Electron microscopic observations of triple immunogold labelling for dystrophin, beta-dystroglycan and adhalin in human skeletal myofibers.

Dystrophin is the Duchenne muscular dystrophy gene product and is a membrane cytoskeletal protein present in the network of the plasma membrane undercoat. Adhalin (50 kDa dystrophin-associated glycoprotein) and beta-dystroglycan (43 kDa dystrophin-associated glycoprotein) are the transmembrane components of the normal muscle plasma membrane, and beta-dystroglycan has been demonstrated to bind dystrophin at the inside surface of normal muscle plasma membrane. This investigation was undertaken to test whether the epitopes of dystrophin, beta-dystroglycan and adhalin are closely associated with each other by using triple immunogold labelling electron microscopy on normal human skeletal myofibers. Although closely associated signals of triplet immunogold particles were observed, there were less numerous than expected. However, closely associated signals of two epitopes of dystrophin and beta-dystroglycan, dystrophin and adhalin, or adhalin and beta-dystroglycan were frequently observed. These ultrastructural findings are consistent with biochemical evidence implying that dystrophin, beta-dystroglycan and adhalin are closely associated with each other at the normal muscle plasma membrane.