Appleyard S T, Dunn M J, Dubowitz V, Scott M L, Pittman S J, Shotton D M
Proc Natl Acad Sci U S A. 1984 Feb;81(3):776-80. doi: 10.1073/pnas.81.3.776.
Spectrin is the major protein of the erythrocyte membrane skeleton, which is bound to the cytoplasmic surface of the membrane's lipid bilayer and is responsible for cell shape and membrane elasticity. Inability to identify spectrin in other cell types led to the assumption that this protein was unique to erythrocytes. However, spectrin-like proteins have been demonstrated recently in a variety of cell types, including skeletal and cardiac muscle, in several species. We used monoclonal antibodies against human erythrocyte spectrin subunits in an immunocytochemical study to detect related proteins in normal and diseased human skeletal muscle. Six of seven monoclonal antibodies against beta-spectrin determinants were bound at the cytoplasmic surface of muscle fiber plasma membranes, whereas none of six monoclonal antibodies against alpha-spectrin determinants was bound. Muscle fibers of patients with neuromuscular diseases showed similar distribution and specificity of antibody binding to those of normal subjects, but the intensity of binding was increased. In contrast, probable regenerating fibers in muscle of patients with muscular dystrophies showed reduced binding of antibodies, but reduced binding was not seen in fetal muscle fibers nor in those of a patient with a myotubular myopathy. We conclude that human skeletal muscle fibers possess a spectrin-related protein associated with their plasma membrane that shows extensive beta-chain similarities to erythrocyte spectrin but differs significantly with respect to the alpha-subunit. Its function may be associated with the maintenance of membrane and myofibril integrity during contraction, and the increased antibody binding in diseased muscle may reflect a structural rearrangement of spectrin or a compensatory increase in spectrin abundance in response to increased stress on these systems.
血影蛋白是红细胞膜骨架的主要蛋白质，它与膜脂双层的细胞质表面结合，负责细胞形状和膜弹性。在其他细胞类型中未能鉴定出血影蛋白，导致人们认为这种蛋白质是红细胞特有的。然而，最近在包括骨骼肌和心肌在内的多种细胞类型中，在几个物种中都发现了血影蛋白样蛋白。我们在一项免疫细胞化学研究中使用针对人红细胞血影蛋白亚基的单克隆抗体，来检测正常和患病的人骨骼肌中的相关蛋白。针对β-血影蛋白决定簇的七种单克隆抗体中有六种与肌纤维质膜的细胞质表面结合，而针对α-血影蛋白决定簇的六种单克隆抗体均未结合。神经肌肉疾病患者的肌纤维显示出与正常受试者相似的抗体结合分布和特异性，但结合强度增加。相比之下，肌营养不良症患者肌肉中可能正在再生的纤维显示出抗体结合减少，但在胎儿肌纤维或患有肌管性肌病的患者的肌纤维中未观察到结合减少。我们得出结论，人骨骼肌纤维拥有一种与其质膜相关的血影蛋白相关蛋白，该蛋白与红细胞血影蛋白在β链上有广泛的相似性，但在α亚基方面有显著差异。其功能可能与收缩过程中膜和肌原纤维完整性的维持有关，患病肌肉中抗体结合增加可能反映了血影蛋白的结构重排或血影蛋白丰度的代偿性增加，以应对这些系统上增加的压力。
