Ervasti J M, Campbell K P
Howard Hughes Medical Institute, University of Iowa College of Medicine, Iowa City 52242.
J Cell Biol. 1993 Aug;122(4):809-23. doi: 10.1083/jcb.122.4.809.
The dystrophin-glycoprotein complex was tested for interaction with several components of the extracellular matrix as well as actin. The 156-kD dystrophin-associated glycoprotein (156-kD dystroglycan) specifically bound laminin in a calcium-dependent manner and was inhibited by NaCl (IC50 = 250 mM) but was not affected by 1,000-fold (wt/wt) excesses of lactose, IKVAV, or YIGSR peptides. Laminin binding was inhibited by heparin (IC50 = 100 micrograms/ml), suggesting that one of the heparin-binding domains of laminin is involved in binding dystroglycan while negatively charged oligosaccharide moieties on dystroglycan were found to be necessary for its laminin-binding activity. No interaction between any component of the dystrophin-glycoprotein complex and fibronectin, collagen I, collagen IV, entactin, or heparan sulfate proteoglycan was detected by 125I-protein overlay and/or extracellular matrix protein-Sepharose precipitation. In addition, laminin-Sepharose quantitatively precipitated purified dystrophin-glycoprotein complex, demonstrating that the laminin-binding site is accessible when dystroglycan is associated with the complex. Dystroglycan of nonmuscle tissues also bound laminin. However, the other proteins of the striated muscle dystrophin-glycoprotein complex appear to be absent, antigenically dissimilar or less tightly associated with dystroglycan in nonmuscle tissues. Finally, we show that the dystrophin-glycoprotein complex cosediments with F-actin but does not bind calcium or calmodulin. Our results support a role for the striated muscle dystrophin-glycoprotein complex in linking the actin-based cytoskeleton with the extracellular matrix. Furthermore, our results suggest that dystrophin and dystroglycan may play substantially different functional roles in nonmuscle tissues.
对肌营养不良蛋白 - 糖蛋白复合物与细胞外基质的几种成分以及肌动蛋白的相互作用进行了检测。156-kD肌营养不良蛋白相关糖蛋白（156-kD肌聚糖）以钙依赖的方式特异性结合层粘连蛋白，并受到NaCl抑制（IC50 = 250 mM），但不受乳糖、IKVAV或YIGSR肽1000倍（wt/wt）过量的影响。层粘连蛋白结合受到肝素抑制（IC50 = 100微克/毫升），这表明层粘连蛋白的一个肝素结合结构域参与了与肌聚糖的结合，同时发现肌聚糖上带负电荷的寡糖部分对其层粘连蛋白结合活性是必需的。通过125I - 蛋白质覆盖和/或细胞外基质蛋白 - 琼脂糖沉淀法未检测到肌营养不良蛋白 - 糖蛋白复合物的任何成分与纤连蛋白、I型胶原、IV型胶原、巢蛋白或硫酸乙酰肝素蛋白聚糖之间的相互作用。此外，层粘连蛋白 - 琼脂糖定量沉淀纯化的肌营养不良蛋白 - 糖蛋白复合物，表明当肌聚糖与该复合物结合时，层粘连蛋白结合位点是可及的。非肌肉组织的肌聚糖也结合层粘连蛋白。然而，横纹肌肌营养不良蛋白 - 糖蛋白复合物的其他蛋白质似乎不存在，在非肌肉组织中与肌聚糖抗原性不同或结合不紧密。最后，我们表明肌营养不良蛋白 - 糖蛋白复合物与F - 肌动蛋白共沉降，但不结合钙或钙调蛋白。我们的结果支持横纹肌肌营养不良蛋白 - 糖蛋白复合物在将基于肌动蛋白 的细胞骨架与细胞外基质连接中发挥作用。此外，我们的结果表明肌营养不良蛋白和肌聚糖在非肌肉组织中可能发挥实质上不同的功能作用。
