Striated muscle cell proteins implicated in muscular dystrophies, dilated cardiomyopathy and lipodystrophy, and their
protein­protein interactions. Myopathies, cardiomyopathy or lipodystrophy known to be caused by particular proteins are indicated in parentheses (red). Spanning the plasma membrane (sarcolemma) of a striated muscle cell (myoblast) is the dystrophin­glycoprotein complex (DGC; bracketed), which provides structural integrity to the cell by crosslinking the cytoskeleton (via actin) to the extracellular matrix (via laminin b1). Mutations in dystrophin cause Duchenne muscular dystrophy (DMD) and mutations in the sarcoglycoproteins cause a variety of limb-girdle muscular dystrophies (LGMD) including 2C, 2D, 2E and 2F. Desmin and actin filaments crosslink the nucleus, sarcomere and sarcolemma. The sarcomere is the structure responsible for muscle contraction, and contains the proteins actin, myosin, titin and telethonin. The muscle LIM protein (MLP; LIM is the term given to a protein­protein interaction domain containing a double zinc finger motif) is a cytoskeletal binding partner of beta-spectrin, itself a cytoskeletal protein. Mutations in lamin A/C can cause LGMD-1B. Other disease abbreviations: AD-EDMD, autosomal dominant Emery­Dreifuss muscular dystrophy; X-EDMD, X-linked EDMD; FPLD, familial Dunnigan-type partial lipodystrophy; CMD, congenital muscular dystrophy; DCM, dilated cardiomyopathy; CMT2, Charcot­Marie­Tooth disorder type 2. The question mark indicates uncertainty as to whether F-actin enters the nucleus from the cytoplasm.