Sandvig K, Sundan A, Olsnes S
J Cell Biol. 1984 Mar;98(3):963-70. doi: 10.1083/jcb.98.3.963.
Inhibition of protein synthesis in Vero cells was measured at different periods of time after treatment with diphtheria toxin and the related plant toxin modeccin. Diphtheria toxin acted much more rapidly than modeccin. Cells were protected against both toxins with antiserum as well as with agents like NH4Cl, procaine, and the ionophores monensin, FCCP, and CCCP, which increase the pH of intracellular vesicles. Antiserum, which is supposed to inactivate toxin only at the cell surface, protected only when it was added within a short period of time after modeccin. Compounds that increase the pH of intracellular vesicles, protected even when added after 2 h, indicating that modeccin remains inside vesicles for a considerable period of time before it enters the cytosol. After addition of diphtheria toxin to the cells, compounds that increase the pH of intracellular vesicles protected only approximately to the same extent as antitoxin. This indicates that after endocytosis diphtheria toxin rapidly enters the cytosol. At 20 degrees C, the cells were more strongly protected against modeccin than against diphtheria toxin. The residual toxic effect of diphtheria toxin at 20 degrees C could be blocked with NH4Cl whereas this was not the case with modeccin. This indicates that at 20 degrees C the uptake of diphtheria toxin occurs by the normal route, whereas the uptake of modeccin occurs by a less efficient route than that dominating at 37 degrees C. The results indicate that after endocytosis diphtheria toxin rapidly enters the cytosol from early endosomes with low pH (receptosomes). Modeccin enters the cytosol much more slowly, possibly after fusion of the endocytic vesicles with another compartment.
在用白喉毒素和相关植物毒素相思豆毒素处理后的不同时间段，测定了其对非洲绿猴肾细胞（Vero细胞）蛋白质合成的抑制作用。白喉毒素的作用比相思豆毒素快得多。用抗血清以及NH4Cl、普鲁卡因和离子载体莫能菌素、羰基氰对三氟甲氧基苯腙（FCCP）和羰基氰间氯苯腙（CCCP）等试剂可保护细胞免受这两种毒素的侵害，这些试剂可提高细胞内囊泡的pH值。抗血清仅在细胞表面使毒素失活，只有在相思豆毒素处理后短时间内加入才具有保护作用。提高细胞内囊泡pH值的化合物，即使在2小时后加入仍有保护作用，这表明相思豆毒素在进入胞质溶胶之前会在囊泡内停留相当长一段时间。向细胞中加入白喉毒素后，提高细胞内囊泡pH值的化合物的保护作用仅与抗毒素大致相同。这表明内吞作用后白喉毒素迅速进入胞质溶胶。在20℃时，细胞对相思豆毒素的抵抗力比对白喉毒素更强。20℃时白喉毒素的残留毒性作用可被NH4Cl阻断，而相思豆毒素则不然。这表明在20℃时，白喉毒素通过正常途径摄取，而相思豆毒素的摄取途径效率低于37℃时占主导地位的途径。结果表明，内吞作用后，白喉毒素从低pH值的早期内体（受体体）迅速进入胞质溶胶。相思豆毒素进入胞质溶胶的速度要慢得多，可能是在内吞囊泡与另一个区室融合之后。
