351
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Takeuchi KI, Nakano Y, Kato U, Kaneda M, Aizu M, Awano W, Yonemura S, Kiyonaka S, Mori Y, Yamamoto D, Umeda M. Changes in temperature preferences and energy homeostasis in dystroglycan mutants. Science 2009; 323:1740-3. [PMID: 19325118 DOI: 10.1126/science.1165712] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Temperature affects the physiology, behavior, and evolution of organisms. We conducted mutagenesis and screens for mutants with altered temperature preference in Drosophila melanogaster and identified a cryophilic (cold-seeking) mutant, named atsugari (atu). Reduced expression of the Drosophila ortholog of dystroglycan (DmDG) induced tolerance to cold as well as preference for the low temperature. A sustained increase in mitochondrial oxidative metabolism caused by the reduced expression of DmDG accounted for the cryophilic phenotype of the atu mutant. Although most ectothermic animals do not use metabolically produced heat to regulate body temperature, our results indicate that their thermoregulatory behavior is closely linked to rates of mitochondrial oxidative metabolism and that a mutation in a single gene can induce a sustained change in energy homeostasis and the thermal responses.
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Affiliation(s)
- Ken-Ichi Takeuchi
- Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
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352
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Herbst R, Iskratsch T, Unger E, Bittner RE. Aberrant development of neuromuscular junctions in glycosylation-defective Large(myd) mice. Neuromuscul Disord 2009; 19:366-78. [PMID: 19346129 DOI: 10.1016/j.nmd.2009.02.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2007] [Revised: 02/17/2009] [Accepted: 02/27/2009] [Indexed: 01/13/2023]
Abstract
Mice deficient in the glycosyltransferase Large are characterized by severe muscle and central nervous system abnormalities. In this study, we show that the formation and maintenance of neuromuscular junctions in Large(myd) mice are greatly compromised. Neuromuscular junctions are not confined to the muscle endplate zone but are widely spread and are frequently accompanied by exuberant nerve sprouting. Nerve terminals are highly fragmented and binding of alpha-bungarotoxin to postsynaptic acetylcholine receptors (AChRs) is greatly reduced. In vitro, Large(myd) myotubes are responsive to agrin but produce aberrant AChR clusters, which are larger in area and less densely packed with AChRs. In addition, AChR expression on the cell surface is diminished suggesting that AChR assembly or transport is defective. These results together with the finding that O-linked glycosylation at neuromuscular junctions of Large(myd) mice is compromised indicate that the action of Large is necessary for proper neuromuscular junction development.
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Affiliation(s)
- Ruth Herbst
- Center for Brain Research, Medical University of Vienna, Vienna, Austria.
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353
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Puckett RL, Moore SA, Winder TL, Willer T, Romansky SG, Covault KK, Campbell KP, Abdenur JE. Further evidence of Fukutin mutations as a cause of childhood onset limb-girdle muscular dystrophy without mental retardation. Neuromuscul Disord 2009; 19:352-6. [PMID: 19342235 PMCID: PMC2698593 DOI: 10.1016/j.nmd.2009.03.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2008] [Revised: 03/02/2009] [Accepted: 03/03/2009] [Indexed: 11/18/2022]
Abstract
The dystroglycanopathies comprise a clinically and genetically heterogeneous group of muscular dystrophies characterized by deficient glycosylation of alpha-dystroglycan. Mutations in the fukutin (FKTN) gene have primarily been identified among patients with classic Fukuyama congenital muscular dystrophy (FCMD), a severe form of dystroglycanopathy characterized by CMD, cobblestone lissencephaly and ocular defects. We describe two brothers of Caucasian and Japanese ancestry with normal intelligence and limb-girdle muscular dystrophy (LGMD) due to compound heterozygous FKTN mutations. Muscle biopsy showed a dystrophy with selectively reduced alpha-dystroglycan glycoepitope immunostaining. Immunoblots revealed hypoglycosylation of alpha-dystroglycan and loss of laminin binding. FKTN gene sequencing identified two variants: c.340G>A and c.527T>C, predicting missense mutations p.A114T and p.F176S, respectively. Our results provide further evidence for ethnic and allelic heterogeneity and the presence of milder phenotypes in FKTN-dystroglycanopathy despite a substantial degree of alpha-dystroglycan hypoglycosylation in skeletal muscle.
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Affiliation(s)
- Rebecca L Puckett
- Children's Hospital of Orange County, Division of Metabolic Disorders, Orange, CA 92868, USA.
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354
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Kunz S. Receptor binding and cell entry of Old World arenaviruses reveal novel aspects of virus-host interaction. Virology 2009; 387:245-9. [PMID: 19324387 DOI: 10.1016/j.virol.2009.02.042] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2008] [Revised: 12/01/2008] [Accepted: 02/26/2009] [Indexed: 01/08/2023]
Abstract
Ten years ago, the first cellular receptor for the prototypic arenavirus lymphocytic choriomeningitis virus (LCMV) and the highly pathogenic Lassa virus (LASV) was identified as alpha-dystroglycan (alpha-DG), a versatile receptor for proteins of the extracellular matrix (ECM). Biochemical analysis of the interaction of alpha-DG with arenaviruses and ECM proteins revealed a strikingly similar mechanism of receptor recognition that critically depends on specific sugar modification on alpha-DG involving a novel class of putative glycosyltransferase, the LARGE proteins. Interestingly, recent genome-wide detection and characterization of positive selection in human populations revealed evidence for positive selection of a locus within the LARGE gene in populations from Western Africa, where LASV is endemic. While most enveloped viruses that enter the host cell in a pH-dependent manner use clathrin-mediated endocytosis, recent studies revealed that the Old World arenaviruses LCMV and LASV enter the host cell predominantly via a novel and unusual endocytotic pathway independent of clathrin, caveolin, dynamin, and actin. Upon internalization, the virus is rapidly delivered to endosomes via an unusual route of vesicular trafficking that is largely independent of the small GTPases Rab5 and Rab7. Since infection of cells with LCMV and LASV depends on DG, this unusual endocytotic pathway could be related to normal cellular trafficking of the DG complex. Alternatively, engagement of arenavirus particles may target DG for an endocytotic pathway not normally used in uninfected cells thereby inducing an entry route specifically tailored to the pathogen's needs.
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Affiliation(s)
- Stefan Kunz
- Institute of Microbiology, University Hospital Center and University of Lausanne, Switzerland.
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355
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Yatsenko AS, Kucherenko MM, Pantoja M, Fischer KA, Madeoy J, Deng WM, Schneider M, Baumgartner S, Akey J, Shcherbata HR, Ruohola-Baker H. The conserved WW-domain binding sites in Dystroglycan C-terminus are essential but partially redundant for Dystroglycan function. BMC DEVELOPMENTAL BIOLOGY 2009; 9:18. [PMID: 19250553 PMCID: PMC2660313 DOI: 10.1186/1471-213x-9-18] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/19/2008] [Accepted: 02/27/2009] [Indexed: 11/23/2022]
Abstract
Background Dystroglycan (Dg) is a transmembrane protein that is a part of the Dystrophin Glycoprotein Complex (DGC) which connects the extracellular matrix to the actin cytoskeleton. The C-terminal end of Dg contains a number of putative SH3, SH2 and WW domain binding sites. The most C-terminal PPXY motif has been established as a binding site for Dystrophin (Dys) WW-domain. However, our previous studies indicate that both Dystroglycan PPXY motives, WWbsI and WWbsII can bind Dystrophin protein in vitro. Results We now find that both WW binding sites are important for maintaining full Dg function in the establishment of oocyte polarity in Drosophila. If either WW binding site is mutated, the Dg protein can still be active. However, simultaneous mutations in both WW binding sites abolish the Dg activities in both overexpression and loss-of-function oocyte polarity assays in vivo. Additionally, sequence comparisons of WW binding sites in 12 species of Drosophila, as well as in humans, reveal a high level of conservation. This preservation throughout evolution supports the idea that both WW binding sites are functionally required. Conclusion Based on the obtained results we propose that the presence of the two WW binding sites in Dystroglycan secures the essential interaction between Dg and Dys and might further provide additional regulation for the cytoskeletal interactions of this complex.
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Affiliation(s)
- A S Yatsenko
- Department of Biochemistry, Institute for Stem Cell and Regenerative Medicine, Program in Neurobiology and Behaviour, University of Washington, Seattle, WA 98195, USA.
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356
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Matsumura CY, Pertille A, Albuquerque TC, Santo Neto H, Marques MJ. Diltiazem and verapamil protect dystrophin-deficient muscle fibers ofMDXmice from degeneration: A potential role in calcium buffering and sarcolemmal stability. Muscle Nerve 2009; 39:167-76. [DOI: 10.1002/mus.21188] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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357
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Hemming ML, Elias JE, Gygi SP, Selkoe DJ. Proteomic profiling of gamma-secretase substrates and mapping of substrate requirements. PLoS Biol 2009; 6:e257. [PMID: 18942891 PMCID: PMC2570425 DOI: 10.1371/journal.pbio.0060257] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2008] [Accepted: 09/12/2008] [Indexed: 11/18/2022] Open
Abstract
The presenilin/γ-secretase complex, an unusual intramembrane aspartyl protease, plays an essential role in cellular signaling and membrane protein turnover. Its ability to liberate numerous intracellular signaling proteins from the membrane and also mediate the secretion of amyloid-β protein (Aβ) has made modulation of γ-secretase activity a therapeutic goal for cancer and Alzheimer disease. Although the proteolysis of the prototypical substrates Notch and β-amyloid precursor protein (APP) has been intensely studied, the full spectrum of substrates and the determinants that make a transmembrane protein a substrate remain unclear. Using an unbiased approach to substrate identification, we surveyed the proteome of a human cell line for targets of γ-secretase and found a relatively small population of new substrates, all of which are type I transmembrane proteins but have diverse biological roles. By comparing these substrates to type I proteins not regulated by γ-secretase, we determined that besides a short ectodomain, γ-secretase requires permissive transmembrane and cytoplasmic domains to bind and cleave its substrates. In addition, we provide evidence for at least two mechanisms that can target a substrate for γ cleavage: one in which a substrate with a short ectodomain is directly cleaved independent of sheddase association, and a second where a substrate requires ectodomain shedding to instruct subsequent γ-secretase processing. These findings expand our understanding of the mechanisms of substrate selection as well as the diverse cellular processes to which γ-secretase contributes. All cells face the challenge of removing transmembrane proteins from the lipid bilayer for the purpose of signaling or degradation. One molecular solution to this problem is the multiprotein enzyme complex γ-secretase, which is able to hydrolyze several known transmembrane proteins within the hydrophobic lipid environment. Due to its central role in the pathogenesis of Alzheimer disease, modulation of γ-secretase activity has become a therapeutic goal. However, the number and diversity of proteins that can be cleaved by this protease remain unknown, and the attributes that target these proteins to γ-secretase are unclear. In this study, we used an unbiased approach to substrate identification and surveyed the proteome for targets of γ-secretase. Of the thousands of proteins detectable, only a relative few were substrates of γ-secretase, all of which were type I transmembrane proteins. In addition to validating several of these novel substrates, we compared them to other proteins that we identified as nonsubstrates and determined that there are specific domains that can activate or inhibit γ-secretase processing. These findings should advance our understanding of the many cellular processes regulated by γ-secretase and may offer insights into how γ-secretase can be exploited for therapeutic purposes. Using an unbiased quantitative proteomics approach, novel substrate targets for the protease γ-secretase are identified and analyzed to determine which domains enable their cleavage.
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Affiliation(s)
- Matthew L Hemming
- Center for Neurologic Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Joshua E Elias
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Steven P Gygi
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Dennis J Selkoe
- Center for Neurologic Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
- * To whom correspondence should be addressed. E-mail:
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358
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Muntoni F, Guicheney P, Voit T. 158th ENMC international workshop on congenital muscular dystrophy (Xth international CMD workshop) 8th-10th February 2008 Naarden, The Netherlands. Neuromuscul Disord 2008; 19:229-34. [PMID: 19097897 DOI: 10.1016/j.nmd.2008.11.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2008] [Indexed: 10/21/2022]
Affiliation(s)
- F Muntoni
- Dubowitz Neuromuscular Centre, Institute of Child Health & Great Ormond Street Hospital, 30 Guilford Street, London WC1N 1EH, UK.
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359
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Manzini MC, Gleason D, Chang BS, Hill RS, Barry BJ, Partlow JN, Poduri A, Currier S, Galvin-Parton P, Shapiro LR, Schmidt K, Davis JG, Basel-Vanagaite L, Seidahmed MZ, Salih MAM, Dobyns WB, Walsh CA. Ethnically diverse causes of Walker-Warburg syndrome (WWS): FCMD mutations are a more common cause of WWS outside of the Middle East. Hum Mutat 2008; 29:E231-41. [PMID: 18752264 DOI: 10.1002/humu.20844] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Walker-Warburg syndrome (WWS) is a genetically heterogeneous autosomal recessive disease characterized by congenital muscular dystrophy, cobblestone lissencephaly, and ocular malformations. Mutations in six genes involved in the glycosylation of á-dystroglycan (POMT1, POMT2, POMGNT1, FCMD, FKRP and LARGE) have been identified in WWS patients, but account for only a portion of WWS cases. To better understand the genetics of WWS and establish the frequency and distribution of mutations across WWS genes, we genotyped all known loci in a cohort of 43 WWS patients of varying geographical and ethnic origin. Surprisingly, we reached a molecular diagnosis for 40% of our patients and found mutations in POMT1, POMT2, FCMD and FKRP, many of which were novel alleles, but no mutations in POMGNT1 or LARGE. Notably, the FCMD gene was a more common cause of WWS than previously expected in the European/American subset of our cohort, including all Ashkenazi Jewish cases, who carried the same founder mutation.
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Affiliation(s)
- M Chiara Manzini
- Division of Genetics, Children's Hospital Boston, Harvard Medical School, Boston, MA 02115, USA
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360
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Kanagawa M, Nishimoto A, Chiyonobu T, Takeda S, Miyagoe-Suzuki Y, Wang F, Fujikake N, Taniguchi M, Lu Z, Tachikawa M, Nagai Y, Tashiro F, Miyazaki JI, Tajima Y, Takeda S, Endo T, Kobayashi K, Campbell KP, Toda T. Residual laminin-binding activity and enhanced dystroglycan glycosylation by LARGE in novel model mice to dystroglycanopathy. Hum Mol Genet 2008; 18:621-31. [PMID: 19017726 PMCID: PMC2638827 DOI: 10.1093/hmg/ddn387] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Hypoglycosylation and reduced laminin-binding activity of α-dystroglycan are common characteristics of dystroglycanopathy, which is a group of congenital and limb-girdle muscular dystrophies. Fukuyama-type congenital muscular dystrophy (FCMD), caused by a mutation in the fukutin gene, is a severe form of dystroglycanopathy. A retrotransposal insertion in fukutin is seen in almost all cases of FCMD. To better understand the molecular pathogenesis of dystroglycanopathies and to explore therapeutic strategies, we generated knock-in mice carrying the retrotransposal insertion in the mouse fukutin ortholog. Knock-in mice exhibited hypoglycosylated α-dystroglycan; however, no signs of muscular dystrophy were observed. More sensitive methods detected minor levels of intact α-dystroglycan, and solid-phase assays determined laminin binding levels to be ∼50% of normal. In contrast, intact α-dystroglycan is undetectable in the dystrophic Largemyd mouse, and laminin-binding activity is markedly reduced. These data indicate that a small amount of intact α-dystroglycan is sufficient to maintain muscle cell integrity in knock-in mice, suggesting that the treatment of dystroglycanopathies might not require the full recovery of glycosylation. To examine whether glycosylation defects can be restored in vivo, we performed mouse gene transfer experiments. Transfer of fukutin into knock-in mice restored glycosylation of α-dystroglycan. In addition, transfer of LARGE produced laminin-binding forms of α-dystroglycan in both knock-in mice and the POMGnT1 mutant mouse, which is another model of dystroglycanopathy. Overall, these data suggest that even partial restoration of α-dystroglycan glycosylation and laminin-binding activity by replacing or augmenting glycosylation-related genes might effectively deter dystroglycanopathy progression and thus provide therapeutic benefits.
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Affiliation(s)
- Motoi Kanagawa
- Division of Clinical Genetics, Department of Medical Genetics, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
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361
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Peter AK, Marshall JL, Crosbie RH. Sarcospan reduces dystrophic pathology: stabilization of the utrophin-glycoprotein complex. ACTA ACUST UNITED AC 2008; 183:419-27. [PMID: 18981229 PMCID: PMC2575773 DOI: 10.1083/jcb.200808027] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Mutations in the dystrophin gene cause Duchenne muscular dystrophy and result in the loss of dystrophin and the entire dystrophin–glycoprotein complex (DGC) from the sarcolemma. We show that sarcospan (SSPN), a unique tetraspanin-like component of the DGC, ameliorates muscular dystrophy in dystrophin-deficient mdx mice. SSPN stabilizes the sarcolemma by increasing levels of the utrophin–glycoprotein complex (UGC) at the extrasynaptic membrane to compensate for the loss of dystrophin. Utrophin is normally restricted to the neuromuscular junction, where it replaces dystrophin to form a functionally analogous complex. SSPN directly interacts with the UGC and functions to stabilize utrophin protein without increasing utrophin transcription. These findings reveal the importance of protein stability in the prevention of muscular dystrophy and may impact the future design of therapeutics for muscular dystrophies.
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Affiliation(s)
- Angela K Peter
- Department of Physiological Science and 2Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA
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362
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Martin PT, Shelton GD, Dickinson PJ, Sturges BK, Xu R, LeCouteur RA, Guo LT, Grahn RA, Lo HP, North KN, Malik R, Engvall E, Lyons LA. Muscular dystrophy associated with alpha-dystroglycan deficiency in Sphynx and Devon Rex cats. Neuromuscul Disord 2008; 18:942-52. [PMID: 18990577 DOI: 10.1016/j.nmd.2008.08.002] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2008] [Revised: 07/27/2008] [Accepted: 08/16/2008] [Indexed: 11/28/2022]
Abstract
Recent studies have identified a number of forms of muscular dystrophy, termed dystroglycanopathies, which are associated with loss of natively glycosylated alpha-dystroglycan. Here we identify a new animal model for this class of disorders in Sphynx and Devon Rex cats. Affected cats displayed a slowly progressive myopathy with clinical and histologic hallmarks of muscular dystrophy including skeletal muscle weakness with no involvement of peripheral nerves or CNS. Skeletal muscles had myopathic features and reduced expression of alpha-dystroglycan, while beta-dystroglycan, sarcoglycans, and dystrophin were expressed at normal levels. In the Sphynx cat, analysis of laminin and lectin binding capacity demonstrated no loss in overall glycosylation or ligand binding for the alpha-dystroglycan protein, only a loss of protein expression. A reduction in laminin-alpha2 expression in the basal lamina surrounding skeletal myofibers was also observed. Sequence analysis of translated regions of the feline dystroglycan gene (DAG1) in affected cats did not identify a causative mutation, and levels of DAG1 mRNA determined by real-time QRT-PCR did not differ significantly from normal controls. Reduction in the levels of glycosylated alpha-dystroglycan by immunoblot was also identified in an affected Devon Rex cat. These data suggest that muscular dystrophy in Sphynx and Devon Rex cats results from a deficiency in alpha-dystroglycan protein expression, and as such may represent a new type of dystroglycanopathy where expression, but not glycosylation, is affected.
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Affiliation(s)
- Paul T Martin
- Center for Gene Therapy, The Research Institute at Nationwide Children's Hospital, Department of Pediatrics, Ohio State University, College of Medicine, Columbus, OH 43205, USA
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363
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Abstract
In the last few years, muscular dystrophies due to reduced glycosylation of alpha-dystroglycan (ADG) have emerged as a common group of conditions, now referred to as dystroglycanopathies. Mutations in six genes (POMT1, POMT2, POMGnT1, Fukutin, FKRP and LARGE) have so far been identified in patients with a dystroglycanopathy. Allelic mutations in each of these genes can result in a wide spectrum of clinical conditions, ranging from severe congenital onset with associated structural brain malformations (Walker Warburg syndrome; muscle-eye-brain disease; Fukuyama muscular dystrophy; congenital muscular dystrophy type 1D) to a relatively milder congenital variant with no brain involvement (congenital muscular dystrophy type 1C), and to limb-girdle muscular dystrophy (LGMD) type 2 variants with onset in childhood or adult life (LGMD2I, LGMD2L, and LGMD2N). ADG is a peripheral membrane protein that undergoes multiple and complex glycosylation steps to regulate its ability to effectively interact with extracellular matrix proteins, such as laminin, agrin, and perlecan. Although the precise composition of the glycans present on ADG are not known, it has been demonstrated that the forced overexpression of LARGE, or its paralog LARGE2, is capable of increasing the glycosylation of ADG in normal cells. In addition, its overexpression is capable of restoring dystroglycan glycosylation and laminin binding properties in primary cell cultures of patients affected by different genetically defined dystroglycanopathy variants. These observations suggest that there could be a role for therapeutic strategies to overcome the glycosylation defect in these conditions via the overexpression of LARGE.
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Affiliation(s)
- Francesco Muntoni
- Department of Neuroscience, Dubowitz Neuromuscular Centre, UCL Institute of Child Health & Great Ormond Street Hospital, London, United Kingdom.
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364
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Oppizzi ML, Akhavan A, Singh M, Fata JE, Muschler JL. Nuclear translocation of beta-dystroglycan reveals a distinctive trafficking pattern of autoproteolyzed mucins. Traffic 2008; 9:2063-72. [PMID: 18764929 DOI: 10.1111/j.1600-0854.2008.00822.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Dystroglycan (DG) is an extracellular matrix receptor implicated in muscular dystrophies and cancers. DG belongs to the membrane-tethered mucin family and is composed of extracellular (alpha-DG) and transmembrane (beta-DG) subunits stably coupled at the cell surface. These two subunits are generated by autoproteolysis of a monomeric precursor within a distinctive protein motif called sea urchin-enterokinase-agrin (SEA) domain, yet the purpose of this cleavage and heterodimer creation is uncertain. In this study, we identify a functional nuclear localization signal within beta-DG and show that, in addition to associating with alpha-DG at the cell surface, the full-length and glycosylated beta-DG autonomously traffics to the cytoplasm and nucleoplasm in a process that occurs independent of alpha-DG ligand binding. The trafficking pattern of beta-DG mirrors that of MUC1-C, the transmembrane subunit of the related MUC1 oncoprotein, also a heterodimeric membrane-tethered mucin created by SEA autoproteolysis. We show that the transmembrane subunits of both MUC1 and DG transit the secretory pathway prior to nuclear targeting and that their monomeric precursors maintain the capacity for nuclear trafficking. A screen of breast carcinoma cell lines of distinct pathophysiological origins revealed considerable variability in the nuclear partitioning of beta-DG, indicating that nuclear localization of beta-DG is regulated, albeit independent of extracellular ligand binding. These findings point to novel intracellular functions for beta-DG, with possible disease implications. They also reveal an evolutionarily conserved role for SEA autoproteolysis, serving to enable independent functions of mucin transmembrane subunits, enacted by a shared and poorly understood pathway of segregated subunit trafficking.
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Affiliation(s)
- Maria Luisa Oppizzi
- California Pacific Medical Center Research Institute, 475 Brannan Street, Suite 220, San Francisco, CA 94107, USA
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365
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Nishimune H, Valdez G, Jarad G, Moulson CL, Müller U, Miner JH, Sanes JR. Laminins promote postsynaptic maturation by an autocrine mechanism at the neuromuscular junction. ACTA ACUST UNITED AC 2008; 182:1201-15. [PMID: 18794334 PMCID: PMC2542479 DOI: 10.1083/jcb.200805095] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
A prominent feature of synaptic maturation at the neuromuscular junction (NMJ) is the topological transformation of the acetylcholine receptor (AChR)-rich postsynaptic membrane from an ovoid plaque into a complex array of branches. We show here that laminins play an autocrine role in promoting this transformation. Laminins containing the alpha4, alpha5, and beta2 subunits are synthesized by muscle fibers and concentrated in the small portion of the basal lamina that passes through the synaptic cleft at the NMJ. Topological maturation of AChR clusters was delayed in targeted mutant mice lacking laminin alpha5 and arrested in mutants lacking both alpha4 and alpha5. Analysis of chimeric laminins in vivo and of mutant myotubes cultured aneurally demonstrated that the laminins act directly on muscle cells to promote postsynaptic maturation. Immunohistochemical studies in vivo and in vitro along with analysis of targeted mutants provide evidence that laminin-dependent aggregation of dystroglycan in the postsynaptic membrane is a key step in synaptic maturation. Another synaptically concentrated laminin receptor, Bcam, is dispensable. Together with previous studies implicating laminins as organizers of presynaptic differentiation, these results show that laminins coordinate post- with presynaptic maturation.
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Affiliation(s)
- Hiroshi Nishimune
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA.
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366
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Aoki K, Porterfield M, Lee SS, Dong B, Nguyen K, McGlamry KH, Tiemeyer M. The diversity of O-linked glycans expressed during Drosophila melanogaster development reflects stage- and tissue-specific requirements for cell signaling. J Biol Chem 2008; 283:30385-400. [PMID: 18725413 DOI: 10.1074/jbc.m804925200] [Citation(s) in RCA: 112] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Appropriate glycoprotein O-glycosylation is essential for normal development and tissue function in multicellular organisms. To comprehensively assess the developmental and functional impact of altered O-glycosylation, we have extensively analyzed the non-glycosaminoglycan, O-linked glycans expressed in Drosophila embryos. Through multidimensional mass spectrometric analysis of glycans released from glycoproteins by beta-elimination, we detected novel as well as previously reported O-glycans that exhibit developmentally modulated expression. The core 1 mucin-type disaccharide (Galbeta1-3GalNAc) is the predominant glycan in the total profile. HexNAcitol, hexitol, xylosylated hexitol, and branching extension of core 1 with HexNAc (to generate core 2 glycans) were also evident following release and reduction. After Galbeta1-3GalNAc, the next most prevalent glycans were a mixture of novel, isobaric, linear, and branched forms of a glucuronyl core 1 disaccharide. Other less prevalent structures were also extended with HexA, including an O-fucose glycan. Although the expected disaccharide product of the Fringe glycosyltransferase, (GlcNAcbeta1-3)fucitol, was not detectable in whole embryos, mass spectrometry fragmentation and exoglycosidase sensitivity defined a novel glucuronyl trisaccharide as GlcNAcbeta1-3(GlcAbeta1-4)fucitol. Consistent with the spatial distribution of the Fringe function, the GlcA-extended form of the Fringe product was enriched in the dorsal portion of the wing imaginal disc. Furthermore, loss of Fringe activity reduced the prevalence of the O-Fuc trisaccharide. Therefore, O-Fuc glycans necessary for the modulation of important signaling events in Drosophila are, as in vertebrates, substrates for extension beyond the addition of a single HexNAc.
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Affiliation(s)
- Kazuhiro Aoki
- Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602-4712, USA
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367
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McNally EM, Pytel P. Muscle diseases: the muscular dystrophies. ANNUAL REVIEW OF PATHOLOGY-MECHANISMS OF DISEASE 2008; 2:87-109. [PMID: 18039094 DOI: 10.1146/annurev.pathol.2.010506.091936] [Citation(s) in RCA: 112] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Dystrophic muscle disease can occur at any age. Early- or childhood-onset muscular dystrophies may be associated with profound loss of muscle function, affecting ambulation, posture, and cardiac and respiratory function. Late-onset muscular dystrophies or myopathies may be mild and associated with slight weakness and an inability to increase muscle mass. The phenotype of muscular dystrophy is an endpoint that arises from a diverse set of genetic pathways. Genes associated with muscular dystrophies encode proteins of the plasma membrane and extracellular matrix, and the sarcomere and Z band, as well as nuclear membrane components. Because muscle has such distinctive structural and regenerative properties, many of the genes implicated in these disorders target pathways unique to muscle or more highly expressed in muscle. This chapter reviews the basic structural properties of muscle and genetic mechanisms that lead to myopathy and muscular dystrophies that affect all age groups.
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Affiliation(s)
- Elizabeth M McNally
- Department of Medicine, Section of Cardiology, University of Chicago, Chicago, Illinois 60637, USA.
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368
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Oliveira J, Santos R, Soares-Silva I, Jorge P, Vieira E, Oliveira ME, Moreira A, Coelho T, Ferreira JC, Fonseca MJ, Barbosa C, Prats J, Aríztegui ML, Martins ML, Moreno T, Heinimann K, Barbot C, Pascual-Pascual SI, Cabral A, Fineza I, Santos M, Bronze-da-Rocha E. LAMA2 gene analysis in a cohort of 26 congenital muscular dystrophy patients. Clin Genet 2008; 74:502-12. [DOI: 10.1111/j.1399-0004.2008.01068.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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369
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Jimenez-Mallebrera C, Torelli S, Feng L, Kim J, Godfrey C, Clement E, Mein R, Abbs S, Brown SC, Campbell KP, Kröger S, Talim B, Topaloglu H, Quinlivan R, Roper H, Childs AM, Kinali M, Sewry CA, Muntoni F. A comparative study of alpha-dystroglycan glycosylation in dystroglycanopathies suggests that the hypoglycosylation of alpha-dystroglycan does not consistently correlate with clinical severity. Brain Pathol 2008; 19:596-611. [PMID: 18691338 PMCID: PMC2860390 DOI: 10.1111/j.1750-3639.2008.00198.x] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Hypoglycosylation of alpha-dystroglycan underpins a subgroup of muscular dystrophies ranging from congenital onset of weakness, severe brain malformations and death in the perinatal period to mild weakness in adulthood without brain involvement. Mutations in six genes have been identified in a proportion of patients. POMT1, POMT2 and POMGnT1 encode for glycosyltransferases involved in the mannosylation of alpha-dystroglycan but the function of fukutin, FKRP and LARGE is less clear. The pathological hallmark is reduced immunolabeling of skeletal muscle with antibodies recognizing glycosylated epitopes on alpha-dystroglycan. If the common pathway of these conditions is the hypoglycosyation of alpha-dystroglycan, one would expect a correlation between clinical severity and the extent of hypoglycosylation. By studying 24 patients with mutations in these genes, we found a good correlation between reduced alpha-dystroglycan staining and clinical course in patients with mutations in POMT1, POMT2 and POMGnT1. However, this was not always the case in patients with defects in fukutin and FKRP, as we identified patients with mild limb-girdle phenotypes without brain involvement with profound depletion of alpha-dystroglycan. These data indicate that it is not always possible to correlate clinical course and alpha-dystroglycan labeling and suggest that there might be differences in alpha-dystroglycan processing in these disorders.
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Affiliation(s)
- Cecilia Jimenez-Mallebrera
- Dubowitz Neuromuscular Centre, Institute of Child Health and Great Ormond Street Hospital for Children, UCL, London, UK.
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370
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Affiliation(s)
- Jakob S Satz
- Howard Hughes Medical Institute, Department of Molecular Physiology and Biophysics, 4283 Carver Biomedical Research Building, 285 Newton Road, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA
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371
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Moore CJ, Goh HT, Hewitt JE. Genes required for functional glycosylation of dystroglycan are conserved in zebrafish. Genomics 2008; 92:159-67. [PMID: 18632251 DOI: 10.1016/j.ygeno.2008.05.008] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2007] [Revised: 05/12/2008] [Accepted: 05/14/2008] [Indexed: 10/21/2022]
Abstract
Mutations in human genes encoding proteins involved in alpha-dystroglycan glycosylation result in dystroglycanopathies: severe congenital muscular dystrophy phenotypes often accompanied by CNS abnormalities and ocular defects. We have identified the zebrafish orthologues of the seven known genes in this pathway and examined their expression during embryonic development. Zebrafish Large, POMT1, POMT2, POMGnT1, Fukutin, and FKRP show in situ hybridization patterns similar to those of dystroglycan, with broad expression throughout early development. By 30 h postfertilization (hpf), transcripts of all these genes are most prominent in the CNS, eye, and muscle, tissues that are predominantly affected in the dystroglycanopathies. In contrast, Large2 expression is more restricted and by 30 hpf is confined to the lens, cerebellum, and pronephric duct. We show that the monoclonal antibody IIH6, which recognizes a glycoform of dystroglycan, also detects the zebrafish protein. Injection of morpholino oligonucleotides against zebrafish Large2 resulted in loss of IIH6 immunostaining. These data indicate that the dystroglycan glycosylation pathway is conserved in zebrafish and suggest this organism is likely to be a useful model system for functional studies.
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Affiliation(s)
- Christopher J Moore
- Institute of Genetics, Queen's Medical Centre, University of Nottingham, Nottingham NG7 2UH, UK
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372
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Bunnell TM, Jaeger MA, Fitzsimons DP, Prins KW, Ervasti JM. Destabilization of the dystrophin-glycoprotein complex without functional deficits in alpha-dystrobrevin null muscle. PLoS One 2008; 3:e2604. [PMID: 18596960 PMCID: PMC2432020 DOI: 10.1371/journal.pone.0002604] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2007] [Accepted: 06/03/2008] [Indexed: 11/20/2022] Open
Abstract
α-Dystrobrevin is a component of the dystrophin-glycoprotein complex (DGC) and is thought to have both structural and signaling roles in skeletal muscle. Mice deficient for α-dystrobrevin (adbn−/−) exhibit extensive myofiber degeneration and neuromuscular junction abnormalities. However, the biochemical stability of the DGC and the functional performance of adbn−/− muscle have not been characterized. Here we show that the biochemical association between dystrophin and β-dystroglycan is compromised in adbn−/− skeletal muscle, suggesting that α-dystrobrevin plays a structural role in stabilizing the DGC. However, despite muscle cell death and DGC destabilization, costamere organization and physiological performance is normal in adbn−/− skeletal muscle. Our results demonstrate that myofiber degeneration alone does not cause functional deficits and suggests that more complex pathological factors contribute to the development of muscle weakness in muscular dystrophy.
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Affiliation(s)
- Tina M. Bunnell
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Michele A. Jaeger
- Program in Cellular and Molecular Biology, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Daniel P. Fitzsimons
- Department of Physiology, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Kurt W. Prins
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - James M. Ervasti
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota, United States of America
- * E-mail:
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373
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Jonas M, Huang H, Kamm RD, So PTC. Fast fluorescence laser tracking microrheometry, II: quantitative studies of cytoskeletal mechanotransduction. Biophys J 2008; 95:895-909. [PMID: 18424489 PMCID: PMC2440459 DOI: 10.1529/biophysj.107.120303] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2007] [Accepted: 03/18/2008] [Indexed: 11/18/2022] Open
Abstract
Fluorescence laser tracking microrheometry (FLTM) is what we believe to be a novel method able to assess the local, frequency-dependent mechanical properties of living cells with nanometer spatial sensitivity at speeds up to 50 kHz. In an earlier article, we described the design, development, and optimization phases of the FLTM before reporting its performances in a variety of viscoelastic materials. In the work presented here, we demonstrate the suitability of FLTM to study local cellular rheology and obtain values for the storage and loss moduli G'(omega) and G''(omega) of fibroblasts consistent with past literature. We further establish that chemically induced cytoskeletal disruption is accompanied by reduced cellular stiffness and viscosity. Next, we provide a systematic study of some experimental variables that may critically influence microrheology measurements. First, we interrogate and justify the relevance of bead endocytosis as a method of cellular internalization of 1-microm probes in FLTM. Second, we show that as sample temperature increases, FLTM findings are elevated toward higher frequencies. Third, we confirm that relevant bead sizes (1 and 2 microm) have no effect on FLTM measurements. Fourth, we report the lack of influence of bead coatings (antiintegrin, antitransferrin, antidystroglycan, or uncoated tracers were surveyed) on their rheological readouts. Finally, we demonstrate the potential of FLTM in studying how substratum rigidity regulates cellular rheological properties. Interestingly, multiple, coupled strain relaxation mechanisms can be observed separated by two plateau moduli. Although these observations can be partly explained by rheological theories describing entangled actin filaments, there is a clear need to extend existing microrheology models to the cytoskeleton, including potentially important factors such as network geometry and remodeling.
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Affiliation(s)
- Maxine Jonas
- Departments of Biological Engineering and Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
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374
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Huxley-Jones J, Foord SM, Barnes MR. Drug discovery in the extracellular matrix. Drug Discov Today 2008; 13:685-94. [PMID: 18583179 DOI: 10.1016/j.drudis.2008.05.005] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2008] [Revised: 05/14/2008] [Accepted: 05/14/2008] [Indexed: 12/30/2022]
Abstract
The extracellular matrix (ECM) is an organised mesh of secreted proteins that provides structure, organisation and orientation to tissues and influences a spectrum of cell behaviours of direct relevance to disease and drug discovery. Many drugs currently in development target components of the ECM, yet most drug discovery teams perceive the ECM as a barrier to efficacious drug action, rather than a therapeutic target. Here we review current therapeutic approaches and consider potentially novel druggable opportunities to target the ECM, taking into account the factors that make it both unique and challenging, including its evolutionary history and innate multi-dimensional complexity.
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Affiliation(s)
- Julie Huxley-Jones
- Computational Biology, Molecular Discovery Research, GlaxoSmithKline Pharmaceuticals, New Frontiers Science Park (North), Third Avenue, Harlow, Essex CM19 5AW, UK.
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375
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Ackroyd MR, Skordis L, Kaluarachchi M, Godwin J, Prior S, Fidanboylu M, Piercy RJ, Muntoni F, Brown SC. Reduced expression of fukutin related protein in mice results in a model for fukutin related protein associated muscular dystrophies. Brain 2008; 132:439-51. [DOI: 10.1093/brain/awn335] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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376
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Budinger GRS, Urich D, DeBiase PJ, Chiarella SE, Burgess ZO, Baker CM, Soberanes S, Mutlu GM, Jones JCR. Stretch-induced activation of AMP kinase in the lung requires dystroglycan. Am J Respir Cell Mol Biol 2008; 39:666-72. [PMID: 18556591 DOI: 10.1165/rcmb.2007-0432oc] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Lung cells are exposed to cyclic stretch during normal respiration and during positive pressure mechanical ventilation administered to support gas exchange. Dystroglycan is a ubiquitously expressed matrix receptor that is required for normal basement membrane formation during embryogenesis and for maintaining the function of skeletal muscle myocytes and neurons where it links cells to matrix. We previously reported that equibiaxial stretch of primary alveolar epithelial cells activated the MAP kinase pathway ERK1/2 through a mechanism that required an interaction between dystroglycan and matrix. We determined whether this mechanism of mechanotransduction activates other signaling cascades in lung epithelium. Exposure of rat epithelial alveolar type II cells (AEC) to cyclic mechanical stretch resulted in activation of 5' AMP-activated protein kinase (AMPK). This response was not affected by pretreatment of AEC with the ERK inhibitor PD98059 but was inhibited by knockdown in dystroglycan expression. Moreover, production of reactive oxygen species was enhanced in mechanically stimulated AEC in which dystroglycan was knocked down. This enhancement was reversed by treatment of AEC with an AMPK activator. Activation of AMPK was also observed in lung homogenates from mice after 15 minutes of noninjurious mechanical ventilation. Furthermore, knockdown of dystroglycan in the lungs of mice using an adenovirus encoding a dystroglycan shRNA prevented the stretch-induced activation of AMPK. These results suggest that exposure to cyclic stretch activates the metabolic sensing pathway AMPK in the lung epithelium and supports a novel role for dystroglycan in this mechanotransduction.
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Affiliation(s)
- G R Scott Budinger
- Division of Pulmonary and Critical Care Medicine, The Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA.
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377
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Lommel M, Willer T, Strahl S. POMT2, a key enzyme in Walker–Warburg syndrome: somatic sPOMT2, but not testis-specific tPOMT2, is crucial for mannosyltransferase activity in vivo. Glycobiology 2008; 18:615-25. [DOI: 10.1093/glycob/cwn042] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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378
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Thornhill P, Bassett D, Lochmüller H, Bushby K, Straub V. Developmental defects in a zebrafish model for muscular dystrophies associated with the loss of fukutin-related protein (FKRP). ACTA ACUST UNITED AC 2008; 131:1551-61. [PMID: 18477595 DOI: 10.1093/brain/awn078] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
A number of muscular dystrophies are associated with the defective glycosylation of alpha-dystroglycan and many are now known to result from mutations in a number of genes encoding putative or known glycosyltransferases. These diseases include severe forms of congenital muscular dystrophy (CMD) such as Fukuyama type congenital muscular dystrophy (FCMD), Muscle-Eye-Brain disease (MEB) and Walker-Warburg syndrome (WWS), which are associated with brain and eye abnormalities. The defective glycosylation of alpha-dystroglycan in these disorders leads to a failure of alpha-dystroglycan to bind to extra-cellular matrix components and previous attempts to model these disorders have shown that the generation of fukutin- and Pomt1-deficient knockout mice results in early embryonic lethality due to basement membrane defects. We have used the zebrafish as an animal model to investigate the pathological consequences of downregulating the expression of the putative glycosyltransferase gene fukutin-related protein (FKRP) on embryonic development. We have found that downregulating FKRP in the zebrafish results in embryos which develop a range of abnormalities reminiscent of the developmental defects observed in human muscular dystrophies associated with mutations in FKRP. FKRP morphant embryos showed a spectrum of phenotypic severity involving alterations in somitic structure and muscle fibre organization as well as defects in developing neuronal structures and eye morphology. The pathological phenotype was found to correlate with a reduction in alpha-dystroglycan glycosylation and reduced laminin binding. Further characterization of the developmental processes affected in FKRP morphant embryos may lead to a better understanding of the pathological spectrum observed in muscular dystrophies associated with mutations in the human FKRP gene.
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Affiliation(s)
- Paul Thornhill
- Institute of Human Genetics, Newcastle University, International Centre for Life, Central Parkway, Newcastle Upon Tyne, NE1 3BZ, UK
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379
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Bello V, Sirour C, Moreau N, Denker E, Darribère T. A function for dystroglycan in pronephros development in Xenopus laevis. Dev Biol 2008; 317:106-20. [DOI: 10.1016/j.ydbio.2008.02.024] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2007] [Revised: 02/01/2008] [Accepted: 02/05/2008] [Indexed: 11/27/2022]
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380
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Casey T, Bond J, Tighe S, Hunter T, Lintault L, Patel O, Eneman J, Crocker A, White J, Tessitore J, Stanley M, Harlow S, Weaver D, Muss H, Plaut K. Molecular signatures suggest a major role for stromal cells in development of invasive breast cancer. Breast Cancer Res Treat 2008; 114:47-62. [DOI: 10.1007/s10549-008-9982-8] [Citation(s) in RCA: 164] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2008] [Accepted: 03/17/2008] [Indexed: 12/16/2022]
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381
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Brown JR, Crawford BE, Esko JD. Glycan antagonists and inhibitors: a fount for drug discovery. Crit Rev Biochem Mol Biol 2008; 42:481-515. [PMID: 18066955 DOI: 10.1080/10409230701751611] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Glycans, the carbohydrate chains of glycoproteins, proteoglycans, and glycolipids, represent a relatively unexploited area for drug development compared with other macromolecules. This review describes the major classes of glycans synthesized by animal cells, their mode of assembly, and available inhibitors for blocking their biosynthesis and function. Many of these agents have proven useful for studying the biological activities of glycans in isolated cells, during embryological development, and in physiology. Some are being used to develop drugs for treating metabolic disorders, cancer, and infection, suggesting that glycans are excellent targets for future drug development.
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382
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Novel synonymous substitution in POMGNT1 promotes exon skipping in a patient with congenital muscular dystrophy. J Hum Genet 2008; 53:565-572. [DOI: 10.1007/s10038-008-0263-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2007] [Accepted: 01/21/2008] [Indexed: 02/07/2023]
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383
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Abstract
The arenaviruses Lassa virus (LASV) in Africa and Machupo (MACV), Guanarito (GTOV) and Junin viruses (JUNV) in South America cause severe haemorrhagic fevers in humans with fatality rates of 15-35%. The present review focuses on the first steps of infection with human pathogenic arenaviruses, the interaction with their cellular receptor molecules and subsequent entry into the host cell. While similarities exist in genomic organization, structure and clinical disease caused by pathogenic Old World and New World arenaviruses these pathogens use different primary receptors. The Old World arenaviruses employ alpha-dystroglycan, a cellular receptor for proteins of the extracellular matrix, and the human pathogenic New World arenaviruses use the cellular cargo receptor transferrin receptor 1. While the New World arenavirus JUNV enters cells via clathrin-dependent endocytosis, evidence occurred for clathrin-independent entry of the prototypic Old World arenavirus lymphocytic choriomeningitis virus. Upon internalization, arenaviruses are delivered to the endosome, where pH-dependent membrane fusion is mediated by the envelope glycoprotein (GP). While arenavirus GPs share characteristics with class I fusion GPs of other enveloped viruses, unusual mechanistic features of GP-mediated membrane fusion have recently been discovered for arenaviruses with important implications for viral entry.
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Affiliation(s)
- Jillian M Rojek
- Viral Immunobiology Laboratory, Molecular and Integrative Neurosciences Department, The Scripps Research Institute, La Jolla, CA 92037, USA
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384
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Haines N, Seabrooke S, Stewart BA. Dystroglycan and protein O-mannosyltransferases 1 and 2 are required to maintain integrity of Drosophila larval muscles. Mol Biol Cell 2007; 18:4721-30. [PMID: 17881734 PMCID: PMC2096576 DOI: 10.1091/mbc.e07-01-0047] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2007] [Accepted: 09/11/2007] [Indexed: 11/11/2022] Open
Abstract
In vertebrates, mutations in Protein O-mannosyltransferase1 (POMT1) or POMT2 are associated with muscular dystrophy due to a requirement for O-linked mannose glycans on the Dystroglycan (Dg) protein. In this study we examine larval body wall muscles of Drosophila mutant for Dg, or RNA interference knockdown for Dg and find defects in muscle attachment, altered muscle contraction, and a change in muscle membrane resistance. To determine if POMTs are required for Dg function in Drosophila, we examine larvae mutant for genes encoding POMT1 or POMT2. Larvae mutant for either POMT, or doubly mutant for both, show muscle attachment and muscle contraction phenotypes identical to those associated with reduced Dg function, consistent with a requirement for O-linked mannose on Drosophila Dg. Together these data establish a central role for Dg in maintaining integrity in Drosophila larval muscles and demonstrate the importance of glycosylation to Dg function in Drosophila. This study opens the possibility of using Drosophila to investigate muscular dystrophy.
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Affiliation(s)
- Nicola Haines
- Department of Biology, University of Toronto, Mississauga, ON, Canada L5L 1C6.
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385
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Abstract
In contrast to most enveloped viruses that enter the host cell via clathrin-dependent endocytosis, the Old World arenavirus lymphocytic choriomeningitis virus (LCMV) enters cells via noncoated vesicles that deliver the virus to endosomes, where pH-dependent membrane fusion occurs. Here, we investigated the initial steps of LCMV infection. We found that the attachment of LCMV to its cellular receptor alpha-dystroglycan occurs rapidly and is not dependent on membrane cholesterol. However, subsequent virus internalization is sensitive to cholesterol depletion, indicating the involvement of a cholesterol-dependent pathway. We provide evidence that LCMV entry involves an endocytotic pathway that is independent of clathrin and caveolin and that does not require the GTPase dynamin. In addition, neither the structural integrity nor the dynamics of the actin cytoskeleton are required for infection. These findings indicate that the prototypic Old World arenavirus LCMV uses a mechanism of entry that is different from clathrin-mediated endocytosis, which is used by the New World arenavirus Junin virus, and pathways used by other enveloped viruses.
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386
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Biochemical characterization of MLC1 protein in astrocytes and its association with the dystrophin-glycoprotein complex. Mol Cell Neurosci 2007; 37:480-93. [PMID: 18165104 DOI: 10.1016/j.mcn.2007.11.003] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2007] [Revised: 10/31/2007] [Accepted: 11/07/2007] [Indexed: 11/23/2022] Open
Abstract
MLC1 gene mutations have been associated with megalencephalic leukoencephalopathy with subcortical cysts (MLC), a rare neurologic disorder in children. The MLC1 gene encodes a membrane protein (MLC1) with unknown function which is mainly expressed in astrocytes. Using a newly developed anti-human MLC1 polyclonal antibody, we have investigated the biochemical properties and localization of MLC1 in cultured astrocytes and brain tissue and searched for evidence of a relationship between MLC1 and proteins of the dystrophin-glycoprotein complex (DGC). Cultured astrocytes express two MLC1 components showing different solubilisation properties and subcellular distribution. Most importantly, we show that the membrane-associated component of MLC1 (60-64 kDa) localizes in astrocytic lipid rafts together with dystroglycan, syntrophin and caveolin-1, and co-fractionates with the DGC in whole rat brain tissue. In the human brain, MLC1 protein is expressed in astrocyte processes and ependymal cells, where it colocalizes with dystroglycan and syntrophin. These data indicate that the DGC may be involved in the organization and function of the MLC1 protein in astrocyte membranes.
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387
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Hultgårdh-Nilsson A, Durbeej M. Role of the extracellular matrix and its receptors in smooth muscle cell function: implications in vascular development and disease. Curr Opin Lipidol 2007; 18:540-5. [PMID: 17885425 DOI: 10.1097/mol.0b013e3282ef77e9] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
PURPOSE OF REVIEW Cardiovascular disease affects millions of people worldwide, while the sarcoglycan deficient cardiomyopathies are rare disorders. One important common feature, however, is the vascular smooth muscle. Here we focus on the roles of extracellular matrix components and their receptors in the functions of vascular smooth muscle cells. RECENT FINDINGS Recent observations highlight the importance of integrins and the dystrophin-glycoprotein complex in development and cardiomyopathy. For example, integrin alpha4 and alpha7 subunits are important for distributing vascular smooth muscle cells during blood vessel development. Studies on delta-sarcoglycan deficient animals have revealed abnormal vascular smooth muscle proliferation and apoptosis. Furthermore, data suggest that perlecan, by affecting smooth muscle cell proliferation, participates in the atherosclerotic process. Overexpression of decorin leads to reduced progression of atherosclerosis and thrombospondin-1 has been implicated in regulation of smooth muscle cell contractility via inhibition of nitric oxide. Novel findings on versican suggest that the binding of versican to fibulin is of great importance for regulating smooth muscle cell function. SUMMARY By regulating migration, proliferation and apoptosis as well as extracellular matrix synthesis and assembly, proteoglycans, integrins and the dystrophin-glycoprotein complex may be of great importance both during development and in vascular disease.
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Affiliation(s)
- Anna Hultgårdh-Nilsson
- Vessel Wall Biology Unit, Sweden bMuscle Biology Unit, University of Lund, Lund, Sweden.
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388
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Christoforou CP, Greer CE, Challoner BR, Charizanos D, Ray RP. The detached locus encodes Drosophila Dystrophin, which acts with other components of the Dystrophin Associated Protein Complex to influence intercellular signalling in developing wing veins. Dev Biol 2007; 313:519-32. [PMID: 18093579 DOI: 10.1016/j.ydbio.2007.09.044] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2007] [Revised: 09/24/2007] [Accepted: 09/24/2007] [Indexed: 11/29/2022]
Abstract
Dystrophin and Dystroglycan are the two central components of the multimeric Dystrophin Associated Protein Complex, or DAPC, that is thought to provide a mechanical link between the extracellular matrix and the actin cytoskeleton, disruption of which leads to muscular dystrophy in humans. We present the characterization of the Drosophila 'crossveinless' mutation detached (det), and show that the gene encodes the fly ortholog of Dystrophin. Our genetic analysis shows that, in flies, Dystrophin is a non-essential gene, and the sole overt morphological defect associated with null mutations in the locus is the variable loss of the posterior crossvein that has been described for alleles of det. Null mutations in Drosophila Dystroglycan (Dg) are similarly viable and exhibit this crossvein defect, indicating that both of the central DAPC components have been co-opted for this atypical function of the complex. In the developing wing, the Drosophila DAPC affects the intercellular signalling pathways involved in vein specification. In det and Dg mutant wings, the early BMP signalling that initiates crossvein specification is not maintained, particularly in the pro-vein territories adjacent to the longitudinal veins, and this results in the production of a crossvein fragment in the intervein between the two longitudinal veins. Genetic interaction studies suggest that the DAPC may exert this effect indirectly by down-regulating Notch signalling in pro-vein territories, leading to enhanced BMP signalling in the intervein by diffusion of BMP ligands from the longitudinal veins.
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Affiliation(s)
- Christina P Christoforou
- Department of Biology and Environmental Science, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QG, UK
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389
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Akhavan A, Crivelli SN, Singh M, Lingappa VR, Muschler JL. SEA domain proteolysis determines the functional composition of dystroglycan. FASEB J 2007; 22:612-21. [PMID: 17905726 DOI: 10.1096/fj.07-8354com] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Post-translational modifications of the extracellular matrix receptor dystroglycan (DG) determine its functional state, and defects in these modifications are linked to muscular dystrophies and cancers. A prominent feature of DG biosynthesis is a precursor cleavage that segregates the ligand-binding and transmembrane domains into the noncovalently attached alpha- and beta-subunits. We investigate here the structural determinants and functional significance of this cleavage. We show that cleavage of DG elicits a conspicuous change in its ligand-binding activity. Mutations that obstruct this cleavage result in increased capacity to bind laminin, in part, due to enhanced glycosylation of alpha-DG. Reconstitution of DG cleavage in a cell-free expression system demonstrates that cleavage takes place in the endoplasmic reticulum, providing a suitable regulatory point for later processing events. Sequence and mutational analyses reveal that the cleavage occurs within a full SEA (sea urchin, enterokinase, agrin) module with traits matching those ascribed to autoproteolysis. Thus, cleavage of DG constitutes a control point for the modulation of its ligand-binding properties, with therapeutic implications for muscular dystrophies. We provide a structural model for the cleavage domain that is validated by experimental analysis and discuss this cleavage in the context of mucin protein and SEA domain evolution.
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Affiliation(s)
- Armin Akhavan
- California Pacific Medical Center Research Institute, 475 Brannan St., Ste. 220, San Francisco, CA 94107, USA
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390
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Rojek JM, Campbell KP, Oldstone MB, Kunz S. Old World arenavirus infection interferes with the expression of functional alpha-dystroglycan in the host cell. Mol Biol Cell 2007; 18:4493-507. [PMID: 17761532 PMCID: PMC2043543 DOI: 10.1091/mbc.e07-04-0374] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
alpha-Dystroglycan (alpha-DG) is an important cellular receptor for extracellular matrix (ECM) proteins as well as the Old World arenaviruses lymphocytic choriomeningitis virus (LCMV) and the human pathogenic Lassa fever virus (LFV). Specific O-glycosylation of alpha-DG is critical for its function as receptor for ECM proteins and arenaviruses. Here, we investigated the impact of arenavirus infection on alpha-DG expression. Infection with an immunosuppressive LCMV isolate caused a marked reduction in expression of functional alpha-DG without affecting biosynthesis of DG core protein or global cell surface glycoprotein expression. The effect was caused by the viral glycoprotein (GP), and it critically depended on alpha-DG binding affinity and GP maturation. An equivalent effect was observed with LFVGP. Viral GP was found to associate with a complex between DG and the glycosyltransferase LARGE in the Golgi. Overexpression of LARGE restored functional alpha-DG expression in infected cells. We provide evidence that virus-induced down-modulation of functional alpha-DG perturbs DG-mediated assembly of laminin at the cell surface, affecting normal cell-matrix interactions.
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Affiliation(s)
- Jillian M. Rojek
- *Viral Immunobiology Laboratory, Molecular and Integrative Neurosciences Department, The Scripps Research Institute, La Jolla, CA 92037; and
| | - Kevin P. Campbell
- Departments of Molecular Physiology and Biophysics, Neurology, and Internal Medicine, Howard Hughes Medical Institute, University of Iowa College of Medicine, Iowa City, IA 52242
| | - Michael B.A. Oldstone
- *Viral Immunobiology Laboratory, Molecular and Integrative Neurosciences Department, The Scripps Research Institute, La Jolla, CA 92037; and
| | - Stefan Kunz
- *Viral Immunobiology Laboratory, Molecular and Integrative Neurosciences Department, The Scripps Research Institute, La Jolla, CA 92037; and
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391
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Percival JM, Froehner SC. Golgi complex organization in skeletal muscle: a role for Golgi-mediated glycosylation in muscular dystrophies? Traffic 2007; 8:184-94. [PMID: 17319799 DOI: 10.1111/j.1600-0854.2006.00523.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The Golgi complex (GC) is the central organelle of the classical secretory pathway, and it receives, modifies and packages proteins and lipids en route to their intracellular or extracellular destinations. Recent studies of congenital muscular dystrophies in skeletal muscle suggest an exciting new role for an old and well-established function of the GC: glycosylation. Glycosylation is the exquisitely regulated enzymatic addition of nucleotide sugars to proteins and lipids mediated by glycosyltransferases (GTs). Mutations in putative Golgi-resident GTs, fukutin, fukutin-related protein and large1 cause these progressive muscle-wasting diseases. The appropriate localization of GTs to specific subcompartments of the Golgi is critical for the correct assembly line-like addition of glycan groups to proteins and lipids as they pass through the GC. Consequently, these studies of congenital muscular dystrophies have focused attention on the organization and function of the GC in skeletal muscle. In contrast to other cells and tissues, the GC in skeletal muscle has received relatively little attention; however, in recent years, several studies have shown that GC distribution in muscle is highly dynamic or plastic and adopts different distributions in muscle cells undergoing myogenesis, denervation, regeneration and maturation. Here, we review the current understanding of the dynamic regulation of GC organization in skeletal muscle and focus on the targeting of fukutin, fukutin-related protein and large1 to the GC in muscle cells.
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Affiliation(s)
- Justin M Percival
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA.
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392
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Cauwe B, Van den Steen PE, Opdenakker G. The biochemical, biological, and pathological kaleidoscope of cell surface substrates processed by matrix metalloproteinases. Crit Rev Biochem Mol Biol 2007; 42:113-85. [PMID: 17562450 DOI: 10.1080/10409230701340019] [Citation(s) in RCA: 274] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Matrix metalloproteinases (MMPs) constitute a family of more than 20 endopeptidases. Identification of specific matrix and non-matrix components as MMP substrates showed that, aside from their initial role as extracellular matrix modifiers, MMPs play significant roles in highly complex processes such as the regulation of cell behavior, cell-cell communication, and tumor progression. Thanks to the comprehensive examination of the expanded MMP action radius, the initial view of proteases acting in the soluble phase has evolved into a kaleidoscope of proteolytic reactions connected to the cell surface. Important classes of cell surface molecules include adhesion molecules, mediators of apoptosis, receptors, chemokines, cytokines, growth factors, proteases, intercellular junction proteins, and structural molecules. Proteolysis of cell surface proteins by MMPs may have extremely diverse biological implications, ranging from maturation and activation, to inactivation or degradation of substrates. In this way, modification of membrane-associated proteins by MMPs is crucial for communication between cells and the extracellular milieu, and determines cell fate and the integrity of tissues. Hence, insights into the processing of cell surface proteins by MMPs and the concomitant effects on physiological processes as well as on disease onset and evolution, leads the way to innovative therapeutic approaches for cancer, as well as degenerative and inflammatory diseases.
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Affiliation(s)
- Bénédicte Cauwe
- Rega Institute for Medical Research, Laboratory of Immunobiology, University of Leuven, Leuven, Belgium
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393
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Martin LT, Glass M, Dosunmu E, Martin PT. Altered expression of natively glycosylated alpha dystroglycan in pediatric solid tumors. Hum Pathol 2007; 38:1657-68. [PMID: 17640712 PMCID: PMC2850815 DOI: 10.1016/j.humpath.2007.03.025] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/10/2006] [Revised: 11/28/2006] [Accepted: 03/12/2007] [Indexed: 10/23/2022]
Abstract
Altered glycosylation and/or expression of dystroglycan have been reported in forms of congenital muscular dystrophy as well as in cancers of the breast, colon, and oral epithelium. To date, however, there has been no study of the expression of dystroglycan in pediatric solid tumors. Using a combination of immunostaining on tissue microarrays and immunoblotting of snap-frozen unfixed tissues, we demonstrate a significant reduction in native alpha dystroglycan expression in pediatric alveolar rhabdomyosarcoma (RMS), embryonal RMS, neuroblastoma (NBL), and medulloblastoma, whereas expression of beta dystroglycan, which is cotranslated with alpha dystroglycan, is largely unchanged. Loss of native alpha dystroglycan expression was significantly more pronounced in stage 4 NBL than in pooled samples of stage 1 and stage 2 NBL, suggesting that loss of native alpha dystroglycan expression increases with advancing tumor stage. Neuroblastoma and RMS samples with reduced expression of native alpha dystroglycan also showed reduced laminin binding in laminin overlay experiments. Expression of natively glycosylated alpha dystroglycan was not altered in several other pediatric tumor types when compared with appropriate normal tissue controls. These data provide the first evidence that alpha dystroglycan glycosylation and laminin binding to alpha dystroglycan are altered in certain pediatric solid tumors and suggest that aberrant dystroglycan glycosylation may contribute to tumor cell biology in patients with RMS, medulloblastoma, and NBL.
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Affiliation(s)
- Laura T Martin
- Division of Pediatric Hematology/Oncology, Department of Pediatrics, Ohio State University College of Medicine and Public Health, Columbus, OH 43205, USA.
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394
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Abstract
The extracellular matrix plays a number of important roles, among them providing structural support and information to cellular structures such as blood vessels imbedded within it. As more complex organisms have evolved, the matrix ability to direct signalling towards the vasculature and remodel in response to signalling from the vasculature has assumed progressively greater importance. This review will focus on the molecules of the extracellular matrix, specifically relating to vessel formation and their ability to signal to the surrounding cells to initiate or terminate processes involved in blood vessel formation.
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Affiliation(s)
- John M Rhodes
- *Correspondence to: Michael SIMONS Section of Cardiology, Dartmouth-Hitchcock Medical Center, One Medical Center Drive, Lebanon, NH 03756, USA.; Tel.: 603 650 3540; E-mail:
| | - Michael Simons
- *Correspondence to: Michael SIMONS Section of Cardiology, Dartmouth-Hitchcock Medical Center, One Medical Center Drive, Lebanon, NH 03756, USA.; Tel.: 603 650 3540; E-mail:
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395
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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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396
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van Reeuwijk J, Grewal PK, Salih MAM, Beltrán-Valero de Bernabé D, McLaughlan JM, Michielse CB, Herrmann R, Hewitt JE, Steinbrecher A, Seidahmed MZ, Shaheed MM, Abomelha A, Brunner HG, van Bokhoven H, Voit T. Intragenic deletion in the LARGE gene causes Walker-Warburg syndrome. Hum Genet 2007; 121:685-90. [PMID: 17436019 PMCID: PMC1914248 DOI: 10.1007/s00439-007-0362-y] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2007] [Accepted: 03/21/2007] [Indexed: 12/08/2022]
Abstract
Intragenic homozygous deletions in the Large gene are associated with a severe neuromuscular phenotype in the myodystrophy (myd) mouse. These mutations result in a virtual lack of glycosylation of alpha-dystroglycan. Compound heterozygous LARGE mutations have been reported in a single human patient, manifesting with mild congenital muscular dystrophy (CMD) and severe mental retardation. These mutations are likely to retain some residual LARGE glycosyltransferase activity as indicated by residual alpha-dystroglycan glycosylation in patient cells. We hypothesized that more severe LARGE mutations are associated with a more severe CMD phenotype in humans. Here we report a 63-kb intragenic LARGE deletion in a family with Walker-Warburg syndrome (WWS), which is characterized by CMD, and severe structural brain and eye malformations. This finding demonstrates that LARGE gene mutations can give rise to a wide clinical spectrum, similar as for other genes that have a role in the post-translational modification of the alpha-dystroglycan protein.
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Affiliation(s)
- Jeroen van Reeuwijk
- Department of Human Genetics 855, Radboud University Nijmegen Medical Center, Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Prabhjit K. Grewal
- Institute of Genetics, Queen’s Medical Centre, University of Nottingham, Nottingham, UK
- Department of Cellular and Molecular Medicine, University of California, San Diego, LA USA
| | - Mustafa A. M. Salih
- Department of Pediatrics, College of Medicine Department of Pediatrics, King Saud University, Riyadh, Saudi Arabia
| | - Daniel Beltrán-Valero de Bernabé
- Department of Human Genetics 855, Radboud University Nijmegen Medical Center, Box 9101, 6500 HB Nijmegen, The Netherlands
- Department of Physiology and Biophysics, University of Iowa College of Medicine, Iowa City, IA USA
| | - Jenny M. McLaughlan
- Institute of Genetics, Queen’s Medical Centre, University of Nottingham, Nottingham, UK
| | - Caroline B. Michielse
- Department of Human Genetics 855, Radboud University Nijmegen Medical Center, Box 9101, 6500 HB Nijmegen, The Netherlands
- Faculty of Science, University of Amsterdam, Amsterdam, The Netherlands
| | - Ralf Herrmann
- Department of Pediatrics and Pediatric Neurology, University Hospital of Essen, Essen, Germany
| | - Jane E. Hewitt
- Institute of Genetics, Queen’s Medical Centre, University of Nottingham, Nottingham, UK
| | - Alice Steinbrecher
- Department of Pediatrics and Pediatric Neurology, University Hospital of Essen, Essen, Germany
| | - Mohamed Z. Seidahmed
- Neonatology Unit and Department of Pediatrics, Security Forces Hospital, Riyadh, Saudi Arabia
| | - Mohamed M. Shaheed
- Neonatology Unit and Department of Pediatrics, Security Forces Hospital, Riyadh, Saudi Arabia
| | - Abdullah Abomelha
- Neonatology Unit and Department of Pediatrics, Security Forces Hospital, Riyadh, Saudi Arabia
| | - Han G. Brunner
- Department of Human Genetics 855, Radboud University Nijmegen Medical Center, Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Hans van Bokhoven
- Department of Human Genetics 855, Radboud University Nijmegen Medical Center, Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Thomas Voit
- Department of Pediatrics and Pediatric Neurology, University Hospital of Essen, Essen, Germany
- Institut de Myologie, Groupe Hospitalier Pitié-Salpêtrière, Paris, France
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397
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Dénes V, Witkovsky P, Koch M, Hunter DD, Pinzón-Duarte G, Brunken WJ. Laminin deficits induce alterations in the development of dopaminergic neurons in the mouse retina. Vis Neurosci 2007; 24:549-62. [PMID: 17711601 PMCID: PMC2935900 DOI: 10.1017/s0952523807070514] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2007] [Accepted: 05/17/2007] [Indexed: 11/05/2022]
Abstract
Genetically modified mice lacking the beta2 laminin chain (beta2null), the gamma3 laminin chain (gamma3 null), or both beta2/gamma3 chains (compound null) were produced. The development of tyrosine hydroxylase (TH) immunoreactive neurons in these mouse lines was studied between birth and postnatal day (P) 20. Compared to wild type mice, no alterations were seen in gamma3 null mice. In beta2 null mice, however, the large, type I TH neurons appeared later in development, were at a lower density and had reduced TH immunoreactivity, although TH process number and size were not altered. In the compound null mouse, the same changes were observed together with reduced TH process outgrowth. Surprisingly, in the smaller, type II TH neurons, TH immunoreactivity was increased in laminin-deficient compared to wild type mice. Other retinal defects we observed were a patchy disruption of the inner limiting retinal basement membrane and a disoriented growth of Müller glial cells. Starburst and AII type amacrine cells were not apparently altered in laminin-deficient relative to wild type mice. We postulate that laminin-dependent developmental signals are conveyed to TH amacrine neurons through intermediate cell types, perhaps the Müller glial cell and/or the retinal ganglion cell.
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Affiliation(s)
- Viktória Dénes
- Department of Anatomy and Cellular Biology, Tufts University School of Medicine, Boston, Massachusetts
- Tufts Center for Vision Research, Boston, Massachusetts
| | - Paul Witkovsky
- Department of Ophthalmology, New York University School of Medicine, New York, New York
| | - Manuel Koch
- Center for Biochemistry and Department of Dermatology, University of Köln, Köln, Germany
| | | | - Germán Pinzón-Duarte
- Department of Anatomy and Cellular Biology, Tufts University School of Medicine, Boston, Massachusetts
- Tufts Center for Vision Research, Boston, Massachusetts
| | - William J. Brunken
- Department of Anatomy and Cellular Biology, Tufts University School of Medicine, Boston, Massachusetts
- Tufts Center for Vision Research, Boston, Massachusetts
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398
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Sciandra F, Gawlik KI, Brancaccio A, Durbeej M. Dystroglycan: a possible mediator for reducing congenital muscular dystrophy? Trends Biotechnol 2007; 25:262-8. [PMID: 17416431 DOI: 10.1016/j.tibtech.2007.04.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2007] [Revised: 02/22/2007] [Accepted: 04/03/2007] [Indexed: 11/30/2022]
Abstract
Alpha-dystroglycan is a highly glycosylated peripheral protein forming a complex with the membrane-spanning beta-dystroglycan and establishing a connection between the extracellular matrix and the cytoskeleton. In skeletal muscle, as part of the larger dystrophin-glycoprotein complex, dystroglycan is believed to be essential for maintaining the structural and functional stability of muscle fibers. Recent work highlights the role of abnormal dystroglycan glycosylation at the basis of glycosyltransferase-deficient congenital muscular dystrophies. Notably, modulation of glycosyltransferase activity can restore alpha-dystroglycan receptor function in these disorders. Moreover, transgenic approaches favoring the interaction between dystroglycan and the extracellular matrix molecules also represent an innovative way to restore skeletal muscle structure. These pioneering approaches might comprise an important first step towards the design of gene-transfer-based strategies for the rescue of congenital muscular dystrophies involving dystroglycan.
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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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399
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Michaluk P, Kolodziej L, Mioduszewska B, Wilczynski GM, Dzwonek J, Jaworski J, Gorecki DC, Ottersen OP, Kaczmarek L. β-Dystroglycan as a Target for MMP-9, in Response to Enhanced Neuronal Activity. J Biol Chem 2007; 282:16036-41. [PMID: 17426029 DOI: 10.1074/jbc.m700641200] [Citation(s) in RCA: 153] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Matrix metalloproteinase-9 has recently emerged as an important molecule in control of extracellular proteolysis in the synaptic plasticity. However, no synaptic targets for its enzymatic activity had been identified before. In this report, we show that beta-dystroglycan comprises such a neuronal activity-driven target for matrix metalloproteinase-9. This notion is based on the following observations. (i) Recombinant, autoactivating matrix metalloproteinase-9 produces limited proteolytic cleavage of beta-dystroglycan. (ii) In neuronal cultures, beta-dystroglycan proteolysis occurs in response to stimulation with either glutamate or bicuculline and is blocked by tissue inhibitor of metalloproteinases-1, a metalloproteinase inhibitor. (iii) Beta-dystroglycan degradation is also observed in the hippocampus in vivo in response to seizures but not in the matrix metalloproteinase-9 knock-out mice. (iv) Beta-dystroglycan cleavage correlates in time with increased matrix metalloproteinase-9 activity. (v) Finally, beta-dystroglycan and matrix metalloproteinase-9 colocalize in postsynaptic elements in the hippocampus. In conclusion, our data identify the beta-dystroglycan as a first matrix metalloproteinase-9 substrate digested in response to enhanced synaptic activity. This demonstration may help to understand the possible role of both proteins in neuronal functions, especially in synaptic plasticity, learning, and memory.
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Affiliation(s)
- Piotr Michaluk
- Department of Molecular and Cellular Neurobiology, Nencki Institute, Pasteura 3, 02-093 Warsaw, Poland
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400
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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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