Mechanisms involved in GPI-anchored-protein signaling dimer formation

各种细胞表面蛋白通过糖基磷脂酰肌醇（GPI）锚定在细胞膜上。尽管这些蛋白具有信号分子的功能，但其信号传递的机制在很大程度上是未知的。在这项研究中，我们将重点放在gpi锚定的补体调节蛋白CD59上，作为阐明gpi锚定蛋白介导信号传导的机制的模型。我们通过化学交联剂将表面蛋白交联，鉴定出一种CD59相关蛋白，并揭示了该蛋白本身就是CD59分子。我们还开发了通过C9肽作为配体直接测量CD59信号的方法。通过与C9肽的连接，检测到细胞内Ca2+的特异性增加。这些发现可以直接评估CD59信号，而不是通过Ab交联激活。gpi锚定蛋白分布在称为“筏”的膜结构域上。小泡蛋白是一种筏（小泡）上的主要蛋白质，在各种类型的信号传导中起关键作用。为了了解小窝蛋白是否参与CD59信号传导，我们测试了小窝蛋白在血液和血细胞系中CD59信号传导的表达。令我们惊讶的是，它们中没有一个表达小窝蛋白。成人T细胞白血病（ATL）细胞系中只有亚系在激活状态下表达小窝蛋白。我们现在正在利用这些阳性细胞阐明小窝蛋白在CD59信号传导中的功能。

Various cell surface proteins are anchored to cell membranes via a glycosyl-phosphatidylinositol (GPI) anchor. Although these proteins function as signaling molecules, mechanisms involved in the signaling are largely unknown. In this study we focused on a GPI-anchored complement regulatory protein, CD59, as a model for elucidating the mechanisms involved in the GPI-anchored protein mediating signaling.We identified a CD59-associating protein by cross-linking surface proteins by chemical cross-linker and revealed that the protein is CD59 molecule itself. We also developed the method for direct measurement of CD59 signaling by means of a C9 peptide as a ligand. By ligation with the C9 peptide, specific increase in intracellular Ca2+ was detected. These findings enable the direct assessment of CD59 signaling rather than by activation with Ab cross-linking.GPI-anchored proteins are distributed on membrane domains designated "rafts". Caveolin, a main protein on one type of rafts (caveolae), functions as a key molecule in various types of signaling. To know whether caveolin is involved in CD59 signaling, we tested caveolin expression in blood and blood cell lines in which CD59 signaling is identified. To our surprise none of them expressed caveolin. Only sub line of adult T cell leukemia (ATL) cell lines in a ctivated states expressed caveolin. We are now on the way to elucidate the function of caveolin in CD59 signaling using these positive cells.