Intermediate filament-like protein syncoilin in normal and myopathic striated muscle.

The intermediate filament-like protein syncoilin is a member of the dystrophin protein complex, and links the complex to the cytoskeleton through binding alpha-dystrobrevin and desmin in muscle. Here, we identify further sites of syncoilin location in normal muscle: at the perinuclear space, myotendinous junction, and enrichment in the sarcolemma and sarcoplasm of oxidative muscle fibers in mice. To understand the importance of the dystrophin protein complex-syncoilin-cytoskeletal link and its implication to disease, we analyzed syncoilin in mice null for alpha-dystrobrevin (adbn-/-) and desmin (des-/-). Syncoilin was upregulated in dystrophic muscles of adbn-/- mice, without alteration in its subcellular location. In des-/- mice, syncoilin was severely reduced in skeletal muscle; lost from sarcomeric Z-lines and neuromuscular junctions, and redistributed from the sub-sarcolemmal cytoskeleton to the cytoplasm. The data show that absence of alpha-dystrobrevin or desmin leads to dynamic changes in syncoilin that may compensate for, or participate in, different muscle myopathies.