Desmuslin, an intermediate filament protein that interacts with α-dystrobrevin and desmin

Abstract

Dystrobrevin is a component of the dystrophin-associated protein complex and has been shown to interact directly with dystrophin, ␣1-syntrophin, and the sarcoglycan complex. The precise role of ␣-dystrobrevin in skeletal muscle has not yet been determined. To study ␣-dystrobrevin's function in skeletal muscle, we used the yeast two-hybrid approach to look for interacting proteins. Three overlapping clones were identified that encoded an intermediate filament protein we subsequently named desmuslin (DMN). Sequence analysis revealed that DMN has a short N-terminal domain, a conserved rod domain, and a long C-terminal domain, all common features of type 6 intermediate filament proteins. A positive interaction between DMN and ␣-dystrobrevin was confirmed with an in vitro coimmunoprecipitation assay. By Northern blot analysis, we find that DMN is expressed mainly in heart and skeletal muscle, although there is some expression in brain. Western blotting detected a 160-kDa protein in heart and skeletal muscle. Immunofluorescent microscopy localizes DMN in a stripe-like pattern in longitudinal sections and in a mosaic pattern in cross sections of skeletal muscle. Electron microscopic analysis shows DMN colocalized with desmin at the Z-lines. Subsequent coimmunoprecipitation experiments confirmed an interaction with desmin. Our findings suggest that DMN may serve as a direct linkage between the extracellular matrix and the Z-discs (through plectin) and may play an important role in maintaining muscle cell integrity.T he severe muscle wasting disorder, Duchenne muscular dystrophy, is caused by abnormalities in the dystrophin gene (1). The dystrophin protein is expressed in heart and skeletal muscle, where it is part of the dystrophin-associated protein complex. Dystrophin's N-terminal domain binds to actin, whereas the WW domain and the total cysteine-rich domain bind to ␤-dystroglycan (2), a component of the dystroglycan subcomplex. This subcomplex links to laminin, a major component of the basal membrane, thereby forming the linkage between an intracellular protein, actin, and the extracellular matrix.A second subcomplex of the dystrophin-associated protein complex includes four transmembrane proteins (␣-, ␤-, ␥-, and ␦-sarcoglycan) (3). Each has been shown to be involved in different forms of limb-girdle muscular dystrophy (LGMD 2D, 2E, 2C, and 2F) (4-8). ␣-Sarcoglycan is a type 1 transmembrane protein and is expressed in heart and skeletal muscle. ␤-, ␥-, and ␦-sarcoglycans are type 2 transmembrane proteins containing a cluster of cysteine residues in their extracellular domains. These four proteins form the sarcoglycan complex, which is thought to be involved in some type of signaling pathway (9).A third subcomplex of the dystrophin-associated protein complex involves ␣-dystrobrevin (10-12) and the syntrophins (␣1, ␤1, and ␤2) (13-15). These intracellular proteins directly bind to dystrophin (16,17). In addition, the N-terminal region of ␣-dystrobrevin associates with the sarcoglycan complex (18). There are at least ...

Specific Interaction of the Actin-binding Domain of Dystrophin with Intermediate Filaments Containing Keratin 19

“…Ultrastructural evidence, as well as studies of mice lacking desmin due to homologous recombination, suggest that desmin-based intermediate filaments are important in linking the Z-disks of superficial myofibrils to costameres at the sarcolemma (Granger and Lazarides, 1979;Pierobon-Bormioli, 1981;Street, 1983;Shear and Bloch, 1985;O'Neill et al, 2002), perhaps through a plectin cross-linker (Hijikata et al, 2003). Consistent with this, two desminassociated proteins, syncoilin and desmuslin or synemin, have been shown to bind dystrobrevin, a ligand of dystrophin (Mizuno et al, 2001;Newey et al, 2001). In addition, synemin, which copolymerizes with desmin (Granger et al, 1982;Bellin et al, 1999;Hirako et al, 2003), binds vinculin (Bellin et al, 2001), the quintessential costameric protein, and may concentrate at costameres (Mizuno et al, 2004).…”

DAMAGE, a Novel α-Dystrobrevin-associated MAGE Protein in Dystrophin Complexes

“…Several ␣-dystrobrevin-associated proteins have been described including the syntrophins (17)(18)(19)(20), syncoilin (21), desmuslin (22), and dysbindin (23). Of these, the syntrophins are the best characterized and are involved in signaling by recruiting neuronal nitric-oxide synthase (1,24), ion channels (6), and kinases (3,5) to the dystrophin complex.…”

Cytoplasmic γ-actin expression in diverse animal models of muscular dystrophy

“…Two-hybrid screens have identified synemin [18] and syncoilin [19,20] as α-dystrobrevin binding proteins. Both are structurally related to intermediate filament proteins and interact with the muscle-specific intermediate filament protein desmin [18][19][20]. Synemin also directly binds to α-actinin [21] and vinculin [22] to provide additional mechanical linkages between the DGC and muscle cytoskeleton.…”