Dickson G, Azad A, Morris G E, Simon H, Noursadeghi M, Walsh F S
Department of Experimental Pathology, UMDS, Guy's Hospital, London Bridge, UK.
J Cell Sci. 1992 Dec;103 ( Pt 4):1223-33. doi: 10.1242/jcs.103.4.1223.
In Duchenne muscular dystrophy (DMD), deficiency of the protein dystrophin results in necrosis of muscle myofibres, associated with lesions in the sarcolemma and surrounding basal lamina. Dystrophin has been proposed to be a major component of the sub-sarcolemmal cytoskeleton involved in maintaining the integrity of the myofibre plasma membrane, and is known to associate with a group of sarcolemmal glycoproteins, one of which exhibits high affinity binding to the basal lamina component laminin. However, a direct or indirect transmembrane association of dystrophin in muscle cells with the myofibre basal lamina has not been demonstrated. To address this question we have examined dystrophin immunostaining and immunoprecipitation patterns in cultured mouse and human myotubes in comparison with that of the basal lamina component, laminin. Dual-immunolabelling revealed virtually complete co-localization of dystrophin on the inside surface of the muscle cell sarcolemma with plaques and veined arrays of laminin accumulating on the extracellular face. This pattern of laminin and dystrophin distribution was distinct from that of other cell surface molecules expressed in myotubes such as the neural cell adhesion molecule, NCAM, and the beta 1 integrin receptor, and immunoprecipitation of dystrophin from solubilized myotube extracts resulted in co-purification of laminin B1 chain confirming an association between these two components. The results thus provide the first direct cellular evidence of a transmembrane linkage between dystrophin in the sarcolemmal cytoskeleton with laminin in the overlying basal lamina. While the immunocytochemical distribution of laminin was apparently normal in dystrophin-deficient muscle cells, elevated levels of soluble laminin were present in extracts of mdx compared with normal mouse skeletal muscle.(ABSTRACT TRUNCATED AT 250 WORDS)
在杜兴氏肌营养不良症（DMD）中，肌营养不良蛋白的缺乏导致肌纤维坏死，这与肌膜和周围基底膜的损伤有关。有人提出肌营养不良蛋白是肌膜下细胞骨架的主要成分，参与维持肌纤维质膜的完整性，并且已知它与一组肌膜糖蛋白相关联，其中一种糖蛋白对基底膜成分层粘连蛋白具有高亲和力结合。然而，尚未证实肌营养不良蛋白在肌肉细胞中与肌纤维基底膜存在直接或间接的跨膜关联。为了解决这个问题，我们检测了培养的小鼠和人类肌管中肌营养不良蛋白的免疫染色和免疫沉淀模式，并与基底膜成分层粘连蛋白进行了比较。双重免疫标记显示，肌营养不良蛋白在肌肉细胞肌膜内表面与在细胞外表面积累的层粘连蛋白斑块和静脉状阵列几乎完全共定位。这种层粘连蛋白和肌营养不良蛋白的分布模式与肌管中表达的其他细胞表面分子不同，如神经细胞粘附分子NCAM和β1整合素受体，并且从溶解的肌管提取物中免疫沉淀肌营养不良蛋白导致层粘连蛋白B1链的共纯化，证实了这两种成分之间的关联。因此，这些结果首次提供了细胞层面的直接证据，证明肌膜细胞骨架中的肌营养不良蛋白与上方基底膜中的层粘连蛋白之间存在跨膜联系。虽然在缺乏肌营养不良蛋白的肌肉细胞中层粘连蛋白的免疫细胞化学分布显然正常，但与正常小鼠骨骼肌相比，mdx小鼠提取物中可溶性层粘连蛋白的水平升高。（摘要截断于250字）
