Localization of sarcoglycan, neuronal nitric oxide synthase, beta-dystroglycan, and dystrophin molecules in normal skeletal myofiber: Triple immunogold labeling electron microscopy

In order to investigate the mode of existence of the sarcoglycan complex, n euronal nitric oxide synthase (nNOS), beta -dystroglycan, and dystrophin in the normal skeletal myofiber, we examined the ultrastructural localization and mutual spatial relationship of nNOS, beta -dystroglycan, dystrophin, a nd the individual components of the sarcoglycan complex by using triple imm unogold labeling electron microscopy. Each molecule of alpha-, beta-, gamma - and delta -sarcoglycans is located intracellularly or extracellularly nea r the muscle plasma membrane mostly in accordance with the sarcoglycan anti genic sites against which the antibodies were generated. The association of different two and/or three sarcoglycan molecules out of alpha-, beta-, gam ma- and delta -sarcoglycan molecules was frequently observed. Each molecule of nNOS, beta -dystroglycan, and dystrophin was ultrastructurally noted al ong the cell surface of normal skeletal myofibers. Moreover, the close rela tion of a sarcoglycan molecule with beta -dystroglycan and dystrophin, and the association of nNOS with dystrophin were also confirmed ultrastructural ly. Thus, this study demonstrated that the constituting molecules of the sa rcoglycan complex, nNOS, beta -dystroglycan, and dystrophin existed in the form of a cluster at the normal muscle plasma membrane. The association of nNOS with dystrophin and its associated glycoproteins may form a macromolec ular signaling complex at the muscle plasma membrane. Microsc. Res. Tech. 5 5:154-163,2001. (C) 2001 Wiley-Liss,Inc.