Gee S H, Montanaro F, Lindenbaum M H, Carbonetto S
Centre for Research in Neuroscience, McGill University, Montreal General Hospital Research Institute, Quebec, Canada.
Cell. 1994 Jun 3;77(5):675-86. doi: 10.1016/0092-8674(94)90052-3.
Aggregation of acetylcholine receptors (AChRs) on skeletal muscle fibers is thought to be mediated by the basal lamina protein agrin. Structural similarities shared by agrin and laminin suggested that the laminin receptor dystroglycan-alpha, part of a dystrophin-receptor complex, might also bind agrin. We show here that dystroglycan-alpha and dystrophin-related protein (DRP/utrophin) are concentrated within AChR aggregates in cultures of C2 myotubes and that agrin binds specifically to dystroglycan-alpha in in vitro assays. This binding is calcium dependent and is inhibited by monoclonal antibody (MAb) IIH6 against dystroglycan-alpha, heparin, and laminin, but not by fibronectin. In S27 cells, which do not aggregate AChRs spontaneously, agrin and laminin binding to dystroglycan-alpha are dramatically decreased. Moreover, MAb IIH6 significantly inhibits agrin-induced AChR aggregation on C2 cells. We conclude that dystroglycan-alpha is an agrin-binding protein and part of a dystrophin-receptor complex involved in AChR aggregation.
骨骼肌纤维上乙酰胆碱受体（AChRs）的聚集被认为是由基底膜蛋白聚集蛋白聚糖介导的。聚集蛋白聚糖和层粘连蛋白共有的结构相似性表明，作为肌营养不良蛋白 - 受体复合物一部分的层粘连蛋白受体α - 肌聚糖，也可能结合聚集蛋白聚糖。我们在此表明，α - 肌聚糖和肌营养不良相关蛋白（DRP/厄布蛋白）在C2肌管培养物中的AChR聚集体内富集，并且在体外试验中聚集蛋白聚糖特异性结合α - 肌聚糖。这种结合是钙依赖性的，并且被针对α - 肌聚糖的单克隆抗体（MAb）IIH6、肝素和层粘连蛋白抑制，但不被纤连蛋白抑制。在不自发聚集AChRs的S27细胞中，聚集蛋白聚糖和层粘连蛋白与α - 肌聚糖的结合显著减少。此外，MAb IIH6显著抑制聚集蛋白聚糖诱导的C2细胞上的AChR聚集。我们得出结论，α - 肌聚糖是一种聚集蛋白聚糖结合蛋白，并且是参与AChR聚集的肌营养不良蛋白 - 受体复合物的一部分。
