He H T, Barbet J, Chaix J C, Goridis C
EMBO J. 1986 Oct;5(10):2489-94. doi: 10.1002/j.1460-2075.1986.tb04526.x.
The rodent neural cell adhesion molecule (NCAM) consists of three glycoproteins with Mr of 180,000, 140,000 and 120,000. The Mr 120,000 protein (NCAM-120) has been shown to exist in membrane-bound and soluble forms but the nature of its membrane association and release has remained obscure. We show here that phosphatidylinositol-specific phospholipase C (PI-PLC), but not a phospholipase C of different specificity, releases a substantial proportion of NCAM-120 from brain membranes and solubilizes almost quantitatively NCAM-120 present at the surface of C6 astroglial cells. The PI-PLC effect was highly selective since only one other protein species was detectably released from C6 cells. These results suggest that NCAM-120 is held in the membrane by covalently bound phosphatidylinositol or a closely related lipid in a way similar to several other surface proteins from eukaryotic cells. The presence of NCAM in a form which can be released from the cell surface by a highly selective mechanism raises additional possibilities for modulation and control of cell--cell adhesion.
啮齿动物神经细胞黏附分子（NCAM）由三种糖蛋白组成，分子量分别为180,000、140,000和120,000。已证实分子量为120,000的蛋白（NCAM - 120）以膜结合形式和可溶性形式存在，但其膜结合和释放的本质仍不清楚。我们在此表明，磷脂酰肌醇特异性磷脂酶C（PI - PLC），而非具有不同特异性的磷脂酶C，能从脑膜中释放相当比例的NCAM - 120，并几乎定量地溶解存在于C6星形胶质细胞表面的NCAM - 120。PI - PLC的作用具有高度选择性，因为从C6细胞中仅可检测到另一种蛋白质被释放。这些结果表明，NCAM - 120通过共价结合的磷脂酰肌醇或与之密切相关的脂质以类似于真核细胞中其他几种表面蛋白的方式锚定在膜上。以一种可通过高度选择性机制从细胞表面释放的形式存在的NCAM，为细胞间黏附的调节和控制带来了更多可能性。
