Moss D J, White C A
Department of Human Anatomy and Cell Biology, Liverpool, United Kingdom.
Eur J Cell Biol. 1992 Feb;57(1):59-65.
GP130 (renamed contactin) has previously been identified by its detergent insolubility and retention with the actin-containing "membrane skeleton" isolated from chicken neurons and brain. The contactin sequence predicted a transmembrane and cytoplasmic domain for the molecule. Recently, F11 was shown to have an identical sequence except for the C terminus, and it was predicted to be linked to the plasma membrane by a glycosylphosphatidylinositol (GPI) group. Here we describe that GP130 can be released both from brain membranes and the detergent-insoluble membrane skeleton by a phosphoinositol-specific phospholipase C (PI-PLC) indicating that F11 and GP130/contactin are probably identical and that surprisingly the lipid anchor is partly or totally responsible for its non-ionic detergent insolubility. The "membrane skeleton" is a rich source of GPI-linked glycoproteins as judged by 1) most glycoproteins can be released by a PI-PLC and 2) most [3H]ethanolamine-labeled glycoproteins are present in, or enriched in the membrane skeleton. Thus, detergent insolubility appears to be a characteristic of GPI-anchored glycoproteins. No evidence has been obtained that GP130/F11 is released or secreted in vivo or in culture. In addition, GP130/F11 has an unusually long half-life in culture of greater than 3 days. The structure of the neuronal membrane skeleton and the potential function of GPI-anchored glycoproteins is discussed.
GP130（现称为接触蛋白）先前是通过其在去污剂中不溶性以及与从鸡神经元和大脑中分离出的含肌动蛋白的“膜骨架”的结合而被鉴定出来的。接触蛋白的序列预测该分子具有一个跨膜结构域和一个胞质结构域。最近发现，F11除了C末端外具有相同的序列，并且预计它通过糖基磷脂酰肌醇（GPI）基团与质膜相连。在此我们描述，磷酸肌醇特异性磷脂酶C（PI-PLC）可从脑细胞膜和去污剂不溶性膜骨架中释放出GP130，这表明F11与GP130/接触蛋白可能是相同的，并且令人惊讶的是，脂质锚定部分或完全导致了其在非离子去污剂中的不溶性。从以下两点判断，“膜骨架”是GPI连接糖蛋白的丰富来源：1）大多数糖蛋白可被PI-PLC释放；2）大多数[3H]乙醇胺标记的糖蛋白存在于膜骨架中或在膜骨架中富集。因此，去污剂不溶性似乎是GPI锚定糖蛋白的一个特征。没有证据表明GP130/F11在体内或培养物中被释放或分泌。此外，GP130/F11在培养物中的半衰期异常长超过3天。本文还讨论了神经元膜骨架的结构以及GPI锚定糖蛋白的潜在功能。
