Raft-targeting and oligomerization of parasporin-2, a Bacillus thuringiensis crystal protein with anti-tumour activity
Raft-targeting and oligomerization of parasporin-2, a Bacillus thuringiensis crystal protein with anti-tumour activity
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DOI：
10.1093/jb/mvm220
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发表时间：
2008-02-01
影响因子：
2.7
通讯作者：
Kitada, Sakae
中科院分区：
文献类型：
--
作者：
Abe, Yuichi;Shimada, Hiroyasu;Kitada, Sakae
副孢素-2是一种新发现的苏云金芽孢杆菌晶体毒素，对人肝癌和结肠癌细胞具有很强的杀伤活性。与其它杀虫剂B相似。苏云金杆菌晶体毒素parasporin-2具有靶向特异性并破坏细胞膜。然而，parasporin-2对细胞膜的作用方式仍然未知。在这里，我们表明，这种抗肿瘤晶体毒素的目标脂筏和组装成低聚复合物的膜中的人肝细胞癌（HepG 2）细胞。在与HepG 2细胞孵育后，外周膜结合的毒素（其在低密度抗洗涤剂膜级分中回收，即具有脂筏）转化为热稳定的抗SDS膜包埋的寡聚体（类似于200 kDa）。毒素寡聚化依赖于温度并与细胞裂解偶联。毒素寡聚化也发生在无细胞膜系统中，并且是与膜蛋白、脂质双层和胆固醇结合所需的。这些结果表明，parasporin-2是一种寡聚和孔形成毒素，积累在脂筏。
Parasporin-2 is a newly classified Bacillus thuringiensis crystal toxin with strong cytocidal activities toward human liver and colon cancer cells. Similar to other insecticidal B. thuringiensis crystal toxins, parasporin-2 shows target specificity and damages the cellular membrane. However, the mode of parasporin-2 actions toward the cell membrane remains unknown. Here, we show that this anti-tumour crystal toxin targets lipid rafts and assembles into oligomeric complexes in the membrane of human hepatocyte cancer (HepG2) cells. Upon incubation with HepG2 cells, peripheral membrane-bound toxins, which were recovered in a low-density detergent-resistant membrane fraction, i.e. with lipid rafts, were transformed into heat-stable SDS-resistant membrane-embedded oligomers (similar to 200 kDa). The toxin oligomerization was dependent on temperature and coupled with cell lysis. The toxin oligomerization also occurred in a cell-free membrane system and was required for binding to membrane proteins, the lipid bilayer and cholesterols. These results indicate that parasporin-2 is an oligomerizing and pore-forming toxin that accumulates in lipid rafts.