Structure and Function of a Ganglioside found Exclusively on the Surface of Neuroblastoma cells

我们用神经母细胞瘤GoTO细胞和黑色素瘤G361细胞的完整细胞免疫小鼠，获得了两种可识别细胞表面抗原的单抗，即单抗I-13和单抗AG23。通过对不同细胞的荧光激活细胞分类(FACS)分析，发现单抗I-13对神经母细胞瘤细胞GOTO和IMR-32有很好的识别作用，但不能识别其他细胞。另一方面，单抗AG23可识别除GOTO外的所有细胞，单抗I-13的抗原为鞘磷脂，AG23的抗原为糖蛋白，CD44.5-溴-2‘-脱氧尿嘧啶核苷(BrdU)处理的Goto细胞分化为雪旺细胞，表面表达CD44。表达的CD44为造血型(CD44H)，编码胞质长尾巴。去血清诱导分化为神经细胞的Goto细胞不表达CD44。另一方面，在分化为雪旺细胞和神经细胞后，Goto细胞对单抗I-13的反应减弱，抗原脂质仅存在于膜微域，称为脂筏。在BrdU处理的Goto细胞中，CD44也被分割成脂筏，尽管在黑色素瘤G361细胞中，CD44既存在于质膜部分，也存在于脂筏部分。我认为BrdU处理的Goto细胞中的CD44可能在细胞分化为雪旺细胞过程中起重要作用。

We immunized mice with intact cells of neuroblastoma GOTO cells and melanoma G361 cells and obtained two interesting monoclonal antibodies(mAbs), mAb I-13 and mAb AG23, which respectively recognized cell surface antigens. I tried to identify the antigens for two mAbs, and I investigated the differentiation of GOTO cells using these mAbs.By fluorescence-activated cell sorter(FACS)analysis of various cells, the mAb I-13 recognized neuroblastoma cells GOTO and IMR-32 very well, but did not recognize other cells tested. On the other hand, the mAb AG23 recognized all cells tested except GOTO.It turned out that the antigen for mAb I-13 was a sphingolipid and that for AG23 was a glycoprotein, CD44.5-Bromo-2' -deoxyuridine(BrdU)-treated GOTo cells, which are differentiated int Schwann cells, expressed CD44 on the cell surface. The CD44 species expressed was the hemopoietic form(CD44H)encoding long cytoplasmic tail. GOTO cells differentiated into neural cells by serum depletion did not express CD44. On the other hand, GOTO cells became a little less responsive with the mAb I-13 after the differentiation into Schwann as well as neural cells.The antigen lipid was found exclusively in membrane microdomain, called lipid rafts. CD44 in BrdU-treated GOTO cells also partitioned itself into lipid rafts, although it was found in both plasma membrane fractions and lipid rafts fractions in the case of melanoma G361 cells. I think that CD44 in BrdU-treated GOTO cells might play an important role in cells differentiated into Schwann cells.