Hijikata T, Fujimaki N, Osawa H, Ishikawa H
Department of Anatomy, Gunma University School of Medicine, Japan.
Biol Cell. 1998 Dec;90(9):629-39.
It has been biochemically shown that dystrophin and alpha- and beta-dystroglycan form an oligomeric complex which links laminin, a component of the basement membrane, to components of the subsarcolemmal cytoskeleton in skeletal 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 rat skeletal muscles. Sarcolemmal vesicles within crude surface membranes were 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-dystroglycan 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 addition, they were often associated with very fine filaments. These results provide morphological evidence for the biochemically proposed model of molecular array of dystrophin complex from the basement membrane to the subsarcolemmal cytoskeleton.
生物化学研究表明，肌营养不良蛋白与α - 和β - 肌营养不良聚糖形成一种寡聚复合物，该复合物将基底膜的一种成分层粘连蛋白与骨骼肌纤维肌膜下细胞骨架的成分连接起来。在本研究中，利用大鼠骨骼肌制备的粗制表面膜，对肌营养不良蛋白 - 糖蛋白复合物及其与层粘连蛋白和肌膜下细胞骨架的结构关系进行了超微结构研究。粗制表面膜内的肌膜小泡通过其外表面的精细突起以及与内表面相关的电子致密物质或斑块来识别和表征。这两个成分在肌膜上彼此对齐。精细突起被抗α - 肌营养不良聚糖免疫标记，并与外源性层粘连蛋白重新结合。免疫标记与层粘连蛋白重新结合表明，电子致密物质在膜的层粘连蛋白结合结构域含有肌营养不良蛋白。此外，它们常常与非常细的细丝相关。这些结果为从基底膜到肌膜下细胞骨架的肌营养不良蛋白复合物分子排列的生化模型提供了形态学证据。
