Fra A M, Williamson E, Simons K, Parton R G
European Molecular Biology Laboratory, Heidelberg, Federal Republic of Germany.
J Biol Chem. 1994 Dec 9;269(49):30745-8.
Antibody binding to glycolipids and glycophosphatidylinositol (GPI)-anchored proteins of lymphocytes can trigger activation of specific signal transduction pathways. The finding that GPI-anchored proteins are present in detergent-insoluble complexes with several tyrosine kinases of the Src family suggested that these complexes may represent membrane microdomains involved in the transduction of signals to the cell interior. Recent work has suggested a link between detergent-insoluble microdomains and plasma membrane invaginations termed caveolae. Here we show that lymphocytes lack plasma membrane domains with the characteristic features of caveolae. Furthermore, VIP21-caveolin was not detectable in four different lymphocyte cell lines at the protein or mRNA level. In addition to the lack of caveolar domains, capping experiments suggested that the bulk of the GPI-anchored protein Thy1 and the glycosphingolipid GM1 were not stably associated in the lymphocyte plasma membrane. Despite this, Thy1 and GM1 were present in detergent-insoluble complexes. We conclude that detergent insolubility does not correlate with the presence of caveolae or of VIP21-caveolin and that caveolae, as defined by a number of different markers, are not involved in signal transduction in lymphocytes.
抗体与淋巴细胞的糖脂及糖基磷脂酰肌醇（GPI）锚定蛋白结合可触发特定信号转导途径的激活。有研究发现，GPI锚定蛋白与Src家族的几种酪氨酸激酶存在于去污剂不溶性复合物中，这表明这些复合物可能代表参与向细胞内部转导信号的膜微区。最近的研究表明，去污剂不溶性微区与称为小窝的质膜内陷之间存在联系。在此我们表明，淋巴细胞缺乏具有小窝特征的质膜结构域。此外，在四种不同的淋巴细胞系中，无论是蛋白质水平还是mRNA水平，均未检测到VIP21-小窝蛋白。除了缺乏小窝结构域外，封帽实验表明，大部分GPI锚定蛋白Thy1和糖鞘脂GM1在淋巴细胞质膜中并非稳定结合。尽管如此，Thy1和GM1仍存在于去污剂不溶性复合物中。我们得出结论，去污剂不溶性与小窝或VIP21-小窝蛋白的存在无关，并且由多种不同标记物定义的小窝不参与淋巴细胞中的信号转导。
