Gordon V M, Nelson K L, Buckley J T, Stevens V L, Tweten R K, Elwood P C, Leppla S H
Oral Infection and Immunity Branch, NIDCR, National Institutes of Health, Bethesda, Maryland 20892, USA.
J Biol Chem. 1999 Sep 17;274(38):27274-80. doi: 10.1074/jbc.274.38.27274.
The alpha toxin produced by Clostridium septicum is a channel-forming protein that is an important contributor to the virulence of the organism. Chinese hamster ovary (CHO) cells are sensitive to low concentrations of the toxin, indicating that they contain toxin receptors. Using retroviral mutagenesis, a mutant CHO line (BAG15) was generated that is resistant to alpha toxin. FACS analysis showed that the mutant cells have lost the ability to bind the toxin, indicating that they lack an alpha toxin receptor. The mutant cells are also resistant to aerolysin, a channel-forming protein secreted by Aeromonas spp., which is structurally and functionally related to alpha toxin and which is known to bind to glycosylphosphatidylinositol (GPI)-anchored proteins, such as Thy-1. We obtained evidence that the BAG15 cells lack N-acetylglucosaminyl-phosphatidylinositol deacetylase-L, needed for the second step in GPI anchor biosynthesis. Several lymphocyte cell lines lacking GPI-anchored proteins were also shown to be less sensitive to alpha toxin. On the other hand, the sensitivity of CHO cells to alpha toxin was increased when the cells were transfected with the GPI-anchored folate receptor. We conclude that alpha toxin, like aerolysin, binds to GPI-anchored protein receptors. Evidence is also presented that the two toxins bind to different subsets of GPI-anchored proteins.
败血梭菌产生的α毒素是一种形成通道的蛋白质，是该生物体毒力的重要促成因素。中国仓鼠卵巢（CHO）细胞对低浓度毒素敏感，这表明它们含有毒素受体。利用逆转录病毒诱变技术，构建了一个对α毒素具有抗性的CHO突变细胞系（BAG15）。荧光激活细胞分选分析表明，突变细胞失去了结合毒素的能力，这表明它们缺乏α毒素受体。这些突变细胞对气单胞菌属分泌的气溶素也具有抗性，气溶素是一种形成通道的蛋白质，在结构和功能上与α毒素相关，已知它能与糖基磷脂酰肌醇（GPI）锚定蛋白如Thy-1结合。我们获得的证据表明，BAG15细胞缺乏GPI锚定生物合成第二步所需的N-乙酰葡糖胺基磷脂酰肌醇脱乙酰酶-L。几个缺乏GPI锚定蛋白的淋巴细胞系对α毒素也表现出较低的敏感性。另一方面，当CHO细胞转染了GPI锚定的叶酸受体后，它们对α毒素的敏感性增加。我们得出结论，α毒素与气溶素一样，能与GPI锚定蛋白受体结合。同时也有证据表明这两种毒素与不同亚群的GPI锚定蛋白结合。
