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Bigotti MG, Klein K, Gan ES, Anastasina M, Andersson S, Vapalahti O, Katajisto P, Erdmann M, Davidson AD, Butcher SJ, Collinson I, Ooi EE, Balistreri G, Brancaccio A, Yamauchi Y. The α-dystroglycan N-terminus is a broad-spectrum antiviral agent against SARS-CoV-2 and enveloped viruses. Antiviral Res 2024; 224:105837. [PMID: 38387750 DOI: 10.1016/j.antiviral.2024.105837] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2023] [Revised: 01/20/2024] [Accepted: 02/13/2024] [Indexed: 02/24/2024]
Abstract
The COVID-19 pandemic has shown the need to develop effective therapeutics in preparedness for further epidemics of virus infections that pose a significant threat to human health. As a natural compound antiviral candidate, we focused on α-dystroglycan, a highly glycosylated basement membrane protein that links the extracellular matrix to the intracellular cytoskeleton. Here we show that the N-terminal fragment of α-dystroglycan (α-DGN), as produced in E. coli in the absence of post-translational modifications, blocks infection of SARS-CoV-2 in cell culture, human primary gut organoids and the lungs of transgenic mice expressing the human receptor angiotensin I-converting enzyme 2 (hACE2). Prophylactic and therapeutic administration of α-DGN reduced SARS-CoV-2 lung titres and protected the mice from respiratory symptoms and death. Recombinant α-DGN also blocked infection of a wide range of enveloped viruses including the four Dengue virus serotypes, influenza A virus, respiratory syncytial virus, tick-borne encephalitis virus, but not human adenovirus, a non-enveloped virus in vitro. This study establishes soluble recombinant α-DGN as a broad-band, natural compound candidate therapeutic against enveloped viruses.
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Affiliation(s)
- Maria Giulia Bigotti
- Bristol Heart Institute, Research Floor Level 7, Bristol Royal Infirmary, Bristol BS2 8HW, UK; School of Biochemistry, Faculty of Life Sciences, University of Bristol, Bristol BS8 1TD, UK.
| | - Katja Klein
- School of Cellular and Molecular Medicine, Faculty of Life Sciences, University of Bristol, Bristol BS8 1TD, UK.
| | - Esther S Gan
- Program in Emerging Infectious Diseases, Duke-NUS Medical School, 8 College Road, Singapore, 169857, Singapore
| | - Maria Anastasina
- Faculty of Biological and Environmental Sciences, Molecular and Integrative Biosciences Research Program, University of Helsinki, Helsinki, Finland; Helsinki Institute of Life Sciences-Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Simon Andersson
- Faculty of Biological and Environmental Sciences, Molecular and Integrative Biosciences Research Program, University of Helsinki, Helsinki, Finland
| | - Olli Vapalahti
- Department of Virology, Medicum, Faculty of Medicine, University of Helsinki, Helsinki, Finland; Department of Virology, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
| | - Pekka Katajisto
- Faculty of Biological and Environmental Sciences, Molecular and Integrative Biosciences Research Program, University of Helsinki, Helsinki, Finland; Helsinki Institute of Life Sciences-Institute of Biotechnology, University of Helsinki, Helsinki, Finland; Department of Biosciences and Nutrition, Karolinska Institutet, 141 83 Huddinge, Sweden; Department of Cell and Molecular Biology, Karolinska Institutet, 171 77 Solna, Sweden
| | - Maximilian Erdmann
- School of Cellular and Molecular Medicine, Faculty of Life Sciences, University of Bristol, Bristol BS8 1TD, UK
| | - Andrew D Davidson
- School of Cellular and Molecular Medicine, Faculty of Life Sciences, University of Bristol, Bristol BS8 1TD, UK
| | - Sarah J Butcher
- Faculty of Biological and Environmental Sciences, Molecular and Integrative Biosciences Research Program, University of Helsinki, Helsinki, Finland; Helsinki Institute of Life Sciences-Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Ian Collinson
- School of Biochemistry, Faculty of Life Sciences, University of Bristol, Bristol BS8 1TD, UK
| | - Eng Eong Ooi
- Program in Emerging Infectious Diseases, Duke-NUS Medical School, 8 College Road, Singapore, 169857, Singapore; Viral Research and Experimental Medicine Centre, SingHealth Duke-NUS Academic Medical Centre, 20 College Road, Singapore, 169856, Singapore; Saw Swee Hock School of Public Health, National University of Singapore, 12 Science Drive 2, #10-01, Singapore, 117549, Singapore
| | - Giuseppe Balistreri
- Faculty of Biological and Environmental Sciences, Molecular and Integrative Biosciences Research Program, University of Helsinki, Helsinki, Finland; Helsinki Institute of Life Sciences-Institute of Biotechnology, University of Helsinki, Helsinki, Finland; Department of Virology, Medicum, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Andrea Brancaccio
- School of Biochemistry, Faculty of Life Sciences, University of Bristol, Bristol BS8 1TD, UK; Institute of Chemical Sciences and Technologies "Giulio Natta" (SCITEC)-CNR, Rome, Italy.
| | - Yohei Yamauchi
- School of Cellular and Molecular Medicine, Faculty of Life Sciences, University of Bristol, Bristol BS8 1TD, UK; Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences (D-CHAB), ETH Zurich, 8093, Zurich, Switzerland; Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan.
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Sciandra F, Bozzi M, Bigotti MG. From adhesion complex to signaling hub: the dual role of dystroglycan. Front Mol Biosci 2023; 10:1325284. [PMID: 38155958 PMCID: PMC10752950 DOI: 10.3389/fmolb.2023.1325284] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Accepted: 11/27/2023] [Indexed: 12/30/2023] Open
Abstract
Dystroglycan (DG) is a transmembrane protein widely expressed in multiple cells and tissues. It is formed by two subunits, α- and β-DG, and represents a molecular bridge between the outside and the inside of the cell, which is essential for the mechanical and structural stability of the plasma membrane. The α-subunit is a cell-surface protein that binds to the extracellular matrix (ECM) and is tightly associated with the plasma membrane via a non-covalent interaction with the β-subunit, which, in turn, is a transmembrane protein that binds to the cytoskeletal actin. DG is a versatile molecule acting not only as a mechanical building block but also as a modulator of outside-inside signaling events. The cytoplasmic domain of β-DG interacts with different adaptor and cytoskeletal proteins that function as molecular switches for the transmission of ECM signals inside the cells. These interactions can modulate the involvement of DG in different biological processes, ranging from cell growth and survival to differentiation and proliferation/regeneration. Although the molecular events that characterize signaling through the ECM-DG-cytoskeleton axis are still largely unknown, in recent years, a growing list of evidence has started to fill the gaps in our understanding of the role of DG in signal transduction. This mini-review represents an update of recent developments, uncovering the dual role of DG as an adhesion and signaling molecule that might inspire new ideas for the design of novel therapeutic strategies for pathologies such as muscular dystrophy, cardiomyopathy, and cancer, where the DG signaling hub plays important roles.
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Affiliation(s)
- Francesca Sciandra
- Istituto di Scienze e Tecnologie Chimiche “Giulio Natta”-SCITEC (CNR), Roma, Italy
| | - Manuela Bozzi
- Istituto di Scienze e Tecnologie Chimiche “Giulio Natta”-SCITEC (CNR), Roma, Italy
- Dipartimento di Scienze Biotecnologiche di Base, Cliniche Intensivologiche e Perioperatorie, Sezione di Biochimica, Università Cattolica del Sacro Cuore di Roma, Roma, Italy
| | - Maria Giulia Bigotti
- School of Biochemistry, University of Bristol, Bristol, United Kingdom
- Bristol Heart Institute, Research Floor Level 7, Bristol Royal Infirmary, Bristol, United Kingdom
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Brancaccio A. A molecular overview of the primary dystroglycanopathies. J Cell Mol Med 2019; 23:3058-3062. [PMID: 30838779 PMCID: PMC6484290 DOI: 10.1111/jcmm.14218] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Revised: 01/22/2019] [Accepted: 01/23/2019] [Indexed: 01/17/2023] Open
Abstract
Dystroglycan is a major non-integrin adhesion complex that connects the cytoskeleton to the surrounding basement membranes, thus providing stability to skeletal muscle. In Vertebrates, hypoglycosylation of α-dystroglycan has been strongly linked to muscular dystrophy phenotypes, some of which also show variable degrees of cognitive impairments, collectively termed dystroglycanopathies. Only a small number of mutations in the dystroglycan gene, leading to the so called primary dystroglycanopathies, has been described so far, as opposed to the ever-growing number of identified secondary or tertiary dystroglycanopathies (caused by genetic abnormalities in glycosyltransferases or in enzymes involved in the synthesis of the carbohydrate building blocks). The few mutations found within the autonomous N-terminal domain of α-dystroglycan seem to destabilise it to different degrees, without influencing the overall folding and targeting of the dystroglycan complex. On the contrary other mutations, some located at the α/β interface of the dystroglycan complex, seem to be able to interfere with its maturation, thus compromising its stability and eventually leading to the intracellular engulfment and/or partial or even total degradation of the dystroglycan uncleaved precursor.
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Affiliation(s)
- Andrea Brancaccio
- School of Biochemistry, University of Bristol, Bristol, UK.,Istituto di Chimica del Riconoscimento Molecolare - CNR c/o Università Cattolica del Sacro Cuore, Roma, Italy
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Signorino G, Covaceuszach S, Bozzi M, Hübner W, Mönkemöller V, Konarev PV, Cassetta A, Brancaccio A, Sciandra F. A dystroglycan mutation (p.Cys667Phe) associated to muscle-eye-brain disease with multicystic leucodystrophy results in ER-retention of the mutant protein. Hum Mutat 2017; 39:266-280. [PMID: 29134705 DOI: 10.1002/humu.23370] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Revised: 10/13/2017] [Accepted: 11/06/2017] [Indexed: 01/11/2023]
Abstract
Dystroglycan (DG) is a cell adhesion complex composed by two subunits, the highly glycosylated α-DG and the transmembrane β-DG. In skeletal muscle, DG is involved in dystroglycanopathies, a group of heterogeneous muscular dystrophies characterized by a reduced glycosylation of α-DG. The genes mutated in secondary dystroglycanopathies are involved in the synthesis of O-mannosyl glycans and in the O-mannosylation pathway of α-DG. Mutations in the DG gene (DAG1), causing primary dystroglycanopathies, destabilize the α-DG core protein influencing its binding to modifying enzymes. Recently, a homozygous mutation (p.Cys699Phe) hitting the β-DG ectodomain has been identified in a patient affected by muscle-eye-brain disease with multicystic leucodystrophy, suggesting that other mechanisms than hypoglycosylation of α-DG could be implicated in dystroglycanopathies. Herein, we have characterized the DG murine mutant counterpart by transfection in cellular systems and high-resolution microscopy. We observed that the mutation alters the DG processing leading to retention of its uncleaved precursor in the endoplasmic reticulum. Accordingly, small-angle X-ray scattering data, corroborated by biochemical and biophysical experiments, revealed that the mutation provokes an alteration in the β-DG ectodomain overall folding, resulting in disulfide-associated oligomerization. Our data provide the first evidence of a novel intracellular mechanism, featuring an anomalous endoplasmic reticulum-retention, underlying dystroglycanopathy.
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Affiliation(s)
- Giulia Signorino
- Istituto di Biochimica e Biochimica Clinica, Università Cattolica del Sacro Cuore, Roma, Italy
| | | | - Manuela Bozzi
- Istituto di Biochimica e Biochimica Clinica, Università Cattolica del Sacro Cuore, Roma, Italy.,Istituto di Chimica del Riconoscimento Molecolare - CNR c/o Istituto di Biochimica e Biochimica Clinica, Università Cattolica del Sacro Cuore, Roma, Italy
| | - Wolfgang Hübner
- Biomolecular Photonics, University of Bielefeld, Bielefeld, Germany
| | | | - Petr V Konarev
- A.V. Shubnikov Institute of Crystallography of Federal Scientific Research Centre "Crystallography and Photonics" of Russian Academy of Sciences, Leninsky prospect 59, Moscow, Russia
| | - Alberto Cassetta
- Istituto di Cristallografia - CNR, Trieste Outstation, Trieste, Italy
| | - Andrea Brancaccio
- Istituto di Chimica del Riconoscimento Molecolare - CNR c/o Istituto di Biochimica e Biochimica Clinica, Università Cattolica del Sacro Cuore, Roma, Italy.,School of Biochemistry, University of Bristol, Bristol, United Kingdom
| | - Francesca Sciandra
- Istituto di Chimica del Riconoscimento Molecolare - CNR c/o Istituto di Biochimica e Biochimica Clinica, Università Cattolica del Sacro Cuore, Roma, Italy
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Palmieri V, Bozzi M, Signorino G, Papi M, De Spirito M, Brancaccio A, Maulucci G, Sciandra F. α-Dystroglycan hypoglycosylation affects cell migration by influencing β-dystroglycan membrane clustering and filopodia length: A multiscale confocal microscopy analysis. Biochim Biophys Acta Mol Basis Dis 2017; 1863:2182-2191. [DOI: 10.1016/j.bbadis.2017.05.025] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2017] [Revised: 05/05/2017] [Accepted: 05/28/2017] [Indexed: 12/26/2022]
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Adams JC, Brancaccio A. The evolution of the dystroglycan complex, a major mediator of muscle integrity. Biol Open 2015; 4:1163-79. [PMID: 26319583 PMCID: PMC4582122 DOI: 10.1242/bio.012468] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Basement membrane (BM) extracellular matrices are crucial for the coordination of different tissue layers. A matrix adhesion receptor that is important for BM function and stability in many mammalian tissues is the dystroglycan (DG) complex. This comprises the non-covalently-associated extracellular α-DG, that interacts with laminin in the BM, and the transmembrane β-DG, that interacts principally with dystrophin to connect to the actin cytoskeleton. Mutations in dystrophin, DG, or several enzymes that glycosylate α-DG underlie severe forms of human muscular dystrophy. Nonwithstanding the pathophysiological importance of the DG complex and its fundamental interest as a non-integrin system of cell-ECM adhesion, the evolution of DG and its interacting proteins is not understood. We analysed the phylogenetic distribution of DG, its proximal binding partners and key processing enzymes in extant metazoan and relevant outgroups. We identify that DG originated after the divergence of ctenophores from porifera and eumetazoa. The C-terminal half of the DG core protein is highly-conserved, yet the N-terminal region, that includes the laminin-binding region, has undergone major lineage-specific divergences. Phylogenetic analysis based on the C-terminal IG2_MAT_NU region identified three distinct clades corresponding to deuterostomes, arthropods, and mollusks/early-diverging metazoans. Whereas the glycosyltransferases that modify α-DG are also present in choanoflagellates, the DG-binding proteins dystrophin and laminin originated at the base of the metazoa, and DG-associated sarcoglycan is restricted to cnidarians and bilaterians. These findings implicate extensive functional diversification of DG within invertebrate lineages and identify the laminin-DG-dystrophin axis as a conserved adhesion system that evolved subsequent to integrin-ECM adhesion, likely to enhance the functional complexity of cell-BM interactions in early metazoans.
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Affiliation(s)
- Josephine C Adams
- School of Biochemistry, University of Bristol, Biomedical Sciences Building, University Walk, Bristol BS8 1TD, UK
| | - Andrea Brancaccio
- Istituto di Chimica del Riconoscimento Molecolare, CNR, Istituto di Biochimica e Biochimica Clinica, Università Cattolica del Sacro Cuore, Largo Francesco Vito 1, Roma 00168, Italy
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A second Ig-like domain identified in dystroglycan by molecular modelling and dynamics. J Mol Graph Model 2011; 29:1015-24. [PMID: 21605994 DOI: 10.1016/j.jmgm.2011.04.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2011] [Revised: 04/19/2011] [Accepted: 04/21/2011] [Indexed: 11/23/2022]
Abstract
Dystroglycan (DG) is a cell surface receptor which is composed of two subunits that interact noncovalently, namely α- and β-DG. In skeletal muscle, DG is the central component of the dystrophin-glycoprotein complex (DGC) that anchors the actin cytoskeleton to the extracellular matrix. To date only the three-dimensional structure of the N-terminal region of α-DG has been solved by X-ray crystallography. To expand such a structural analysis, a theoretical molecular model of the murine α-DG C-terminal region was built based on folding recognition/threading techniques. Although there is no a significant (<30%) sequence homology with the N-terminal region of α-DG, protein fold recognition methods found a significant resemblance to the α-DG N-terminal crystallographic structure. Our in silico structural prediction identified two subdomains in this region. Amino acid residues ∼ 500-600 of α-DG were predicted to adopt an immunoglobulin-like (Ig-like) β-sandwich fold. Such modeled domain includes the β-DG binding epitope of α-DG and, confirming our previous experimental results, suggests that the linear epitope (residues 550-565) assumes a β-strand conformation. The remaining segment of the α-DG C-terminal region (residues 601-653) is organized in a coil-helix-coil motif. A 20-ns molecular dynamics simulation in explicit water solvent provided support to the predicted Ig-like model structure. The identification of a second Ig-like domain in DG represents another important step towards a full structural and functional description of the α/β DG interface. Preliminary characterization of a novel recombinant peptide (505-600) encompassing this second Ig-like domain demonstrates that it is soluble and stable, further corroborating our in silico analysis.
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Sciandra F, Bozzi M, Morlacchi S, Galtieri A, Giardina B, Brancaccio A. Mutagenesis at the alpha-beta interface impairs the cleavage of the dystroglycan precursor. FEBS J 2009; 276:4933-45. [PMID: 19694806 DOI: 10.1111/j.1742-4658.2009.07196.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The interaction between a-dystroglycan (alpha-DG) and beta-dystroglycan (beta-DG), the two constituent subunits of the adhesion complex dystroglycan, is crucial in maintaining the integrity of the dystrophin-glycoprotein complex. The importance of the alpha-beta interface can be seen in the skeletal muscle of humans affected by severe conditions, such as Duchenne muscular dystrophy, where the alpha-beta interaction can be secondarily weakened or completely lost, causing sarcolemmal instability and muscular necrosis. The reciprocal binding epitopes of the two subunits reside within the C-terminus of alpha-DG and the ectodomain of beta-DG. As no ultimate structural data are yet available on the alpha-beta interface, site-directed mutagenesis was used to identify which specific amino acids are involved in the interaction. A previous alanine-scanning analysis of the recombinant beta-DG ectodomain allowed the identification of two phenylalanines important for alpha-DG binding, namely F692 and F718. In this article, similar experiments performed on the alpha-DG C-terminal domain pinpointed two residues, G563 and P565, as possible binding counterparts of the two beta-DG phenylalanines. In 293-Ebna cells, the introduction of alanine residues instead of F692, F718, G563 and P565 prevented the cleavage of the DG precursor that liberates alpha- and beta-DG, generating a pre-DG of about 160 kDa. This uncleaved pre-DG tetramutant is properly targeted at the cell membrane, is partially glycosylated and still binds laminin in pull-down assays. These data reinforce the notion that DG processing and its membrane targeting are two independent processes, and shed new light on the molecular mechanism that drives the maturation of the DG precursor.
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Affiliation(s)
- Francesca Sciandra
- Istituto di Chimica del Riconoscimento Molecolare (CNR), c/o Istituto di Biochimica e Biochimica Clinica, Università Cattolica del Sacro Cuore, Rome, Italy
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G.P.14.15 Evaluating the role of the dystroglycan α/β interface in human muscular dystrophies. Neuromuscul Disord 2008. [DOI: 10.1016/j.nmd.2008.06.329] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Gong Y, Zhang R, Zhang J, Xu L, Zhang F, Xu W, Wang Y, Chu Y, Xiong S. Alpha-dystroglycan is involved in positive selection of thymocytes by participating in immunological synapse formation. FASEB J 2008; 22:1426-39. [PMID: 18171694 DOI: 10.1096/fj.07-9264com] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Alpha-dystroglycan has been proved to be involved in lymphocyte activation by participating in immunological synapse (IS) formation. Considering the existence of IS formation in thymic development, we questioned whether alpha-dystroglycan was expressed in thymus and influenced thymic development. In this study, we demonstrated that alpha-dystroglycan was expressed on fetal thymocytes, especially on double-positive (DP, CD4(+)CD8(+)) cells. Blocking alpha-dystroglycan by treatment of fetal thymus organ culture (FTOC) with anti-alpha-dystroglycan antibody IIH6C4 decreased the number of DP cells compared with nontreated or isotype antibody controls. Down-regulation of alpha-dystroglycan by retroviruses carrying antisense cDNA of dystroglycan in reaggregate thymus organ culture (RTOC) further confirmed these results. Enhanced apoptosis of DP cells was observed after blocking alpha-dystroglycan. Interestingly, we found that blocking alpha-dystroglycan reduced IS formation between DP cells and thymic epithelial cells. Furthermore, blocking alpha-dystroglycan up-regulated CD95/CD95L expression and reduced Bcl-2 expression on DP cells in the developing thymus. Finally, the increase in the apoptosis of DP cells was associated with a consequent decrease in the positive selection, as indicated by the reduction of both ERK phosphorylation in DP cells and single-positive (SP, CD4(+) or CD8(+)) cell outcome. Altogether, these results indicated that alpha-dystroglycan was involved in positive selection of thymocytes by participating in the IS formation.
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Affiliation(s)
- Yanping Gong
- Department of Immunology, Shanghai Medical College of Fudan University, 138 Yixueyuan Rd., Shanghai 200032, China
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Schröder JE, Tegeler MR, Grosshans U, Porten E, Blank M, Lee J, Esapa C, Blake DJ, Kröger S. Dystroglycan regulates structure, proliferation and differentiation of neuroepithelial cells in the developing vertebrate CNS. Dev Biol 2007; 307:62-78. [PMID: 17512925 DOI: 10.1016/j.ydbio.2007.04.020] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2007] [Revised: 04/08/2007] [Accepted: 04/16/2007] [Indexed: 10/23/2022]
Abstract
In the developing CNS alpha- and beta-dystroglycan are highly concentrated in the endfeet of radial neuroepithelial cells at the contact site to the basal lamina. We show that injection of anti-dystroglycan Fab fragments, knockdown of dystroglycan using RNAi, and overexpression of a dominant-negative dystroglycan protein by microelectroporation in neuroepithelial cells of the chick retina and optic tectum in vivo leads to the loss of their radial morphology, to hyperproliferation, to an increased number of postmitotic neurons, and to an altered distribution of several basally concentrated proteins. Moreover, these treatments also altered the oriented growth of axons from retinal ganglion cells and from tectal projection neurons. In contrast, expression of non-cleavable dystroglycan protein in neuroepithelial cells reduced their proliferation and their differentiation to postmitotic neurons. These results demonstrate that dystroglycan plays a key role in maintaining neuroepithelial cell morphology, and that interfering with dystroglycan function influences proliferation and differentiation of neuroepithelial cells. These data also suggest that an impaired dystroglycan function in neuroepithelial cells might be responsible for some of the severe brain abnormalities observed in certain forms of congenital muscular dystrophy.
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Affiliation(s)
- Jörn E Schröder
- Department of Physiological Chemistry, University of Mainz, Duesbergweg 6, D-55099 Mainz, Germany
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Duplication of the dystroglycan gene in most branches of teleost fish. BMC Mol Biol 2007; 8:34. [PMID: 17509131 PMCID: PMC1885269 DOI: 10.1186/1471-2199-8-34] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2006] [Accepted: 05/17/2007] [Indexed: 11/24/2022] Open
Abstract
Background The dystroglycan (DG) complex is a major non-integrin cell adhesion system whose multiple biological roles involve, among others, skeletal muscle stability, embryonic development and synapse maturation. DG is composed of two subunits: α-DG, extracellular and highly glycosylated, and the transmembrane β-DG, linking the cytoskeleton to the surrounding basement membrane in a wide variety of tissues. A single copy of the DG gene (DAG1) has been identified so far in humans and other mammals, encoding for a precursor protein which is post-translationally cleaved to liberate the two DG subunits. Similarly, D. rerio (zebrafish) seems to have a single copy of DAG1, whose removal was shown to cause a severe dystrophic phenotype in adult animals, although it is known that during evolution, due to a whole genome duplication (WGD) event, many teleost fish acquired multiple copies of several genes (paralogues). Results Data mining of pufferfish (T. nigroviridis and T. rubripes) and other teleost fish (O. latipes and G. aculeatus) available nucleotide sequences revealed the presence of two functional paralogous DG sequences. RT-PCR analysis proved that both the DG sequences are transcribed in T. nigroviridis. One of the two DG sequences harbours an additional mini-intronic sequence, 137 bp long, interrupting the uncomplicated exon-intron-exon pattern displayed by DAG1 in mammals and D. rerio. A similar scenario emerged also in D. labrax (sea bass), from whose genome we have cloned and sequenced a new DG sequence that also harbours a shorter additional intronic sequence of 116 bp. Western blot analysis confirmed the presence of DG protein products in all the species analysed including two teleost Antarctic species (T. bernacchii and C. hamatus). Conclusion Our evolutionary analysis has shown that the whole-genome duplication event in the Class Actinopterygii (ray-finned fish) involved also DAG1. We unravelled new important molecular genetic details about fish orthologous DGs, which might help to increase the current knowledge on DG expression, maturation and targeting and on its physiopathological role in higher organisms.
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Watanabe N, Sasaoka T, Noguchi S, Nishino I, Tanaka T. Cys669-Cys713 disulfide bridge formation is a key to dystroglycan cleavage and subunit association. Genes Cells 2007; 12:75-88. [PMID: 17212656 DOI: 10.1111/j.1365-2443.2006.01033.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Dystroglycan (DG) is a widely expressed, transmembrane glycoprotein complex that plays important roles by connecting the extracellular matrix to the cytoskeleton. The alpha- and beta-DG subunits are produced by the cleavage of residues 653 and 654 of the precursor. To clarify the mechanisms involved in cleavage and subunit association, we performed a series of mutation analyses and made the following discoveries: (i) Disruption of the intramolecular disulfide bridge between Cys669 and Cys713 in beta-DG completely abolishes the cleavage, (ii) deletions in the loop region (669-713) and in the C-terminal region of alpha-DG (550-645) abolish the cleavage, (iii) disruption of the disulfide bridge and deletions in the loop region deteriorate the alpha- and beta-DG subunit association, and (iv) at the cleavage site, especially, positions P1' (Ser654) and P6' (Trp659) are critical. Thus, the critical role of the Cys669-Cys713 disulfide bridge formation is, most likely, to form a specific tertiary structure, in which the alpha- and beta-DG domains interact and the cleavage site becomes susceptible to proteolytic reactions. The Cys669 and Cys713 pair is broadly conserved in vertebrates and in some invertebrates, suggesting that the disulfide bridge formation was established early in the evolution of DG.
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Affiliation(s)
- Noriyuki Watanabe
- Division of Infectious Disease Control, Advanced Medical Research Center, Nihon University School of Medicine, 30-1 Oyaguchi-Kamimachi, Itabashi-ku, Tokyo 173-8610, Japan
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Concolino P, Capoluongo E, Santonocito C, Vento G, Tana M, Romagnoli C, Zuppi C, Ameglio F, Brancaccio A, Sciandra F. Genetic analysis of the dystroglycan gene in bronchopulmonary dysplasia affected premature newborns. Clin Chim Acta 2006; 378:164-7. [PMID: 17196572 DOI: 10.1016/j.cca.2006.11.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2006] [Accepted: 11/17/2006] [Indexed: 10/23/2022]
Abstract
BACKGROUND Dystroglycan (DG) is an extracellular matrix receptor that serves as an adhesion molecule and is essential for the stability of the plasma membrane. DG is highly expressed within the epithelial cell layer where it supports morphogenesis, adhesion and wound repair. Mechanically ventilated newborns often develop bronchopulmonary dysplasia (BPD), characterized by a progressive impairment of wound repair capacity in their lung. METHODS To verify if the susceptibility to BPD might be linked to genetic abnormalities in the DG gene (DAG1), we searched for possible mutations in 33 premature newborns with gestational age<34 weeks with risk of developing BPD. DAG1 genotype was determined in 11 premature newborns with BPD as compared to 22 premature infants without lung complications. RESULTS Eight polymorphisms were found, four of them being new DAG1 single nucleotide polymorphisms (SNPs). Only one significant association was found with BPD positive infants: the N494H homozygous genotype (p=0.033). The same polymorphism was found significantly associated with BPD when allelic frequencies were considered (p=0.0015). CONCLUSIONS Our data enrich the list of DAG1 SNPs and could be useful to trigger further genetic studies about the involvement of DG in human diseases.
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Affiliation(s)
- Paola Concolino
- Laboratorio di Biologia Molecolare, Università Cattolica del Sacro Cuore, Italy
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15
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Bozzi M, Sciandra F, Ferri L, Torreri P, Pavoni E, Petrucci TC, Giardina B, Brancaccio A. Concerted mutation of Phe residues belonging to the ?-dystroglycan ectodomain strongly inhibits the interaction with ?-dystroglycan in�vitro. FEBS J 2006; 273:4929-43. [PMID: 17018058 DOI: 10.1111/j.1742-4658.2006.05492.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The dystroglycan adhesion complex consists of two noncovalently interacting proteins: alpha-dystroglycan, a peripheral extracellular subunit that is extensively glycosylated, and the transmembrane beta-dystroglycan, whose cytosolic tail interacts with dystrophin, thus linking the F-actin cytoskeleton to the extracellular matrix. Dystroglycan is thought to play a crucial role in the stability of the plasmalemma, and forms strong contacts between the extracellular matrix and the cytoskeleton in a wide variety of tissues. Abnormal membrane targeting of dystroglycan subunits and/or their aberrant post-translational modification are often associated with several pathologic conditions, ranging from neuromuscular disorders to carcinomas. A putative functional hotspot of dystroglycan is represented by its intersubunit surface, which is contributed by two amino acid stretches: approximately 30 amino acids of beta-dystroglycan (691-719), and approximately 15 amino acids of alpha-dystroglycan (550-565). Exploiting alanine scanning, we have produced a panel of site-directed mutants of our two consolidated recombinant peptides beta-dystroglycan (654-750), corresponding to the ectodomain of beta-dystroglycan, and alpha-dystroglycan (485-630), spanning the C-terminal domain of alpha-dystroglycan. By solid-phase binding assays and surface plasmon resonance, we have determined the binding affinities of mutated peptides in comparison to those of wild-type alpha-dystroglycan and beta-dystroglycan, and shown the crucial role of two beta-dystroglycan phenylalanines, namely Phe692 and Phe718, for the alpha-beta interaction. Substitution of the alpha-dystroglycan residues Trp551, Phe554 and Asn555 by Ala does not affect the interaction between dystroglycan subunits in vitro. As a preliminary analysis of the possible effects of the aforementioned mutations in vivo, detection through immunofluorescence and western blot of the two dystroglycan subunits was pursued in dystroglycan-transfected 293-Ebna cells.
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Affiliation(s)
- Manuela Bozzi
- Istituto di Biochimica e Biochimica Clinica, Università Cattolica del Sacro Cuore, Largo Francesco Vito 1, 00168 Rome, Italy
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16
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Schneider M, Khalil AA, Poulton J, Castillejo-Lopez C, Egger-Adam D, Wodarz A, Deng WM, Baumgartner S. Perlecan and Dystroglycan act at the basal side of the Drosophila follicular epithelium to maintain epithelial organization. Development 2006; 133:3805-15. [PMID: 16943280 PMCID: PMC2753471 DOI: 10.1242/dev.02549] [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] [Indexed: 11/20/2022]
Abstract
Dystroglycan (Dg) is a widely expressed extracellular matrix (ECM) receptor required for muscle viability, synaptogenesis, basementmembrane formation and epithelial development. As an integral component of the Dystrophin-associated glycoprotein complex, Dg plays a central role in linking the ECM and the cytoskeleton. Disruption of this linkage in skeletal muscle leads to various types of muscular dystrophies. In epithelial cells, reduced expression of Dg is associated with increased invasiveness of cancer cells. We have previously shown that Dg is required for epithelial cell polarity in Drosophila, but the mechanisms of this polarizing activity and upstream/downstream components are largely unknown. Using the Drosophila follicle-cell epithelium (FCE) as a model system, we show that the ECM molecule Perlecan (Pcan) is required for maintenance of epithelial-cell polarity. Follicle cells that lack Pcan develop polarity defects similar to those of Dg mutant cells. Furthermore, Dg depends on Pcan but not on Laminin A for its localization in the basal-cell membrane, and the two proteins bind in vitro. Interestingly, the Dg form that interacts with Pcan in the FCE lacks the mucin-like domain, which is thought to be essential for Dg ligand binding activity. Finally, we describe two examples of how Dg promotes the differentiation of the basal membrane domain: (1) by recruiting/anchoring the cytoplasmic protein Dystrophin; and (2) by excluding the transmembrane protein Neurexin. We suggest that the interaction of Pcan and Dg at the basal side of the epithelium promotes basal membrane differentiation and is required for maintenance of cell polarity in the FCE.
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Affiliation(s)
- Martina Schneider
- Department for Experimental Medical Science, Section for Developmental Biology, Lund University, Lund, Sweden.
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17
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Johnson RP, Kang SH, Kramer JM. C. elegans dystroglycan DGN-1 functions in epithelia and neurons, but not muscle, and independently of dystrophin. Development 2006; 133:1911-21. [PMID: 16611689 DOI: 10.1242/dev.02363] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The C. elegans dystroglycan (DG) homolog DGN-1 is expressed in epithelia and neurons, and localizes to basement membrane (BM) surfaces. Unlike vertebrate DG, DGN-1 is not expressed in muscle or required for muscle function. dgn-1 null mutants are viable but sterile owing to severe disorganization of the somatic gonad epithelium, and show defects in vulval and excretory cell epithelia and in motoneuron axon guidance. The defects resemble those of epi-1 laminin alphaB mutants, suggesting that DGN-1 serves as a receptor for laminin. dgn-1(0)/+ animals are fertile but show gonad migration defects in addition to the defects seen in homozygotes, indicating that DGN-1 function is dosage sensitive. Phenotypic analyses show that DGN-1 and dystrophin-associated protein complex (DAPC) components have distinct and independent functions, in contrast to the situation in vertebrate muscle. The DAPC-independent functions of DGN-1 in epithelia and neurons suggest that vertebrate DG may also act independently of dystrophin/utrophin in non-muscle tissues.
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Affiliation(s)
- Robert P Johnson
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
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18
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Shah WA, Peng H, Carbonetto S. Role of non-raft cholesterol in lymphocytic choriomeningitis virus infection via alpha-dystroglycan. J Gen Virol 2006; 87:673-678. [PMID: 16476990 DOI: 10.1099/vir.0.81444-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Dystroglycan (DG) is an extracellular matrix receptor necessary for the development of metazoans from flies to humans and is also an entry route for various pathogens. Lymphocytic choriomeningitis virus (LCMV), a member of the family Arenaviridae, infects by binding to alpha-DG. Here, the role of cholesterol lipid rafts in infection by LCMV via alpha-DG was investigated. The cholesterol-sequestering drugs methyl-beta-cyclodextrin (MbetaCD), filipin and nystatin inhibited the infectivity of LCMV selectively, but did not affect infection by vesicular stomatitis virus. Cholesterol loading after depletion with MbetaCD restored infectivity to control levels. DG was not found in lipid rafts identified with the raft marker ganglioside GM1. Treatment with MbetaCD, however, enhanced the solubility of DG. This may reflect the association of DG with cholesterol outside lipid rafts and suggests that association of DG with non-raft cholesterol is critical for infection by LCMV through alpha-DG.
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Affiliation(s)
- Waris A Shah
- Center for Research in Neuroscience and Department of Neurology and Neurosurgery, McGill University, Montréal General Hospital Research Institute, 1650 Cedar Avenue, Montréal, Québec H3G 1A4, Canada
| | - Huashan Peng
- Center for Research in Neuroscience and Department of Neurology and Neurosurgery, McGill University, Montréal General Hospital Research Institute, 1650 Cedar Avenue, Montréal, Québec H3G 1A4, Canada
| | - Salvatore Carbonetto
- Center for Research in Neuroscience and Department of Neurology and Neurosurgery, McGill University, Montréal General Hospital Research Institute, 1650 Cedar Avenue, Montréal, Québec H3G 1A4, Canada
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19
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Zhang J, Wang Y, Chu Y, Su L, Gong Y, Zhang R, Xiong S. Agrin is involved in lymphocytes activation that is mediated by alpha-dystroglycan. FASEB J 2006; 20:50-8. [PMID: 16394267 DOI: 10.1096/fj.04-3303com] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
It is well established that agrin, an extracellular matrix protein, plays a crucial role in the formation of neuromuscular junctions. Recent evidence indicates that agrin also contributes to immunological synapse formation. However, little is known about how agrin induces the activation of lymphocytes and whose receptors mediate its regulatory effects on these cells. In the present study, agrin was detected in lymphocytes. Up-regulation of agrin expression was involved in lymphocyte activation whereas down-regulation of its expression led to inhibition of both antigen-specific and nonspecific lymphocyte activation, indicating an intrinsic role for agrin in the activation of lymphocytes. Unexpectedly, unlike that found in muscle cells where there is coexpression of muscle-specific kinase (MuSK) and alpha-dystroglycan receptors for agrin, only alpha-dystroglycan could be detected in lymphocytes. Confocal examination showed that alpha-dystroglycan colocalized with agrin in forming the immunological synapse. Down-regulation of alpha-dystroglycan expression inhibited lymphocyte activation even in the presence of agrin. However, agrin involved in down-regulation of alpha-dystroglycan receptors did not increase the inhibitory effect on lymphocytes activation. The anti-alpha-dystroglycan antibody also induced lymphocytes activation. Taken together, these findings strongly indicate that agrin and alpha-dystroglycan mediate lymphocyte activation. Furthermore, agrin-involved lymphocyte activation is mediated by alpha-dystroglycan.
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Affiliation(s)
- Jinping Zhang
- Department of Immunology, Shanghai Medical College of Fudan University, 138 Yixueyuan Road, Shanghai, 200032, China
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20
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Vogtländer NPJ, Dijkman H, Bakker MAH, Campbell KP, van der Vlag J, Berden JHM. Localization of alpha-dystroglycan on the podocyte: from top to toe. J Histochem Cytochem 2005; 53:1345-53. [PMID: 15956031 DOI: 10.1369/jhc.4a6596.2005] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
alpha-Dystroglycan (DG) is a negatively charged membrane-associated glycoprotein that links the cytoskeleton to the extracellular matrix. Previously, we described that alpha-DG covers the whole podocyte cell membrane in the rat. However, our finding was challenged by the description of a strictly basolateral localization in human kidney biopsies, using a different antibody against alpha-DG. Therefore, we studied the exact localization of glomerular alpha-DG by using these two antibodies in both species. The studies were performed by using monoclonal antibodies (MoAbs) IIH6 and VIA4.1 in immunofluorescence, confocal microscopy, and immunoelectron microscopy on both rat and human kidney sections, as well as on cultured mouse podocytes. The apical localization of alpha-DG on podocytes was more dominant than the basolateral localization. The basolateral staining with MoAb VIA4.1 was more pronounced than that of MoAb IIH6. With both MoAbs, the staining in rat kidneys was more prominent, in comparison to human kidneys. We conclude that alpha-DG is expressed at both the basolateral and apical sides of the podocyte. This localization suggests that alpha-DG plays a dual role in the maintenance of the unique architecture of podocytes by its binding to the glomerular basement membrane, and in the maintenance of the integrity of the filtration slit, respectively.
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Affiliation(s)
- Nils P J Vogtländer
- Division of Nephrology (545), Radboud University Nijmegen Medical Centre, PO Box 9101, 6500 HB Nijmegen, The Netherlands
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21
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Pavoni E, Sciandra F, Barca S, Giardina B, Petrucci TC, Brancaccio A. Immunodetection of partially glycosylated isoforms of alpha-dystroglycan by a new monoclonal antibody against its beta-dystroglycan-binding epitope. FEBS Lett 2005; 579:493-9. [PMID: 15642365 DOI: 10.1016/j.febslet.2004.10.111] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2004] [Revised: 10/04/2004] [Accepted: 10/19/2004] [Indexed: 11/17/2022]
Abstract
The alpha/beta dystroglycan (DG) complex links the extracellular matrix to the actin cytoskeleton. The extensive glycosylation of alpha-DG is believed to be crucial for the interaction with its extracellular matrix-binding partners. We characterized a monoclonal antibody, directed against the beta-DG-binding epitope ( approximately positions 550-565), which recognizes preferentially hypoglycosylated alpha-DG. In Western blot, the antibody was able to detect a number of partially glycosylated alpha-DG isoforms from rat brain and chicken skeletal muscle tissue samples. In addition, we demonstrated its inhibitory effect on the interaction between alpha- and beta-DG in vitro and preliminary immunostaining experiments suggest that such hypoglycosylated alpha-DG isoforms could play a role within cells.
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Affiliation(s)
- Ernesto Pavoni
- CNR, Istituto di Chimica del Riconoscimento Molecolare c/o Istituto di Biochimica e Biochimica Clinica, Università Cattolica del Sacro Cuore, Largo F. Vito 1, 00168 Roma, Italy
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22
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Abstract
Dystroglycan (DG), a non-integrin adhesion molecule, is a pivotal component of the dystrophin-glycoprotein complex, that is expressed in skeletal muscle and in a wide variety of tissues at the interface between the basement membrane (BM) and the cell membrane. DG has been mainly studied for its role in skeletal muscle cell stability and its alterations in muscular diseases, such as dystrophies. However, accumulating evidence have implicated DG in a variety of other biological functions, such as maturation of post-synaptic elements in the central and peripheral nervous system, early morphogenesis, and infective pathogens targeting. Moreover, DG has been reported to play a role in regulating cytoskeletal organization, cell polarization, and cell growth in epithelial cells. Recent studies also indicate that abnormalities in the expression of DG frequently occur in human cancers and may play a role in both the process of tumor progression and in the maintenance of the malignant phenotype. This paper reviews the available information on the biology of DG, the abnormalities found in human cancers, and the implications of these findings with respect to our understanding of cancer pathogenesis and to the development of novel strategies for a better management of cancer patients.
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Affiliation(s)
- Alessandro Sgambato
- Centro di Ricerche Oncologiche Giovanni XXIII, Istituto di Patologia Generale, Catholic University, Rome, Italy.
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23
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Bozic D, Sciandra F, Lamba D, Brancaccio A. The Structure of the N-terminal Region of Murine Skeletal Muscle α-Dystroglycan Discloses a Modular Architecture. J Biol Chem 2004; 279:44812-6. [PMID: 15326183 DOI: 10.1074/jbc.c400353200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Dystroglycan (DG) is a cell surface receptor consisting of two subunits: alpha-dystroglycan, extracellular and highly glycosylated, and beta-dystroglycan, spanning the cell membrane. It is a pivotal member of the dystrophin-glycoprotein complex and is involved in a wide variety of important cellular processes such as the stabilization of the muscle fiber sarcolemma or the clustering of acetylcholine receptors. We report the 2.3-A resolution crystal structure of the murine skeletal muscle N-terminal alpha-DG region, which confirms the presence of two autonomous domains; the first finally identified as an Ig-like and the second resembling ribosomal RNA-binding proteins. Solid-phase laminin binding assays show the occurrence of protein-protein type of interactions involving the Ig-like domain of alpha-DG.
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Affiliation(s)
- Damir Bozic
- Biochemisches Institut der Universität Zürich, Zürich 8044, Switzerland.
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24
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Di Stasio E, Bizzarri P, Misiti F, Pavoni E, Brancaccio A. A fast and accurate procedure to collect and analyze unfolding fluorescence signal: the case of dystroglycan domains. Biophys Chem 2004; 107:197-211. [PMID: 14962600 DOI: 10.1016/j.bpc.2003.09.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2003] [Revised: 09/15/2003] [Accepted: 09/15/2003] [Indexed: 11/15/2022]
Abstract
Monitoring the fluorescence signal upon unfolding often represents a very effective method to rapidly retrieve the first preliminary structural information on a protein domain. The relationship between intrinsic fluorescence signals and unfolding of proteins are discussed, including several practical considerations for properly setting fluorescence experiments and the phenomenological equations required to analyze the spectra. In particular, a fast and accurate method which allows to minimize the deleterious effect of photobleaching is provided. A number of unfolding reactions relative to immunoglobulins (IgG and IgM) and to the different domains of the adhesion molecule dystroglycan are presented. Special attention is dedicated to a alpha-dystroglycan immunoglobulin-like domain showing a "reverse" behavior of the fluorescence signal as a function of the denaturing agent concentration.
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Affiliation(s)
- Enrico Di Stasio
- Istituto di Biochimica e Biochimica Clinica, Università Cattolica del Sacro Cuore, Largo F. Vito no 1, 00168 Rome, Italy.
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25
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Bozzi M, Di Stasio E, Cicero DO, Giardina B, Paci M, Brancaccio A. The effect of an ionic detergent on the natively unfolded beta-dystroglycan ectodomain and on its interaction with alpha-dystroglycan. Protein Sci 2004; 13:2437-45. [PMID: 15295116 PMCID: PMC2280000 DOI: 10.1110/ps.04762504] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Dystroglycan (DG) is an adhesion complex, expressed in a wide variety of tissues, formed by an extracellular and a transmembrane subunit, alpha-DG and beta-DG, respectively, interacting noncovalently. Recently, we have shown that the recombinant ectodomain of beta-DG, beta-DG(654-750), behaves as a natively unfolded protein, as it is able to bind the C-terminal domain of alpha-DG, while not displaying a defined structural organization. We monitored the effect of a commonly used denaturing agent, the anionic detergent sodium dodecylsulphate (SDS), on beta-DG(654-750) using a number of biophysical techniques. Very low concentrations of SDS (< or =2 mM) affect both tryptophan fluorescence and circular dichroism of beta-DG, and significantly perturb the interaction with the alpha-DG subunit as shown by solid-phase binding assays and fluorescence titrations in solution. This result confirms, as recently proposed for natively unfolded proteins, that beta-DG(654-750) exists in a native state, which is crucial to fulfill its biological function. Two-dimensional NMR analysis shows that SDS does not induce any evident conformational rearrangement within the ectodomain of beta-DG. Its first 70 amino acids, which show a lower degree of mobility, interact with the detergent, but this does not change the amount of secondary structure, whereas the highly flexible and mobile C-terminal region of beta-DG(654-750) remains largely unaffected, even at a very high SDS concentration (up to 50 mM). Our data indicate that SDS can be used as a useful tool for investigating natively unfolded proteins, and confirm that the beta-DG ectodomain is an interesting model system.
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Affiliation(s)
- Manuela Bozzi
- Consiglio Nazionale delle Richerche (CNR), Istituto di Chimica del Riconoscimento Molecolare, c/o Istituto di Biochimica e Biochimica Clinica, Università Cattolica del Sacro Cuore, 00168 Rome, Italy
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26
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Royuela M, Chazalette D, Hugon G, Paniagua R, Guerlavais V, Fehrentz JA, Martinez J, Labbe JP, Rivier F, Mornet D. Formation of multiple complexes between beta-dystroglycan and dystrophin family products. J Muscle Res Cell Motil 2004; 24:387-97. [PMID: 14677641 DOI: 10.1023/a:1027309822007] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Beta-dystroglycan is expressed in a wide variety of tissues and has generally been reported with an Mr of 43 kDa, sometimes accompanied with a 31 kDa protein assumed to be a truncated product. This molecule was recently identified as the anomalous beta-dystroglycan expressed in various carcinoma cell lines. We produced and characterized a G5 polyclonal antibody specific to beta-dystroglycan that is directed against the C-terminal portion of the molecule. We provide evidence that beta-dystroglycan may vary in size and properties by studying different Xenopus tissues. Besides normal beta-dystroglycan with an Mr of 43 kDa in smooth and cardiac muscle and sciatic nerve extracts, we found it in skeletal muscle and brain proteins with an Mr of 38 and 65 kDa, respectively. Glycosylation properties and proteolytic susceptibilities of these different beta-dystroglycans are analysed and compared in this work. Crosslinking experiments with various beta-dystroglycan preparations obtained from skeletal and cardiac muscles and brain gave rise to specific new covalent products with Mr of 125 kDa (doublet band), or 120 and 130 kDa, or 140 and 240 kDa, respectively. We provide evidence, using various similar beta-dystroglycan preparations, that the immunoprecipitation procedure with G5 specific polyclonal antibody allows consistent pelleting of various dystrophin-family isoforms. Skeletal muscles from Xenopus reveals the presence of two distinct beta-dystroglycan complexes, one with dystrophin and another one which involves alpha-dystrobrevin. Cardiac muscle and brain from Xenopus are shown to contain three beta-dystroglycan complexes related to various dystrophin-family isoforms. Dystrophin or alpha-dystrobrevin or Dp71 were found in cardiac muscle and dystrophin or Dp180 or Up71 in brain. This variability in the relationship between beta-dystroglycan and dystrophin-family isoforms suggests that each protein--currently known as dystrophin associated protein--could not be present in each of these complexes.
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Affiliation(s)
- M Royuela
- Department of Cell Biology and Genetics, University of Alcalá, E-28871 Alcalá de Henares, Madrid, Spain
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27
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Herzog C, Has C, Franzke CW, Echtermeyer FG, Schlötzer-Schrehardt U, Kröger S, Gustafsson E, Fässler R, Bruckner-Tuderman L. Dystroglycan in skin and cutaneous cells: beta-subunit is shed from the cell surface. J Invest Dermatol 2004; 122:1372-80. [PMID: 15175026 DOI: 10.1111/j.0022-202x.2004.22605.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In skin, hemidesmosomal protein complexes attach the epidermis to the dermis and are critical for stable connection of the basal epithelial cell cytoskeleton with the basement membrane (BM). In muscle, a similar supramolecular aggregate, the dystrophin glycoprotein complex links the inside of muscle cells with the BM. A component of the muscle complex, dystroglycan (DG), also occurs in epithelia. In this study, we characterized the expression and biochemical properties of authentic and recombinant DG in human skin and cutaneous cells in vitro. We show that DG is present at the epidermal BM zone, and it is produced by both keratinocytes and fibroblasts in vitro. The biosynthetic precursor is efficiently processed to the alpha- and beta-DG subunits; and, in addition, a distinct extracellular segment of the transmembranous beta-subunit is shed from the cell surface by metalloproteinases. Shedding of the beta-subunit releases the alpha-subunit from the DG complex on the cell surface into the extracellular space. The shedding is enhanced by IL-1beta and phorbol esters, and inhibited by metalloproteinase inhibitors. Deficiency of perlecan, a major ligand of alpha-DG, enhanced shedding suggesting that lack of a binding partner destabilizes the epithelial DG complex and makes it accessible to proteolytic processing.
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Affiliation(s)
- Christine Herzog
- Institute for Physiological Chemistry and Pathobiochemistry, University of Münster, Münster, Germany
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28
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Kunz S, Campbell KP, Oldstone MBA. Alpha-dystroglycan can mediate arenavirus infection in the absence of beta-dystroglycan. Virology 2004; 316:213-20. [PMID: 14644604 DOI: 10.1016/j.virol.2003.07.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Dystroglycan (DG) is a highly versatile cell surface molecule that provides a molecular link between the extracellular matrix (ECM) and the actin-based cytoskeleton. Encoded by a single gene, DG is posttranslationally processed to form alpha-DG, a peripheral protein identified as the cellular receptor for lymphocytic choriomeningitis virus (LCMV) and Lassa fever virus (LFV), and the membrane-spanning subunit beta-DG. The link of beta-DG to the actin-based cytoskeleton and its association with the cellular signal transduction network suggest that it may function as an essential cofactor for the activity of alpha-DG as a virus receptor. To address this issue, we constructed a deletion mutant lacking the cytoplasmic domain of beta-DG and a C-terminal fusion between alpha-DG and the transmembrane domain of PDGF receptor. Both mutants were functional as virus receptors, indicating that beta-DG does not act as a cofactor with alpha-DG for arenavirus binding and entry. These observations are in agreement with the fact that LCMV infection is independent from the structural integrity of the actin-based cytoskeleton and suggest that alpha-DG functions primarily in the attachment of arenaviruses to the cell surface.
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Affiliation(s)
- Stefan Kunz
- The Scripps Research Institute, Department of Neuropharmacology, 10550 N Torrey Pines Road, La Jolla, CA 92037, USA.
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29
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Bozzi M, Bianchi M, Sciandra F, Paci M, Giardina B, Brancaccio A, Cicero DO. Structural characterization by NMR of the natively unfolded extracellular domain of beta-dystroglycan: toward the identification of the binding epitope for alpha-dystroglycan. Biochemistry 2004; 42:13717-24. [PMID: 14622018 DOI: 10.1021/bi034867w] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Dystroglycan (DG) is an adhesion molecule playing a crucial role for tissue stability during both early embriogenesis and adulthood and is composed by two tightly interacting subunits: alpha-DG, membrane-associated and highly glycosylated, and the transmembrane beta-DG. Recently, by solid-phase binding assays and NMR experiments, we have shown that the C-terminal domain of alpha-DG interacts with a recombinant extracellular fragment of beta-DG (positions 654-750) independently from glycosylation and that the linear binding epitope is located between residues 550 and 565 of alpha-DG. In order to elucidate which moieties of beta-DG are specifically involved in the complex with alpha-DG, the ectodomain has been recombinantly expressed and purified in a labeled ((13)C,(15)N) form and studied by multidimensional NMR. Although it represents a natively unfolded protein domain, we obtained an almost complete backbone assignment. Chemical shift index, (1)H-(15)N heteronuclear single-quantum coherence and nuclear Overhauser effect (HSQC-NOESY) spectra and (3)J(HN,H)(alpha) coupling constant values confirm that this protein is highly disordered, but (1)H-(15)N steady-state NOE experiments indicate that the protein presents two regions of different mobility. The first one, between residues 659 and 722, is characterized by a limited degree of mobility, whereas the C-terminal portion, containing about 30 amino acids, is highly flexible. The binding of beta-DG(654-750) to the C-terminal region of the alpha subunit, alpha-DG(485-620), has been investigated, showing that the region of beta-DG(654-750) between residues 691 and 719 is involved in the interaction.
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Affiliation(s)
- Manuela Bozzi
- Istituto di Chimica del Riconoscimento Molecolare c/o Istituto di Biochimica e Biochimica Clinica, Consiglio Nazionale della Ricerche, Università Cattolica del Sacro Cuore, Largo Francesco Vito 1, 00168 Rome, Italy
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Bonuccelli G, Sotgia F, Schubert W, Park DS, Frank PG, Woodman SE, Insabato L, Cammer M, Minetti C, Lisanti MP. Proteasome inhibitor (MG-132) treatment of mdx mice rescues the expression and membrane localization of dystrophin and dystrophin-associated proteins. THE AMERICAN JOURNAL OF PATHOLOGY 2003; 163:1663-75. [PMID: 14507673 PMCID: PMC1868305 DOI: 10.1016/s0002-9440(10)63523-7] [Citation(s) in RCA: 102] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Dystrophin, the protein product of the Duchenne muscular dystrophy (DMD) gene, is absent in the skeletal muscle of DMD patients and mdx mice. At the plasma membrane of skeletal muscle fibers, dystrophin associates with a multimeric protein complex, termed the dystrophin-glycoprotein complex (DGC). Protein members of this complex are normally absent or greatly reduced in dystrophin-deficient skeletal muscle fibers, and are thought to undergo degradation through an unknown pathway. As such, we reasoned that inhibition of the proteasomal degradation pathway might rescue the expression and subcellular localization of dystrophin-associated proteins. To test this hypothesis, we treated mdx mice with the well-characterized proteasomal inhibitor MG-132. First, we locally injected MG-132 into the gastrocnemius muscle, and observed the outcome after 24 hours. Next, we performed systemic treatment using an osmotic pump that allowed us to deliver different concentrations of the proteasomal inhibitor, over an 8-day period. By immunofluorescence and Western blot analysis, we show that administration of the proteasomal inhibitor MG-132 effectively rescues the expression levels and plasma membrane localization of dystrophin, beta-dystroglycan, alpha-dystroglycan, and alpha-sarcoglycan in skeletal muscle fibers from mdx mice. Furthermore, we show that systemic treatment with the proteasomal inhibitor 1) reduces muscle membrane damage, as revealed by vital staining (with Evans blue dye) of the diaphragm and gastrocnemius muscle isolated from treated mdx mice, and 2) ameliorates the histopathological signs of muscular dystrophy, as judged by hematoxylin and eosin staining of muscle biopsies taken from treated mdx mice. Thus, the current study opens new and important avenues in our understanding of the pathogenesis of DMD. Most importantly, these new findings may have clinical implications for the pharmacological treatment of patients with DMD.
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Affiliation(s)
- Gloria Bonuccelli
- Department of Molecular Pharmacology and The Albert Einstein Cancer Center, Albert Einstein School of Medicine, Bronx, New York 10461, USA
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Michele DE, Campbell KP. Dystrophin-glycoprotein complex: post-translational processing and dystroglycan function. J Biol Chem 2003; 278:15457-60. [PMID: 12556455 DOI: 10.1074/jbc.r200031200] [Citation(s) in RCA: 340] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Affiliation(s)
- Daniel E Michele
- Department of Physiology and Biophysics, Howard Hughes Medical Institute, 400 ERMB, Carver College of Medicine, University of Iowa, Iowa City, IA 52242-1101, USA
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Sgambato A, Migaldi M, Montanari M, Camerini A, Brancaccio A, Rossi G, Cangiano R, Losasso C, Capelli G, Trentini GP, Cittadini A. Dystroglycan expression is frequently reduced in human breast and colon cancers and is associated with tumor progression. THE AMERICAN JOURNAL OF PATHOLOGY 2003; 162:849-60. [PMID: 12598319 PMCID: PMC1868099 DOI: 10.1016/s0002-9440(10)63881-3] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Dystroglycan (DG) is an adhesion molecule responsible for crucial interactions between extracellular matrix and cytoplasmic compartment. It is formed by two subunits, alpha-DG (extracellular) and beta-DG (transmembrane), that bind to laminin in the matrix and dystrophin in the cytoskeleton, respectively. In this study we evaluated by Western blot analysis the expression of DG in a series of human cancer cell lines of various histogenetic origin and in a series of human primary colon and breast cancers. Decreased expression of DG was observed in most of the cell lines and in both types of tumors and correlated with higher tumor grade and stage. Analysis of the mRNA levels suggested that expression of DG protein is likely regulated at a posttranscriptional level. Evaluation of alpha-DG expression by immunostaining in a series of archival cases of primary breast carcinomas confirmed that alpha-DG expression is lost in a significant fraction of tumors (66%). Loss of DG staining correlated with higher tumor stage (P = 0.022), positivity for p53 (P = 0.033), and high proliferation index (P = 0.045). A significant correlation was also observed between loss of alpha-DG and overall survival (P = 0.013 by log-rank test) in an univariate analysis. These data indicate that DG expression is frequently lost in human malignancies and suggest that this glycoprotein might play an important role in human tumor development and progression.
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Affiliation(s)
- Alessandro Sgambato
- Centro di Ricerche Oncologiche Giovanni XXIII, Istituto di Patologia Generale, Catholic University, Rome, Italy.
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Dickens NJ, Beatson S, Ponting CP. Cadherin-like domains in alpha-dystroglycan, alpha/epsilon-sarcoglycan and yeast and bacterial proteins. Curr Biol 2002; 12:R197-9. [PMID: 11909544 DOI: 10.1016/s0960-9822(02)00748-0] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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