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Boehler JF, Brown KJ, Beatka M, Gonzalez JP, Donisa Dreghici R, Soustek-Kramer M, McGonigle S, Ganot A, Palmer T, Lowie C, Chamberlain JS, Lawlor MW, Morris CA. Clinical potential of microdystrophin as a surrogate endpoint. Neuromuscul Disord 2023; 33:40-49. [PMID: 36575103 DOI: 10.1016/j.nmd.2022.12.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Revised: 11/28/2022] [Accepted: 12/13/2022] [Indexed: 12/15/2022]
Abstract
Accelerated approval based on a likely surrogate endpoint can be life-changing for patients suffering from a rare progressive disease with unmet medical need, as it substantially hastens access to potentially lifesaving therapies. In one such example, antisense morpholinos were approved to treat Duchenne muscular dystrophy (DMD) based on measurement of shortened dystrophin in skeletal muscle biopsies as a surrogate biomarker. New, promising therapeutics for DMD include AAV gene therapy to restore another form of dystrophin termed mini- or microdystrophin. AAV-microdystrophins are currently in clinical trials but have yet to be accepted by regulatory agencies as reasonably likely surrogate endpoints. To evaluate microdystrophin expression as a reasonably likely surrogate endpoint for DMD, this review highlights dystrophin biology in the context of functional and clinical benefit to support the argument that microdystrophin proteins have a high probability of providing clinical benefit based on their rational design. Unlike exon-skipping based strategies, the approach of rational design allows for functional capabilities (i.e. quality) of the protein to be maximized with every patient receiving the same optimized microdystrophin. Therefore, the presence of rationally designed microdystrophin in a muscle biopsy is likely to predict clinical benefit and is consequently a strong candidate for a surrogate endpoint analysis to support accelerated approval.
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Affiliation(s)
- Jessica F Boehler
- Solid Biosciences, 500 Rutherford Avenue 3rd Floor, Boston, MA 02129, United States
| | - Kristy J Brown
- Solid Biosciences, 500 Rutherford Avenue 3rd Floor, Boston, MA 02129, United States
| | - Margaret Beatka
- Diverge TSL, 247 Freshwater Way Suite 610, Milwaukee, WI 53204, United States
| | - J Patrick Gonzalez
- Solid Biosciences, 500 Rutherford Avenue 3rd Floor, Boston, MA 02129, United States
| | | | | | - Sharon McGonigle
- Solid Biosciences, 500 Rutherford Avenue 3rd Floor, Boston, MA 02129, United States
| | - Annie Ganot
- Solid Biosciences, 500 Rutherford Avenue 3rd Floor, Boston, MA 02129, United States
| | - Timothy Palmer
- Solid Biosciences, 500 Rutherford Avenue 3rd Floor, Boston, MA 02129, United States
| | - Caitlin Lowie
- Solid Biosciences, 500 Rutherford Avenue 3rd Floor, Boston, MA 02129, United States
| | - Jeffrey S Chamberlain
- Department of Neurology, University of Washington School of Medicine, Seattle, United States
| | - Michael W Lawlor
- Diverge TSL, 247 Freshwater Way Suite 610, Milwaukee, WI 53204, United States
| | - Carl A Morris
- Solid Biosciences, 500 Rutherford Avenue 3rd Floor, Boston, MA 02129, United States.
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Leier A, Bedwell DM, Chen AT, Dickson G, Keeling KM, Kesterson RA, Korf BR, Marquez Lago TT, Müller UF, Popplewell L, Zhou J, Wallis D. Mutation-Directed Therapeutics for Neurofibromatosis Type I. MOLECULAR THERAPY. NUCLEIC ACIDS 2020; 20:739-753. [PMID: 32408052 PMCID: PMC7225739 DOI: 10.1016/j.omtn.2020.04.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Revised: 04/20/2020] [Accepted: 04/23/2020] [Indexed: 02/07/2023]
Abstract
Significant advances in biotechnology have led to the development of a number of different mutation-directed therapies. Some of these techniques have matured to a level that has allowed testing in clinical trials, but few have made it to approval by drug-regulatory bodies for the treatment of specific diseases. While there are still various hurdles to be overcome, recent success stories have proven the potential power of mutation-directed therapies and have fueled the hope of finding therapeutics for other genetic disorders. In this review, we summarize the state-of-the-art of various therapeutic approaches and assess their applicability to the genetic disorder neurofibromatosis type I (NF1). NF1 is caused by the loss of function of neurofibromin, a tumor suppressor and downregulator of the Ras signaling pathway. The condition is characterized by a variety of phenotypes and includes symptoms such as skin spots, nervous system tumors, skeletal dysplasia, and others. Hence, depending on the patient, therapeutics may need to target different tissues and cell types. While we also discuss the delivery of therapeutics, in particular via viral vectors and nanoparticles, our main focus is on therapeutic techniques that reconstitute functional neurofibromin, most notably cDNA replacement, CRISPR-based DNA repair, RNA repair, antisense oligonucleotide therapeutics including exon skipping, and nonsense suppression.
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Affiliation(s)
- Andre Leier
- Department of Genetics, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - David M Bedwell
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Ann T Chen
- Department of Neurosurgery, Yale University, New Haven, CT 06510, USA
| | - George Dickson
- Centre of Biomedical Sciences, Department of Biological Sciences, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK
| | - Kim M Keeling
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Robert A Kesterson
- Department of Genetics, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Bruce R Korf
- Department of Genetics, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | | | - Ulrich F Müller
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA 92093, USA
| | - Linda Popplewell
- Centre of Biomedical Sciences, Department of Biological Sciences, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK
| | - Jiangbing Zhou
- Department of Neurosurgery, Yale University, New Haven, CT 06510, USA
| | - Deeann Wallis
- Department of Genetics, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
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3
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Mirza A, Sagathevan M, Sahni N, Choi L, Menhart N. A biophysical map of the dystrophin rod. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2010; 1804:1796-809. [DOI: 10.1016/j.bbapap.2010.03.009] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2010] [Revised: 03/16/2010] [Accepted: 03/24/2010] [Indexed: 11/26/2022]
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4
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Dystrophin: more than just the sum of its parts. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2010; 1804:1713-22. [PMID: 20472103 DOI: 10.1016/j.bbapap.2010.05.001] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2010] [Revised: 04/30/2010] [Accepted: 05/03/2010] [Indexed: 01/05/2023]
Abstract
Dystrophin is one of a number of large cytoskeleton associated proteins that connect between various cytoskeletal elements and often are tethered to the membrane through other transmembrane protein complexes. These cytolinker proteins often provide structure and support to the cells where they are expressed, and mutations in genes encoding these proteins frequently gives rise to disease. Dystrophin is no exception in any of these respects, providing connections between a transmembrane complex known as the dystrophin-glycoprotein complex and the underlying cytoskeleton. The most established connection and possibly the most important is that to F-actin, but more recently evidence has been forthcoming of connections to membrane phospholipids, intermediate filaments and microtubules. Moreover it is becoming increasingly clear that the multiple spectrin-like repeats in the centre of the molecule, that had hitherto been thought to be largely redundant, harbour binding activities that have a significant impact on dystrophin functionality. This functionality is particularly apparent when assessed by the ability to rescue the dystrophic phenotype in mdx mice. This review will focus on the relatively neglected but functionally vital coiled-coil region of dystrophin, highlighting the structural relationships and interactions of the coiled-coil region and providing new insights into the functional role of this region.
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5
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Banks GB, Judge LM, Allen JM, Chamberlain JS. The polyproline site in hinge 2 influences the functional capacity of truncated dystrophins. PLoS Genet 2010; 6:e1000958. [PMID: 20502633 PMCID: PMC2873924 DOI: 10.1371/journal.pgen.1000958] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2009] [Accepted: 04/20/2010] [Indexed: 01/01/2023] Open
Abstract
Mutations in dystrophin can lead to Duchenne muscular dystrophy or the more mild form of the disease, Becker muscular dystrophy. The hinge 3 region in the rod domain of dystrophin is particularly prone to deletion mutations. In-frame deletions of hinge 3 are predicted to lead to BMD, however the severity of disease can vary considerably. Here we performed extensive structure-function analyses of truncated dystrophins with modified hinges and spectrin-like repeats in mdx mice. We found that the polyproline site in hinge 2 profoundly influences the functional capacity of a microdystrophin(DeltaR4-R23/DeltaCT) with a large deletion in the hinge 3 region. Inclusion of polyproline in microdystrophin(DeltaR4-R23/DeltaCT) led to small myofibers (12% smaller than wild-type), Achilles myotendinous disruption, ringed fibers, and aberrant neuromuscular junctions in the mdx gastrocnemius muscles. Replacing hinge 2 of microdystrophin(DeltaR4-R23/DeltaCT) with hinge 3 significantly improved the functional capacity to prevent muscle degeneration, increase muscle fiber area, and maintain the junctions. We conclude that the rigid alpha-helical structure of the polyproline site significantly impairs the functional capacity of truncated dystrophins to maintain appropriate connections between the cytoskeleton and extracellular matrix.
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Affiliation(s)
- Glen B. Banks
- Department of Neurology, Senator Paul D. Wellstone Muscular Dystrophy Cooperative Research Center, University of Washington, Seattle, Washington, United States of America
| | - Luke M. Judge
- Department of Neurology, Senator Paul D. Wellstone Muscular Dystrophy Cooperative Research Center, University of Washington, Seattle, Washington, United States of America
| | - James M. Allen
- Department of Neurology, Senator Paul D. Wellstone Muscular Dystrophy Cooperative Research Center, University of Washington, Seattle, Washington, United States of America
- Department of Medicine, University of Washington, Seattle, Washington, United States of America
| | - Jeffrey S. Chamberlain
- Department of Neurology, Senator Paul D. Wellstone Muscular Dystrophy Cooperative Research Center, University of Washington, Seattle, Washington, United States of America
- Department of Medicine, University of Washington, Seattle, Washington, United States of America
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
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6
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Kaspar RW, Allen HD, Ray WC, Alvarez CE, Kissel JT, Pestronk A, Weiss RB, Flanigan KM, Mendell JR, Montanaro F. Analysis of dystrophin deletion mutations predicts age of cardiomyopathy onset in becker muscular dystrophy. ACTA ACUST UNITED AC 2009; 2:544-51. [PMID: 20031633 DOI: 10.1161/circgenetics.109.867242] [Citation(s) in RCA: 115] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
BACKGROUND Becker muscular dystrophy (BMD) and X-linked dilated cardiomyopathy often result from deletion mutations in the dystrophin gene that may lead to expression of an altered dystrophin protein in cardiac muscle. Cardiac involvement is present in approximately 70% of BMD and all X-linked dilated cardiomyopathy cases. To date, the timing of cardiomyopathy development remains unpredictable. We analyzed 78 BMD and X-linked dilated cardiomyopathy patients with common deletion mutations predicted to alter the dystrophin protein and correlated their mutations to cardiomyopathy age of onset. This approach was chosen to connect dystrophin structure with function in the heart. METHODS AND RESULTS Detailed cardiac information was collected for BMD and X-linked dilated cardiomyopathy patients with defined dystrophin gene deletion mutations. Patients were grouped based on the dystrophin protein domain affected by the deletion. Deletions affecting the amino-terminal domain are associated with early-onset dilated cardiomyopathy (DCM; mid-20s), whereas deletions removing part of the rod domain and hinge 3 have a later-onset DCM (mid-40s). Further, we modeled the effects of the most common mutations occurring in the rod domain on the overall structure of the dystrophin protein. By combining genetic and protein information, this analysis revealed a strong correlation between specific protein structural modifications and DCM age of onset. CONCLUSIONS We identified specific regions of the dystrophin gene that when mutated predispose BMD patients to early-onset DCM. In addition, we propose that some mutations lead to early-onset DCM by specific alterations in protein folding. These findings have potential implications for early intervention in the cardiac care of BMD patients and for therapeutic approaches that target the heart in dystrophinopathies.
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Affiliation(s)
- Rita Wen Kaspar
- Center for Gene Therapy, The Research Institute at Nationwide Children's Hospital; College of Nursing, The Ohio State University, Columbus, Ohio, USA
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7
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Jørgensen LH, Larochelle N, Orlopp K, Dunant P, Dudley RW, Stucka R, Thirion C, Walter MC, Laval SH, Lochmüller H. Efficient and Fast Functional Screening of Microdystrophin ConstructsIn VivoandIn Vitrofor Therapy of Duchenne Muscular Dystrophy. Hum Gene Ther 2009; 20:641-50. [DOI: 10.1089/hum.2008.162] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Louise H. Jørgensen
- Institute of Human Genetics, University of Newcastle, Newcastle upon Tyne NE1 3BZ, United Kingdom
| | - Nancy Larochelle
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC H3A 2B4, Canada
| | - Kristian Orlopp
- Friedrich Baur Institute and Department of Neurology, Ludwig Maximilians University, Munich 81377, Germany
| | - Patrick Dunant
- Friedrich Baur Institute and Department of Neurology, Ludwig Maximilians University, Munich 81377, Germany
| | - Roy W.R. Dudley
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC H3A 2B4, Canada
| | - Rolf Stucka
- Friedrich Baur Institute and Department of Neurology, Ludwig Maximilians University, Munich 81377, Germany
| | - Christian Thirion
- Friedrich Baur Institute and Department of Neurology, Ludwig Maximilians University, Munich 81377, Germany
| | - Maggie C. Walter
- Friedrich Baur Institute and Department of Neurology, Ludwig Maximilians University, Munich 81377, Germany
| | - Steven H. Laval
- Institute of Human Genetics, University of Newcastle, Newcastle upon Tyne NE1 3BZ, United Kingdom
| | - Hanns Lochmüller
- Institute of Human Genetics, University of Newcastle, Newcastle upon Tyne NE1 3BZ, United Kingdom
- Friedrich Baur Institute and Department of Neurology, Ludwig Maximilians University, Munich 81377, Germany
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8
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Abstract
In this article, we review the molecular pathology of muscular dystrophies caused by defects of proteins located within or near cell membranes. These disorders include Bethlem myopathy, merosinopathy, dystrophinopathy, sarcoglycanopathies, integrinopathy, dysferlinopathy and caveolinopathy. We refer to these diseases collectively as sarcolemmopathy. Here, we describe the biological functions of these proteins in the context of muscular contractions and their roles in the infrastructure of muscle; defects of muscle infrastructures cause those diseases. As an example, in dystrophinopathy, cell membranes have mechanical defects due to the absence of dystrophin. Cracks of the cell membrane induced by muscle contraction may allow the influx and efflux of substances that trigger muscle cell degeneration. However, such cracks may be resealed on relaxation. In addition, dystrophinopathy causes secondary defects of various dystrophin-associated proteins suggesting that defects in cell signaling participate in the pathologic process. With regard to other sarcolemmopathies, we discuss pathological mechanisms based on available data.
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Affiliation(s)
- E Ozawa
- National Institute of Neuroscience, NCNP, Tokyo, Japan.
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9
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Saadat L, Pittman L, Menhart N. Structural cooperativity in spectrin type repeats motifs of dystrophin. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2006; 1764:943-54. [PMID: 16603424 DOI: 10.1016/j.bbapap.2006.02.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2005] [Revised: 02/16/2006] [Accepted: 02/17/2006] [Indexed: 11/21/2022]
Abstract
Dystrophin is a member of the spectrin family of proteins, which are characterized as being predominantly composed the spectrin-type-repeat, a triple alpha-helical bundle motif present in multiple tandem copies, producing a rod-like shape. Whether or not this motif, which is determined by sequence homology, is correlated with biophysical domains in the intact protein is uncertain. The nature of the domain structure impacts the flexibility and shape of the rod region of this protein, which is a target for modification in several therapeutic approaches aimed at Duchenne Muscular Dystrophy, a common and fatal genetic disease caused by defective dystrophin. We examined three such motifs in dystrophin, expressing them recombinantly both singly and in tandem, and studying their thermodynamic properties by solvent and thermal denaturation. We have found that the degree to which they are independently stable and expressible varies considerably. The fourth motif appears to be largely stable and independent, whereas the third and second motifs interact strongly.
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Affiliation(s)
- Laleh Saadat
- Department of Biological, Chemical and Physical Sciences, Illinois Institute of Technology, 3101 S. Dearborn, Chicago, IL 60616, USA
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10
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Le Rumeur E, Fichou Y, Pottier S, Gaboriau F, Rondeau-Mouro C, Vincent M, Gallay J, Bondon A. Interaction of dystrophin rod domain with membrane phospholipids. Evidence of a close proximity between tryptophan residues and lipids. J Biol Chem 2003; 278:5993-6001. [PMID: 12480947 DOI: 10.1074/jbc.m207321200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Dystrophin is assumed to act via the central rod domain as a flexible linker between the amino-terminal actin binding domain and carboxyl-terminal proteins associated with the membrane. The rod domain is made up of 24 spectrin-like repeats and has been shown to modify the physical properties of lipid membranes. The nature of this association still remains unclear. Tryptophan residues tend to cluster at or near to the water-lipid interface of the membrane. To assess dystrophin rod domain-membrane interactions, tryptophan residues properties of two recombinant proteins of the rod domain were examined by (1)H NMR and fluorescence techniques in the presence of membrane lipids. F114 (residues 439-553) is a partly folded protein as inferred from (1)H NMR, tryptophan fluorescence emission intensity, and the excited state lifetime. By contrast, F125 (residues 439-564) is a folded compact protein. Tryptophan fluorescence quenching shows that both proteins are characterized by structural fluctuations with their tryptophan residues only slightly buried from the surface. In the presence of negatively charged small vesicles, the fluorescence characteristics of F125 change dramatically, indicating that tryptophan residues are in a more hydrophobic environment. Interestingly, these modifications are not observed with F114. Fluorescence quenching experiments confirm that tryptophan residues are shielded from the solvent in the complex F125 lipids by a close contact with lipids. The use of membrane-bound quenchers allowed us to conclude that dystrophin rod domain lies along the membrane surface and may be involved in a structural array comprising membrane and cytoskeletal proteins as well as membrane lipids.
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Affiliation(s)
- Elisabeth Le Rumeur
- Laboratoire de Résonance Magnétique Nucléaire en Biologie et Médecine, Unité Propre de Recherche de l'Enseignement Supérieur EA 2230, Faculté de Médecine, CS 34317, Rennes 35043 cedex, France.
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11
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Harper SQ, Hauser MA, DelloRusso C, Duan D, Crawford RW, Phelps SF, Harper HA, Robinson AS, Engelhardt JF, Brooks SV, Chamberlain JS. Modular flexibility of dystrophin: implications for gene therapy of Duchenne muscular dystrophy. Nat Med 2002; 8:253-61. [PMID: 11875496 DOI: 10.1038/nm0302-253] [Citation(s) in RCA: 412] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Attempts to develop gene therapy for Duchenne muscular dystrophy (DMD) have been complicated by the enormous size of the dystrophin gene. We have performed a detailed functional analysis of dystrophin structural domains and show that multiple regions of the protein can be deleted in various combinations to generate highly functional mini- and micro-dystrophins. Studies in transgenic mdx mice, a model for DMD, reveal that a wide variety of functional characteristics of dystrophy are prevented by some of these truncated dystrophins. Muscles expressing the smallest dystrophins are fully protected against damage caused by muscle activity and are not morphologically different from normal muscle. Moreover, injection of adeno-associated viruses carrying micro-dystrophins into dystrophic muscles of immunocompetent mdx mice results in a striking reversal of histopathological features of this disease. These results demonstrate that the dystrophic pathology can be both prevented and reversed by gene therapy using micro-dystrophins.
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Affiliation(s)
- Scott Q Harper
- Department of Neurology, University of Washington School of Medicine, Seattle, Washington, USA
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12
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Abstract
The spectrin family of proteins represents a discrete group of cytoskeletal proteins comprising principally alpha-actinin, spectrin, dystrophin, and homologues and isoforms. They all share three main structural and functional motifs, namely, the spectrin repeat, EF-hands, and a CH domain-containing actin-binding domain. These proteins are variously involved in organisation of the actin cytoskeleton, membrane cytoskeleton architecture, cell adhesion, and contractile apparatus. The highly modular nature of these molecules has been a hindrance to the determination of their complete structures due to the inherent flexibility imparted on the proteins, but has also been an asset, inasmuch as the individual modules were of a size amenable to structural analysis by both crystallographic and NMR approaches. Representative structures of all the major domains shared by spectrin family proteins have now been solved at atomic resolution, including in some cases multiple domains from several family members. High-resolution structures, coupled with lower resolution methods to determine the overall molecular shape of these proteins, allow us for the first time to build complete atomic structures of the spectrin family of proteins.
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Affiliation(s)
- Michael J F Broderick
- Institute of Biomedical and Life Sciences, Glasgow Cell Biology Group, University of Glasgow, Scotland, United Kingdom
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13
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De la Porte S, Morin S, Koenig J. Characteristics of skeletal muscle in mdx mutant mice. INTERNATIONAL REVIEW OF CYTOLOGY 1999; 191:99-148. [PMID: 10343393 DOI: 10.1016/s0074-7696(08)60158-8] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
We review the extensive research conducted on the mdx mouse since 1987, when demonstration of the absence of dystrophin in mdx muscle led to X-chromosome-linked muscular dystrophy (mdx) being considered as a homolog of Duchenne muscular dystrophy. Certain results are contradictory. We consider most aspects of mdx skeletal muscle: (i) the distribution and roles of dystrophin, utrophin, and associated proteins; (ii) morphological characteristics of the skeletal muscle and hypotheses put forward to explain the regeneration characteristic of the mdx mouse; (iii) special features of the diaphragm; (iv) changes in basic fibroblast growth factor, ion flux, innervation, cytoskeleton, adhesive proteins, mastocytes, and metabolism; and (v) different lines of therapeutic research.
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Affiliation(s)
- S De la Porte
- Laboratoire de Neurobiologie Cellulaire et Moléculaire, CNRS UPR 9040, Gif sur Yvette, France
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14
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Amann KJ, Renley BA, Ervasti JM. A cluster of basic repeats in the dystrophin rod domain binds F-actin through an electrostatic interaction. J Biol Chem 1998; 273:28419-23. [PMID: 9774469 DOI: 10.1074/jbc.273.43.28419] [Citation(s) in RCA: 123] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The dystrophin rod domain is composed of 24 spectrin-like repeats and was thought to act mainly as a flexible spacer between the amino-terminal actin binding domain and carboxyl-terminal membrane-associated domains. We previously demonstrated that a fragment of the dystrophin rod domain also binds F-actin. However, the nature and extent of rod domain association with F-actin is presently unclear. To begin addressing these questions, we characterized two recombinant proteins representing adjacent regions of the dystrophin rod. DYS1416 (amino acids 1416-1880) bound F-actin with a Kd of 14.2 +/- 5.2 microM and a stoichiometry of 1 mol:mol of actin. However, DYS1030 (amino acids 1030-1494) failed to bind F-actin, suggesting that not all rod domain repeats are capable of binding F-actin. Interestingly, DYS1416 corresponds to a unique region of the dystrophin rod rich in basic amino acids, whereas DYS1030 is composed mainly of acidic repeats. This observation suggested that DYS1416 may interact with acidic actin filaments through an electrostatic interaction. Supporting this hypothesis, actin binding by DYS1416 was dramatically inhibited by increasing ionic strength. We suggest that electrostatic interactions between basic spectrin-like repeats and actin filaments may contribute to the actin binding activity of other members of the actin cross-linking protein family.
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Affiliation(s)
- K J Amann
- Graduate Program in Cellular and Molecular Biology, University of Wisconsin Medical School, Madison, Wisconsin 53706, USA
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15
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Dickson G, Brown SC. Duchenne muscular dystrophy. MOLECULAR AND CELL BIOLOGY OF HUMAN DISEASES SERIES 1998; 5:261-80. [PMID: 9532571 DOI: 10.1007/978-94-011-0547-7_14] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- G Dickson
- Department of Biochemistry, Royal Holloway, University of London, Egham, Surrey, UK
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16
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Fassati A, Murphy S, Dickson G. Gene therapy of Duchenne muscular dystrophy. ADVANCES IN GENETICS 1997; 35:117-53. [PMID: 9348647 DOI: 10.1016/s0065-2660(08)60449-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- A Fassati
- School of Biological Sciences, Division of Biochemistry, Royal Holloway College, University of London, Egham, Surrey, United Kingdom
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17
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Abstract
Dystrophin, a component of the muscle membrane cytoskeleton, is the protein altered in Duchenne Muscular Dystrophy (DMD) and Becker Muscular Dystrophy (BMD). Dystrophin shares significant homology with other cytoskeletal proteins, such as alpha-actinin and spectrin. On the basis of its sequence similarity with alpha-actinin and spectrin, dystrophin has been proposed to function as dimer. However, the existence of both dimers and monomers have been observed by electron microscopy. To address this apparent discrepancy, we expressed dystrophin fragments composed of different domains in an in vitro translation system. The expressed fragments were tested for their ability to interact with each other and full-length dystrophin by both immunoprecipitation and blot overlay assays. These assays were successfully used to demonstrate the dimerization of alpha-actinin and spectrin, yet failed to detect any interaction between dystrophin fragments. Although these in vitro results do not prove that dystrophin is not a dimer in vivo, they do indicate that this interaction is not like that of the alpha-actinin and spectrin.
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Affiliation(s)
- Y Chan
- Howard Hughes Medical Institute, and Division of Genetics at Children's Hospital, Boston, MA 02115, USA
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18
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DeWolf C, McCauley P, Sikorski AF, Winlove CP, Bailey AI, Kahana E, Pinder JC, Gratzer WB. Interaction of dystrophin fragments with model membranes. Biophys J 1997; 72:2599-604. [PMID: 9168035 PMCID: PMC1184457 DOI: 10.1016/s0006-3495(97)78903-3] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The interaction with membrane lipids of recombinant fragments of human dystrophin, corresponding to a single structural repeating unit of the rod domain, was examined. Surface plasmon resonance, constant-pressure isotherms in a Langmuir surface film balance, and interfacial rheology were used to observe binding of the polypeptides and its effects on the properties of the lipid film. Modification of the monolayer properties was found to depend on the presence of phosphatidylserine in the lipid mixture and on the native tertiary fold of the polypeptide; thus a fragment with the minimum chain length required for folding (117 residues) or longer caused a contraction of the surface area at constant pressure, whereas fragments of 116 residues or less had no effect. The full extent of contraction was reached at a surface concentration of lipid corresponding to an average area of about 42 A2 per lipid molecule. A dystrophin fragment with the native, folded conformation induced a large increase in surface shear viscosity of the lipid film, whereas an unfolded fragment had no effect. Within a wide range of applied shear, the shear viscosity remained Newtonian. Binding of liposomes to immobilized dystrophin fragments could be observed by surface plasmon resonance and was again related to the conformational state of the polypeptide and the presence of phosphatidylserine in the liposomes. Our results render it likely that intact dystrophin interacts directly and strongly with the sarcolemmal lipid bilayer and grossly modifies its material properties.
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Affiliation(s)
- C DeWolf
- Department of Chemical Engineering, Imperial College, London, England
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19
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Rivier F, Robert A, Hugon G, Mornet D. Different utrophin and dystrophin properties related to their vascular smooth muscle distributions. FEBS Lett 1997; 408:94-8. [PMID: 9180276 DOI: 10.1016/s0014-5793(97)00398-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Monoclonal antibodies used to distinguish between dystrophin and utrophin were systematically applied to skeletal muscles containing arteries and veins. Small arteries were found to contain long forms of both utrophin and dystrophin, while small veins contained only long forms of utrophin. In addition, all sizes of vascular smooth muscles were demonstrated to contain another related Mr 80 kDa protein (possibly a short utrophin transcript). Regardless of their tissue distributions, we assumed that each of these molecules had distinct properties, i.e. dystrophin with a mechanical function and utrophin with an architectural function. This difference in the roles of dystrophin and utrophin could reduce the efficiency of protection against muscle membrane degeneration when utrophin overexpression is programmed.
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Affiliation(s)
- F Rivier
- Pathologie Moleculaire du Muscle, INSERM U 300, Bât K, Faculté de Pharmacie, Montpellier, France
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20
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Calvert R, Kahana E, Gratzer WB. Stability of the dystrophin rod domain fold: evidence for nested repeating units. Biophys J 1996; 71:1605-10. [PMID: 8874034 PMCID: PMC1233627 DOI: 10.1016/s0006-3495(96)79363-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
An examination of fragments of the human dystrophin rod domain, corresponding to a single structural repeating unit, showed that a critical chain length, defined with a precision of one residue at the C-terminal end, is required for formation of the native tertiary fold. We report here that extending the chain by six residues beyond this minimum results in a large increase in conformational stability. This is not related to a change in association state of the polypeptide. The results support the conjecture that successive repeating units in the rod domain of the spectrinlike proteins form a nested structure, in which the N-terminal part of the three-helix bundle of one repeat packs into the overlapping structure of the preceding repeat. This would be expected to affect functional characteristics related to flexibility of the dystrophin rod domain.
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Affiliation(s)
- R Calvert
- Medical Research Council Muscle and Cell Motility Unit, King's College, London, UK
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21
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22
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Caron A, Viader F, Lechevalier B, Chapon F. Cytoplasmic body myopathy: familial cases with accumulation of desmin and dystrophin. An immunohistochemical, immunoelectron microscopic and biochemical study. Acta Neuropathol 1995; 90:150-7. [PMID: 7484090 DOI: 10.1007/bf00294314] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Muscle biopsy samples from five patients with cytoplasmic body myopathy (CBM) were investigated by immunohistochemical (antibodies to desmin, actin, dystrophin, spectrin, alpha actinin and utrophin), immunoelectron microscopic (antibodies to desmin, actin and dystrophin) and biochemical (desmin, dystrophin, actin and utrophin western blots) methods. Using immunofluorescence it was shown that the centers of cytoplasmic bodies (CB) were stained by anti-actin, anti-utrophin and three different anti-dystrophin antibodies. The peripheries were labeled by the anti-desmin antibody. Moreover, fibers containing CB showed a markedly increased staining of their entire sarcoplasm with the anti-desmin antibody. Using immunoelectron microscopy it was shown that anti-dystrophin antibodies selectively stained the external limit of the central granular region. Anti-desmin antibody labeled the filamentous halo, and anti-actin antibody stained the central core and the radiating filaments. Biochemical studies showed storage of desmin and dystrophin, both of normal molecular weight. Our results suggest that CBM should be considered along with a wider group of intermediate filament pathologies that include desmin-storage myopathies.
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Affiliation(s)
- A Caron
- Laboratory of Neuropathology, CHU Côte de Nacre, Caen, France
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23
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Abstract
There is considerable sequence homology between dystrophin and utrophin, both at the protein and DNA level, and consequently it was assumed that their domain structures and functions would be similar. As more of the detailed biochemical and cell biological properties of these two proteins become known, so it becomes clear that there are subtle if not significant differences between them. We review recent findings and present new hypotheses into the structural and functional properties of the actin-binding domain, central coiled-coil region and regulatory/membrane protein-binding regions of dystrophin and utrophin.
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Affiliation(s)
- S J Winder
- MRC Laboratory of Molecular Biology, Cambridge, UK
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24
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Winder SJ, Kendrick-Jones J. Calcium/calmodulin-dependent regulation of the NH2-terminal F-actin binding domain of utrophin. FEBS Lett 1995; 357:125-8. [PMID: 7805877 DOI: 10.1016/0014-5793(94)01347-4] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The cytoskeletal proteins utrophin, dystrophin and alpha-actinin are predicted to form antiparallel dimers thus potentially bringing their NH2-terminal F-actin binding domains in close proximity to their EF-hand containing COOH-terminal domains. This arrangement would allow for calcium-dependent regulation of F-actin binding. We tested this hypothesis by determining the effect of the ubiquitous calcium binding protein calmodulin on their F-actin binding capabilities. Binding of the NH2-terminal F-actin binding domain of utrophin to F-actin was inhibited by increasing concentrations of calmodulin in a calcium-dependent manner. The homologous F-actin binding domains from dystrophin and alpha-actinin were not regulated by calmodulin in the presence or absence of calcium. These findings have implications for the structural organisation of utrophin dimers and also for the replacement of dystrophin by over-expression of utrophin in dystrophic muscle.
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Affiliation(s)
- S J Winder
- MRC Laboratory of Molecular Biology, Cambridge, UK
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25
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Affiliation(s)
- R G Roberts
- Division of Medical and Molecular Genetics, United Medical and Dental Schools, London, United Kingdom
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26
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Fabbrizio E, Pons F, Robert A, Hugon G, Bonet-Kerrache A, Mornet D. The dystrophin superfamily: variability and complexity. J Muscle Res Cell Motil 1994; 15:595-606. [PMID: 7706416 DOI: 10.1007/bf00121067] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- E Fabbrizio
- INSERM U300, Faculté de Pharmacie, Montpellier, France
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27
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Dunckley MG, Wells KE, Piper TA, Wells DJ, Dickson G. Independent localization of dystrophin N- and C-terminal regions to the sarcolemma of mdx mouse myofibres in vivo. J Cell Sci 1994; 107 ( Pt 6):1469-75. [PMID: 7962190 DOI: 10.1242/jcs.107.6.1469] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Dystrophin has been proposed to associate with the skeletal muscle membrane by way of a glycoprotein complex that interacts with its C-terminal domains. Transfection of mdx mouse myotubes in culture or myofibres in vivo with recombinant genes encoding human dystrophin deletion mutants shows, however, that not only the C terminus of dystrophin but also its N-terminal actin-binding domain can locate independently to the muscle sarcolemma. This observation suggests that lack of sarcolemma-associated dystrophin in Duchenne muscular dystrophy (DMD) muscle may result from enhanced degradation of truncated mutation products rather than their inability per se to associate with the sarcolemma.
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Affiliation(s)
- M G Dunckley
- Department of Experimental Pathology, UMDS, Guy's Hospital, London, UK
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28
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Fabbrizio E, Nudel U, Hugon G, Robert A, Pons F, Mornet D. Characterization and localization of a 77 kDa protein related to the dystrophin gene family. Biochem J 1994; 299 ( Pt 2):359-65. [PMID: 8172595 PMCID: PMC1138280 DOI: 10.1042/bj2990359] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The Duchenne muscular dystrophy gene gives rise to transcripts of several lengths. These mRNAs differ in their coding content and tissue distribution. The 14 kb mRNA encodes dystrophin, a 427 kDa protein found in muscle and brain, and the short transcripts described encode DP71, a 77 kDa protein found in various organs. These short transcripts have many features common to the deduced primary structure of dystrophin, especially in the cysteine-rich specific C-terminal domains. The dystrophin C-terminal domain could be involved in membrane anchorage via the glycoprotein complex, but such a functional role for these short transcript products has yet to be demonstrated. Here we report the first isolation of a short transcript product from saponin-solubilized cardiac muscle membranes using alkaline buffer and affinity chromatography procedures. This molecule was found to be glycosylated and could be easily dissociated from cardiac muscle and other non-muscle tissues such as brain and liver. DP71-specific monoclonal antibody helped to identify this molecule as being related to the dystrophin gene family. Immunofluorescence analysis of bovine or chicken cardiac muscle showed a periodic distribution of DP71 in transverse T tubules and this protein was co-localized with the dystrophin glycoprotein complex in the Z-disk area.
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Affiliation(s)
- E Fabbrizio
- INSERM U.300, Faculté de Pharmacie, Montpellier, France
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29
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MacDonald RI, Musacchio A, Holmgren RA, Saraste M. Invariant tryptophan at a shielded site promotes folding of the conformational unit of spectrin. Proc Natl Acad Sci U S A 1994; 91:1299-303. [PMID: 8108405 PMCID: PMC43145 DOI: 10.1073/pnas.91.4.1299] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The tryptophan that is highly conserved among repeating structural units of spectrin is reported to promote the conformational stability of one such unit of chicken brain alpha-spectrin. Four constructs were inserted into pET vectors for overexpression in Escherichia coli of the following spectrin peptides: (i) two adjacent but separately expressed "conformationally phased" repeating units, R16 and R17, one of which (R17) contains a single tryptophan; (ii) a mutant, M17, of the single tryptophan-containing unit with alanine substituted for the tryptophan; and (iii) a conformationally unphased unit, 1617, composed of half of each of the phased units. Both the mutant unit and the unphased unit were much more readily digested by chymotrypsin and by elastase than the phased units and exhibited only 38% and 54% as much alpha-helical structure, respectively, as the phased units by their far UV CD spectra; 90 degrees light scattering measurements revealed the folded peptides to be predominantly monomeric in solution, whereas the unfolded, protease-sensitive peptides consisted of dimers and/or trimers. This trend was corroborated by their dynamic light scattering. Both the blue-shifted wavelength of maximal emission and the relative inaccessibility to acrylamide of the single tryptophan in the folded unit indicate that the invariant tryptophan occupies a site that is shielded from the aqueous phase.
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Affiliation(s)
- R I MacDonald
- Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, IL 60208
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30
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Gratzer WB. From helix to haemolysis. NATURE STRUCTURAL BIOLOGY 1994; 1:78-9. [PMID: 7656020 DOI: 10.1038/nsb0294-78] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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31
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Yan Y, Winograd E, Viel A, Cronin T, Harrison SC, Branton D. Crystal structure of the repetitive segments of spectrin. Science 1993; 262:2027-30. [PMID: 8266097 DOI: 10.1126/science.8266097] [Citation(s) in RCA: 295] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The elongated proteins of the spectrin family (dystrophin, alpha-actinin, and spectrin) contain tandemly repeated segments and form resilient cellular meshworks by cross-linking actin filaments. The structure of one of the repetitive segments of alpha-spectrin was determined at a 1.8 angstrom resolution. A segment consists of a three-helix bundle. A model of the interface between two tandem segments suggests that hydrophobic interactions between segments may constrain intersegment flexibility. The helix side chain interactions explain how mutations that are known to produce hemolytic anemias disrupt spectrin associations that sustain the integrity of the erythrocyte membrane.
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Affiliation(s)
- Y Yan
- Department of Biochemistry, Harvard University, Cambridge, MA 02138
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32
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Caron A, Chapon F, Berthelin C, Viader F, Lechevalier B. Inclusions in familial cytoplasmic body myopathy are stained by anti-dystrophin antibodies. Neuromuscul Disord 1993; 3:541-6. [PMID: 8186708 DOI: 10.1016/0960-8966(93)90112-w] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
We report here for the first time positive anti-dystrophin labelling of inclusions in three cases belonging to the same family affected by familial cytoplasmic body myopathy (CBM). Inclusions are also stained, as reported previously, by anti-actin antibodies. The anti-desmin reaction was negative in the centre of cytoplasmic bodies (CB) but showed an enhancement of staining in the peripheral part. Abnormal sarcoplasmic staining of fibres with CB was also observed with that antibody. Anti-vimentin antibody labelling was negative. At present, the significance of this labelling by anti-dystrophin antibodies is unknown, but will open new fields for further investigations in an attempt to understand CB pathogenesis.
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Affiliation(s)
- A Caron
- Laboratory of Neuropathology, CHU Côte de Nâcre, Caen, France
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33
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Bushby KM, Gardner-Medwin D, Nicholson LV, Johnson MA, Haggerty ID, Cleghorn NJ, Harris JB, Bhattacharya SS. The clinical, genetic and dystrophin characteristics of Becker muscular dystrophy. II. Correlation of phenotype with genetic and protein abnormalities. J Neurol 1993; 240:105-12. [PMID: 8437017 DOI: 10.1007/bf00858726] [Citation(s) in RCA: 99] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
We have correlated a detailed clinical assessment of 67 patients with proven Becker muscular dystrophy with the results from genetic and protein analyses. There was an overall deletion frequency of 80%, rising to 92.6% in the large group of patients defined on clinical grounds as being of "typically" mild severity. The deletions in this group were all clustered in the region of the gene between exons 45 and 59; the most common deletion was of exons 45-47 and all but one started at exon 45. No similar deletions were seen in the patients with more severe disease, in whom the diverse genetic defects included a duplication and a very large deletion. Dystrophin patterns in the "typical" group were also very characteristic, and in both groups were as predicted from the genetic defect, the size of deletions being inversely proportional to the size of the protein produced.
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Affiliation(s)
- K M Bushby
- Department of Human Genetics, Newcastle upon Tyne, UK
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34
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Love DR, Byth BC, Tinsley JM, Blake DJ, Davies KE. Dystrophin and dystrophin-related proteins: a review of protein and RNA studies. Neuromuscul Disord 1993; 3:5-21. [PMID: 8329888 DOI: 10.1016/0960-8966(93)90037-k] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The analysis of dystrophin gene expression has led to the identification of multiple transcripts and varying isoforms. The data indicate that transcription of the dystrophin gene occurs from several promoters, which involves developmental and tissue-dependent regulation. These discoveries have complicated the interpretation of immunolocalization studies, although there is a strong correlation between the amount and size of dystrophin and the severity of the clinical phenotype. The importance of using protein-specific antibodies for dystrophin analysis has been underscored by the identification of a protein, designated utrophin, which exhibits significant sequence homology with dystrophin. This review addresses the recent studies of dystrophin and utrophin expression in an attempt to illustrate the transcriptional diversity of these large genes and the localization of their protein products within various tissues.
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Affiliation(s)
- D R Love
- Department of Pathology, University of Cambridge, U.K
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35
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Affiliation(s)
- K M Bushby
- Department of Human Genetics, Newcastle upon Tyne
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36
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Way M, Pope B, Cross RA, Kendrick-Jones J, Weeds AG. Expression of the N-terminal domain of dystrophin in E. coli and demonstration of binding to F-actin. FEBS Lett 1992; 301:243-5. [PMID: 1577159 DOI: 10.1016/0014-5793(92)80249-g] [Citation(s) in RCA: 114] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The N-terminal head domain of human dystrophin has been expressed in soluble form and high yield in E. coli, allowing us to test the previously unconfirmed assumption that dystrophin binds actin. DMD246, the first 246 amino acid residues of dystrophin, binds F-actin in a strongly co-operative manner with a Hill constant of 3.5, but does not bind G-actin. Dystrophin heads are thus functionally competent actin-binding proteins. This result opens the way to identifying critical residues in the actin-binding site and encourages us that the other domains of dystrophin might also be treated as functionally autonomous modules, accessible to a similar approach.
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Affiliation(s)
- M Way
- MRC Laboratory of Molecular Biology, Cambridge, UK
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37
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Augier N, Leger J, Robert A, Pons F, Leger JJ, Mornet D. Proteolytic susceptibility of the central domain in chicken gizzard and skeletal muscle dystrophins. BIOCHIMICA ET BIOPHYSICA ACTA 1992; 1138:297-304. [PMID: 1562616 DOI: 10.1016/0925-4439(92)90007-a] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
We investigated proteolytic susceptibility of the central domain in dystrophin molecules from chicken smooth and skeletal muscles. Dystrophin-enriched preparations from both muscles were made as described in Pons et al. (Proc. Natl. Acad. Sci. USA (1990) 87, 7851-7855). These preparations contained other protein components in addition to dystrophin. Three enzymes (Staphylococcus aureus proteinase, chymotrypsin and trypsin) having different proteolytic specificities were used. Time-courses of proteinase degradation were examined by the Western immunoblot technique using a specific polyclonal serum directed against a fragment (residues 1173-1728) of the dystrophin central domain. We observed accumulation of some major proteinase-resistant fragments, in the 110-160 kDa range originating from that central region of the molecule. Cleavage patterns of the smooth and skeletal muscle preparations were quite similar, but molecular weights of the breakdown products differed slightly. Interpretation of the results was based on two predictive structural models of the dystrophin central domain (Koenig and Kunkel (1990) J. Biol. Chem. 265, 4560-4566 and Cross et al. (1990) FEBS Lett. 262, 87-90). Skip residues at the end of repeat 13 (around the 1740th residue of the dystrophin amino acid sequence), as hypothesized in the Cross model, constitute probably the most sensitive site within the dystrophin central domain for any exogenous (or even endogenous) proteinase. Variations observed between dystrophins from skeletal and smooth muscles also suggest that the structures of both dystrophins differ slightly even within the dystrophin central domain. This precise identification of proteinase-resistant dystrophin fragments of variable lengths is a first step towards further physicochemical studies on the very large and rare dystrophin molecule.
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Affiliation(s)
- N Augier
- Pathologie Moléculaire du Muscle, INSERM U.300, Faculté de Pharmacie, Montpellier France
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38
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Parry DA, Dixon TW, Cohen C. Analysis of the three-alpha-helix motif in the spectrin superfamily of proteins. Biophys J 1992; 61:858-67. [PMID: 1581500 PMCID: PMC1260345 DOI: 10.1016/s0006-3495(92)81893-3] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Members of the spectrin superfamily of proteins contain different numbers of homologous repeats arranged in tandem. Each of these consists of a three-alpha-helix motif, comprising two similarly and one oppositely directed alpha-helical segment joined by nonhelical linkers of characteristic length. The right-handed alpha-helices each display a heptad repeat in their amino acid sequences indicative of left-handed coiled-coil-like packing. We have calculated the potential number of inter-helix ionic interactions that specify the spatial arrangement of the helices in the motif in terms of both the handedness of helix connectivity (left or right) and the relative axial stagger between the three alpha-helices. All of the models examined were constrained to have optimal coiled-coil packing. For alpha-spectrin and alpha-actinin the results provide strong support for a left-handed connectivity of the three helices and axial repeat lengths of 5.05 and 6.24 nm, respectively. Furthermore, the axial staggers between homologous segments in the preferred models are identical. The insights provided into the topography of this widespread tertiary fold may prove of value to those concerned with the problem of de novo protein design.
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Affiliation(s)
- D A Parry
- Department of Physics and Biophysics, Massey University, Palmerston North, New Zealand
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39
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Kahana E, Pinder JC, Smith KS, Gratzer WB. Fluorescence quenching of spectrin and other red cell membrane cytoskeletal proteins. Relation to hydrophobic binding sites. Biochem J 1992; 282 ( Pt 1):75-80. [PMID: 1540147 PMCID: PMC1130891 DOI: 10.1042/bj2820075] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The intrinsic fluorescence of spectrin is strongly quenched by low concentrations of 2-bromostearate. This results from binding at a series of hydrophobic sites. Analysis of dynamic fluorescence quenching by acrylamide, iodide and caesium ions, separately and in conjunction with 2-bromostearate, leads to the conclusion that most of the tryptophan side-chains are exposed to solvent. The sites at which the fatty-acid-quenched tryptophans are located apparently interact with the lipid bilayer in the cell, as judged by quenching by bromostearate dissolved in the lipid phase. A minor proportion of the side-chains in native spectrin give rise to sharp proton magnetic resonance signals, indicative of segmental mobility; these chain elements contain some tryptophan residues, as revealed by weak downfield signals from the heterocyclic ring protons. These signals are not appreciably perturbed by stearic acid or by phosphatidylserine liposomes, suggesting that the hydrophobic binding sites are not in mobile chain elements. By contrast with a series of globular proteins which, with the exception of serum albumins, show little or no quenching by 2-bromostearate, the peripheral red cell membrane skeletal proteins ankyrin (and its spectrin-binding domain), protein 4.1 and (to a lesser extent) actin show evidence of a high affinity for the hydrophobic ligand and may, like spectrin, interact directly with the bilayer in situ.
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Affiliation(s)
- E Kahana
- Medical Research Council Muscle and Cell Motility Unit, King's College, London, U.K
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40
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Récan D, Chafey P, Leturcq F, Hugnot JP, Vincent N, Tomé F, Collin H, Simon D, Czernichow P, Nicholson LV. Are cysteine-rich and COOH-terminal domains of dystrophin critical for sarcolemmal localization? J Clin Invest 1992; 89:712-6. [PMID: 1737859 PMCID: PMC442907 DOI: 10.1172/jci115640] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
It has been hypothesized that the tight localization of dystrophin at the muscle membrane is carried out by its cysteine-rich and/or carboxyl domains. We report the results of biochemical and immunocytochemical investigations of dystrophin in muscle from a 1-yr-old patient with a large deletion that removes the distal part of the dystrophin gene, thus spanning the exons coding for the cysteine-rich and the carboxy-terminal domains, and extends beyond the glycerol kinase and congenital adrenal hypoplasia genes. Immunological analysis of muscle dystrophin shows that the deletion results in the production of a truncated, but stable, polypeptide correctly localized at the sarcolemma. These data indicate that neither the cysteine-rich domain, nor the carboxyl domain, are necessary for the appearance of normal dystrophin sarcolemmal localization.
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Affiliation(s)
- D Récan
- Institut National de la Santé et de la Recherche Médicale (INSERM) U129, Institut Cochin de Génétique Moléculaire, Paris, France
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41
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Abstract
Many proteins contain a repetitive sequence motif, which implies that they contain a repetitive structural motif. Spectrin and the related proteins dystrophin and alpha-actinin consist largely of repeated motifs of 100-120 residues. But the repeating motif is degenerate and it has been difficult to define the boundaries of the repeating sequence unit or its corresponding structural unit. We have determined at which residues the structural units that correspond to spectrin's repeating 106-amino acid motifs begin and end. Drosophila alpha-spectrin cDNAs were expressed in bacteria to show that single segments (106 amino acids) and pairs of segments encoded by selected regions of spectrin cDNA can fold into stable conformations whose biophysical and biochemical properties are similar to those of native spectrin. Because such folding was critically dependent on the phasing of the expressed sequence with respect to the apparent boundaries of the repeating motifs, our data provide experimental evidence that relates the boundaries of the folded, conformational unit to the chemical sequence of repeating motifs.
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Affiliation(s)
- E Winograd
- Department of Cellular and Developmental Biology, Harvard University, Cambridge, MA 02138
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Sedgwick SG, Nguyen TM, Ellis JM, Crowne H, Morris GE. Rapid mapping by transposon mutagenesis of epitopes on the muscular dystrophy protein, dystrophin. Nucleic Acids Res 1991; 19:5889-94. [PMID: 1719482 PMCID: PMC329043 DOI: 10.1093/nar/19.21.5889] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Antibody-binding epitopes in the central helical region of the muscular dystrophy protein, dystrophin, have been mapped using a new strategy of transposon mutagenesis. Tn1000 transposons carrying translation termination codons were introduced randomly by bacterial mating into a large fragment of dystrophin cDNA in a pEX2 plasmid to produce a library of transformants expressing truncated dystrophin fusion proteins. Epitopes were progressively lost as the expressed sequences were shortened, enabling the epitopes recognised by 22 monoclonal antibodies to be placed in order along the dystrophin molecule without in vitro manipulation of DNA. The C-terminus of each truncated fusion protein was precisely located within the dystrophin sequence by direct sequencing of pEX2 transformants using transposon-specific primers. Sequences as short as 7 and 17 amino-acids have been identified as essential for antibody binding in this way. Nineteen of the 22 monoclonal antibodies had been selected for their ability to bind both native and SDS-denatured dystrophin and 15 of these bind to one sequence of 74 amino-acids (residues 1431-1505 of the 3684 residue sequence). This may be an area of high immunogenicity or of close structural similarity between native dystrophin and the SDS-treated recombinant fragment used for immunization.
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Affiliation(s)
- S G Sedgwick
- Genetics Division, MRC National Institute for Medical Research, Mill Hill, London, UK
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Abstract
Protein structure prediction from sequence remains a major goal in molecular biology. The methods described in this review concentrate on deriving structural information through the detection of similarities between a test sequence and a database of known structures. Such methods are often referred to as knowledge-based strategies reflecting the use of a structural database in the analyses. The past year has seen considerable advances in both the development of automated procedures and their application to protein sequences of outstanding biological interest.
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Wiche G, Becker B, Luber K, Weitzer G, Castañon MJ, Hauptmann R, Stratowa C, Stewart M. Cloning and sequencing of rat plectin indicates a 466-kD polypeptide chain with a three-domain structure based on a central alpha-helical coiled coil. J Cell Biol 1991; 114:83-99. [PMID: 2050743 PMCID: PMC2289051 DOI: 10.1083/jcb.114.1.83] [Citation(s) in RCA: 164] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
We have determined the complete cDNA sequence of rat plectin from a number of well-characterized overlapping lambda gt11 clones. The 4,140-residue predicted amino acid sequence (466,481 D) is consistent with a three-domain structural model in which a long central rod domain, having mainly an alpha-helical coiled coil conformation, is flanked by globular NH2- and COOH-terminal domains. The plectin sequence has a number of repeating motifs. The rod domain has five subregions approximately 200-residues long in which there is a strong repeat in the charged amino acids at 10.4 residues that may be involved in association between plectin molecules. The globular COOH-terminal domain has a prominent six-fold tandem repeat, with each repeat having a strongly conserved central region based on nine tandem repeats of a 19-residue motif. The plectin sequence has several marked similarities to that of desmoplakin (Green, K. J., D. A. D. Parry, P. M. Steinert, M. L. A. Virata, R. M. Wagner, B. D. Angst, and L.A. Nilles. 1990. J. Biol. Chem. 265:2,603-2,612), which has a shorter coiled-coil rod domain with a similar 10.4 residue charge periodicity and a COOH-terminal globular domain with three tandem repeats homologous to the six found in plectin. The plectin sequence also has homologies to that of the bullous pemphigoid antigen. Northern blot analysis indicated that there is a significant degree of conservation of plectin genes between rat, human, and chicken and that, as shown previously at the protein level, plectin has a wide tissue distribution. There appeared to be a single rat plectin gene that gave rise to a 15-kb message. Expression of polypeptides encoded by defined fragments of plectin cDNA in E. coli has also been used to localize the epitopes of a range of monoclonal and serum antibodies. This enabled us to tentatively map a sequence involved in plectin-vimentin and plectin-lamin B interactions to a restricted region of the rod domain.
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Affiliation(s)
- G Wiche
- Institute of Biochemistry, University of Vienna, Austria
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Abstract
A family of actin-crosslinking proteins share a conserved 125 residue sequence that lies within a 250 residue actin-binding domain. This domain is combined with spacer segments consisting of a variable number of repeated alpha-helical or beta-sheet motifs and other functional domains, which generate proteins that differ in their ability to form actin bundles or networks and to associate with the plasma membrane. These functional domains are not in other actin-crosslinking proteins, one of which is elongation factor 1a (EF-1a) suggesting there are several pathways for the evolution of actin-crosslinking function.
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Affiliation(s)
- P Matsudaira
- Whitehead Institute for Biomedical Research, Massachusetts Institute of Technology, Nine Cambridge Center, MA 02142
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Cullen MJ, Walsh J, Nicholson LV, Harris JB, Zubrzycka-Gaarn EE, Ray PN, Worton RG. Immunogold labelling of dystrophin in human muscle, using an antibody to the last 17 amino acids of the C-terminus. Neuromuscul Disord 1991; 1:113-9. [PMID: 1822781 DOI: 10.1016/0960-8966(91)90058-z] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Immunolabelling with a 10 nm gold probe was used to localize dystrophin at the ultrastructural level in human skeletal muscle. The primary antibody was raised against a synthetic peptide containing the last 17 amino acids at the C-terminus of dystrophin. Using this antibody, labelling was almost entirely confined to a narrow band enclosing 40 nm either side of the plasma membrane and including the membrane itself. Histograms of the position of the gold probe relative to the plasma membrane showed modes lying over the membrane itself or the extracellular face of the membrane. One interpretation of these results is that the C-terminus of dystrophin is inserted in the plasma membrane alongside the glycoproteins with which it is tightly associated. Histograms of the distances between gold probes displayed modes at approximately 120 nm in both transverse and longitudinal sections suggesting that dystrophin forms a lattice-like network adjacent to the plasma membrane.
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Affiliation(s)
- M J Cullen
- Muscular Dystrophy Research Laboratories, Newcastle General Hospital, Newcastle upon Tyne, U.K
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Kahana E, Gratzer WB. Properties of the spectrin-like structural element of smooth-muscle alpha-actinin. CELL MOTILITY AND THE CYTOSKELETON 1991; 20:242-8. [PMID: 1773450 DOI: 10.1002/cm.970200307] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The fragment of smooth muscle alpha-actinin, comprising the four spectrin-like structural repeating units, has a high alpha-helix content, similar to that of spectrin, and a hydrodynamic frictional coefficient, indicative of an elongated, probably bent or kinked rod-like structure, as found for spectrin dimer and tetramer. The fragment exists in solution as an extremely stable dimer, which is dissociated only under denaturing conditions and is much more resistant to dissociation by urea than is the spectrin heterodimer. High-resolution proton magnetic resonance spectra reveal that a part of the polypeptide chain gives rise to sharp resonances; this is also true of spectrin and it implies that the individual structural repeating units contain segmentally mobile elements, which may be required to generate the elastic properties of the spectrin family of proteins. Again like spectrin, the alpha-actinin fragment contains multiple binding sites for long-chain fatty acids, as revealed by quenching of tryptophan fluorescence by 2-bromostearate (though not by 9(10)-bromostearate). The results point to extensive structural and functional similarities between the repeating units of all the proteins of the spectrin family.
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Affiliation(s)
- E Kahana
- Medical Research Council Muscle and Cell Motility Unit, King's College, London, England
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