Arni S, Ilangumaran S, van Echten-Deckert G, Sandhoff K, Poincelet M, Briol A, Rungger-Brändle E, Hoessli D C
Department of Pathology, Faculty of Medicine, Centre Médical Universitaire, Geneva, Switzerland.
Biochem Biophys Res Commun. 1996 Aug 23;225(3):801-7. doi: 10.1006/bbrc.1996.1254.
The association of glycosylphosphatidylinositol (GPI)-anchored cell surface glycoproteins with Src-family protein tyrosine kinases was analysed in intact T lymphocyte plasma membranes. Following subcellular fractionation without detergent, 25% of the recovered plasma membranes were light density vesicles enriched in GPI-anchored glycoproteins and sphingolipids (GPI domains), while the remainder behaved as heavier density vesicles containing equal amounts of lipids and proteins. Qualitatively similar lipids were found in both vesicle types, but only light density vesicles made of 65-75% lipids yielded a Triton X-100 resistant, sedimentable fraction containing GPI-linked glycoproteins and sphingolipids. The GPI-rich vesicles phosphotyrosylated an exogenous substrate as efficiently as the denser vesicles, despite a low Lck and Fyn kinase content. Likewise, these kinases were more efficiently phosphorylated in GPI domains than in denser vesicles. GPI domains thus could constitute plasma membrane "hot spots" where associated Src kinases assume an optimally active conformation that contributes to signaling via GPI-anchored cell surface glycoproteins.
在完整的T淋巴细胞质膜中分析了糖基磷脂酰肌醇（GPI）锚定的细胞表面糖蛋白与Src家族蛋白酪氨酸激酶的关联。在不使用去污剂进行亚细胞分级分离后，回收的质膜中有25%是富含GPI锚定糖蛋白和鞘脂的低密度囊泡（GPI结构域），而其余的则表现为含有等量脂质和蛋白质的较高密度囊泡。在两种囊泡类型中都发现了定性相似的脂质，但只有由65 - 75%脂质组成的低密度囊泡产生了含有GPI连接糖蛋白和鞘脂的对 Triton X - 100 有抗性的可沉淀部分。尽管Lck和Fyn激酶含量较低，但富含GPI的囊泡对外源底物进行磷酸酪氨酸化的效率与密度较高的囊泡相同。同样，这些激酶在GPI结构域中比在密度较高的囊泡中更有效地被磷酸化。因此，GPI结构域可能构成质膜“热点”，与之相关的Src激酶在其中呈现出有助于通过GPI锚定的细胞表面糖蛋白进行信号传导的最佳活性构象。
