Mutoh T, Tokuda A, Guroff G, Fujiki N
Second Department of Internal Medicine, Fukui Medical School, Japan.
J Neurochem. 1993 Apr;60(4):1540-7. doi: 10.1111/j.1471-4159.1993.tb03319.x.
Exogenous gangliosides, especially ganglioside GM1 (GM1), seem to potentiate the action of nerve growth factor (NGF). We have examined the possible regulation of the NGF signaling pathway in PC12 cells by the B subunit of cholera toxin (CTB), which binds to endogenous GM1 specifically and with a high affinity. CTB treatment (1 micrograms/ml) enhanced NGF-induced neurite outgrowth from PC12 cells, NGF-induced activation of ribosomal protein S6 kinase, and NGF-induced stimulation of trk phosphorylation. CTB plus NGF also caused a greater inhibition of [3H]thymidine incorporation into DNA than did NGF alone. These enhancing effects of CTB were blocked by the presence of cytochalasin B in the culture medium but were not affected by the presence of colchicine or by the depletion of Ca2+ in the medium. 125I-NGF binding experiments revealed that CTB treatment did not affect the specific binding of NGF to the cells. These results strongly suggest that the binding of cell surface GM1 by CTB modulates the pathway of intracellular signaling initiated by NGF and that the association of CTB with a cytoskeletal component is essential for these effects.
外源性神经节苷脂，尤其是神经节苷脂GM1（GM1），似乎能增强神经生长因子（NGF）的作用。我们研究了霍乱毒素B亚基（CTB）对PC12细胞中NGF信号通路的可能调节作用，CTB能特异性且高亲和力地结合内源性GM1。CTB处理（1微克/毫升）增强了NGF诱导的PC12细胞神经突生长、NGF诱导的核糖体蛋白S6激酶激活以及NGF诱导的trk磷酸化。与单独使用NGF相比，CTB加NGF对[3H]胸腺嘧啶核苷掺入DNA的抑制作用也更强。培养基中细胞松弛素B的存在可阻断CTB的这些增强作用，但秋水仙碱的存在或培养基中Ca2+的耗尽对其无影响。125I-NGF结合实验表明，CTB处理不影响NGF与细胞的特异性结合。这些结果强烈表明，CTB与细胞表面GM1的结合调节了由NGF启动的细胞内信号通路，并且CTB与细胞骨架成分的结合对于这些效应至关重要。
