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Woolstenhulme MT, Conlee RK, Drummond MJ, Stites AW, Parcell AC. Temporal response of desmin and dystrophin proteins to progressive resistance exercise in human skeletal muscle. J Appl Physiol (1985) 2006; 100:1876-82. [PMID: 16439510 DOI: 10.1152/japplphysiol.01592.2005] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We have investigated the adaptations of the cytoskeletal proteins desmin and dystrophin in relationship to known muscular adaptations of resistance exercise. We measured desmin, dystrophin, and actin protein contents, myosin heavy chain (MHC) isoform distribution, muscle strength, and muscle cross-sectional area (CSA) during 8 wk of progressive resistance training or after a single bout of unaccustomed resistance exercise. Muscle biopsies were taken from the vastus lateralis of 12 untrained men. For the single-bout group (n=6) biopsies were taken 1 wk before the single bout of exercise (week 0) and 1, 2, 4, and 8 wk after this single bout of exercise. For the training group (n=6), biopsies were taken 1 wk before the beginning of the program (week 0) and at weeks 1, 2, 4, and 8 of the progressive resistance training program. Desmin, dystrophin, and actin protein levels were determined with immunoblotting, and MHC isoform distribution was determined using SDS-PAGE at each time point for each group. In the training group, desmin was significantly increased compared with week 0 beginning at week 4 (182% of week 0; P<0.0001) and remained elevated through week 8 (172% of week 0; P<0.0001). Desmin did not change at any time point for the single-bout group. Actin and dystrophin protein contents were not changed in either group at any time point. The percentage of MHC type IIa increased and MHC type IIx decreased at week 8 in the training group with no changes occurring in the single-bout group. Strength was significantly increased by week 2 (knee extension) and week 4 (leg press), and it further increased at week 8 for both these exercises in the training group only. Muscle CSA was significantly increased at week 4 for type II fibers in the training group only (5,719+/-382 and 6,582+/-640 microm2, weeks 0 and 4, respectively; P<0.05). Finally, a significant negative correlation was observed between the desmin-to-actin ratio and the percentage of MHC IIx (R=-0.31; P<0.05, all time points from both groups). These data demonstrate a time course for muscular adaptation to resistance training in which desmin increases shortly after strength gains and in conjunction with hypertrophy, but before changes in MHC isoforms, whereas dystrophin remains unchanged.
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Affiliation(s)
- Mandy T Woolstenhulme
- Human Performance Research Center, 120-E Richards Bldg., Brigham Young University, Provo, UT 84602, USA
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273
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Frank D, Kuhn C, Katus HA, Frey N. The sarcomeric Z-disc: a nodal point in signalling and disease. J Mol Med (Berl) 2006; 84:446-68. [PMID: 16416311 DOI: 10.1007/s00109-005-0033-1] [Citation(s) in RCA: 179] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2005] [Accepted: 11/23/2005] [Indexed: 12/11/2022]
Abstract
The perception of the Z-disc in striated muscle has undergone significant changes in the past decade. Traditionally, the Z-disc has been viewed as a passive constituent of the sarcomere, which is important only for the cross-linking of thin filaments and transmission of force generated by the myofilaments. The recent discovery of multiple novel molecular components, however, has shed light on an emerging role for the Z-disc in signal transduction in both cardiac and skeletal muscles. Strikingly, mutations in several Z-disc proteins have been shown to cause cardiomyopathies and/or muscular dystrophies. In addition, the elusive cardiac stretch receptor appears to localize to the Z-disc. Various signalling molecules have been shown to interact with Z-disc proteins, several of which shuttle between the Z-disc and other cellular compartments such as the nucleus, underlining the dynamic nature of Z-disc-dependent signalling. In this review, we provide a systematic view on the currently known Z-disc components and the functional significance of the Z-disc as an interface between biomechanical sensing and signalling in cardiac and skeletal muscle functions and diseases.
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Affiliation(s)
- Derk Frank
- Department of Internal Medicine III, University of Heidelberg, Im Neuenheimer Feld 410, 69120, Heidelberg, Germany
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274
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Abstract
Mechanotransduction refers to the cellular mechanisms by which load-bearing cells sense physical forces, transduce the forces into biochemical signals, and generate appropriate responses leading to alterations in cellular structure and function. This process affects the beat-to-beat regulation of cardiac performance but also affects the proliferation, differentiation, growth, and survival of the cellular components that comprise the human myocardium. This review focuses on the experimental evidence indicating that the costamere and its structurally related structure the focal adhesion complex are critical cytoskeletal elements involved in cardiomyocyte mechanotransduction. Biochemical signals originating from the extracellular matrix-integrin-costameric protein complex share many common features with those signals generated by growth factor receptors. The roles of key regulatory kinases and other muscle-specific proteins involved in mechanotransduction and growth factor signaling are discussed, and issues requiring further study in this field are outlined.
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Affiliation(s)
- Allen M Samarel
- Cardiovascular Institute, Loyola Univ. Medical Center, Bldg. 110, Rm. 5222, 2160 South First Ave., Maywood, IL 60153, USA.
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275
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McGrath MJ, Cottle DL, Nguyen MA, Dyson JM, Coghill ID, Robinson PA, Holdsworth M, Cowling BS, Hardeman EC, Mitchell CA, Brown S. Four and a half LIM protein 1 binds myosin-binding protein C and regulates myosin filament formation and sarcomere assembly. J Biol Chem 2006; 281:7666-83. [PMID: 16407297 DOI: 10.1074/jbc.m512552200] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Four and a half LIM protein 1 (FHL1/SLIM1) is highly expressed in skeletal and cardiac muscle; however, the function of FHL1 remains unknown. Yeast two-hybrid screening identified slow type skeletal myosin-binding protein C as an FHL1 binding partner. Myosin-binding protein C is the major myosin-associated protein in striated muscle that enhances the lateral association and stabilization of myosin thick filaments and regulates actomyosin interactions. The interaction between FHL1 and myosin-binding protein C was confirmed using co-immunoprecipitation of recombinant and endogenous proteins. Recombinant FHL2 and FHL3 also bound myosin-binding protein C. FHL1 impaired co-sedimentation of myosin-binding protein C with reconstituted myosin filaments, suggesting FHL1 may compete with myosin for binding to myosin-binding protein C. In intact skeletal muscle and isolated myofibrils, FHL1 localized to the I-band, M-line, and sarcolemma, co-localizing with myosin-binding protein C at the sarcolemma in intact skeletal muscle. Furthermore, in isolated myofibrils FHL1 staining at the M-line appeared to extend partially into the C-zone of the A-band, where it co-localized with myosin-binding protein C. Overexpression of FHL1 in differentiating C2C12 cells induced "sac-like" myotube formation (myosac), associated with impaired Z-line and myosin thick filament assembly. This phenotype was rescued by co-expression of myosin-binding protein C. FHL1 knockdown using RNAi resulted in impaired myosin thick filament formation associated with reduced incorporation of myosin-binding protein C into the sarcomere. This study identified FHL1 as a novel regulator of myosin-binding protein C activity and indicates a role for FHL1 in sarcomere assembly.
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Affiliation(s)
- Meagan J McGrath
- Department of Biochemistry and Molecular Biology, Monash University, Wellington Road, Clayton, Victoria 3800, Australia
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276
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Rönty M, Taivainen A, Moza M, Kruh GD, Ehler E, Carpen O. Involvement of palladin and alpha-actinin in targeting of the Abl/Arg kinase adaptor ArgBP2 to the actin cytoskeleton. Exp Cell Res 2005; 310:88-98. [PMID: 16125169 DOI: 10.1016/j.yexcr.2005.06.026] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2005] [Revised: 06/28/2005] [Accepted: 06/30/2005] [Indexed: 11/20/2022]
Abstract
Palladin and alpha-actinin are major components of stress fiber dense bodies, cardiomyocyte Z-discs and neuronal synapses. They function as structural molecules and cytoskeletal regulators but also as docking sites to other proteins. Both antisense and transient overexpression experiments have shown that palladin plays an important role in the regulation of actin cytoskeleton. ArgBP2 is a multi-domain scaffolding protein which shares both the tissue distribution and subcellular localization with palladin. ArgBP2 is directly linked to intracellular signaling cascades by its interaction with Abl family kinases, Pyk2 and the ubiquitin ligase Cbl. It has several actin associated binding partners and has been shown to regulate cytoskeletal dynamics. Here, we show by in vivo and in vitro methods that palladin's amino-terminal poly-proline sequences directly interact with the first carboxy-terminal SH3 domain of ArgBP2. We further demonstrate a direct interaction between alpha-actinin and the amino-terminal segment of ArgBP2. Immunoprecipitation and targeting assays suggest that a three-way complex of the proteins occurs in vivo. The interactions provide an explanation to the previously observed Z-disc-specific localization of ArgBP2 and indicate interplay between signaling adaptors and structural proteins of the Z-disc.
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Affiliation(s)
- Mikko Rönty
- Biomedicum Helsinki, Department of Pathology and Neuroscience Program, University of Helsinki and Helsinki University Central Hospital, Helsinki, Finland.
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277
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Combs A, Ervasti J. Enhanced laminin binding by alpha-dystroglycan after enzymatic deglycosylation. Biochem J 2005; 390:303-9. [PMID: 15865602 PMCID: PMC1184583 DOI: 10.1042/bj20050375] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Carbohydrate modifications are clearly important to the function of alpha-dystroglycan but their composition and structure remain poorly understood. In the present study, we describe experiments aimed at identifying the alpha-dystroglycan oligosaccharides important for its binding to laminin-1 and carbohydrate-dependent mAbs (monoclonal antibodies) IIH6 and VIA4(1). We digested highly purified skeletal muscle alpha-dystroglycan with an array of linkage-specific endo- and exoglycosidases, which were verified for action on alpha-dystroglycan by loss/gain of reactivity for lectins with defined glyco-epitopes. Notably, digestion with a combination of Arthrobacter ureafaciens sialidase, beta(1-4)galactosidase and beta-N-acetylglucosaminidase substantially degraded SiaAalpha2-3Galbeta1-4GlcNAcbeta1-2Man glycans on highly purified alpha-dystroglycan that nonetheless exhibited enhanced IIH6, VIA4(1) and laminin-1 binding activity. Additional results indicate that alpha-dystroglycan is probably modified with other anionic sugars besides sialic acid and suggest that rare alpha-linked GlcNAc moieties may block its complete deglycosylation with currently available enzymes.
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Affiliation(s)
- Ariana C. Combs
- Department of Physiology, Madison Medical School, University of Wisconsin, 127 Service Memorial Institute, 1300 University Avenue, Madison, WI 53706, U.S.A
| | - James M. Ervasti
- Department of Physiology, Madison Medical School, University of Wisconsin, 127 Service Memorial Institute, 1300 University Avenue, Madison, WI 53706, U.S.A
- To whom correspondence should be addressed (email )
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278
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Schindeler A, Lavulo L, Harvey RP. Muscle costameric protein, Chisel/Smpx, associates with focal adhesion complexes and modulates cell spreading in vitro via a Rac1/p38 pathway. Exp Cell Res 2005; 307:367-80. [PMID: 15893749 DOI: 10.1016/j.yexcr.2005.04.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2005] [Revised: 04/07/2005] [Accepted: 04/09/2005] [Indexed: 10/25/2022]
Abstract
The murine X-linked gene Chisel (Csl/Smpx) encodes a 9-kDa protein that associates in heart and skeletal muscle cells with the costameric cytoskeleton, implicated in maintaining muscle integrity and responses to biomechanical stress. After expression in C2C12 myoblasts, MYC epitope-tagged Csl co-localized with actin networks at peripheral membranes, and with focal adhesion proteins vinculin, paxillin, integrin beta1, and the small GTPase Rac1. Csl could be co-immunoprecipitated with vinculin from extracts of C2C12 cells and native muscle. MYC-Csl induced cell spreading and lamellipodia formation in C2C12 cells at the expense of filopodia, suggestive of modulation of Rac1 activity. Lamellipodia formation was indeed Rac1-dependent, and in MYC-Csl cells replated on fibronectin, Rac1 activity was increased relative to controls. Expression of MYC-Csl led to an increased association between vinculin and p34, a subunit of the Arp2/3 actin nucleation complex, a Rac1-dependent event. Induced cell spreading was also dependent upon p38 kinases that act downstream of Rac1 to control the actin capping activity of heat shock protein 27. Our data suggest that Csl localizes to the costameric cytoskeleton of muscle cells through an association with focal adhesion proteins, where it may participate in regulation of cytoskeletal dynamics through the Rac1-p38 pathway.
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Affiliation(s)
- Aaron Schindeler
- Developmental Biology Program, Victor Chang Cardiac Research Institute, 384 Victoria Street, Darlinghurst NSW 2010, Australia
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279
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Defranchi E, Bonaccurso E, Tedesco M, Canato M, Pavan E, Raiteri R, Reggiani C. Imaging and elasticity measurements of the sarcolemma of fully differentiated skeletal muscle fibres. Microsc Res Tech 2005; 67:27-35. [PMID: 16025488 DOI: 10.1002/jemt.20177] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
This study aimed to describe the three-dimensional structure and the elastic properties of the sarcolemma of adult, fully differentiated, skeletal muscle fibres combining Atomic Force Microscopy (AFM) and optical microscopy. Single fibres were enzymatically dissociated from Flexor Digitorum Brevis of adult mice and were maintained in culture up to 3 weeks. On the sixth day after dissociation, the upper surface of intact fibres, either alive in solution or fixed and kept in solution or fixed and exposed in air, was analysed with AFM. The most prominent features in AFM images were periodic transversal foldings with an interval that corresponded to the sarcomere length. More detailed analysis of the topography profile showed that the depth in the folding decreased with increasing sarcomere length and that the crests of the foldings corresponded to the Z-lines. Minor periodic structures could be detected in the valleys between the major foldings. AFM images also showed deep depressions on the sarcolemma likely corresponding to openings of T tubules and caveolae. Two-dimensional elasticity maps were obtained using AFM as an indenter and showed that the crests of the transversal foldings correspond to higher stiffness regions. This study provides the first complete three-dimensional topography and mechanical characterization of intact, living skeletal muscle fibres and might form the basis for further investigations aimed to compare healthy and dystrophic muscles.
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Affiliation(s)
- Enrico Defranchi
- Department of Biophysical and Electronic Engineering, University of Genova, 16145 Genova, Italy
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280
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Wang J, Shaner N, Mittal B, Zhou Q, Chen J, Sanger JM, Sanger JW. Dynamics of Z-band based proteins in developing skeletal muscle cells. ACTA ACUST UNITED AC 2005; 61:34-48. [PMID: 15810059 PMCID: PMC1993831 DOI: 10.1002/cm.20063] [Citation(s) in RCA: 125] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
During myofibril formation, Z-bodies, small complexes of alpha-actinin and associated proteins, grow in size, fuse and align to produce Z-bands. To determine if there were changes in protein dynamics during the assembly process, Fluorescence Recovery after Photobleaching was used to measure the exchange of Z-body and Z-band proteins with cytoplasmic pools in cultures of quail myotubes. Myotubes were transfected with plasmids encoding Yellow, Green, or Cyan Fluorescent Protein linked to the Z-band proteins: actin, alpha-actinin, cypher, FATZ, myotilin, and telethonin. Each Z-band protein showed a characteristic recovery rate and mobility. All except telethonin were localized in both Z-bodies and Z-bands. Proteins that were present both early in development in Z-bodies and later in Z-bands had faster exchange rates in Z-bodies. These results suggest that during myofibrillogenesis, molecular interactions develop between the Z-band proteins that decrease their mobility and increase the stability of the Z-bands. A truncated construct of alpha-actinin, which localized in Z-bands in myotubes and exhibited a very low rate of exchange, led to disruption of myofibrils, suggesting the importance of dynamic, intact alpha-actinin molecules for the formation and maintenance of Z-bands. Our experiments reveal the Z-band to be a much more dynamic structure than its appearance in electron micrographs of cross-striated muscle cells might suggest.
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Affiliation(s)
- Jushuo Wang
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6058
| | - Nathan Shaner
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6058
| | - Balraj Mittal
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6058
| | - Qiang Zhou
- Department of Medicine, Institute of Molecular Medicine, University of California, San Diego, La Jolla, CA 92093
| | - Ju Chen
- Department of Medicine, Institute of Molecular Medicine, University of California, San Diego, La Jolla, CA 92093
| | - Jean M. Sanger
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6058
| | - Joseph W. Sanger
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6058
- +Corresponding Author: Dr. J. W. Sanger, Dept. Cell & Develop. Biol., Univ. Penn. Sch. Med., 421 Curie Blvd., BRB II/III, Phila., PA 19104-6058, Tel:215-898-6919, FAX:215-898-9871,
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281
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Chen H, Cohen DM, Choudhury DM, Kioka N, Craig SW. Spatial distribution and functional significance of activated vinculin in living cells. ACTA ACUST UNITED AC 2005; 169:459-70. [PMID: 15883197 PMCID: PMC2171941 DOI: 10.1083/jcb.200410100] [Citation(s) in RCA: 137] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Conformational change is believed to be important to vinculin's function at sites of cell adhesion. However, nothing is known about vinculin's conformation in living cells. Using a Forster resonance energy transfer probe that reports on changes in vinculin's conformation, we find that vinculin is in the actin-binding conformation in a peripheral band of adhesive puncta in spreading cells. However, in fully spread cells with established polarity, vinculin's conformation is variable at focal adhesions. Time-lapse imaging reveals a gradient of conformational change that precedes loss of vinculin from focal adhesions in retracting regions. At stable or protruding regions, recruitment of vinculin is not necessarily coupled to the actin-binding conformation. However, a different measure of vinculin conformation, the recruitment of vinexin beta by activated vinculin, shows that autoinhibition of endogenous vinculin is relaxed at focal adhesions. Beyond providing direct evidence that vinculin is activated at focal adhesions, this study shows that the specific functional conformation correlates with regional cellular dynamics.
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Affiliation(s)
- Hui Chen
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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282
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Abonia JP, Friend DS, Austen WG, Moore FD, Carroll MC, Chan R, Afnan J, Humbles A, Gerard C, Knight P, Kanaoka Y, Yasuda S, Morokawa N, Austen KF, Stevens RL, Gurish MF. Mast cell protease 5 mediates ischemia-reperfusion injury of mouse skeletal muscle. THE JOURNAL OF IMMUNOLOGY 2005; 174:7285-91. [PMID: 15905575 PMCID: PMC2951006 DOI: 10.4049/jimmunol.174.11.7285] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Ischemia with subsequent reperfusion (IR) injury is a significant clinical problem that occurs after physical and surgical trauma, myocardial infarction, and organ transplantation. IR injury of mouse skeletal muscle depends on the presence of both natural IgM and an intact C pathway. Disruption of the skeletal muscle architecture and permeability also requires mast cell (MC) participation, as revealed by the fact that IR injury is markedly reduced in c-kit defective, MC-deficient mouse strains. In this study, we sought to identify the pathobiologic MC products expressed in IR injury using transgenic mouse strains with normal MC development, except for the lack of a particular MC-derived mediator. Histologic analysis of skeletal muscle from BALB/c and C57BL/6 mice revealed a strong positive correlation (R(2) = 0.85) between the extent of IR injury and the level of MC degranulation. Linkage between C activation and MC degranulation was demonstrated in mice lacking C4, in which only limited MC degranulation and muscle injury were apparent. No reduction in injury was observed in transgenic mice lacking leukotriene C(4) synthase, hemopoietic PGD(2) synthase, N-deacetylase/N-sulfotransferase-2 (enzyme involved in heparin biosynthesis), or mouse MC protease (mMCP) 1. In contrast, muscle injury was significantly attenuated in mMCP-5-null mice. The MCs that reside in skeletal muscle contain abundant amounts of mMCP-5 which is the serine protease that is most similar in sequence to human MC chymase. We now report a cytotoxic activity associated with a MC-specific protease and demonstrate that mMCP-5 is critical for irreversible IR injury of skeletal muscle.
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Affiliation(s)
- J. Pablo Abonia
- Department of Medicine, Brigham and Women's Hospital, and Harvard Medical School, Boston, MA 02115
| | - Daniel S. Friend
- Department of Pathology, Brigham and Women's Hospital, and Harvard Medical School, Boston, MA 02115
| | - William G. Austen
- Department of Surgery, Massachusetts General Hospital, and Harvard Medical School, Boston, MA 02129
| | - Francis D. Moore
- Department of Surgery, Brigham and Women's Hospital, and Harvard Medical School, Boston, MA 02115
| | - Michael C. Carroll
- Department of Pediatrics, CBR Institute for Biomedical Research, and Harvard Medical School, Boston, MA, 02115
| | - Rodney Chan
- Department of Surgery, Brigham and Women's Hospital, and Harvard Medical School, Boston, MA 02115
| | - Jalil Afnan
- Department of Surgery, Brigham and Women's Hospital, and Harvard Medical School, Boston, MA 02115
| | - Alison Humbles
- Department of Pediatrics, Beth Israel Hospital, Children's Hospital, and Harvard Medical School, Boston, MA, 02115
| | - Craig Gerard
- Department of Pediatrics, Beth Israel Hospital, Children's Hospital, and Harvard Medical School, Boston, MA, 02115
| | - Pamela Knight
- Department of Veterinary Clinical Studies, Royal School of Veterinary Studies, University of Edinburgh, Easter Bush, United Kingdom
| | - Yoshihide Kanaoka
- Department of Medicine, Brigham and Women's Hospital, and Harvard Medical School, Boston, MA 02115
| | - Shinsuke Yasuda
- Department of Medicine, Brigham and Women's Hospital, and Harvard Medical School, Boston, MA 02115
| | - Nasa Morokawa
- Department of Medicine, Brigham and Women's Hospital, and Harvard Medical School, Boston, MA 02115
| | - K. Frank Austen
- Department of Medicine, Brigham and Women's Hospital, and Harvard Medical School, Boston, MA 02115
| | - Richard L. Stevens
- Department of Medicine, Brigham and Women's Hospital, and Harvard Medical School, Boston, MA 02115
| | - Michael F. Gurish
- Department of Medicine, Brigham and Women's Hospital, and Harvard Medical School, Boston, MA 02115
- Address correspondence and reprint requests to Dr. Michael F. Gurish, Brigham and Women's Hospital, Smith Building, Room 624, 1 Jimmy Fund Way, Boston, MA 02115.
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283
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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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284
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Chopard A, Arrighi N, Carnino A, Marini JF. Changes in dysferlin, proteins from dystrophin glycoprotein complex, costameres, and cytoskeleton in human soleus and vastus lateralis muscles after a long-term bedrest with or without exercise. FASEB J 2005; 19:1722-4. [PMID: 16046473 DOI: 10.1096/fj.04-3336fje] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
This study was designed to evaluate the effects of hypokinesia and hypodynamia on cytoskeletal and related protein contents in human skeletal muscles. Twelve proteins: dystrophin and its associated proteins (DGC), dysferlin, talin, vinculin and meta-vinculin, alpha-actinin, desmin, actin, and myosin, were quantitatively analyzed during an 84-day long-term bedrest (LTBR). The preventive or compensatory effects of maximal resistance exercise (MRE) as a countermeasure were evaluated. Most of these proteins are involved in several myopathies, and they play an important role in muscle structure, fiber cohesion, cell integrity maintenance, and force transmission. This is the first comparison of the cytoskeletal protein contents between slow postural soleus (SOL) and mixed poly-functional vastus lateralis (VL) human muscles. Protein contents were higher in VL than in SOL (from 12 to 94%). These differences could be mainly explained by the differential mechanical constraints imposed on the muscles, i.e., cytoskeletal protein contents increase with mechanical constraints. After LTBR, proteins belonging to the DGC, dysferlin, and proteins of the costamere exhibited large increases, higher in SOL (from 67 to 216%) than in VL (from 32 to 142%). Plasma membrane remodeling during muscle atrophy is probably one of the key points for interpreting these modifications, and mechanisms other than those involved in the resistance of the cytoskeleton to mechanical constraints may be implicated (membrane repair). MRE compensates the cytoskeletal changes induced by LTBR in SOL, except for gamma-sarcoglycan (+70%) and dysferlin (+108%). The exercise only partly compensated the DGC changes induced in VL, and, as for SOL, dysferlin remained largely increased (+132%). Moreover, vinculin and metavinculin, which exhibited no significant change in VL after LTBR, were increased with MRE during LTBR, reinforcing the pre-LTBR differences between SOL and VL. This knowledge will contribute to the development of efficient space flight countermeasures and rehabilitation methods in clinical situations where musculoskeletal unloading is a component.
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Affiliation(s)
- A Chopard
- Laboratoire de Physiologie des Systèmes Intégrés, CNRS UMR 6548, Nice, France.
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285
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Turk R, Sterrenburg E, de Meijer EJ, van Ommen GJB, den Dunnen JT, 't Hoen PAC. Muscle regeneration in dystrophin-deficient mdx mice studied by gene expression profiling. BMC Genomics 2005; 6:98. [PMID: 16011810 PMCID: PMC1190170 DOI: 10.1186/1471-2164-6-98] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2005] [Accepted: 07/13/2005] [Indexed: 01/19/2023] Open
Abstract
Background Duchenne muscular dystrophy (DMD), caused by mutations in the dystrophin gene, is lethal. In contrast, dystrophin-deficient mdx mice recover due to effective regeneration of affected muscle tissue. To characterize the molecular processes associated with regeneration, we compared gene expression levels in hindlimb muscle tissue of mdx and control mice at 9 timepoints, ranging from 1–20 weeks of age. Results Out of 7776 genes, 1735 were differentially expressed between mdx and control muscle at at least one timepoint (p < 0.05 after Bonferroni correction). We found that genes coding for components of the dystrophin-associated glycoprotein complex are generally downregulated in the mdx mouse. Based on functional characteristics such as membrane localization, signal transduction, and transcriptional activation, 166 differentially expressed genes with possible functions in regeneration were analyzed in more detail. The majority of these genes peak at the age of 8 weeks, where the regeneration activity is maximal. The following pathways are activated, as shown by upregulation of multiple members per signalling pathway: the Notch-Delta pathway that plays a role in the activation of satellite cells, and the Bmp15 and Neuregulin 3 signalling pathways that may regulate proliferation and differentiation of satellite cells. In DMD patients, only few of the identified regeneration-associated genes were found activated, indicating less efficient regeneration processes in humans. Conclusion Based on the observed expression profiles, we describe a model for muscle regeneration in mdx mice, which may provide new leads for development of DMD therapies based on the improvement of muscle regeneration efficacy.
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Affiliation(s)
- R Turk
- Center for Human and Clinical Genetics, Leiden University Medical Center, Wassenaarseweg 72, 2333 AL Leiden, Nederland
- Department of Physiology and Biophysics, Howard Hughes Medical Institute, University of Iowa, 400 Eckstein Medical Research Building, Iowa City, IA52240-1101, U.S.A
| | - E Sterrenburg
- Center for Human and Clinical Genetics, Leiden University Medical Center, Wassenaarseweg 72, 2333 AL Leiden, Nederland
| | - EJ de Meijer
- Center for Human and Clinical Genetics, Leiden University Medical Center, Wassenaarseweg 72, 2333 AL Leiden, Nederland
| | - G-JB van Ommen
- Center for Human and Clinical Genetics, Leiden University Medical Center, Wassenaarseweg 72, 2333 AL Leiden, Nederland
| | - JT den Dunnen
- Center for Human and Clinical Genetics, Leiden University Medical Center, Wassenaarseweg 72, 2333 AL Leiden, Nederland
- Leiden Genome Technology Center, Leiden University Medical Center, Wassenaarseweg 72, 2333 AL Leiden, Nederland
| | - PAC 't Hoen
- Center for Human and Clinical Genetics, Leiden University Medical Center, Wassenaarseweg 72, 2333 AL Leiden, Nederland
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286
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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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287
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Mermelstein CS, Amaral LM, Rebello MIL, Reis JSN, Borojevic R, Costa ML. Changes in cell shape and desmin intermediate filament distribution are associated with down-regulation of desmin expression in C2C12 myoblasts grown in the absence of extracellular Ca2+. Braz J Med Biol Res 2005; 38:1025-32. [PMID: 16007273 DOI: 10.1590/s0100-879x2005000700005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Desmin is the main intermediate filament (IF) protein of muscle cells. In skeletal muscle, desmin IFs form a scaffold that interconnects the entire contractile apparatus with the subsarcolemmal cytoskeleton and cytoplasmic organelles. The interaction between desmin and the sarcolemma is mediated by a number of membrane proteins, many of which are Ca2+-sensitive. In the present study, we analyzed the effects of the Ca2+ chelator EGTA (1.75 mM) on the expression and distribution of desmin in C2C12 myoblasts grown in culture. We used indirect immunofluorescence microscopy and reverse transcription polymerase chain reaction (RT-PCR) to analyze desmin distribution and expression in C2C12 cells grown in the presence or absence of EGTA. Control C2C12 myoblasts showed a well-spread morphology after a few hours in culture and became bipolar when grown for 24 h in the presence of EGTA. Control C2C12 cells showed a dense network of desmin from the perinuclear region to the cell periphery, whereas EGTA-treated cells showed desmin aggregates in the cytoplasm. RT-PCR analysis revealed a down-regulation of desmin expression in EGTA-treated C2C12 cells compared to untreated cells. The present results suggest that extracellular Ca2+ availability plays a role in the regulation of desmin expression and in the spatial distribution of desmin IFs in myoblasts, and is involved in the generation and maintenance of myoblast cell shape.
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Affiliation(s)
- C S Mermelstein
- Departamento de Histologia e Embriologia, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, RJ, Brasil.
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288
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Vassilopoulos S, Thevenon D, Rezgui SS, Brocard J, Chapel A, Lacampagne A, Lunardi J, De Waard M, Marty I. Triadins are not triad-specific proteins: two new skeletal muscle triadins possibly involved in the architecture of sarcoplasmic reticulum. J Biol Chem 2005; 280:28601-9. [PMID: 15927957 PMCID: PMC2739232 DOI: 10.1074/jbc.m501484200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
We have cloned two new triadin isoforms from rat skeletal muscle, Trisk 49 and Trisk 32, which were named according to their theoretical molecular masses (49 and 32 kDa, respectively). Specific antibodies directed against each protein were produced to characterize both new triadins. Both are expressed in adult rat skeletal muscle, and their expression in slow twitch muscle is lower than that in fast twitch muscle. Using double immunofluorescent labeling, the localization of these two triadins was studied in comparison to well-characterized proteins such as ryanodine receptor, calsequestrin, desmin, Ca(2+)-ATPase, and titin. None of these two triadins are localized within the rat skeletal muscle triad. Both are instead found in different parts of the longitudinal sarcoplasmic reticulum. We attempted to identify partners for each isoform: neither is associated with ryanodine receptor; Trisk 49 could be associated with titin or another sarcomeric protein; and Trisk 32 could be associated with IP(3) receptor. These results open further fields of research concerning the functions of these two proteins; in particular, they could be involved in the set up and maintenance of a precise sarcoplasmic reticulum structure.
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Affiliation(s)
- Stéphane Vassilopoulos
- Canaux calciques , fonctions et pathologies
INSERM : U607CEA : DSV/IRTSVUniversité Joseph Fourier - Grenoble I17, rue des martyrs 38054 Grenoble,FR
| | - Dominique Thevenon
- Canaux calciques , fonctions et pathologies
INSERM : U607CEA : DSV/IRTSVUniversité Joseph Fourier - Grenoble I17, rue des martyrs 38054 Grenoble,FR
| | - Sophia Smida Rezgui
- Canaux calciques , fonctions et pathologies
INSERM : U607CEA : DSV/IRTSVUniversité Joseph Fourier - Grenoble I17, rue des martyrs 38054 Grenoble,FR
| | - Julie Brocard
- Canaux calciques , fonctions et pathologies
INSERM : U607CEA : DSV/IRTSVUniversité Joseph Fourier - Grenoble I17, rue des martyrs 38054 Grenoble,FR
| | - Agnès Chapel
- DRDC, Département réponse et dynamique cellulaire
INSERM : IFR27CNRS : IFR27INRACEAbat. C3 17 Rue des martyrs 38054 GRENOBLE CEDEX 9,FR
| | - Alain Lacampagne
- Physiopathologie cardiovasculaire
INSERM : U637IFR3Université Montpellier IHopital Arnaud de Villeneuve 171, Avenue du Doyen Gaston Giraud 34295 MONTPELLIER CEDEX 5,FR
- CHU Arnaud de Villeneuve
CHRU MontpellierMontpellier F-3400,,FR
| | - Joël Lunardi
- Canaux calciques , fonctions et pathologies
INSERM : U607CEA : DSV/IRTSVUniversité Joseph Fourier - Grenoble I17, rue des martyrs 38054 Grenoble,FR
| | - Michel De Waard
- Canaux calciques , fonctions et pathologies
INSERM : U607CEA : DSV/IRTSVUniversité Joseph Fourier - Grenoble I17, rue des martyrs 38054 Grenoble,FR
| | - Isabelle Marty
- Canaux calciques , fonctions et pathologies
INSERM : U607CEA : DSV/IRTSVUniversité Joseph Fourier - Grenoble I17, rue des martyrs 38054 Grenoble,FR
- * Correspondence should be adressed to: Isabelle Marty
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289
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Abstract
Muscle injuries are one of the most common traumas occurring in sports. Despite their clinical importance, few clinical studies exist on the treatment of these traumas. Thus, the current treatment principles of muscle injuries have either been derived from experimental studies or been tested only empirically. Although nonoperative treatment results in good functional outcomes in the majority of athletes with muscle injuries, the consequences of failed treatment can be very dramatic, possibly postponing an athlete's return to sports for weeks or even months. Moreover, the recognition of some basic principles of skeletal muscle regeneration and healing processes can considerably help in both avoiding the imminent dangers and accelerating the return to competition. Accordingly, in this review, the authors have summarized the prevailing understanding on the biology of muscle regeneration. Furthermore, they have reviewed the existing data on the different treatment modalities (such as medication, therapeutic ultrasound, physical therapy) thought to influence the healing of injured skeletal muscle. In the end, they extend these findings to clinical practice in an attempt to propose an evidence-based approach for the diagnosis and optimal treatment of skeletal muscle injuries.
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Affiliation(s)
- Tero A H Järvinen
- Department of Orthopaedics, Tampere University Hospital and University of Tampere, PO Box 2000, FIN-33521 Tampere, Finland
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290
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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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291
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Abstract
Cell-extracellular matrix (ECM) adhesion is crucial for control of cell behavior. It connects the ECM to the intracellular cytoskeleton and transduces bidirectional signals between the extracellular and intracellular compartments. The subcellular machinery that mediates cell-ECM adhesion and signaling is complex. It consists of transmembrane proteins (e.g., integrins) and at least several dozens of membrane-proximal proteins that assemble into a network through multiple protein interactions. Furthermore, despite sharing certain common components, cell-ECM adhesions exhibit considerable heterogeneity in different types of cells (e.g., the cell-ECM adhesions in cardiac myocytes are considerably different from those in fibroblasts). Here, we will first briefly describe the general properties of the integrin-mediated cell-ECM adhesion and signal transduction. Next, we will focus on one of the recently discovered cell-ECM adhesion protein complexes consisting of PINCH, integrin-linked kinase (ILK), and Parvin and use it as an example to illustrate the molecular basis underlying the assembly and functions of cell-ECM adhesions. Finally, we will discuss in detail the structure and regulation of cell-ECM adhesion complexes in cardiac myocytes, which illustrate the importance and complexity of the cell-ECM adhesion structures in organogenesis and diseases.
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Affiliation(s)
- Jorge L Sepulveda
- Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA
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292
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Abstract
In this review, we draw attention to the multiple mechanisms responsible for the pathogenesis of cardiomyopathies in patients with muscular dystrophies. More than one single mechanism is likely to be involved in the development of skeletal and cardiac muscle pathology even when there is a single protein defect. The best example is dystrophin deficiency, in which increased sarcolemmal permeability following eccentric exercise, reduced force generation, and abnormal signaling are all likely to contribute to the progressive muscle damage observed. In other conditions, such as the sarcoglycanopathies, a protein deficiency both in the striated cardiomyocte and the vascular smooth muscle appears to play a significant role. An entirely different mechanism of disease is likely in defects of nuclear envelope proteins, although the precise pathogenesis of this group of conditions is still not clear. Differences between the organization of skeletal and cardiac muscle protein complex are also only starting to emerge and will very likely be the focus of future research.
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Affiliation(s)
- Fiona C Goodwin
- Dubowitz Neuromuscular Centre, Imperial College London, Hammersmith Hospital Campus, UK
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293
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Green KJ, Böhringer M, Gocken T, Jones JCR. Intermediate filament associated proteins. ADVANCES IN PROTEIN CHEMISTRY 2005; 70:143-202. [PMID: 15837516 DOI: 10.1016/s0065-3233(05)70006-1] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Intermediate filament associated proteins (IFAPs) coordinate interactions between intermediate filaments (IFs) and other cytoskeletal elements and organelles, including membrane-associated junctions such as desmosomes and hemidesmosomes in epithelial cells, costameres in striated muscle, and intercalated discs in cardiac muscle. IFAPs thus serve as critical connecting links in the IF scaffolding that organizes the cytoplasm and confers mechanical stability to cells and tissues. However, in recent years it has become apparent that IFAPs are not limited to structural crosslinkers and bundlers but also include chaperones, enzymes, adapters, and receptors. IF networks can therefore be considered scaffolding upon which associated proteins are organized and regulated to control metabolic activities and maintain cell homeostasis.
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Affiliation(s)
- Kathleen J Green
- Departments of Pathology and Dermatology and R.H. Lurie Cancer Center, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA
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294
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Abstract
Skeletal muscle tissue is made up of highly organized multinuclear cells. The internal organization of the muscle cell is dictated by the necessary regular arrangement of repeated units within the protein myofibrils that mediate muscle contraction. Skeletal muscle cells have the usual membrane traffic pathways for partitioning newly synthesized proteins, internalizing cell surface receptors for hormones and nutrients, and mediating membrane repair. However, in muscle, these pathways must be further specialized to deal with targeting to and organizing muscle-specific membrane structures, satisfying the unique metabolic requirements of muscle and meeting the high demand for membrane repair in a tissue that is constantly under mechanical stress. Specialized membrane traffic pathways in muscle also play a role in the formation of muscle through fusion of myoblast membranes and the development of internal muscle-specific membrane structures during myogenesis and regeneration. It has recently become apparent that muscle-specific isoforms of proteins that are known to mediate ubiquitous membrane traffic pathways, as well as novel muscle-specific proteins, are involved in tissue-specific aspects of muscle membrane traffic. Here we describe the specialized membrane structures of skeletal muscle, how these are developed, maintained and repaired by specialized and generic membrane traffic pathways, and how defects in these pathways result in muscle disease.
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Affiliation(s)
- Mhairi C Towler
- Department of Microbiology and Immunology, University of California, San Francisco, CA, USA
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295
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Costa ML, Escaleira R, Cataldo A, Oliveira F, Mermelstein CS. Desmin: molecular interactions and putative functions of the muscle intermediate filament protein. Braz J Med Biol Res 2004; 37:1819-30. [PMID: 15558188 DOI: 10.1590/s0100-879x2004001200007] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Desmin is the intermediate filament (IF) protein occurring exclusively in muscle and endothelial cells. There are other IF proteins in muscle such as nestin, peripherin, and vimentin, besides the ubiquitous lamins, but they are not unique to muscle. Desmin was purified in 1977, the desmin gene was characterized in 1989, and knock-out animals were generated in 1996. Several isoforms have been described. Desmin IFs are present throughout smooth, cardiac and skeletal muscle cells, but can be more concentrated in some particular structures, such as dense bodies, around the nuclei, around the Z-line or in costameres. Desmin is up-regulated in muscle-derived cellular adaptations, including conductive fibers in the heart, electric organs, some myopathies, and experimental treatments with drugs that induce muscle degeneration, like phorbol esters. Many molecules have been reported to associate with desmin, such as other IF proteins (including members of the membrane dystroglycan complex), nebulin, the actin and tubulin binding protein plectin, the molecular motor dynein, the gene regulatory protein MyoD, DNA, the chaperone alphaB-crystallin, and proteases such as calpain and caspase. Desmin has an important medical role, since it is used as a marker of tumors' origin. More recently, several myopathies have been described, with accumulation of desmin deposits. Yet, after almost 30 years since its identification, the function of desmin is still unclear. Suggested functions include myofibrillogenesis, mechanical support for the muscle, mitochondrial localization, gene expression regulation, and intracellular signaling. This review focuses on the biochemical interactions of desmin, with a discussion of its putative functions.
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Affiliation(s)
- M L Costa
- Laboratório de Diferenciação Muscular e Citoesqueleto, Departamento de Histologia e Embriologia, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
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296
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Kee AJ, Schevzov G, Nair-Shalliker V, Robinson CS, Vrhovski B, Ghoddusi M, Qiu MR, Lin JJC, Weinberger R, Gunning PW, Hardeman EC. Sorting of a nonmuscle tropomyosin to a novel cytoskeletal compartment in skeletal muscle results in muscular dystrophy. ACTA ACUST UNITED AC 2004; 166:685-96. [PMID: 15337777 PMCID: PMC2172434 DOI: 10.1083/jcb.200406181] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Tropomyosin (Tm) is a key component of the actin cytoskeleton and >40 isoforms have been described in mammals. In addition to the isoforms in the sarcomere, we now report the existence of two nonsarcomeric (NS) isoforms in skeletal muscle. These isoforms are excluded from the thin filament of the sarcomere and are localized to a novel Z-line adjacent structure. Immunostained cross sections indicate that one Tm defines a Z-line adjacent structure common to all myofibers, whereas the second Tm defines a spatially distinct structure unique to muscles that undergo chronic or repetitive contractions. When a Tm (Tm3) that is normally absent from muscle was expressed in mice it became associated with the Z-line adjacent structure. These mice display a muscular dystrophy and ragged-red fiber phenotype, suggestive of disruption of the membrane-associated cytoskeletal network. Our findings raise the possibility that mutations in these tropomyosin and these structures may underpin these types of myopathies.
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MESH Headings
- Animals
- Cell Compartmentation/genetics
- Cell Membrane/metabolism
- Cell Membrane/pathology
- Cell Membrane/ultrastructure
- Cytoskeleton/metabolism
- Cytoskeleton/pathology
- Cytoskeleton/ultrastructure
- Disease Models, Animal
- Female
- Mice
- Mice, Transgenic
- Muscle Fibers, Skeletal/metabolism
- Muscle Fibers, Skeletal/pathology
- Muscle Fibers, Skeletal/ultrastructure
- Muscle, Skeletal/metabolism
- Muscle, Skeletal/pathology
- Muscle, Skeletal/ultrastructure
- Muscular Dystrophy, Animal/etiology
- Muscular Dystrophy, Animal/metabolism
- Muscular Dystrophy, Animal/physiopathology
- Mutation/genetics
- Phenotype
- Protein Isoforms/genetics
- Protein Isoforms/metabolism
- Protein Isoforms/ultrastructure
- Protein Transport/genetics
- Sarcomeres/metabolism
- Sarcomeres/pathology
- Sarcomeres/ultrastructure
- Tropomyosin/genetics
- Tropomyosin/metabolism
- Tropomyosin/ultrastructure
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Affiliation(s)
- Anthony J Kee
- Muscle Development Unit, Children's Medical Research Institute, Locked Bag 23, Wentworthville, New South Wales 2145, Australia
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297
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Griffin MA, Engler AJ, Barber TA, Healy KE, Sweeney HL, Discher DE. Patterning, prestress, and peeling dynamics of myocytes. Biophys J 2004; 86:1209-22. [PMID: 14747355 PMCID: PMC1303913 DOI: 10.1016/s0006-3495(04)74195-8] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
As typical anchorage-dependent cells myocytes must balance contractility against adequate adhesion. Skeletal myotubes grown as isolated strips from myoblasts on micropatterned glass exhibited spontaneous peeling after one end of the myotube was mechanically detached. Such results indicate the development of a prestress in the cells. To assess this prestress and study the dynamic adhesion strength of single myocytes, the shear stress of fluid aspirated into a large-bore micropipette was then used to forcibly peel myotubes. The velocity at which cells peeled from the surface, V(peel), was measured as a continuously increasing function of the imposed tension, T(peel), which ranges from approximately 0 to 50 nN/ micro m. For each cell, peeling proved highly heterogeneous, with V(peel) fluctuating between 0 micro m/s ( approximately 80% of time) and approximately 10 micro m/s. Parallel studies of smooth muscle cells expressing GFP-paxillin also exhibited a discontinuous peeling in which focal adhesions fractured above sites of strong attachment (when pressure peeled using a small-bore pipette). The peeling approaches described here lend insight into the contractile-adhesion balance and can be used to study the real-time dynamics of stressed adhesions through both physical detection and the use of GFP markers; the methods should prove useful in comparing normal versus dystrophic muscle cells.
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Affiliation(s)
- Maureen A Griffin
- Department of Chemical and Biomolecular Engineering, Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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298
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Tidball JG, Wehling-Henricks M. Expression of a NOS transgene in dystrophin-deficient muscle reduces muscle membrane damage without increasing the expression of membrane-associated cytoskeletal proteins. Mol Genet Metab 2004; 82:312-20. [PMID: 15308129 DOI: 10.1016/j.ymgme.2004.06.006] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2004] [Revised: 06/09/2004] [Accepted: 06/10/2004] [Indexed: 10/26/2022]
Abstract
Muscular dystrophy that is caused by mutation of the membrane-associated, cytoskeletal protein called dystrophin, is accompanied by loss of a dystrophin-associated protein complex (DPC) that includes neuronal nitric oxide synthase (nNOS). Previous work showed that expression of a nNOS transgene in the dystrophin-deficient, mdx mouse greatly reduces muscle membrane damage. In this investigation, we test whether expression of a nNOS transgene in wild-type or mdx muscle increases expression of DPC proteins, or functionally related proteins in the integrin complex that are upregulated in dystrophin-deficiency, or affects expression of the dystrophin homolog, utrophin. Many members of the DPC are enriched in Western blots of cell membranes isolated from NOS transgenic muscle, compared to wild-type. Similarly, alpha7-integrin and the associated cytoskeletal proteins talin and vinculin are increased in NOS transgenic, non-dystrophic muscle. However, utrophin expression is unaffected by elevated NOS expression in healthy muscle. A similar trend in mRNA levels for these proteins was observed by expression profiling. Analysis of membrane preparations from mdx mice and NOS transgenic mdx mice shows that expression of the NOS transgene causes significant reductions in utrophin, talin, and vinculin. Expression profiling of mRNA from mdx and NOS transgenic mdx muscles also shows reduced expression of talin. Immunohistochemistry of mdx and NOS transgenic mdx muscle indicates that reduction in utrophin in NOS transgenic mdx muscle results from a decrease in regenerative fibers that express high levels of utrophin. Together, these findings indicate that the NOS transgene does not reduce dystrophinopathy by increasing the expression of compensatory, structural proteins.
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Affiliation(s)
- James G Tidball
- Department of Physiological Science, University of California, Los Angeles, CA 90095, USA.
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299
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Pyle WG, Solaro RJ. At the crossroads of myocardial signaling: the role of Z-discs in intracellular signaling and cardiac function. Circ Res 2004; 94:296-305. [PMID: 14976140 DOI: 10.1161/01.res.0000116143.74830.a9] [Citation(s) in RCA: 178] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Understanding the molecular interactions among components of cardiac Z-discs and their role in signaling has become pivotal in explaining long- and short-term regulation of cardiac function. In striated muscle, the ends of the thin filaments from opposing sarcomeres overlap and are cross-linked by an elaborate array of proteins to form a highly ordered, yet dynamic network that is the Z-disc. We review here a current picture of the function and structure of the Z-disc of mammalian cardiac myocytes. We emphasize provocative findings that advance new theories about the place of cardiac Z-discs in myocardial intra- and intercellular signaling in myocardial physiology and pathology. Relatively new approaches, especially yeast two-hybrid screens, immunoprecipitation, and pull down assays, as well as immunohistochemical analysis have significantly altered previous views of the protein content of the Z-disc. These studies have generally defined domain structure and binding partners for Z-disc proteins, but the functional significance of the binding network and of the domains in cardiac cell biology remains an unfolding story. Yet, even at the present level of understanding, perceptions of potential functions of the Z-disc proteins are expanding greatly and leading to new and exciting experimental approaches toward mechanistic understanding. The theme of the following discussion of these Z-disc proteins centers on their potential to function not only as a physical anchor for myofilament and cytoskeletal proteins, but also as a pivot for reception, transduction, and transmission of mechanical and biochemical signals.
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Affiliation(s)
- W Glen Pyle
- Department of Biomedical Sciences, University of Guelph, Guelph, Ontario, Canada
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300
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Towler MC, Gleeson PA, Hoshino S, Rahkila P, Manalo V, Ohkoshi N, Ordahl C, Parton RG, Brodsky FM. Clathrin isoform CHC22, a component of neuromuscular and myotendinous junctions, binds sorting nexin 5 and has increased expression during myogenesis and muscle regeneration. Mol Biol Cell 2004; 15:3181-95. [PMID: 15133132 PMCID: PMC452575 DOI: 10.1091/mbc.e04-03-0249] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The muscle isoform of clathrin heavy chain, CHC22, has 85% sequence identity to the ubiquitously expressed CHC17, yet its expression pattern and function appear to be distinct from those of well-characterized clathrin-coated vesicles. In mature muscle CHC22 is preferentially concentrated at neuromuscular and myotendinous junctions, suggesting a role at sarcolemmal contacts with extracellular matrix. During myoblast differentiation, CHC22 expression is increased, initially localized with desmin and nestin and then preferentially segregated to the poles of fused myoblasts. CHC22 expression is also increased in regenerating muscle fibers with the same time course as embryonic myosin, indicating a role in muscle repair. CHC22 binds to sorting nexin 5 through a coiled-coil domain present in both partners, which is absent in CHC17 and coincides with the region on CHC17 that binds the regulatory light-chain subunit. These differential binding data suggest a mechanism for the distinct functions of CHC22 relative to CHC17 in membrane traffic during muscle development, repair, and at neuromuscular and myotendinous junctions.
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Affiliation(s)
- Mhairi C Towler
- The G.W. Hooper Foundation, Department of Microbiology and Immunology and Department of Biopharmaceutical Sciences, University of California, San Francisco, California 94143-0552, USA
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