Hernández-Deviez Delia J, Howes Mark T, Laval Steven H, Bushby Kate, Hancock John F, Parton Robert G
Institute for Molecular Bioscience, Centre for Microscopy and Microanalysis, University of Queensland, Brisbane, Queensland 4072, Australia.
J Biol Chem. 2008 Mar 7;283(10):6476-88. doi: 10.1074/jbc.M708776200. Epub 2007 Dec 20.
Dysferlin and Caveolin-3 are plasma membrane proteins associated with muscular dystrophy. Patients with mutations in the CAV3 gene show dysferlin mislocalization in muscle cells. By utilizing caveolin-null cells, expression of caveolin mutants, and different mutants of dysferlin, we have dissected the site of action of caveolin with respect to dysferlin trafficking pathways. We now show that Caveolin-1 or -3 can facilitate exit of a dysferlin mutant that accumulates in the Golgi complex of Cav1(-/-) cells. In contrast, wild type dysferlin reaches the plasma membrane but is rapidly endocytosed in Cav1(-/-) cells. We demonstrate that the primary effect of caveolin is to cause surface retention of dysferlin. Caveolin-1 or Caveolin-3, but not specific caveolin mutants, inhibit endocytosis of dysferlin through a clathrin-independent pathway colocalizing with internalized glycosylphosphatidylinositol-anchored proteins. Our results provide new insights into the role of this endocytic pathway in surface remodeling of specific surface components. In addition, they highlight a novel mechanism of action of caveolins relevant to the pathogenic mechanisms underlying caveolin-associated disease.
肌膜蛋白和小窝蛋白-3是与肌肉萎缩症相关的质膜蛋白。CAV3基因突变的患者在肌肉细胞中表现出肌膜蛋白定位错误。通过利用小窝蛋白缺失细胞、小窝蛋白突变体的表达以及不同的肌膜蛋白突变体，我们剖析了小窝蛋白在肌膜蛋白运输途径方面的作用位点。我们现在表明，小窝蛋白-1或-3可以促进在Cav1(-/-)细胞的高尔基体中积累的肌膜蛋白突变体的输出。相比之下，野生型肌膜蛋白到达质膜，但在Cav1(-/-)细胞中会迅速被内吞。我们证明小窝蛋白的主要作用是导致肌膜蛋白在表面滞留。小窝蛋白-1或小窝蛋白-3，但不是特定的小窝蛋白突变体，通过与内化的糖基磷脂酰肌醇锚定蛋白共定位的网格蛋白非依赖途径抑制肌膜蛋白的内吞作用。我们的结果为这种内吞途径在特定表面成分的表面重塑中的作用提供了新的见解。此外，它们突出了与小窝蛋白相关疾病潜在致病机制相关的小窝蛋白的一种新作用机制。
