Qu Xiaoling, Qing Liuting
Institute of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, P.R. China.
J Biochem Mol Biol. 2004 Jul 31;37(4):445-53. doi: 10.5483/bmbrep.2004.37.4.445.
We identified apoptosis as being a significant mechanism of toxicity following the exposure of HeLa cell cultures to abrin holotoxin, which is in addition to its inhibition of protein biosynthesis by N-glycosidase activity. The treatment of HeLa cell cultures with abrin resulted in apoptotic cell death, as characterized by morphological and biochemical changes, i.e., cell shrinkage, internucleosomal DNA fragmentation, the occurrence of hypodiploid DNA, chromatin condensation, nuclear breakdown, DNA single strand breaks by TUNEL assay, and phosphatidylserine (PS) externalization. This apoptotic cell death was accompanied by caspase-9 and caspase-3 activation, as indicated by the cleavage of caspase substrates, which was preceded by mitochondrial cytochrome c release. The broad-spectrum caspase inhibitor, benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (zVADfmk), prevented abrin-triggered caspase activation and partially abolished apoptotic cell death, but did not affect mitochondrial cytochrome c release. These results suggest that the release of mitochondrial cytochrome c, and the sequential caspase-9 and caspase-3 activations are important events in the signal transduction pathway of abrin-induced apoptotic cell death in the HeLa cell line.
我们发现，将HeLa细胞培养物暴露于相思子毒素全毒素后，凋亡是一种重要的毒性机制，此外它还通过N-糖苷酶活性抑制蛋白质生物合成。用相思子毒素处理HeLa细胞培养物会导致凋亡性细胞死亡，其特征为形态学和生化变化，即细胞皱缩、核小体间DNA断裂、亚二倍体DNA出现、染色质凝聚、核破裂、通过TUNEL检测法检测到DNA单链断裂以及磷脂酰丝氨酸（PS）外化。这种凋亡性细胞死亡伴随着caspase-9和caspase-3的激活，这通过caspase底物的裂解得以表明，而在此之前线粒体细胞色素c会释放。广谱caspase抑制剂苄氧羰基-Val-Ala-Asp-氟甲基酮（zVADfmk）可阻止相思子毒素引发的caspase激活，并部分消除凋亡性细胞死亡，但不影响线粒体细胞色素c的释放。这些结果表明，线粒体细胞色素c的释放以及caspase-9和caspase-3的依次激活是HeLa细胞系中相思子毒素诱导的凋亡性细胞死亡信号转导途径中的重要事件。
