Binding of Ricinus communis I lectin to the muscle cell plasma membrane in diseased muscle

Lectin-binding characterizes the healthy human skeletal muscle glycophenotype and identifies disease-specific changes in dystrophic muscle

Our understanding of muscle glycosylation to date has derived from studies in mouse models and a limited number of human lectin histochemistry studies. As various therapeutic approaches aimed at treating patients with muscular dystrophies are being translated from rodent models to human, it is critical to better understand human muscle glycosylation and relevant disease-specific differences between healthy and dystrophic muscle. Here, we report the first quantitative characterization of human muscle glycosylation, and identify differentiation- and disease-specific differences in human muscle glycosylation. Utilizing a panel of 13 lectins with varying glycan specificities, we surveyed lectin binding to primary and immortalized myoblasts and myotubes from healthy and dystrophic sources. Following differentiation of primary and immortalized healthy human muscle cells, we observed increased binding of Narcissus pseudonarcissus agglutinin (NPA), PNA, MAA-II and WFA to myotubes compared to myoblasts. Following differentiation of immortalized healthy and dystrophic human muscle cells, we observed disease-specific differences in binding of NPA, Jac and Tricosanthes japonica agglutinin-I (TJA-I) to differentiated myotubes. We also observed differentiation- and disease-specific differences in binding of NPA, Jac, PNA, TJA-I and WFA to glycoprotein receptors in muscle cells. Additionally, Jac, PNA and WFA precipitated functionally glycosylated α-DG, that bound laminin, while NPA and TJA-I did not. Lectin histochemistry of healthy and dystrophic human muscle sections identified disease-specific differences in binding of O-glycan and sialic acid-specific lectins between healthy and dystrophic muscle. These results indicate that specific and discrete changes in glycosylation occur following differentiation, and identify specific lectins as potential biomarkers sensitive to changes in healthy human muscle glycosylation.

Lectin binding in skeletal muscle. Evaluation of alkaline phosphatase conjugated avidin staining procedures

Cryostat sections from rat gracilis muscles were incubated with different biotinylated lectins: Con A (Concanavilin A), WGA (Wheat germ agglutinin), SBA (soybean agglutinin), GS I and GS II (Griffonia simplicifolia agglutinin), LCA (Lens culinaris agglutinin), PNA (peanut agglutinin) and PSA (Pisum sativum agglutinin). The sections were subsequently treated with alkaline phosphatase conjugated avidin. The lectin binding sites were visualized after incubation in substrate media containing: (1) 5-bromo-4-chloro indoxyl phosphate and Nitro Blue tetrazolium or copper sulphate; (2) naphthol AS-MX phosphate or naphthol AS-BI phosphate and various types of diazonium salts; (3) alpha-naphthylphosphate and Fast Blue BB; (4) beta-glycerophosphate according to the method of Gomori. The results obtained with the alkaline phosphatase methods were compared with those seen with a streptavidin-horseradish peroxidase procedure. Several chromogen protocols for visualizing alkaline phosphatase activity showed differences in the ability to detect lectin binding sites. A sarcoplasmic reaction was evident for Con A, GS II, WGA, LCA, and PSA after incubation in the indoxyl phosphate medium. Sarcoplasmic reaction for GS II was also noticed after incubation with naphthol AS-MX Fast Blue BB and beta-glycerophosphate. The latter substrate also gave rise to a sarcoplasmic Con A reaction. With the indoxylphosphate tetrazolium salt method some muscle fibres showed a very strong intracellular reaction after incubation with Con A and GS II while the staining intensity was weak in other fibres. The same muscle fibres were stained with PAS. No sarcoplasmic reactions were observed with either naphthol phosphate media or with the diaminobenzidine peroxidase methods. Further, the staining of the muscle fibre periphery, connective tissue, an capillaries was intensified using the indoxyl method. The indoxylphosphate-tetrazolium salt method seems to be suitable for future investigations of lectin binding sites in muscle sections.

Dystrophin abnormalities in polymyositis and dermatomyositis

The expression of dystrophin in muscle biopsies from nine cases of polymyositis, ten cases of juvenile dermatomyositis and three adults with dermatomyositis was studied by Western blot analysis and immunocytochemistry. Five antibodies corresponding to different N- and C-terminal regions of the dystrophin gene were used. Sixteen of the 22 cases (73%) showed an abnormality in the expression of dystrophin on Western blot analysis, either with a reduced molecular weight protein or a reduced amount. Immunostaining was abnormal in 11 out of 19 cases (58%) and showed varying degrees of discontinuity or loss of sarcolemmal staining. Immunolabelling of these areas with antibodies to beta-spectrin was normal implying that the changes were not caused by a loss of the sarcolemma. These results show that secondary changes in the expression of dystrophin can occur in the absence of an abnormality in the corresponding gene and that dystrophin cannot be used in isolation as a diagnostic marker for muscular dystrophy.

Lectin binding and desmin expression during necrosis, regeneration, and neurogenic atrophy of human skeletal muscle

Changes in the cytoplasm of skeletal muscle fibres during necrosis, regeneration, and neurogenic atrophy have been studied in a wide range of human neuromuscular diseases with a panel of eleven biotinylated lectins and by immunohistochemical staining for the cytoskeletal protein desmin. Increased binding of several lectins was observed in both necrotic and regenerating fibres, with Concanavalin A the most consistently positive lectin. Staining for desmin was strong in the cytoplasm of regenerating and partially damaged fibres and was lost in necrotic fibres, although there were differences in the staining reactions of the two antidesmin antibodies used. In fibres which had undergone neurogenic atrophy, cytoplasmic lectin binding was seen only with Griffonia simplicifolia 1 lectin, and desmin was expressed more strongly than in normal fibres. Lectin binding and immunohistochemical staining from desmin can supplement the information obtained from muscle biopsies by conventional histochemical methods and lead to a better understanding of the mechanisms of muscle damage.

Localization of neural cell adhesion molecule in denervated muscle to both the plasma membrane and extracellular compartments by immuno-electron microscopy

The location of neural cell adhesion molecule in mouse skeletal muscle has been investigated using two immuno-electron microscopical techniques. In the first method, 6-micron frozen sections of a normal and a hemi-denervated gluteus muscle were stained by an indirect immunoperoxidase method using a rabbit-derived polyclonal antiserum to neural adhesion molecule as the primary antibody. The stain was visualized with the electron-dense chromogen, diaminobenzidine and the sections fixed, osmicated and processed for electron microscopy whilst still on the slide. Ultrathin sections were cut and viewed in the electron microscope, where the reaction product appeared to be localized in the plasma membrane and on the basal lamina of the muscle fibres. The second method, using a 5-nm immunogold-labelled secondary antibody, confirmed and extended these initial observations. In these experiments, the primary antibody to neural cell adhesion molecule was applied in vivo to hemi-denervated mouse gluteus muscles. The muscles were dissected out 24 h later, divided into denervated and innervated halves and then into junctional and extrajunctional regions. Together with the junctional and extrajunctional regions of normal, control pieces of muscle which had not been incubated with anti-neural cell adhesion molecule, they were lightly fixed, and incubated with the secondary gold-labelled antibody, before further fixation and processing for electron microscopy. Semi-thin, 0.5-micron sections of each were cut and viewed at 20,000 x magnification. Randomly sampled fibres from the extrajunctional regions of the denervated and innervated halves of the hemi-denervated gluteus and the normal, control gluteus were photographed for quantitative analysis. Five micrographs were randomly selected from each group and in these, the numbers, density and position of gold particles were measured using a digitizing tablet. By far the highest number of gold particles was found in the denervated half of the gluteus muscle, there being much less in the innervated half and practically none in the control. The density of gold particles in the denervated muscles was maximal in the plasma membrane-basal lamina complex, but most were located in the extracellular spaces outside this region, where they usually occurred in clusters apparently in association with collagen fibres. We conclude that neural cell adhesion molecule in denervated skeletal muscle is present not only in the plasma membrane but also in the basal lamina and extracellular space.

Binding of Ricinus communis I lectin to developing dystrophic muscle in human fetus

In previous studies it was shown that a D-galactose-specific lectin, Ricinus communis I (RCA I), does not bind to the plasma membrane of muscle fibres from patients with Duchenne muscular dystrophy (DMD) in contrast to normal muscle. We have now studied RCA I binding to the membranes of developing human fetal muscle in fetuses at 95% risk of DMD (n = 6) and normal controls (n = 5) with a developmental range of 12-20 weeks of gestation. The results were compared to the membrane appearance with conventional ultrastructure. Binding of RCA I to the muscle basement membrane was consistently strong from the early stages of myogenesis, such as in fusing myoblasts/myocytes. RCA I binding to the plasma membrane was weak but detectable in both DMD and normal fetuses at 12-14 weeks of gestation. Both the normal and diseased condition showed an increase of RCA I labelling of the muscle plasma membrane at 15-17 weeks and strong labelling at 18-20 weeks of gestation. No difference was observed in the RCA I localization of normal and diseased human fetal muscle plasma membrane. It is concluded that (a) the plasma membrane in developing fetal muscle undergoes a maturation process between 12 and 20 weeks gestational age leading to an increase in expression of RCA I binding carbohydrate moieties; and (b) that the absence of RCA I binding glycoprotein in mature DMD muscle plasma membrane reflects a change acquired during the course of disease.

Electron cytochemical study of the muscle cell surface

The lectins wheat germ agglutinin and limulus polyphemus were used as cytochemical probes to study the ultrastructural localization of sialic acid at the cell surface of rat muscle fibers. In addition cytochemical studies employing strontium as an electron-dense marker were also carried out to investigate cation binding sites at the muscle cell surface. The results showed binding of the lectins to the glycocalyx, caveolae and the basal lamina of the muscle fibers. These binding sites matched the ones observed in the cytochemical studies using strontium as a marker. Based on these observations we suggest that the glycocalyx, caveolae and the basal lamina of the muscle fiber may be involved in the binding of Ca++ and that significant amounts of Ca++ may be normally present at the muscle cell surface.

Lectin blotting of human muscle. Identification of a high molecular weight glycoprotein which is absent or altered in Duchenne muscular dystrophy

Using a combination of sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting, a high molecular weight Ricinus communis I (RCA I)-binding glycoprotein (approx. Mr 370000) has been identified in human muscle that is consistently altered or absent in muscle from patients with Duchenne muscular dystrophy (DMD). In addition, a Mr 54000 RCA I-binding glycoprotein was identified in 4 out and 8 DMD muscle samples that was not present in normal muscle. The possibility that the Mr 370000 glycoprotein could be a muscle membrane glycoprotein which is altered or absent in DMD is discussed.

Lectin binding in human skeletal muscle: a comparison of 15 different lectins

Fifteen lectin-horseradish peroxidase conjugates have been used in a comprehensive histochemical study of human skeletal muscle. The staining patterns of many lectins were found to be coincident with the known distributions of types I, III, IV and V collagen, fibronectin and laminin. One lectin, Bandeiraea simplicifolia (BSA I), selectively stained capillaries in a blood group-specific manner, the significance of which is unknown. The results show that although lectins are useful cytochemical probes for identifying tissue glycoconjugates, lectin binding is not solely determined by monosaccharide specificity as lectins which interact with the same sugars may have completely different staining patterns. Factors such as accessibility, glycan conformation and oligosaccharide sequence also affect lectin binding in tissues. For these reasons, we conclude that a comprehensive histochemical investigation of tissue glycoconjugates should employ a large number of lectins, preferably with overlapping sugar specificities.