Crosbie R H, Yamada H, Venzke D P, Lisanti M P, Campbell K P
Howard Hughes Medical Institute, Department of Physiology and Biophysics, University of Iowa College of Medicine, Iowa City 52242, USA.
FEBS Lett. 1998 May 8;427(2):279-82. doi: 10.1016/s0014-5793(98)00442-6.
The dystrophin-glycoprotein complex is a multi-subunit protein complex that spans the muscle plasma membrane (sarcolemma) and forms a link between the intracellular cytoskeleton and the extracellular matrix. Caveolin-3, the muscle specific form of caveolin, is also a major structural and regulatory integral membrane protein found at the sarcolemma. Oligomers of caveolin-3 form the structural framework for small membrane pockets known as caveolae. We directly examined whether caveolin-3 is an integral component of the dystrophin-glycoprotein complex by examining four common biochemical and cellular properties of proteins integrally bound to the dystrophin-glycoprotein complex. We found that caveolin-3 de-enriches with partial purification of the dystrophin-glycoprotein complex although a small amount of caveolin-3 is present. Sucrose gradient fractionation and laminin affinity chromatography completely separate this residual caveolin-3 from the core components of the dystrophin-glycoprotein complex. We also show that caveolin-3 expression at the sarcolemma is not reduced in patients with primary mutations in either dystrophin or the sarcoglycans. This data demonstrates that localization of caveolin-3 to the sarcolemma occurs independently of the dystrophin-glycoprotein complex and that caveolin-3 is not an integral component of the dystrophin-glycoprotein complex.
肌营养不良蛋白-糖蛋白复合物是一种多亚基蛋白复合物，它横跨肌肉质膜（肌膜），并在细胞内细胞骨架和细胞外基质之间形成连接。小窝蛋白-3是小窝蛋白的肌肉特异性形式，也是在肌膜中发现的一种主要的结构和调节性整合膜蛋白。小窝蛋白-3的寡聚体形成了称为小窝的小膜囊的结构框架。我们通过检测与肌营养不良蛋白-糖蛋白复合物紧密结合的蛋白质的四种常见生化和细胞特性，直接研究了小窝蛋白-3是否是肌营养不良蛋白-糖蛋白复合物的一个组成部分。我们发现，尽管存在少量小窝蛋白-3，但随着肌营养不良蛋白-糖蛋白复合物的部分纯化，小窝蛋白-3的含量减少。蔗糖梯度分级分离和层粘连蛋白亲和层析将这种残留的小窝蛋白-3与肌营养不良蛋白-糖蛋白复合物的核心成分完全分离。我们还表明，在肌营养不良蛋白或肌聚糖发生原发性突变的患者中，肌膜处的小窝蛋白-3表达并未降低。这些数据表明，小窝蛋白-3在肌膜上的定位独立于肌营养不良蛋白-糖蛋白复合物，并且小窝蛋白-3不是肌营养不良蛋白-糖蛋白复合物的一个组成部分。
