scholarly journals Sarcoglycan Subcomplex Expression in Normal Human Smooth Muscle

2007 ◽  
Vol 55 (8) ◽  
pp. 831-843 ◽  
Author(s):  
Giuseppe Anastasi ◽  
Giuseppina Cutroneo ◽  
Antonina Sidoti ◽  
Carmen Rinaldi ◽  
Daniele Bruschetta ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Smooth Muscle ◽  
Muscle Type ◽  
Common Assumption ◽  
Glycoprotein Complex ◽  
Dystrophin Glycoprotein Complex ◽  
Normal Human ◽  
First Time ◽  
Dystrophin Glycoprotein ◽  
Lower Expression

The sarcoglycan complex (SGC) is a multimember transmembrane complex interacting with other members of the dystrophin–glycoprotein complex (DGC) to provide a mechanosignaling connection from the cytoskeleton to the extracellular matrix. The SGC consists of four proteins (α, β, γ, and δ). A fifth sarcoglycan subunit, ∊-sarcoglycan, shows a wider tissue distribution. Recently, a novel sarcoglycan, the ζ-sarcoglycan, has been identified. All reports about the structure of SGC showed a common assumption of a tetrameric arrangement of sarcoglycans. Addressing this issue, our immunofluorescence and molecular results showed, for the first time, that all sarcoglycans are always detectable in all observed samples. Therefore, one intriguing possibility is the existence of a pentameric or hexameric complex considering ζ-sarcoglycan of SGC, which could present a higher or lower expression of a single sarcoglycan in conformity with muscle type—skeletal, cardiac, or smooth—or also in conformity with the origin of smooth muscle. (J Histochem Cytochem 55:831–843, 2007)

Expression of the dystrophin-glycoprotein complex is a marker for human airway smooth muscle phenotype maturation

2008 ◽  
Vol 294 (1) ◽  
pp. L57-L68 ◽  
Author(s):  
Pawan Sharma ◽  
Thai Tran ◽  
Gerald L. Stelmack ◽  
Karol McNeill ◽  
Reinoud Gosens ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Serum Deprivation ◽  
Muscle Physiology ◽  
Smooth Muscle Tissue ◽  
Glycoprotein Complex ◽  
Contractile Phenotype ◽  
Dystrophin Glycoprotein Complex ◽  
Health And Disease ◽  
Dystrophin Glycoprotein

Airway smooth muscle (ASM) cells may contribute to asthma pathogenesis through their capacity to switch between a synthetic/proliferative and a contractile phenotype. The multimeric dystrophin-glycoprotein complex (DGC) spans the sarcolemma, linking the actin cytoskeleton and extracellular matrix. The DGC is expressed in smooth muscle tissue, but its functional role is not fully established. We tested whether contractile phenotype maturation of human ASM is associated with accumulation of DGC proteins. We compared subconfluent, serum-fed cultures and confluent cultures subjected to serum deprivation, which express a contractile phenotype. Western blotting confirmed that β-dystroglycan, β-, δ-, and ε-sarcoglycan, and dystrophin abundance increased six- to eightfold in association with smooth muscle myosin heavy chain (smMHC) and calponin accumulation during 4-day serum deprivation. Immunocytochemistry showed that the accumulation of DGC subunits was specifically localized to a subset of cells that exhibit robust staining for smMHC. Laminin competing peptide (YIGSR, 1 μM) and phosphatidylinositol 3-kinase (PI3K) inhibitors (20 μM LY-294002 or 100 nM wortmannin) abrogated the accumulation of smMHC, calponin, and DGC proteins. These studies demonstrate that the accumulation of DGC is an integral feature for phenotype maturation of human ASM cells. This provides a strong rationale for future studies investigating the role of the DGC in ASM smooth muscle physiology in health and disease.

scholarly journals Increasing α7β1-integrin promotes muscle cell proliferation, adhesion, and resistance to apoptosis without changing gene expression

2008 ◽  
Vol 294 (2) ◽  
pp. C627-C640 ◽  
Author(s):  
Jianming Liu ◽  
Dean J. Burkin ◽  
Stephen J. Kaufman
Keyword(s):  
Gene Expression ◽  
Skeletal Muscle ◽  
Extracellular Matrix ◽  
Muscular Dystrophy ◽  
Expression Profiles ◽  
C2c12 Cells ◽  
Glycoprotein Complex ◽  
Dystrophin Glycoprotein Complex ◽  
Dystrophin Glycoprotein

The dystrophin-glycoprotein complex maintains the integrity of skeletal muscle by associating laminin in the extracellular matrix with the actin cytoskeleton. Several human muscular dystrophies arise from defects in the components of this complex. The α7β1-integrin also binds laminin and links the extracellular matrix with the cytoskeleton. Enhancement of α7-integrin levels alleviates pathology in mdx/utrn−/− mice, a model of Duchenne muscular dystrophy, and thus the integrin may functionally compensate for the absence of dystrophin. To test whether increasing α7-integrin levels affects transcription and cellular functions, we generated α7-integrin-inducible C2C12 cells and transgenic mice that overexpress the integrin in skeletal muscle. C2C12 myoblasts with elevated levels of integrin exhibited increased adhesion to laminin, faster proliferation when serum was limited, resistance to staurosporine-induced apoptosis, and normal differentiation. Transgenic expression of eightfold more integrin in skeletal muscle did not result in notable toxic effects in vivo. Moreover, high levels of α7-integrin in both myoblasts and in skeletal muscle did not disrupt global gene expression profiles. Thus increasing integrin levels can compensate for defects in the extracellular matrix and cytoskeleton linkage caused by compromises in the dystrophin-glycoprotein complex without triggering apparent overt negative side effects. These results support the use of integrin enhancement as a therapy for muscular dystrophy.

scholarly journals A role for the dystrophin-glycoprotein complex as a transmembrane linker between laminin and actin

1993 ◽  
Vol 122 (4) ◽  
pp. 809-823 ◽  
Author(s):  
JM Ervasti ◽  
KP Campbell
Keyword(s):  
Extracellular Matrix ◽  
Matrix Protein ◽  
Striated Muscle ◽  
Extracellular Matrix Protein ◽  
Dependent Manner ◽  
Heparin Binding ◽  
Glycoprotein Complex ◽  
Dystrophin Glycoprotein Complex ◽  
Dystrophin Glycoprotein ◽  
Laminin Binding

The dystrophin-glycoprotein complex was tested for interaction with several components of the extracellular matrix as well as actin. The 156-kD dystrophin-associated glycoprotein (156-kD dystroglycan) specifically bound laminin in a calcium-dependent manner and was inhibited by NaCl (IC50 = 250 mM) but was not affected by 1,000-fold (wt/wt) excesses of lactose, IKVAV, or YIGSR peptides. Laminin binding was inhibited by heparin (IC50 = 100 micrograms/ml), suggesting that one of the heparin-binding domains of laminin is involved in binding dystroglycan while negatively charged oligosaccharide moieties on dystroglycan were found to be necessary for its laminin-binding activity. No interaction between any component of the dystrophin-glycoprotein complex and fibronectin, collagen I, collagen IV, entactin, or heparan sulfate proteoglycan was detected by 125I-protein overlay and/or extracellular matrix protein-Sepharose precipitation. In addition, laminin-Sepharose quantitatively precipitated purified dystrophin-glycoprotein complex, demonstrating that the laminin-binding site is accessible when dystroglycan is associated with the complex. Dystroglycan of nonmuscle tissues also bound laminin. However, the other proteins of the striated muscle dystrophin-glycoprotein complex appear to be absent, antigenically dissimilar or less tightly associated with dystroglycan in nonmuscle tissues. Finally, we show that the dystrophin-glycoprotein complex cosediments with F-actin but does not bind calcium or calmodulin. Our results support a role for the striated muscle dystrophin-glycoprotein complex in linking the actin-based cytoskeleton with the extracellular matrix. Furthermore, our results suggest that dystrophin and dystroglycan may play substantially different functional roles in nonmuscle tissues.

scholarly journals Enhanced Expression of the α7β1 Integrin Reduces Muscular Dystrophy and Restores Viability in Dystrophic Mice

2001 ◽  
Vol 152 (6) ◽  
pp. 1207-1218 ◽  
Author(s):  
Dean J. Burkin ◽  
Gregory Q. Wallace ◽  
Kimberly J. Nicol ◽  
David J. Kaufman ◽  
Stephen J. Kaufman
Keyword(s):  
Extracellular Matrix ◽  
Muscular Dystrophy ◽  
Congenital Muscular Dystrophy ◽  
Transgenic Animals ◽  
Muscle Disease ◽  
Muscle Creatine Kinase ◽  
Glycoprotein Complex ◽  
Enhanced Expression ◽  
Dystrophin Glycoprotein Complex ◽  
Dystrophin Glycoprotein

Muscle fibers attach to laminin in the basal lamina using two distinct mechanisms: the dystrophin glycoprotein complex and the α7β1 integrin. Defects in these linkage systems result in Duchenne muscular dystrophy (DMD), α2 laminin congenital muscular dystrophy, sarcoglycan-related muscular dystrophy, and α7 integrin congenital muscular dystrophy. Therefore, the molecular continuity between the extracellular matrix and cell cytoskeleton is essential for the structural and functional integrity of skeletal muscle. To test whether the α7β1 integrin can compensate for the absence of dystrophin, we expressed the rat α7 chain in mdx/utr−/− mice that lack both dystrophin and utrophin. These mice develop a severe muscular dystrophy highly akin to that in DMD, and they also die prematurely. Using the muscle creatine kinase promoter, expression of the α7BX2 integrin chain was increased 2.0–2.3-fold in mdx/utr−/− mice. Concomitant with the increase in the α7 chain, its heterodimeric partner, β1D, was also increased in the transgenic animals. Transgenic expression of the α7BX2 chain in the mdx/utr−/− mice extended their longevity by threefold, reduced kyphosis and the development of muscle disease, and maintained mobility and the structure of the neuromuscular junction. Thus, bolstering α7β1 integrin–mediated association of muscle cells with the extracellular matrix alleviates many of the symptoms of disease observed in mdx/utr−/− mice and compensates for the absence of the dystrophin- and utrophin-mediated linkage systems. This suggests that enhanced expression of the α7β1 integrin may provide a novel approach to treat DMD and other muscle diseases that arise due to defects in the dystrophin glycoprotein complex. A video that contrasts kyphosis, gait, joint contractures, and mobility in mdx/utr−/− and α7BX2-mdx/utr−/−mice can be accessed at http://www.jcb.org/cgi/content/full/152/6/1207.

The association of caveolae, actin, and the dystrophin–glycoprotein complex: a role in smooth muscle phenotype and function?

2005 ◽  
Vol 83 (10) ◽  
pp. 877-891 ◽  
Author(s):  
Andrew J Halayko ◽  
Gerald L Stelmack
Keyword(s):  
Smooth Muscle ◽  
Structural Proteins ◽  
Actin Dynamics ◽  
Actin Binding ◽  
Contractile Apparatus ◽  
Caveolin 1 ◽  
Glycoprotein Complex ◽  
Dystrophin Glycoprotein Complex ◽  
And Function ◽  
Dystrophin Glycoprotein

Smooth muscle cells exhibit phenotypic and mechanical plasticity. During maturation, signalling pathways controlling actin dynamics modulate contractile apparatus-associated gene transcription and contractile apparatus remodelling resulting from length change. Differentiated myocytes accumulate abundant caveolae that evolve from the structural association of lipid rafts with caveolin-1, a protein with domains that confer unique functional properties. Caveolae and caveolin-1 modulate and participate in receptor-mediated signalling, and thus contribute to functional diversity of phenotypically similar myocytes. In mature smooth muscle, caveolae are partitioned into discrete linear domains aligned with structural proteins that tether actin to the extracellular matrix. Caveolin-1 binds with β-dystroglycan, a subunit of the dystrophin glycoprotein complex (DGC), and with filamin, an actin binding protein that organizes cortical actin, to which integrins and focal adhesion complexes are anchored. The DGC is linked to the actin cytoskeleton by a dystrophin subunit and is a receptor for extracellular laminin. Thus, caveolae and caveolin-associated signalling proteins and receptors are linked via structural proteins to a dynamic filamentous actin network. Despite development of transgenic models to investigate caveolins and membrane-associated actin-linking proteins in skeletal and cardiac muscle function, only superficial understanding of this association in smooth muscle phenotype and function has emerged.Key words: caveolin, dystroglycan, filamin, mechanical plasticity, G-protein-coupled receptors.

Sarcospan increases laminin binding capacity of α-dystroglycan to ameliorate DMD independent of Galgt2

2021 ◽  
Author(s):  
Hafsa Mamsa ◽  
Rachelle L Stark ◽  
Kara M Shin ◽  
Aaron M Beedle ◽  
Rachelle H Crosbie
Keyword(s):  
Extracellular Matrix ◽  
Duchenne Muscular Dystrophy ◽  
Binding Capacity ◽  
Cellular Adhesion ◽  
Muscle Pathology ◽  
Glycoprotein Complex ◽  
Dystrophin Glycoprotein Complex ◽  
Dystrophin Glycoprotein ◽  
Partial Dependence ◽  
Laminin Binding

Abstract In Duchenne muscular dystrophy (DMD), mutations in dystrophin result in a loss of the dystrophin-glycoprotein complex at the myofiber membrane, which functions to connect the extracellular matrix with the intracellular actin cytoskeleton. The dystroglycan subcomplex interacts with dystrophin and spans the sarcolemma where its extensive carbohydrates (matriglycan and CT2 glycan) directly interact with the extracellular matrix. In the current manuscript, we show that sarcospan overexpression enhances the laminin-binding capacity of dystroglycan in DMD muscle by increasing matriglycan glycosylation of α-dystroglycan. Furthermore, we find that this modification is not affected by loss of Galgt2, a glycotransferase which catalyzes the CT2 glycan. Our findings reveal that the matriglycan carbohydrates, and not the CT2 glycan, are necessary for sarcospan-mediated amelioration of DMD. Overexpression of Galgt2 in the DMD mdx murine model prevents muscle pathology by increasing CT2 modified α-dystroglycan. Galgt2 also increases expression of utrophin, which compensates for the loss of dystrophin in DMD muscle. We found that combined loss of Galgt2 and dystrophin reduced utrophin expression; however, it did not interfere with sarcospan rescue of disease. These data reveal a partial dependence of sarcospan on Galgt2 for utrophin upregulation. In addition, sarcospan alters the cross-talk between the adhesion complexes by decreasing the association of integrin β1D with dystroglycan complexes. In conclusion, sarcospan functions to re-wire the cell to matrix connections by strengthening the cellular adhesion and signaling which, in turn, increases the resilience of the myofiber membrane.

Non-neural agrin codistributes with acetylcholine receptors during early differentiation of Torpedo electrocytes

1996 ◽  
Vol 109 (7) ◽  
pp. 1837-1846 ◽  
Author(s):  
A. Cartaud ◽  
M.A. Ludosky ◽  
M. Haasemann ◽  
D. Jung ◽  
K. Campbell ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Acetylcholine Receptor ◽  
Acetylcholine Receptors ◽  
Synaptic Proteins ◽  
Receptor Clustering ◽  
Glycoprotein Complex ◽  
Stage Of Development ◽  
Extracellular Matrix Components ◽  
Dystrophin Glycoprotein Complex ◽  
Dystrophin Glycoprotein

Agrin, an extracellular matrix protein synthesized by nerves and muscles is known to promote the clustering of acetylcholine receptors and other synaptic proteins in cultured myotubes. This observation suggests that agrin may provide at least part of the signal for synaptic specialization in vivo. The extracellular matrix components agrin, laminin and merosin bind to alpha-dystroglycan, a heavily glycosylated peripheral protein part of the dystrophin-glycoprotein complex, previously characterized in the sarcolemma of skeletal and cardiac muscles and at the neuromuscular junction. In order to understand further the function of agrin and alpha DG in the genesis of the acetylcholine receptor-rich membrane domain, the settling of components of the dystrophin-glycoprotein complex and agrin was followed by immunofluorescence localization in developing Torpedo marmorata electrocytes. In 40–45 mm Torpedo embryos, a stage of development at which the electrocytes exhibit a definite structural polarity, dystrophin, alpha/beta-dystroglycan and agrin accumulated concomitantly with acetylcholine receptors at the ventral pole of the cells. Among these components, agrin appeared as the most intensely concentrated and sharply localized. The scarcity of the nerve-electrocyte synaptic contacts at this stage of development, monitored by antibodies against synaptic vesicles, further indicates that before innervation, the machinery for acetylcholine receptor clustering is provided by electrocyte-derived agrin rather than by neural agrin. These observations suggest a two-step process of acetylcholine receptor clustering involving: (i) an instructive role of electrocyte-derived agrin in the formation of a dystrophin-based membrane scaffold upon which acetylcholine receptor molecules would accumulate according to a diffusion trap model; and (ii) a maturation and/or stabilization step controlled by neural agrin. In the light of these data, the existence of more than one agrin receptor is postulated to account for the action of agrin variants at different stages of the differentiation of the postsynaptic membrane in Torpedo electrocytes.

Characterization of the dystrophin–glycoprotein complex in airway smooth muscle: role of δ-sarcoglycan in airway responsiveness

2015 ◽  
Vol 93 (3) ◽  
pp. 195-202 ◽  
Author(s):  
Pawan Sharma ◽  
Aruni Jha ◽  
Gerald L. Stelmack ◽  
Karen Detillieux ◽  
Sujata Basu ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Lung Function ◽  
Airway Smooth Muscle ◽  
Caveolin 1 ◽  
Glycoprotein Complex ◽  
Airway Mechanics ◽  
Age Dependent ◽  
Dystrophin Glycoprotein Complex ◽  
Dystrophin Glycoprotein

The dystrophin–glycoprotein complex (DGC) is an integral part of caveolae microdomains, and its interaction with caveolin-1 is essential for the phenotype and functional properties of airway smooth muscle (ASM). The sarcoglycan complex provides stability to the dystroglycan complex, but its role in ASM contraction and lung physiology in not understood. We tested whether δ-sarcoglycan (δ-SG), through its interaction with the DGC, is a determinant of ASM contraction ex vivo and airway mechanics in vivo. We measured methacholine (MCh)-induced isometric contraction and airway mechanics in δ-SG KO and wild-type mice. Last, we performed immunoblotting and transmission electron microscopy to assess DGC protein expression and the ultrastructural features of tracheal smooth muscle. Our results reveal an age-dependent reduction in the MCh-induced tracheal isometric force and significant reduction in airway resistance at high concentrations of MCh (50.0 mg/mL) in δ-SG KO mice. The changes in contraction and lung function correlated with decreased caveolin-1 and β-dystroglycan abundance, as well as an age-dependent loss of caveolae in the cell membrane of tracheal smooth muscle in δ-SG KO mice. Collectively, these results confirm and extend understanding of a functional role for the DGC in the contractile properties of ASM and demonstrate that this results in altered lung function in vivo.

scholarly journals ε-Sarcoglycan Replaces α-Sarcoglycan in Smooth Muscle to Form a Unique Dystrophin-Glycoprotein Complex

1999 ◽  
Vol 274 (39) ◽  
pp. 27989-27996 ◽  
Author(s):  
Volker Straub ◽  
Audrey J. Ettinger ◽  
Madeleine Durbeej ◽  
David P. Venzke ◽  
Susan Cutshall ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Glycoprotein Complex ◽  
Dystrophin Glycoprotein Complex ◽  
Dystrophin Glycoprotein
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