INSOLUBILITY AND REDISTRIBUTION OF GPI-ANCHORED PROTEINS AT THE CELL-SURFACE AFTER DETERGENT TREATMENT
INSOLUBILITY AND REDISTRIBUTION OF GPI-ANCHORED PROTEINS AT THE CELL-SURFACE AFTER DETERGENT TREATMENT
复制标题
DOI：
10.1091/mbc.6.7.929
复制
发表时间：
1995-07-01
影响因子：
3.3
通讯作者：
MAXFIELD, FR
中科院分区：
文献类型：
--
作者：
MAYOR, S;MAXFIELD, FR
一组不同的细胞表面真核蛋白，包括受体、酶和黏附分子，在羧基末端具有糖基磷脂(GPI)修饰，作为它们唯一的膜锚定手段。这些GPI锚定的蛋白在非离子洗涤剂如Triton X-100中的增溶作用很差。此外，这些来自质膜的不溶于洗涤剂的复合体显著富含几种细胞质蛋白，包括非受体类型的酪氨酸激酶和小凹条纹外套的成分小窝/VIP-21。这些观察结果表明，洗涤剂不溶性复合体是纯化的腔泡膜制剂。然而，我们最近的免疫荧光和电子显微镜显示，GPI锚定蛋白广泛分布在细胞表面，但只有在交联后才可能在小窝中浓缩。虽然小凹只占细胞表面的一小部分(4%)，但几乎所有细胞表面的GPI锚定蛋白都被结合到不溶于洗涤剂的低密度复合体中。在这篇文章中，我们表明，在洗涤剂处理后，GPI锚定的蛋白在剩余的膜结构中重新分布到明显更聚集的分布中。这些结果表明，GPI锚定蛋白在质膜环境中本质上是洗涤剂不溶的，它们与小窝蛋白的共纯化不能反映它们的天然分布。这些结果还表明，必须严格重新检查小窝、GPI锚定蛋白和信号蛋白之间的联系。
A diverse set of cell surface eukaryotic proteins including receptors, enzymes, and adhesion molecules have a glycosylphosphoinositol-lipid (GPI) modification at the carboxy-terminal end that serves as their sole means of membrane anchoring. These GPI-anchored proteins are poorly solubilized in nonionic detergent such as Triton X-100. In addition these detergent-insoluble complexes from plasma membranes are significantly enriched in several cytoplasmic proteins including nonreceptor-type tyrosine kinases and caveolin/VIP-21, a component of the striated coat of caveolae. These observations have suggested that the detergent-insoluble complexes represent purified caveolar membrane preparations. However, we have recently shown by immunofluorescence and electron microscopy that GPI-anchored proteins are diffusely distributed at the cell surface but may be enriched in caveolae only after cross-linking. Although caveolae occupy only a small fraction of the cell surface (< 4%), almost all of the GPI-anchored protein at the cell surface becomes incorporated into detergent-insoluble low-density complexes. In this paper we show that upon detergent treatment the GPI-anchored proteins are redistributed into a significantly more clustered distribution in the remaining membranous structures. These results show that GPI-anchored proteins are intrinsically detergent-insoluble in the milieu of the plasma membrane, and their co-purification with caveolin is not reflective of their native distribution. These results also indicate that the association of caveolae, GPI-anchored proteins, and signalling proteins must be critically re-examined.