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.

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 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 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.

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)

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.

scholarly journals Contraction-Induced Loss of Plasmalemmal Electrophysiological Function Is Dependent on the Dystrophin Glycoprotein Complex

2021 ◽  
Vol 12 ◽  
Author(s):  
Cory W. Baumann ◽  
Angus Lindsay ◽  
Sylvia R. Sidky ◽  
James M. Ervasti ◽  
Gordon L. Warren ◽  
...  
Keyword(s):  
M Wave ◽  
Glycoprotein Complex ◽  
Dystrophic Mouse ◽  
Dystrophin Deficiency ◽  
Torque Loss ◽  
Dystrophin Glycoprotein Complex ◽  
The Many ◽  
Dystrophin Glycoprotein ◽  
Mouse Lines

Weakness and atrophy are key features of Duchenne muscular dystrophy (DMD). Dystrophin is one of the many proteins within the dystrophin glycoprotein complex (DGC) that maintains plasmalemmal integrity and cellular homeostasis. The dystrophin-deficient mdx mouse is also predisposed to weakness, particularly when subjected to eccentric (ECC) contractions due to electrophysiological dysfunction of the plasmalemma. Here, we determined if maintenance of plasmalemmal excitability during and after a bout of ECC contractions is dependent on intact and functional DGCs rather than, solely, dystrophin expression. Wild-type (WT) and dystrophic mice (mdx, mL172H and Sgcb−/− mimicking Duchenne, Becker and Limb-girdle Type 2E muscular dystrophies, respectively) with varying levels of dystrophin and DGC functionality performed 50 maximal ECC contractions with simultaneous torque and electromyographic measurements (M-wave root-mean-square, M-wave RMS). ECC contractions caused all mouse lines to lose torque (p<0.001); however, deficits were greater in dystrophic mouse lines compared to WT mice (p<0.001). Loss of ECC torque did not correspond to a reduction in M-wave RMS in WT mice (p=0.080), while deficits in M-wave RMS exceeded 50% in all dystrophic mouse lines (p≤0.007). Moreover, reductions in ECC torque and M-wave RMS were greater in mdx mice compared to mL172H mice (p≤0.042). No differences were observed between mdx and Sgcb−/− mice (p≥0.337). Regression analysis revealed ≥98% of the variance in ECC torque loss could be explained by the variance in M-wave RMS in dystrophic mouse lines (p<0.001) but not within WT mice (R2=0.211; p=0.155). By comparing mouse lines that had varying amounts and functionality of dystrophin and other DGC proteins, we observed that (1) when all DGCs are intact, plasmalemmal action potential generation and conduction is maintained, (2) deficiency of the DGC protein β-sarcoglycan is as disruptive to plasmalemmal excitability as is dystrophin deficiency and, (3) some functionally intact DGCs are better than none. Our results highlight the significant role of the DGC plays in maintaining plasmalemmal excitability and that a collective synergism (via each DGC protein) is required for this complex to function properly during ECC contractions.

Abstract 15657: Regulation of Cardiac Regeneration by Hippo Pathway and Dystrophin Glycoprotein Complex

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Yuka Morikawa ◽  
James F Martin
Keyword(s):  
Hippo Pathway ◽  
Myocardial Damage ◽  
Cardiac Regeneration ◽  
Myocardial Cell ◽  
Damage Area ◽  
Glycoprotein Complex ◽  
Dystrophin Glycoprotein Complex ◽  
Heart Size ◽  
The Hippo Pathway ◽  
Dystrophin Glycoprotein

Regeneration of the mammalian heart is limited in adults. In rodents, endogenous regenerative capacity exists during development and in neonate but is rapidly repressed after birth. We are elucidating the mechanisms responsible for regenerative repression and applying this knowledge to reactivate cardiac regeneration in adult hearts. We have previously shown that the Hippo pathway is responsive for regenerative repression, however, the molecular and cellular mechanism responsible remain unclear. The Hippo pathway controls heart size by repressing myocardial cell proliferation during development. By deleting Salv, a modulator of Hippo pathway, we found myocardial damage in the postnatal and adult heart was repaired anatomically and functionally. This heart repair occurred primarily through proliferation of preexisting cardiomyocyte. We observed that cardiomyocytes in border the zone protrude and fill the damage area during Hippo-mediated cardiac regeneration and thus preventing formation of fibrotic scars. The molecular analysis identified components of dystrophin glycoprotein complex (DGC) as downstream targets of Hippo pathway. The DGC anchors the cytoskeleton and extracellular matrix and is involved in cell migration. The studies using the muscular dystrophy mouse model, mdx, reveals that DGC is required for endogenous cardiac regeneration and cardiomyocyte protrusion. Taken together, we show that cardiomyocyte protrusion is an essential process for cardiac regeneration and the Hippo pathway regulates it through regulating DGC. Our studies provide insights into the mechanisms leading to repair of damaged hearts from endogenous cardiomyocytes and novel information into DGC function.

scholarly journals Impact of sarcoglycan complex on mechanical signal transduction in murine skeletal muscle

2006 ◽  
Vol 290 (2) ◽  
pp. C411-C419 ◽  
Author(s):  
Elisabeth R. Barton
Keyword(s):  
Skeletal Muscle ◽  
Mechanical Load ◽  
Eccentric Contraction ◽  
Eccentric Contractions ◽  
Normal Muscle ◽  
Glycoprotein Complex ◽  
Dystrophin Glycoprotein Complex ◽  
Severe Pathology ◽  
Murine Skeletal Muscle ◽  
Dystrophin Glycoprotein

Loss of the dystrophin glycoprotein complex (DGC) or a subset of its components can lead to muscular dystrophy. However, the patterns of symptoms differ depending on which proteins are affected. Absence of dystrophin leads to loss of the entire DGC and is associated with susceptibility to contractile injury. In contrast, muscles lacking γ-sarcoglycan (γ-SG) display little mechanical fragility and still develop severe pathology. Animals lacking dystrophin or γ-SG were used to identify DGC components critical for sensing dynamic mechanical load. Extensor digitorum longus muscles from 7-wk-old normal (C57), dystrophin- null ( mdx), and γ-SG-null ( gsg−/−) mice were subjected to a series of eccentric contractions, after which ERK1/2 phosphorylation levels were determined. At rest, both dystrophic strains had significantly higher ERK1 phosphorylation, and gsg−/− muscle also had heightened ERK2 phosphorylation compared with wild-type controls. Eccentric contractions produced a significant and transient increase in ERK1/2 phosphorylation in normal muscle, whereas the mdx strain displayed no significant proportional change of ERK1/2 phosphorylation after eccentric contraction. Muscles from gsg−/− mice had no significant increase in ERK1 phosphorylation; however, ERK2 phosphorylation was more robust than in C57 controls. The reduction in mechanically induced ERK1 phosphorylation in gsg−/− muscle was not dependent on age or severity of phenotype, because muscle from both young and old (age 20 wk) animals exhibited a reduced response. Immunoprecipitation experiments revealed that γ-SG was phosphorylated in normal muscle after eccentric contractions, indicating that members of the DGC are modified in response to mechanical perturbation. This study provides evidence that the SGs are involved in the transduction of mechanical information in skeletal muscle, potentially unique from the entire DGC.

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