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Swiderski K, Naim T, Trieu J, Chee A, Herold MJ, Kueh AJ, Goodman CA, Gregorevic P, Lynch GS. Dystrophin S3059 phosphorylation partially attenuates denervation atrophy in mouse tibialis anterior muscles. Physiol Rep 2024; 12:e16145. [PMID: 39001580 PMCID: PMC11245571 DOI: 10.14814/phy2.16145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2024] [Revised: 07/02/2024] [Accepted: 07/02/2024] [Indexed: 07/16/2024] Open
Abstract
The dystrophin protein has well-characterized roles in force transmission and maintaining membrane integrity during muscle contraction. Studies have reported decreased expression of dystrophin in atrophying muscles during wasting conditions, and that restoration of dystrophin can attenuate atrophy, suggesting a role in maintaining muscle mass. Phosphorylation of S3059 within the cysteine-rich region of dystrophin enhances binding between dystrophin and β-dystroglycan, and mimicking phosphorylation at this site by site-directed mutagenesis attenuates myotube atrophy in vitro. To determine whether dystrophin phosphorylation can attenuate muscle wasting in vivo, CRISPR-Cas9 was used to generate mice with whole body mutations of S3059 to either alanine (DmdS3059A) or glutamate (DmdS3059E), to mimic a loss of, or constitutive phosphorylation of S3059, on all endogenous dystrophin isoforms, respectively. Sciatic nerve transection was performed on these mice to determine whether phosphorylation of dystrophin S3059 could attenuate denervation atrophy. At 14 days post denervation, atrophy of tibialis anterior (TA) but not gastrocnemius or soleus muscles, was partially attenuated in DmdS3059E mice relative to WT mice. Attenuation of atrophy was associated with increased expression of β-dystroglycan in TA muscles of DmdS3059E mice. Dystrophin S3059 phosphorylation can partially attenuate denervation-induced atrophy, but may have more significant impact in less severe modes of muscle wasting.
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Affiliation(s)
- Kristy Swiderski
- Department of Anatomy and Physiology, Centre for Muscle ResearchThe University of MelbourneMelbourneVictoriaAustralia
| | - Timur Naim
- Department of Anatomy and Physiology, Centre for Muscle ResearchThe University of MelbourneMelbourneVictoriaAustralia
| | - Jennifer Trieu
- Department of Anatomy and Physiology, Centre for Muscle ResearchThe University of MelbourneMelbourneVictoriaAustralia
| | - Annabel Chee
- Department of Anatomy and Physiology, Centre for Muscle ResearchThe University of MelbourneMelbourneVictoriaAustralia
| | - Marco J. Herold
- The Walter and Eliza Hall Institute of Medical ResearchParkvilleVictoriaAustralia
- Department of Medical BiologyThe University of MelbourneMelbourneVictoriaAustralia
- Olivia Newton‐John Cancer Research InstituteHeidelbergVictoriaAustralia
- School of Cancer MedicineLa Trobe UniversityHeidelbergVictoriaAustralia
| | - Andrew J. Kueh
- The Walter and Eliza Hall Institute of Medical ResearchParkvilleVictoriaAustralia
- Department of Medical BiologyThe University of MelbourneMelbourneVictoriaAustralia
- Olivia Newton‐John Cancer Research InstituteHeidelbergVictoriaAustralia
- School of Cancer MedicineLa Trobe UniversityHeidelbergVictoriaAustralia
| | - Craig A. Goodman
- Department of Anatomy and Physiology, Centre for Muscle ResearchThe University of MelbourneMelbourneVictoriaAustralia
| | - Paul Gregorevic
- Department of Anatomy and Physiology, Centre for Muscle ResearchThe University of MelbourneMelbourneVictoriaAustralia
| | - Gordon S. Lynch
- Department of Anatomy and Physiology, Centre for Muscle ResearchThe University of MelbourneMelbourneVictoriaAustralia
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2
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Swiderski K, Brock CJ, Trieu J, Chee A, Thakur SS, Baum DM, Gregorevic P, Murphy KT, Lynch GS. Phosphorylation of ERK and dystrophin S3059 protects against inflammation-associated C2C12 myotube atrophy. Am J Physiol Cell Physiol 2021; 320:C956-C965. [PMID: 33729835 DOI: 10.1152/ajpcell.00513.2020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The dystrophin-glycoprotein complex (DGC) is a multiprotein structure required to maintain muscle fiber membrane integrity, transmit force by linking the actin cytoskeleton with the extracellular matrix, and maintain muscle homeostasis. Membrane localization of dystrophin is perturbed in muscles wasting as a consequence of cancer cachexia, tenotomy, and advanced aging, which are all associated with low level, chronic inflammation. Strategies to preserve dystrophin expression at the sarcolemma might therefore combat muscle wasting. Phosphorylation of dystrophin serine 3059 (S3059) enhances the interaction between dystrophin and β-dystroglycan. To test the contribution of amino acid phosphorylation to muscle fiber size changes, dystrophin constructs with phospho-null and phosphomimetic mutations were transfected into C2C12 muscle cells or AAV-293 cells in the presence or absence of kinase inhibitors/activators to assess effects on myotube diameter and protein function. Overexpression of a dystrophin construct with a phospho-null mutation at S3059 in vitro reduced myotube size in healthy C2C12 cells. Conversely overexpression of a phosphomimetic mutation at S3059 attenuated inflammation-induced myotube atrophy. Increased ERK activation by addition of phorbol myristate acetate (PMA) also reduced inflammation-associated myotube atrophy and increased the interaction between dystrophin and β-dystroglycan. These findings demonstrate a link between increased ERK activation, dystrophin S3059 phosphorylation, stabilization of the DGC, and the regulation of muscle fiber size. Interventions that increase dystrophin S3059 phosphorylation to promote stronger binding of dystrophin to β-dystroglycan may have therapeutic potential for attenuation of inflammation-associated muscle wasting.
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Affiliation(s)
- Kristy Swiderski
- Centre for Muscle Research, Department of Anatomy and Physiology, The University of Melbourne, Melbourne, Victoria, Australia
| | - Christopher J Brock
- Centre for Muscle Research, Department of Anatomy and Physiology, The University of Melbourne, Melbourne, Victoria, Australia
| | - Jennifer Trieu
- Centre for Muscle Research, Department of Anatomy and Physiology, The University of Melbourne, Melbourne, Victoria, Australia
| | - Annabel Chee
- Centre for Muscle Research, Department of Anatomy and Physiology, The University of Melbourne, Melbourne, Victoria, Australia
| | - Savant S Thakur
- Centre for Muscle Research, Department of Anatomy and Physiology, The University of Melbourne, Melbourne, Victoria, Australia
| | - Dale M Baum
- Centre for Muscle Research, Department of Anatomy and Physiology, The University of Melbourne, Melbourne, Victoria, Australia
| | - Paul Gregorevic
- Centre for Muscle Research, Department of Anatomy and Physiology, The University of Melbourne, Melbourne, Victoria, Australia
| | - Kate T Murphy
- Centre for Muscle Research, Department of Anatomy and Physiology, The University of Melbourne, Melbourne, Victoria, Australia
| | - Gordon S Lynch
- Centre for Muscle Research, Department of Anatomy and Physiology, The University of Melbourne, Melbourne, Victoria, Australia
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3
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Allen DG, Whitehead NP, Froehner SC. Absence of Dystrophin Disrupts Skeletal Muscle Signaling: Roles of Ca2+, Reactive Oxygen Species, and Nitric Oxide in the Development of Muscular Dystrophy. Physiol Rev 2016; 96:253-305. [PMID: 26676145 DOI: 10.1152/physrev.00007.2015] [Citation(s) in RCA: 272] [Impact Index Per Article: 34.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Dystrophin is a long rod-shaped protein that connects the subsarcolemmal cytoskeleton to a complex of proteins in the surface membrane (dystrophin protein complex, DPC), with further connections via laminin to other extracellular matrix proteins. Initially considered a structural complex that protected the sarcolemma from mechanical damage, the DPC is now known to serve as a scaffold for numerous signaling proteins. Absence or reduced expression of dystrophin or many of the DPC components cause the muscular dystrophies, a group of inherited diseases in which repeated bouts of muscle damage lead to atrophy and fibrosis, and eventually muscle degeneration. The normal function of dystrophin is poorly defined. In its absence a complex series of changes occur with multiple muscle proteins showing reduced or increased expression or being modified in various ways. In this review, we will consider the various proteins whose expression and function is changed in muscular dystrophies, focusing on Ca(2+)-permeable channels, nitric oxide synthase, NADPH oxidase, and caveolins. Excessive Ca(2+) entry, increased membrane permeability, disordered caveolar function, and increased levels of reactive oxygen species are early changes in the disease, and the hypotheses for these phenomena will be critically considered. The aim of the review is to define the early damage pathways in muscular dystrophy which might be appropriate targets for therapy designed to minimize the muscle degeneration and slow the progression of the disease.
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Affiliation(s)
- David G Allen
- Sydney Medical School & Bosch Institute, University of Sydney, New South Wales, Australia; and Department of Physiology & Biophysics, University of Washington, Seattle, Washington
| | - Nicholas P Whitehead
- Sydney Medical School & Bosch Institute, University of Sydney, New South Wales, Australia; and Department of Physiology & Biophysics, University of Washington, Seattle, Washington
| | - Stanley C Froehner
- Sydney Medical School & Bosch Institute, University of Sydney, New South Wales, Australia; and Department of Physiology & Biophysics, University of Washington, Seattle, Washington
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4
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Swiderski K, Shaffer SA, Gallis B, Odom GL, Arnett AL, Scott Edgar J, Baum DM, Chee A, Naim T, Gregorevic P, Murphy KT, Moody J, Goodlett DR, Lynch GS, Chamberlain JS. Phosphorylation within the cysteine-rich region of dystrophin enhances its association with β-dystroglycan and identifies a potential novel therapeutic target for skeletal muscle wasting. Hum Mol Genet 2014; 23:6697-711. [PMID: 25082828 DOI: 10.1093/hmg/ddu388] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Mutations in dystrophin lead to Duchenne muscular dystrophy, which is among the most common human genetic disorders. Dystrophin nucleates assembly of the dystrophin-glycoprotein complex (DGC), and a defective DGC disrupts an essential link between the intracellular cytoskeleton and the basal lamina, leading to progressive muscle wasting. In vitro studies have suggested that dystrophin phosphorylation may affect interactions with actin or syntrophin, yet whether this occurs in vivo or affects protein function remains unknown. Utilizing nanoflow liquid chromatography mass spectrometry, we identified 18 phosphorylated residues within endogenous dystrophin. Mutagenesis revealed that phosphorylation at S3059 enhances the dystrophin-dystroglycan interaction and 3D modeling utilizing the Rosetta software program provided a structural model for how phosphorylation enhances this interaction. These findings demonstrate that phosphorylation is a key mechanism regulating the interaction between dystrophin and the DGC and reveal that posttranslational modification of a single amino acid directly modulates the function of dystrophin.
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Affiliation(s)
- Kristy Swiderski
- Basic and Clinical Myology Laboratory, Department of Physiology, University of Melbourne, VIC 3010, Australia Department of Neurology, University of Washington School of Medicine, Seattle, WA 98195-7720, USA
| | - Scott A Shaffer
- Department of Medicinal Chemistry, University of Washington School of Medicine, Seattle, WA 98195-7610, USA
| | - Byron Gallis
- Department of Medicinal Chemistry, University of Washington School of Medicine, Seattle, WA 98195-7610, USA
| | - Guy L Odom
- Department of Neurology, University of Washington School of Medicine, Seattle, WA 98195-7720, USA
| | - Andrea L Arnett
- Department of Neurology, University of Washington School of Medicine, Seattle, WA 98195-7720, USA
| | - J Scott Edgar
- Department of Medicinal Chemistry, University of Washington School of Medicine, Seattle, WA 98195-7610, USA
| | - Dale M Baum
- Basic and Clinical Myology Laboratory, Department of Physiology, University of Melbourne, VIC 3010, Australia
| | - Annabel Chee
- Basic and Clinical Myology Laboratory, Department of Physiology, University of Melbourne, VIC 3010, Australia
| | - Timur Naim
- Basic and Clinical Myology Laboratory, Department of Physiology, University of Melbourne, VIC 3010, Australia
| | - Paul Gregorevic
- Muscle Biology and Therapeutics Laboratory, Baker IDI Heart and Diabetes Institute, Melbourne, VIC 3004, Australia
| | - Kate T Murphy
- Basic and Clinical Myology Laboratory, Department of Physiology, University of Melbourne, VIC 3010, Australia
| | - James Moody
- Department of Biochemistry, University of Washington School of Medicine, Seattle, WA 98195-7350, USA and Program in Molecular and Cellular Biology, University of Washington School of Medicine, Seattle, WA 98195-7275, USA
| | - David R Goodlett
- Department of Medicinal Chemistry, University of Washington School of Medicine, Seattle, WA 98195-7610, USA
| | - Gordon S Lynch
- Basic and Clinical Myology Laboratory, Department of Physiology, University of Melbourne, VIC 3010, Australia
| | - Jeffrey S Chamberlain
- Department of Neurology, University of Washington School of Medicine, Seattle, WA 98195-7720, USA Department of Biochemistry, University of Washington School of Medicine, Seattle, WA 98195-7350, USA and Program in Molecular and Cellular Biology, University of Washington School of Medicine, Seattle, WA 98195-7275, USA
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5
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Rees MLJ, Lien CF, Górecki DC. Dystrobrevins in muscle and non-muscle tissues. Neuromuscul Disord 2007; 17:123-34. [PMID: 17251025 DOI: 10.1016/j.nmd.2006.11.003] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2006] [Revised: 10/26/2006] [Accepted: 11/20/2006] [Indexed: 01/23/2023]
Abstract
The alpha- and beta-dystrobrevins belong to the family of dystrophin-related and dystrophin-associated proteins. As constituents of the dystrophin-associated protein complex, alpha-dystrobrevin was believed to have a role predominantly in muscles and beta-dystrobrevin in non-muscle tissues. Recent reports described novel localisations and molecular characteristics of alpha-dystrobrevin isoforms in non-muscle tissues (developing and adult). While single and double knockout studies have revealed distinct functions of dystrobrevin in some tissues, these also suggested a strong compensatory mechanism, where dystrobrevins displaying overlapping tissue expression pattern and structure/function similarity can substitute each other. No human disease has been unequivocally associated within mutations of dystrobrevin genes. However, some significant exceptions to these overlapping expression patterns, mainly in the brain, suggest that dystrobrevin mutations might underlie some specific motor, behavioural or cognitive defects. Dystrobrevin binding partner DTNBP1 (dysbindin) is a probable susceptibility gene for schizophrenia and bipolar affective disorder in some populations. As dysbindin abnormality is linked to Hermansky-Pudlak syndrome, dystrobrevins and/or their binding partners may also be required for proper function of other non-muscle tissues.
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Affiliation(s)
- Melissa L J Rees
- Department of Molecular Medicine, Institute of Biomedical and Biomolecular Sciences, School of Pharmacy and Biomedical Sciences, University of Portsmouth, UK
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6
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Compton AG, Cooper ST, Hill PM, Yang N, Froehner SC, North KN. The syntrophin-dystrobrevin subcomplex in human neuromuscular disorders. J Neuropathol Exp Neurol 2005; 64:350-61. [PMID: 15835271 DOI: 10.1093/jnen/64.4.350] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The syntrophins and alpha-dystrobrevin form a subcomplex with dystrophin at the skeletal muscle membrane, and are also highly concentrated at the neuromuscular synapse. Here we demonstrate that the different syntrophins and alpha-dystrobrevin isoforms have distinct expression patterns during human skeletal muscle development, and are differentially affected by loss of dystrophin anchorage and denervation in human neuromuscular disease. During normal fetal development, and in Duchenne muscular dystrophy and denervation disorders, alpha1-syntrophin and alpha-dystrobrevin are absent or markedly reduced at the sarcolemmal membrane. beta1-Syntrophin is the predominant syntrophin isoform expressed at the muscle membrane during development, and it undergoes upregulation in response to loss of alpha1-syntrophin in Duchenne muscular dystrophy and in denervation. Upregulation of beta1-syntrophin in neuromuscular disorders is associated with re-expression of the fetal nicotinic acetylcholine receptor gamma-subunit, cardiac actin, and neonatal myosin, suggesting reversion of muscle fibers to an immature phenotype. We show that denervation specifically affects expression of the syntrophin-dystrobrevin subcomplex and does not affect levels or localization of other members of the dystrophin-associated protein complex. Our results confirm that dystrophin is required for anchorage of the syntrophin-dystrobrevin subcomplex and suggest that expression of the syntrophin-dystrobrevin complex may be independently regulated through neuromuscular transmission.
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Affiliation(s)
- Alison G Compton
- Institute for Neuromuscular Research, Children's Hospital at Westmead, NSW, Australia
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7
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Blake DJ, Weir A, Newey SE, Davies KE. Function and genetics of dystrophin and dystrophin-related proteins in muscle. Physiol Rev 2002; 82:291-329. [PMID: 11917091 DOI: 10.1152/physrev.00028.2001] [Citation(s) in RCA: 827] [Impact Index Per Article: 37.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The X-linked muscle-wasting disease Duchenne muscular dystrophy is caused by mutations in the gene encoding dystrophin. There is currently no effective treatment for the disease; however, the complex molecular pathology of this disorder is now being unravelled. Dystrophin is located at the muscle sarcolemma in a membrane-spanning protein complex that connects the cytoskeleton to the basal lamina. Mutations in many components of the dystrophin protein complex cause other forms of autosomally inherited muscular dystrophy, indicating the importance of this complex in normal muscle function. Although the precise function of dystrophin is unknown, the lack of protein causes membrane destabilization and the activation of multiple pathophysiological processes, many of which converge on alterations in intracellular calcium handling. Dystrophin is also the prototype of a family of dystrophin-related proteins, many of which are found in muscle. This family includes utrophin and alpha-dystrobrevin, which are involved in the maintenance of the neuromuscular junction architecture and in muscle homeostasis. New insights into the pathophysiology of dystrophic muscle, the identification of compensating proteins, and the discovery of new binding partners are paving the way for novel therapeutic strategies to treat this fatal muscle disease. This review discusses the role of the dystrophin complex and protein family in muscle and describes the physiological processes that are affected in Duchenne muscular dystrophy.
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Affiliation(s)
- Derek J Blake
- Medical Research Council, Functional Genetics Unit, Department of Human Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
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8
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Royuela M, Hugon G, Rivier F, Fehrentz JA, Martinez J, Paniagua R, Mornet D. Variations in dystrophin complex in red and white caudal muscles from Torpedo marmorata. J Histochem Cytochem 2001; 49:857-65. [PMID: 11410610 DOI: 10.1177/002215540104900706] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
We present an up-to-date study on the nature, at the protein level, of various members of the dystrophin complex at the muscle cell membrane by comparing red and white caudal muscles from Torpedo marmorata. Our investigations involved immunodetection approaches and Western blotting analysis. We determined the presence or absence of different molecules belonging to the dystrophin family complex by analyzing their localization and molecular weight. Specific antibodies directed against dystrophin, i.e., DRP2 alpha-dystrobrevin, beta-dystroglycan, alpha-syntrophin, alpha-, beta-, gamma-, and delta-sarcoglycan, and sarcospan, were used. The immunofluorescence study (confocal microscopy) showed differences in positive immunoreactions at the sarcolemmal membrane in these slow-type and fast-type skeletal muscle fibers. Protein extracts from T. marmorata red and white muscles were analyzed by Western blotting and confirmed the presence of dystrophin and associated proteins at the expected molecular weights. Differences were confirmed by comparative immunoprecipitation analysis of enriched membrane preparations with anti-beta-dystroglycan polyclonal antibody. These experiments revealed clear complex or non-complex formation between members of the dystrophin system, depending on the muscle type analyzed. Differences in the potential function of these various dystrophin complexes in fast or slow muscle fibers are discussed in relation to previous data obtained in corresponding mammalian tissues. (J Histochem Cytochem 49:857-865, 2001)
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Affiliation(s)
- M Royuela
- Department of Cell Biology and Genetics, University of Alcalá, Alcalá de Henares, Madrid, Spain.
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9
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Src-class kinases act within the agrin/MuSK pathway to regulate acetylcholine receptor phosphorylation, cytoskeletal anchoring, and clustering. J Neurosci 2001. [PMID: 11356869 DOI: 10.1523/jneurosci.21-11-03806.2001] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Synaptogenesis at the neuromuscular junction requires agrin-induced stable localization of acetylcholine receptors (AChRs) at the endplate. The effects of agrin are transduced by the muscle-specific receptor tyrosine kinase (MuSK). This study provides evidence that Src-class protein tyrosine kinases mediate the effects of agrin-activated MuSK to regulate clustering and anchoring of AChRs in skeletal muscle. MuSK was complexed with both Src and Fyn in the C2 mouse muscle cell line. These associations were enhanced by agrin and by increasing protein tyrosine phosphorylation with pervanadate. Coupling between MuSK and the Src-class kinases in vivo appeared to be caused by a phosphotyrosine-SH2 domain interaction because binding of MuSK to the SH2 domains of Fyn and Src in vitro was specific, enhanced by phosphorylation, and dependent on MuSK autophosphorylation. In addition, Src and Fyn phosphorylated MuSK. AChR phosphorylation, stimulated by agrin or pervanadate, was inhibited by blocking Src-class kinases with PP1. Furthermore, agrin-induced clustering and cytoskeletal anchoring of AChRs was dependent on Src-family kinases. These data support the conclusion that Fyn and Src act downstream of MuSK to regulate the stable localization of AChRs at the neuromuscular endplate during agrin-induced synaptogenesis.
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10
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James M, Nuttall A, Ilsley JL, Ottersbach K, Tinsley JM, Sudol M, Winder SJ. Adhesion-dependent tyrosine phosphorylation of (beta)-dystroglycan regulates its interaction with utrophin. J Cell Sci 2000; 113 ( Pt 10):1717-26. [PMID: 10769203 DOI: 10.1242/jcs.113.10.1717] [Citation(s) in RCA: 93] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Many cell adhesion-dependent processes are regulated by tyrosine phosphorylation. In order to investigate the role of tyrosine phosphorylation of the utrophin-dystroglycan complex we treated suspended or adherent cultures of HeLa cells with peroxyvanadate and immunoprecipitated (beta)-dystroglycan and utrophin from cell extracts. Western blotting of (β)-dystroglycan and utrophin revealed adhesion- and peroxyvanadate-dependent mobility shifts which were recognised by anti-phospho-tyrosine antibodies. Using maltose binding protein fusion constructs to the carboxy-terminal domains of utrophin we were able to demonstrate specific interactions between the WW, EF and ZZ domains of utrophin and (beta)-dystroglycan by co-immunoprecipitation with endogenous (beta)-dystroglycan. In extracts from cells treated with peroxyvanadate, where endogenous (beta)-dystroglycan was tyrosine phosphorylated, (beta)-dystroglycan was no longer co-immunoprecipitated with utrophin fusion constructs. Peptide ‘SPOTs’ assays confirmed that tyrosine phosphorylation of (beta)-dystroglycan regulated the binding of utrophin. The phosphorylated tyrosine was identified as Y(892) in the (beta)-dystroglycan WW domain binding motif PPxY thus demonstrating the physiological regulation of the (beta)-dystroglycan/utrophin interaction by adhesion-dependent tyrosine phosphorylation.
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Affiliation(s)
- M James
- Institute of Cell and Molecular Biology, University of Edinburgh, King's Buildings, Mayfield Road, Edinburgh, EH9 3JR, UK
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11
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Lumeng C, Phelps S, Crawford GE, Walden PD, Barald K, Chamberlain JS. Interactions between beta 2-syntrophin and a family of microtubule-associated serine/threonine kinases. Nat Neurosci 1999; 2:611-7. [PMID: 10404183 DOI: 10.1038/10165] [Citation(s) in RCA: 122] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A screen for proteins that interact with beta 2-syntrophin led to the isolation of MAST205 (microtubule-associated serine/threonine kinase-205 kD) and a newly identified homologue, SAST (syntrophin-associated serine/threonine kinase). Binding studies showed that beta 2-syntrophin and MAST205/SAST associated via a PDZ-PDZ domain interaction. MAST205 colocalized with beta 2-syntrophin and utrophin at neuromuscular junctions. SAST colocalized with syntrophin in cerebral vasculature, spermatic acrosomes and neuronal processes. SAST and syntrophin were highly associated with purified microtubules and microtubule-associated proteins, whereas utrophin and dystrophin were only partially associated with microtubules. Our data suggest that MAST205 and SAST link the dystrophin/utrophin network with microtubule filaments via the syntrophins.
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Affiliation(s)
- C Lumeng
- Department of Human Genetics, University of Michigan Medical School, Ann Arbor 48109-0618, USA
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12
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Balasubramanian S, Huganir RL. Characterization of phosphotyrosine containing proteins at the cholinergic synapse. FEBS Lett 1999; 446:95-102. [PMID: 10100622 DOI: 10.1016/s0014-5793(99)00171-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Tyrosine phosphorylation has been associated with several aspects of the regulation of cholinergic synaptic function, including nicotinic acetylcholine receptor (AChR) desensitization as well as the synthesis and clustering of synaptic components. While some progress has been made in elucidating the molecular events initiating such signals, the downstream targets of these tyrosine kinase pathways have yet to be characterized. In this paper we have used molecular cloning techniques to identify proteins which are tyrosine phosphorylated at the cholinergic synapse. Phosphotyrosine containing proteins (PYCPs) were isolated from the electric organ of Torpedo californica by anti-phosphotyrosine immunoaffinity chromatography. Peptide sequencing and expression cloning then identified the isolated proteins. The proteins identified included heat shock protein 90, type III intermediate filament from Torpedo electric organ, alpha-fodrin, beta-tubulin, actin and rapsyn. These tyrosine phosphorylated proteins may play a role in the regulation of synaptic function by tyrosine kinases.
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Affiliation(s)
- S Balasubramanian
- Department of Neuroscience, Howard Hughes Medical Institute, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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13
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Nawrotzki R, Loh NY, Ruegg MA, Davies KE, Blake DJ. Characterisation of alpha-dystrobrevin in muscle. J Cell Sci 1998; 111 ( Pt 17):2595-605. [PMID: 9701558 DOI: 10.1242/jcs.111.17.2595] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Dystrophin-related and associated proteins are important for the formation and maintenance of the mammalian neuromuscular junction. Initial studies in the electric organ of Torpedo californica showed that the dystrophin-related protein dystrobrevin (87K) co-purifies with the acetylcholine receptors and other postsynaptic proteins. Dystrobrevin is also a major phosphotyrosine-containing protein in the postsynaptic membrane. Since inhibitors of tyrosine protein phosphorylation block acetylcholine receptor clustering in cultured muscle cells, we examined the role of alpha-dystrobrevin during synapse formation and in response to agrin. Using specific antibodies, we show that C2 myoblasts and early myotubes only produce alpha-dystrobrevin-1, the mammalian orthologue of Torpedo dystrobrevin, whereas mature skeletal muscle expresses three distinct alpha-dystrobrevin isoforms. In myotubes, alpha-dystrobrevin-1 is found on the cell surface and also in acetylcholine receptor-rich domains. Following agrin stimulation, alpha-dystrobrevin-1 becomes re-localised beneath the cell surface into macroclusters that contain acetylcholine receptors and another dystrophin-related protein, utrophin. This redistribution is not associated with tyrosine phosphorylation of alpha-dystrobrevin-1 by agrin. Furthermore, we show that alpha-dystrobrevin-1 is associated with both utrophin in C2 cells and dystrophin in mature skeletal muscle. Thus alpha-dystrobrevin-1 is a component of two protein complexes in muscle, one with utrophin at the neuromuscular junction and the other with dystrophin at the sarcolemma. These results indicate that alpha-dystrobrevin-1 is not involved in the phosphorylation-dependent, early stages of receptor clustering, but rather in the stabilisation and maturation of clusters, possibly via an interaction with utrophin.
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Affiliation(s)
- R Nawrotzki
- Genetics Unit, Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
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14
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Abstract
Recent studies with transgenic animals have considerably advanced our knowledge of the roles of dystrophin and utrophin in both muscle and non-muscle tissues. Rigorous analyses of the roles of the various mdx mutations in mice, as well as the use of artificial transgenes in an mdx background, are beginning to define the functional importance of various regions of the dystrophin protein in normal muscle. Furthermore, recent biochemical analyses have revealed new insights into the role and organization of dystrophin at the membrane-cytoskeleton interface. Transgenic approaches have also revealed surprising and encouraging results with respect to utrophin. Against expectations, the long-awaited utrophin knockout mice have a remarkably mild phenotype with only subtle changes in neuromuscular junction architecture. On the other hand, mdx mice transgenic for a mini-utrophin construct showed rescue of the muscular dystrophy phenotype, clearly an encouraging finding with obvious therapeutic possibilities. These and other recent findings are discussed in the context of the structure and function of dystrophin and utrophin at the membrane-cytoskeleton interface.
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Affiliation(s)
- S J Winder
- Institute of Cell and Molecular Biology, University of Edinburgh, UK
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15
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Fuhrer C, Hall ZW. Functional interaction of Src family kinases with the acetylcholine receptor in C2 myotubes. J Biol Chem 1996; 271:32474-81. [PMID: 8943314 DOI: 10.1074/jbc.271.50.32474] [Citation(s) in RCA: 74] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Tyrosine phosphorylation of the beta subunit of the acetylcholine receptor (AChR) has been postulated to play a role in AChR clustering during development of the neuromuscular junction. We have investigated the mechanism of this phosphorylation in mammalian C2 myotubes and report that the tyrosine kinase Src binds and phosphorylates glutathione S-transferase fusion proteins containing the N-terminal half of the cytoplasmic loop of the beta subunit. No binding occurs to the related kinases Fyn or Yes or to the corresponding regions from the gamma and delta subunits. Furthermore, AChRs affinity-isolated from C2 myotubes using alpha-bungarotoxin-Sepharose were specifically associated with Src and Fyn and had tyrosine-phosphorylated beta subunits. We suggest that AChRs are initially phosphorylated by Src and subsequently bind Fyn in a phosphotyrosine-dependent manner. These interactions are likely to play an important role in construction of the specialized postsynaptic membrane during synaptogenesis.
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Affiliation(s)
- C Fuhrer
- Department of Physiology, University of California, San Francisco, California 94143, USA
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16
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Namba T, Scheller RH. Inhibition of agrin-mediated acetylcholine receptor clustering by utrophin C-terminal peptides. Genes Cells 1996; 1:755-64. [PMID: 9077444 DOI: 10.1111/j.1365-2443.1996.tb00015.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
BACKGROUND Agrin is an extracellular matrix protein that is required for neuromuscular synaptogenesis and is particularly important in the clustering of acetylcholine receptors at post-synaptic sites. Little is known about the signal transduction pathway of agrin-mediated receptor clustering, although cytoskeletal elements and a dystrophin associated glycoprotein complex (DGC) have been implicated. Because agrin binds to alpha-dystroglycan, a member of the DGC, and the DGC is linked to actin through utrophin at postsynaptic sites, it has been suggested that binding of utrophin to the DGC plays a central role in agrin mediated receptor clustering. RESULTS To test this hypothesis, we expressed at high levels the DGC binding domains of utrophin in cultured myotubes using recombinant Semliki Forest Virus. Myotubes expressing the utrophin and dystrophin DGC binding domain formed significantly fewer acetylcholine receptor clusters in response to agrin than myotubes expressing other proteins. CONCLUSIONS These results suggest involvement of the DGC and utrophin in the signal transduction pathway of agrin-mediated acetylcholine receptor cluster formation or stabilization.
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Affiliation(s)
- T Namba
- Department of Molecular and Cellular Physiology, Stanford University Medical School, CA 94305, USA
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17
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Michalak M, Fu SY, Milner RE, Busaan JL, Hance JE. Phosphorylation of the carboxyl-terminal region of dystrophin. Biochem Cell Biol 1996; 74:431-7. [PMID: 8960349 DOI: 10.1139/o96-047] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Dystrophin is a protein product of the gene responsible for Duchenne and Becker muscular dystrophy. The protein is localized to the inner surface of sarcolemma and is associated with a group of membrane (glyco)proteins. Dystrophin links cytoskeletal actins via the dystrophin-associated protein complex to extracellular matrix protein, laminin. This structural organization implicates the role of dystrophin in stabilizing the sarcolemma of muscle fibers. Precisely how dystrophin functions is far from clear. The presence of an array of isoforms of the C-terminal region of dystrophin suggests that dystrophin may have functions other than structural. In agreement, many potential phosphorylation sites are found in the C-terminal region of dystrophin, and the C-terminal region of dystrophin is phosphorylated both in vitro and in vivo by many protein kinases, including MAP kinase, p34cdc2 kinase, CaM kinase, and casein kinase, and is dephosphorylated by calcineurin. The C-terminal domain of dystrophin is also a substrate for hierarchical phosphorylation by casein kinase-2 and GSK-3. These observations, in accordance with the finding that the cysteine-rich region binds to Ca2+, Zn2+, and calmodulin, suggest an active involvement of dystrophin in transducing signals across muscle sarcolemma. Phosphorylation-dephosphorylation of the C-terminal region of dystrophin may play a role in regulating dystrophin-protein interactions and (or) transducing signal from the extracellular matrix via the dystrophin molecule to the cytoskeleton.
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Affiliation(s)
- M Michalak
- Department of Biochemistry, University of Alberta, Edmonton, Canada
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18
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Blake DJ, Nawrotzki R, Peters MF, Froehner SC, Davies KE. Isoform diversity of dystrobrevin, the murine 87-kDa postsynaptic protein. J Biol Chem 1996; 271:7802-10. [PMID: 8631824 DOI: 10.1074/jbc.271.13.7802] [Citation(s) in RCA: 120] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Dystrophin-related and -associated proteins are important in the formation and maintenance of the mammalian neuromuscular junction. We have characterized mouse cDNA clones encoding isoforms of the dystrophin-homologous 87-kDa postsynaptic protein, dystrobrevin. In Torpedo, the 87-kDa protein is multiply phosphorylated and closely associated with proteins in the postsynaptic cytoskeleton, including the acetylcholine receptor. In contrast to Torpedo, where only a single transcript is seen, the mouse expresses several mRNAs encoding different isoforms. A 6.0-kilobase transcript in brain encodes a 78-kDa protein (dystrobrevin-2) that has a different C terminus, lacking the putative tyrosine kinase substrate domain. In skeletal and cardiac muscle, transcripts of 1.7 and 3.3/3.5 kilobases predominate and encode additional isoforms. Alternative splicing within the coding region and differential usage of untranslated regions produce additional variation. Multiple dystrobrevin-immunoreactive proteins copurify with syntrophin from mouse tissues. In skeletal muscle, dystrobrevin immunoreactivity is restricted to the neuromuscular junction and sarcolemma. The occurrence of many dystrobrevin isoforms is significant because alternative splicing and phosphorylation often have profound effects upon the biological activity of synaptic proteins.
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Affiliation(s)
- D J Blake
- Molecular Genetics Group, Institute of Molecular Medicine, John Radcliffe Hospital, Headington, Oxford, United Kingdom
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19
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Anderson JT, Rogers RP, Jarrett HW. Ca2+-calmodulin binds to the carboxyl-terminal domain of dystrophin. J Biol Chem 1996; 271:6605-10. [PMID: 8636075 DOI: 10.1074/jbc.271.12.6605] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The unique COOH-terminal domain of dystrophin (mouse dystrophin protein sequences 3266-3678) was expressed as a chimeric fusion protein (with the maltose-binding protein), and its binding to calmodulin was assessed. This fusion protein, called DysS9, bound to calmodulin-Sepharose, bound biotinylated calmodulin, caused characteristic changes in the fluorescence emission spectrum of dansyl-calmodulin, and had an apparent affinity for dansyl-calmodulin of 54 nM. Binding in each case was Ca2+-dependent. The maltose-binding protein does not bind calmodulin, and thus binding resides in the dystrophin-derived sequences. Deletion mutation experiments further localize the high affinity calmodulin binding to mouse dystrophin protein sequences 3293-3349, and this domain contains regions with chemical characteristics found in the calmodulin-binding sequences in other proteins. The COOH-terminal domain provides sites of attachment of dystrophin to membrane proteins, and calmodulin binding may modulate these interactions.
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Affiliation(s)
- J T Anderson
- Department of Biochemistry, University of Tennessee, Memphis, Tennessee 38163, USA
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20
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Ahn AH, Freener CA, Gussoni E, Yoshida M, Ozawa E, Kunkel LM. The three human syntrophin genes are expressed in diverse tissues, have distinct chromosomal locations, and each bind to dystrophin and its relatives. J Biol Chem 1996; 271:2724-30. [PMID: 8576247 DOI: 10.1074/jbc.271.5.2724] [Citation(s) in RCA: 132] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The syntrophins are a biochemically heterogeneous group of 58-kDa intracellular membrane-associated dystrophin-binding proteins. We have cloned and characterized human acidic (alpha 1-) syntrophin and a second isoform of human basic (beta 2-) syntrophin. Comparison of the deduced amino acid structure of the three human isoforms of syntrophin (together with the previously reported human beta 1-syntrophin) demonstrates their overall similarity. The deduced amino acid sequences of human alpha 1- and beta 2-syntrophin are nearly identical to their homologues in mouse, suggesting a strong functional conservation among the individual isoforms, Much like beta 1-syntrophin, human beta 2-syntrophin has multiple transcript classes and is expressed widely, although in a distinct pattern of relative abundance. In contrast, human alpha 1-syntrophin is most abundant in heart and skeletal muscle, and less so in other tissues. Somatic cell hybrids and fluorescent in situ hybridization were both used to determine their chromosomal locations: beta 2-syntrophin to chromosome 16q22-23 and alpha 1-syntrophin to chromosome 20q11.2. Finally, we used in vitro translated proteins in an immunoprecipitation assay to show that, like beta 1-syntrophin, both beta 2- and alpha 1-syntrophin interact with peptides encoding the syntrophin-binding region of dystrophin, utrophin/dystrophin related protein, and the Torpedo 87K protein.
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Affiliation(s)
- A H Ahn
- Program in Neuroscience, Harvard Medical School, Boston, Massachusetts 02115, USA
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21
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Chapter 12 Regulation of Membrane Protein Organization at the Neuromuscular Junction. CURRENT TOPICS IN MEMBRANES 1996. [DOI: 10.1016/s0070-2161(08)60392-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/03/2023]
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22
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Carbonetto S, Lindenbaum M. The basement membrane at the neuromuscular junction: a synaptic mediatrix. Curr Opin Neurobiol 1995; 5:596-605. [PMID: 8580711 DOI: 10.1016/0959-4388(95)80064-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The basement membrane at the neuromuscular junction directs formation of pre- and postsynaptic elements at this synapse. Efforts to understand the molecular basis for development of the postsynaptic specialization have brought new insights into extracellular matrix proteins and their cell-surface receptors. Recent evidence for an agrin receptor and mice null for the s-laminin gene have reinforced the function of the basement membrane in both orthograde and retrograde signalling across the synapse.
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Affiliation(s)
- S Carbonetto
- Centre for Neuroscience Research, McGill University, Montreal General Hospital Research Institute, PQ, Canada.
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23
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Abstract
Dystrophin, the protein product of the Duchenne muscular dystrophy locus, is a protein of the membrane cytoskeleton that associates with a complex of integral and membrane-associated proteins. Of these, the 58-kD intracellular membrane-associated protein, syntrophin, was recently shown to consist of a family of three related but distinct genes. We expressed the cDNA of human beta 1-syntrophin and the COOH terminus of human dystrophin in reticulocyte lysates using an in vitro transcription/translation system. Using antibodies to dystrophin we immunoprecipitated these two interacting proteins in a variety of salt and detergent conditions. We demonstrate that the 53 amino acids encoded on exon 74 of dystrophin, an alternatively spliced exon, are necessary and sufficient for interaction with translated beta 1-syntrophin in our assay. On the basis of its alternative splicing, dystrophin may thus be present in two functionally distinct populations. In this recombinant expression system, the dystrophin relatives, human dystrophin related protein (DRP or utrophin) and the 87K postsynaptic protein from Torpedo electric organ, also bind to translated beta 1-syntrophin. We have found a COOH-terminal 37-kD fragment of beta 1-syntrophin sufficient to interact with translated dystrophin and its homologues, suggesting that the dystrophin binding site on beta 1-syntrophin occurs on a region that is conserved among the three syntrophin homologues.
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Affiliation(s)
- A H Ahn
- Program in Neuroscience, Harvard Medical School, Boston, Massachusetts 02115
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