The direct visualization of structural array from laminin to dystrophin insarcolemmal vesicles prepared from rat skeletal muscles

It has been biochemically shown that dystrophin and alpha- and beta-dystrog lycan form an oligomeric complex which links laminin, a component of the ba sement membrane, to components of the subsarcolemmal cytoskeleton in skelet al muscle fibers. In the present study the dystrophin-glycoprotein complex and its structural relationships to laminin and subsarcolemmal cytoskeleton were ultrastructurally examined in crude surface membranes prepared from r at skeletal muscles. Sarcolemmal vesicles within crude surface membranes we re identified and characterized by fine protrusions on their outer surface and electron-dense materials or patches associated with the inner surface. These two components were seen to be in register with each other across the sarcolemma. The fine protrusions were immunolabeled by anti-alpha-dystrogl ycan and reassociated with exogenous laminin. Immunolabeling in combination with laminin reassociation demonstrated that the electron-dense materials contained dystrophin at laminin-binding domains of the membrane. In additio n, they were often associated with very fine filaments. These results provi de morphological evidence for the biochemically proposed model of molecular array of dystrophin complex from the basement membrane to the subsarcolemm al cytoskeleton. ((C) Elsevier, Paris).