Relationship of a dystrophin-associated glycoprotein to junctional acetylcholine receptor clusters in rat skeletal muscle

doi:10.1016/0960-8966(93)90105-S

Neuromuscular Disorders

Volume 3, Issues 5–6, 1993, Pages 503-506

https://doi.org/10.1016/0960-8966(93)90105-S Get rights and content

Abstract

The relationship of a member of the transmembrane dystrophin-associated glycoprotein (DAG) complex to acetylcholine receptors (AChRs) was investigated using immunofluorescence techniques at rat neuromuscular junctions (NMJs) viewed en face. These results were compared with those from a similar previous study of dystrophin and an autosomal homologue (utrophin or dystrophin-related protein, DRP) (Bewick et al. NeuroReport 1992; 3; 857–860). The region of highest 43 K DAG (43DAG) labelling projected beyond the AChRs by ∼0.3 μm, as does that for dystrophin. By contrast DRP labelling precisely co-localizes with the AChRs. These results suggest that at the NMJ, the region of high 43DAG concentration encompasses the area of highest intensity labelling for both DRP and dystrophin.

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Cited by (23)

α7β1 integrin does not alleviate disease in a mouse model of limb girdle muscular dystrophy type 2F
2007, American Journal of Pathology
Transgenic expression of the α7β1 integrin in the dystrophic mdx/utr^−/− mouse decreases development of muscular dystrophy and enhances longevity. To explore the possibility that elevating α7β1 integrin expression could also ameliorate different forms of muscular dystrophy, we used transgenic technology to enhance integrin expression in mice lacking δ-sarcoglycan (δ sgc), a mouse model for human limb girdle muscular dystrophy type 2F. Unlike α7 transgenic mdx/utr^−/− mice, enhanced α7β1 integrin expression in the δ sgc-null mouse did not alleviate muscular dystrophy in these animals. Expression of the transgene in the δ sgc-null did not alleviate dystrophic histopathology, nor did it decrease cardiomyopathy or restore exercise tolerance. One hallmark of integrin-mediated alleviation of muscular dystrophy in the mdx/utr^−/− background is the restoration of myotendinous junction integrity. As assessed by atomic force microscopy, myotendinous junctions from normal and δ sgc-null mice were indistinguishable, thus suggesting the important influence of myotendinous junction integrity on the severity of muscular dystrophy and providing a possible explanation for the inability of enhanced integrin expression to alleviate dystrophy in the δ sgc-null mouse. These results suggest that distinct mechanisms underlie the development of the diseases that arise from deficiencies in dystrophin and sarcoglycan.
Molecular diversity of the dystrophin-like protein complex in the developing and adult avian retina
2002, Neuroscience
Mutations in dystrophin cause muscular dystrophy but also affect the CNS, including information processing in the retina. To better understand the molecular basis of these CNS deficits, we analyzed the molecular composition and developmental appearance of dystrophin and of the dystrophin-associated protein complex (DPC) in the embryonic and adult avian retina. We detected a concentration of the DPC at the vitreal border and in the outer plexiform layer of the adult retina. At both locations the complex had a different molecular composition and different developmental expression pattern. At the vitreal border, the complex was composed of utrophin, α-dystrobrevin-1, and dystroglycan, and was present at all stages of retinal development even before neurogenesis and gliogenesis. On the other hand, the complex in the outer plexiform layer consisted of dystrophin, β-dystrobrevin and dystroglycan. The distribution of this complex changed from a diffusely distributed to an aggregated form during development concomitant with synapse formation in the outer plexiform layer. Solubilization of the retinal extracellular matrix by intravitreal injection of collagenase resulted in a redistribution of the complex at the retinal vitreal border but had no influence on the distribution of the dystrophin-associated proteins in the outer plexiform layer.
These results demonstrate two types of dystrophin-like complexes in the chick retina with differential molecular compositions, different anchorage to the extracellular matrix, and different developmental expression patterns, suggesting distinct functions for the DPC at both locations.
Expression of agrin, dystroglycan, and utrophin in normal renal tissue and in experimental glomerulopathies
2000, American Journal of Pathology
Citation Excerpt :
Sections were fixed in acetone at 4°C during 10 minutes, except for incubations with the anti-dystrophin and anti-sarcoglycan antibodies, which was performed on nonfixed sections. Details on the used antibodies are given inTable 2.17,43–48 Primary antibodies were diluted in PBS containing 1% bovine serum albumin (BSA) and 0.05% sodium azide (IF-buffer), fluorescein isothiocyanate-labeled secondary antibodies were diluted in IF-buffer containing 10% normal rat serum (for IF on rat tissue), all antibodies were incubated during 45 minutes at room temperature.
The dystrophin-glycoprotein complex, which comprises α. and β-dystroglycan, sarcoglycans, and utrophin/dystrophin, links the cytoskeleton to agrin and laminin in the basal lamina in muscle and epithelial cells. Recently, agrin was identified as a major heparan sulfate proteoglycan in the glomerular basement membrane. In the present study, we found mRNA expression for agrin, dystroglycan, and utrophin in kidney cortex, isolated glomeruli, and cultured podocytes and mesangial cells. In immunofluorescence, agrin was found in the glomerular basement membrane. The antibodies against α- and β-dystroglycan and utrophin revealed a granular podocyte-like staining pattern along the glomerular capillary wall. With immunoelectron microscopy, agrin was found in the glomerular basement membrane, dystroglycan was diffusely found over the entire cell surface of the podocytes, and utrophin was localized in the cytoplasm of the podocyte foot processes. In adriamycin nephropathy, a decrease in the glomerular capillary wall staining for dystroglycan was observed probably secondary to the extensive fusion of foot processes. Immunoelectron microscopy showed a different distribution pattern as compared to the normal kidney, with segmentally enhanced expression of dystroglycan at the basal side of the extensively fused podocyte foot processes. In passive Heymann nephritis we observed no changes in the staining intensity and distribution of the dystrophin-glycoprotein complex by immunofluorescence and immunoelectron microscopy. From these data, we conclude that agrin, dystroglycan, and utrophin are present in the glomerular capillary wall and their ultrastructural localization supports the concept that these molecules are involved in linking the podocyte cytoskeleton to the glomerular basement membrane.
Agrin is a high-affinity binding protein of dystroglycan in non-muscle tissue
1998, Journal of Biological Chemistry
Agrin is a basement membrane-associated proteoglycan that induces the formation of postsynaptic specializations at the neuromuscular junction. This activity is modulated by alternative splicing and is thought to be mediated by receptors expressed in muscle fibers. An isoform of agrin that does not induce postsynaptic specializations binds with high affinity to dystroglycan, a component of the dystrophin-glycoprotein complex. Transcripts encoding this agrin isoform are expressed in a variety of non-muscle tissues. Here, we analyzed the tissue distribution of agrin and dystroglycan on the protein level and determined their binding affinities. We found that agrin is most abundant in lung, kidney, and brain. Only a little agrin was detected in skeletal muscle, and no agrin was found in liver. Dystroglycan was highly expressed in all tissues examined except in liver. In a solid-phase radioligand binding assay, agrin bound to dystroglycan from lung, kidney, and skeletal muscle with a dissociation constant between 1.8 and 2.2 nm, while the affinity to brain-derived dystroglycan was 4.6 nm. In adult kidney and lung, agrin co-purified and co-immunoprecipitated with dystroglycan, and both molecules were co-localized in embryonic tissue. These data show that the agrin isoform expressed in non-muscle tissue is a high-affinity binding partner of dystroglycan and they suggest that this interaction, like that between laminin and dystroglycan, may be important for the mechanical integrity of the tissue.
Supramolecular organization of the subsarcolemmal cytoskeleton of adult skeletal muscle fibers. A review
1997, Biology of the Cell
This review is focused on the composition and organization of the junctional subsarcolemmal cytoskeleton of adult muscle fibers. The cytoskeleton of muscle fibers is organized in functionally distinct compartments and the subsarcolemmal cytoskeleton itself can be broadly divided into junctional (myotendinous junction, neuromuscular junction and costameres) and non-junctional domains. In junctional zones three different multimolecular cytoskeletal complexes coexist: the focal adhesion-type, the spectrin-based and the dystrophin vs utrophin-based membrane skeleton systems. These complexes extend over several levels, from intracytoplasmic to subsarcolemmal and transmembranous; their common feature is the anchorage of actin filaments emanating from the intracytoplasmic level. The different cytoskeletal proteins, their putative roles and their interactions with various signaling pathways are presented here in detail. The subsarcolemmal cytoskeleton complexes are thought to play distinct physiological roles (membrane stabilization, force transmission to extracellular matrix, ionic channel anchorage, etc) but their colocalization on the three sarcolemmal junctional domains strongly suggests interrelated or common functions.
Nitric oxide synthase and cyclic GMP-dependent protein kinase concentrated at the neuromuscular endplate
1996, Neuroscience
Nitric oxide mediates diverse functions in development and physiology of vertebrate skeletal muscle. Neuronal type nitric oxide synthase-μ is enriched in fast-twitch fibers and binds to syntrophin, a component of the sarcolemmal dystrophin glycoprotein complex. Here, we show that cyclic GMP-dependent protein kinase type I, a primary effector for nitric oxide, occurs selectively at the neuromuscular junction, in mice and rats, and both neuronal type nitric oxide synthase-μ and cyclic GMP-dependent protein kinase type I remain at skeletal muscle endplates at least two weeks following muscle denervation. Expression of neuronal type nitric oxide synthase-μ and cyclic GMP-dependent protein kinase type I are up-regulated following fusion of cultured primary myotubes. Interestingly, the highest levels of neuronal type nitric oxide synthase-μ in muscle are found complexed with dystrophin at the sarcolemma of intrafusal fibers in muscle spindles.
Localization of neuronal type nitric oxide synthase-μ and cyclic GMP-dependent protein kinase type I at the neuromuscular junction suggests functions for nitric oxide and cyclic GMP in the regulation of synaptic actions of intra- and extrafusal muscle fibers.

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Relationship of a dystrophin-associated glycoprotein to junctional acetylcholine receptor clusters in rat skeletal muscle

Abstract

Neuron

J Neurol Sci

Different distributions of dystrophin and related proteins at nerve-muscle junctions

NeuroReport

Localization of the DMDL gene-encoded dystrophin-related protein using a panel of nineteen monoclonal antibodies: presence at neuromuscular junctions, in the sarcolemma of dystrophic skeletal muscle, in vascular and other smooth muscles, and in proliferating brain cell lines

J Cell Biol