BIOSYNTHESIS AND FUNCTION OF GLYCOSPHINGOLIPIDS AND OTHER GLYCOCONJUGATES

神经节苷脂似乎是细胞上重要的识别分子 并被认为是某些细菌毒素的受体 和病毒。然而，人们对正常的生理状态知之甚少。 这些质膜成分的作用(S)。我们已经开发了几个 解决这一问题的方法和模式系统。荧光衍生物 含有罗丹明或荧光黄CH的神经节苷脂GM1 合成并显示出与天然GM1一样有效的受体 霍乱毒素。将荧光神经节苷脂插入血浆中 小鼠和大鼠胸腺细胞的膜，并在细胞 接触过霍乱毒素或抗罗丹明抗体，这两种抗体都是 多价的。霍乱毒素还可诱导内源性斑贴和封顶 胸腺细胞表面的GM1。大鼠胸腺细胞暴露于B或 毒素的结合亚单位导致增殖反应，如 通过增加DNA合成来衡量。即使在25 ng/m1的浓度下，B亚基也是 作为有丝分裂原有效。B亚单位与抗霍乱药物的预先孵育 毒素抗体阻止了它与细胞的结合和刺激。 B亚基是有效的有丝分裂原。预先孵化B 带有抗霍乱毒素抗体的亚基阻断了其与 对细胞的刺激。B亚基被证明不含任何 腺苷环化酶激活A亚单位和环磷酸腺苷被抑制 有丝分裂。因此，几个GM1分子与胸腺细胞的结合 通过B亚基的表面导致跨血浆的转导 有丝分裂信号的膜。

Gangliosides appear to be important recognition molecules on the cell surface and have been implicated as receptors for certain bacterial toxins and viruses. Little is known, however, about the normal physiological role(s) of these plasma membrane components. We have developed several approaches and model sysems to address this issue. Fluorescent derivatives of ganglioside GM1 containing either rhodamine or Lucifer yellow CH were synthesized and shown to be as effective as native GM1 as receptors for cholera toxin. The fluorescent gangliosides were inserted into the plasma membrane of mouse and rat thymocytes and underwent capping when the cells were exposed to cholera toxin or anti-rhodamine antibodies, which are both multivalent. Cholera toxin also induced patching and capping of endogenous GM1 on the thymocyte surface. Exposure of rat thymocytes to the B or binding subunit of the toxin resulted in a proliferative response as measured by increased DNA synthesis. Even at 25 ng/M1, the B subunit was effective as a mitogen. Prior incubation of the B subunit with anticholera toxin antibodies blocked both its binding to and stimulation of the cells. The B subunit was effective as a mitogen. Prior incubation of the B subunit with anticholera toxin antibodies blocked both its binding to and stimulation of the cells. The B subunit was shown to be free of any adenylate cyclase-activating A subunit; and cyclic AMP inhibited mitogenesis. Thus, binding of several molecules of GM1 on the thymocyte surface by the B subunit leads to the transduction across the plasma membrane of a mitogenic signal.