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Comparative proteomic profiling of dystroglycan-associated proteins in wild type, mdx, and Galgt2 transgenic mouse skeletal muscle.

ABSTRACT: Dystroglycan is a major cell surface glycoprotein receptor for the extracellular matrix in skeletal muscle. Defects in dystroglycan glycosylation cause muscular dystrophy and alterations in dystroglycan glycosylation can impact extracellular matrix binding. Here we describe an immunoprecipitation technique that allows isolation of beta dystroglycan with members of the dystrophin-associated protein complex (DAPC) from detergent-solubilized skeletal muscle. Immunoprecipitation, coupled with shotgun proteomics, has allowed us to identify new dystroglycan-associated proteins and define changed associations that occur within the DAPC in dystrophic skeletal muscles. In addition, we describe changes that result from overexpression of Galgt2, a normally synaptic muscle glycosyltransferase that can modify alpha dystroglycan and inhibit the development of muscular dystrophy when it is overexpressed. These studies identify new dystroglycan-associated proteins that may participate in dystroglycan's roles, both positive and negative, in muscular dystrophy.

SUBMITTER: Yoon JH

PROVIDER: S-EPMC3436944 | biostudies-literature | 2012 Sep

REPOSITORIES: biostudies-literature

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Comparative proteomic profiling of dystroglycan-associated proteins in wild type, mdx, and Galgt2 transgenic mouse skeletal muscle.

Yoon Jung Hae JH Johnson Eric E Xu Rui R Martin Laura T LT Martin Paul T PT Montanaro Federica F

Journal of proteome research 20120730 9

Dystroglycan is a major cell surface glycoprotein receptor for the extracellular matrix in skeletal muscle. Defects in dystroglycan glycosylation cause muscular dystrophy and alterations in dystroglycan glycosylation can impact extracellular matrix binding. Here we describe an immunoprecipitation technique that allows isolation of beta dystroglycan with members of the dystrophin-associated protein complex (DAPC) from detergent-solubilized skeletal muscle. Immunoprecipitation, coupled with shotgu ...[more]

PMID: 22775139

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Project description:Transgenic overexpression of Galgt2 in the skeletal muscles of mdx mice inhibits the development of disease pathology associated with muscular dystrophy. This is the case both in transgenic mice, where Galgt2 overexpression occurs from embryonic timepoints onward and in mdx mice where Galgt2 is overexpressed in the early postnatal period using Adeno-associated virus (AAV). Here, we use gene expression profiling to compare transcriptional changes resulting from embryonic and postnatal Galgt2 overexpression in mdx skeletal muscle. A surprising number of changes were in genes known to ameliorate muscular dystrophy when overexpressed (agrin, integrin alpha 7, ADAM12, Bcl2) or to cause muscular dystrophy when mutated (collagen VI (alpha1,alpha2), plectin 1, dystroglycan, selenoprotein N1, integrin alpha7, biglycan, dysferlin). Several genes involved in calcium homeostasis were also changed. In Galgt2 transgenic mice, where embryonic overexpression of Galgt2 in skeletal muscles alters neuromuscular development and muscle growth, the number of gene expression changes was vastly greater, however, 14% of genes altered in postnatal AAV-Galgt2 infected mdx muscles were also changed with embryonic overexpression. These experiments suggest that postnatal overexpression of Galgt2 inhibits muscular dystrophy in mdx mice via induction of a group of genes that, in aggregate, can govern membrane stability, membrane repair, calcium homeostasis, and apoptosis. Transgenic overexpression of Galgt2 in the skeletal muscles of mdx mice inhibits the development of disease pathology associated with muscular dystrophy. This is the case both in transgenic mice, where Galgt2 overexpression occurs from embryonic timepoints onward and in mdx mice where Galgt2 is overexpressed in the early postnatal period using Adeno-associated virus (AAV). Here, we use gene expression profiling to compare transcriptional changes resulting from embryonic and postnatal Galgt2 overexpression in mdx skeletal muscle. A surprising number of changes were in genes known to ameliorate muscular dystrophy when overexpressed (agrin, integrin alpha7, ADAM12, Bcl2) or to cause muscular dystrophy when mutated (collagen VI (alpha1,alpha2), plectin 1, dystroglycan, selenoprotein N1, integrin alpha7, biglycan, dysferlin). Several genes involved in calcium homeostasis were also changed. In Galgt2 transgenic mice, where embryonic overexpression of Galgt2 in skeletal muscles alters neuromuscular development and muscle growth, the number of gene expression changes was vastly greater, however, 14% of genes altered in postnatal AAV-Galgt2 infected mdx muscles were also changed with embryonic overexpression. These experiments suggest that postnatal overexpression of Galgt2 inhibits muscular dystrophy in mdx mice via induction of a group of genes that, in aggregate, can govern membrane stability, membrane repair, calcium homeostasis, and apoptosis. Experiment Overall Design: Microarrays were done in three groups at a time. 1) Transgenic Overexpression of Galgt2 - comprised to Wild Type (WT), Galgt2 Transgenic (CT), Dystrophin-Deficient (mdx), and Galgt2 Transgenic and Dystrophin-Deficient (CTmdx) each in duplicate 2) AAV-Mediated Galgt2 Gene Delivery in to the mdx gastrocnemius muscle in the postnatal period - comprised of AAVGalgt2 and PBS each in duplicate, and 3) Myoblasts and myotubes - comptised of one sample each of C1C12 myoblasts and myotubes, C2C12 myoblasts and myotubes stably transfected with Galgt2

Project description:BACKGROUND:LARGE is one of seven putative or demonstrated glycosyltransferase enzymes defective in a common group of muscular dystrophies with reduced glycosylation of ?-dystroglycan. Overexpression of LARGE induces hyperglycosylation of ?-dystroglycan in both wild type and in cells from dystroglycanopathy patients, irrespective of their primary gene defect, restoring functional glycosylation. Viral delivery of LARGE to skeletal muscle in animal models of dystroglycanopathy has identical effects in vivo, suggesting that the restoration of functional glycosylation could have therapeutic applications in these disorders. Pharmacological strategies to upregulate Large expression are also being explored. METHODOLOGY/PRINCIPAL FINDINGS:In order to asses the safety and efficacy of long term LARGE over-expression in vivo, we have generated four mouse lines expressing a human LARGE transgene. On observation, LARGE transgenic mice were indistinguishable from the wild type littermates. Tissue analysis from young mice of all four lines showed a variable pattern of transgene expression: highest in skeletal and cardiac muscles, and lower in brain, kidney and liver. Transgene expression in striated muscles correlated with ?-dystroglycan hyperglycosylation, as determined by immunoreactivity to antibody IIH6 and increased laminin binding on an overlay assay. Other components of the dystroglycan complex and extracellular matrix ligands were normally expressed, and general muscle histology was indistinguishable from wild type controls. Further detailed muscle physiological analysis demonstrated a loss of force in response to eccentric exercise in the older, but not in the younger mice, suggesting this deficit developed over time. However this remained a subclinical feature as no pathology was observed in older mice in any muscles including the diaphragm, which is sensitive to mechanical load-induced damage. CONCLUSIONS/SIGNIFICANCE:This work shows that potential therapies in the dystroglycanopathies based on LARGE upregulation and ?-dystroglycan hyperglycosylation in muscle should be safe.

Dataset Information

Comparative proteomic profiling of dystroglycan-associated proteins in wild type, mdx, and Galgt2 transgenic mouse skeletal muscle.

Publications

Comparative proteomic profiling of dystroglycan-associated proteins in wild type, mdx, and Galgt2 transgenic mouse skeletal muscle.

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