The human cancer cell active toxin Cry41Aa from Bacillus thuringiensis acts like its insecticidal counterparts
The human cancer cell active toxin Cry41Aa from Bacillus thuringiensis acts like its insecticidal counterparts
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DOI：
10.1042/bcj20170122
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发表时间：
2017-05-15
影响因子：
4.1
通讯作者：
Crickmore, Neil
中科院分区：
文献类型：
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作者：
Krishnan, Vidisha;Domanska, Barbara;Crickmore, Neil
了解通常具有杀虫作用的苏云金芽孢杆菌 (Bt) 中的某些蛋白质毒素如何靶向人类细胞系，对于含有这些毒素的产品的风险评估以及潜在的癌症治疗都有重要意义。这种理解需要了解人类细胞活性毒素是否通过与杀虫剂相同的机制或替代机制发挥作用。 Bt Cry41Aa（也称为 Parasporin3）毒素在结构上与商业化生产的转基因抗虫植物合成的毒素相关，但值得注意的是额外的 C 端 β-三叶蓖麻毒素结构域。为了更好地了解其作用机制，我们开发了一种有效的毒素表达系统，并在可能涉及毒性机制的区域中创建了突变。删除蓖麻毒素结构域并没有显着影响该毒素针对人 HepG2 细胞系的活性，表明该区域与 Cry41Aa 的哺乳动物特异性无关。各种生化测定表明，与其他一些人类细胞活性毒素不同，Bt Cry41Aa 不会诱导细胞凋亡，但其作用机制与成孔毒素的作用机制一致。该毒素导致代谢活动迅速而显着降低。还观察到三磷酸腺苷消耗、细胞肿胀和膜损伤。据信参与杀虫 Cry 毒素受体结合的暴露环区域对于 Cry41Aa 对抗 HepG2 细胞的活性非常重要。
Understanding how certain protein toxins from the normally insecticidal bacterium Bacillus thuringiensis (Bt) target human cell lines has implications for both the risk assessment of products containing these toxins and potentially for cancer therapy. This understanding requires knowledge of whether the human cell active toxins work by the same mechanism as their insecticidal counterparts or by alternative ones. The Bt Cry41Aa (also known as Parasporin3) toxin is structurally related to the toxins synthesised by commercially produced transgenic insect-resistant plants, with the notable exception of an additional C-terminal beta-trefoil ricin domain. To better understand its mechanism of action, we developed an efficient expression system for the toxin and created mutations in regions potentially involved in the toxic mechanism. Deletion of the ricin domain did not significantly affect the activity of the toxin against the human HepG2 cell line, suggesting that this region was not responsible for the mammalian specificity of Cry41Aa. Various biochemical assays suggested that unlike some other human cell active toxins from Bt Cry41Aa did not induce apoptosis, but that its mechanism of action was consistent with that of a pore-forming toxin. The toxin induced a rapid and significant decrease in metabolic activity. Adenosine triphosphate depletion, cell swelling and membrane damage were also observed. An exposed loop region believed to be involved in receptor binding of insecticidal Cry toxins was shown to be important for the activity of Cry41Aa against HepG2 cells.