Induction of cell cycle arrest in lymphocytes by Actinobacillus actinomycetemcomitans cytolethal distending toxin requires three Subunits for maximum activity
Induction of cell cycle arrest in lymphocytes by Actinobacillus actinomycetemcomitans cytolethal distending toxin requires three Subunits for maximum activity
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DOI：
10.4049/jimmunol.174.4.2228
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发表时间：
2005-02-15
影响因子：
4.4
通讯作者：
Demuth, DR
中科院分区：
文献类型：
--
作者：
Shenker, BJ;Besack, D;Demuth, DR
我们以前已经表明，放线共生放线杆菌产生的免疫抑制因子编码的细胞致死膨胀毒素（cdt）B基因。在这项研究中，我们使用rCdt肽来研究每个亚基对毒素活性的贡献。如前所述，CdtB是唯一能够自身诱导细胞周期停滞的Cdt亚基。虽然CdtA和CdtC不单独表现出活性，但每个亚基都能够显著增强CdtB在Jurkat细胞中诱导G1停滞的能力;这些作用依赖于蛋白质浓度。此外，CdtA和CdtC两者的组合添加使CdtB的ED 50增加> 7000倍。在另一系列实验中，我们证明了三种Cdt肽能够在细胞表面形成功能性毒素单位。然而，这些相互作用首先需要CdtA和CdtC亚基之间形成复合物，表明这些肽是细胞和全毒素之间相互作用所必需的。这一结论得到了实验的进一步支持，在这些实验中，Jurkat细胞和正常人淋巴细胞通过预先暴露于CdtA和CdtC而免受Cdt全毒素诱导的G1阻滞。最后，我们已经使用光学生物传感器技术来显示CdtA和CdtC彼此具有强亲和力（10（-7）M）。此外，虽然CdtB不能单独与CdtA或CdtC结合，但它能够与CdtA/CdtC形成稳定的复合物。我们的研究结果与Cdt全毒素的功能和结构的影响进行了讨论。
We have previously shown that Actinobacillus actinomycetemcomitans produces an immunosuppressive factor encoded by the cytolethal distending toxin (cdt)B gene. In this study, we used rCdt peptides to study the contribution of each subunit to toxin activity. As previously reported, CdtB is the only Cdt subunit that is capable of inducing cell cycle arrest by itself. Although CdtA and CdtC do not exhibit activity alone, each subunit is able to significantly enhance the ability of CdtB to induce G, arrest in Jurkat cells; these effects were dependent upon protein concentration. Moreover, the combined addition of both CdtA and CdtC increased the ED50 for CdtB > 7000-fold. In another series of experiments, we demonstrate that the three Cdt peptides are able to form a functional toxin unit on the cell surface. However, these interactions first require that a complex forms between the CdtA and CdtC subunits, indicating that these peptides are required for interaction between the cell and the holotoxin. This conclusion is further supported by experiments in which both Jurkat cells and normal human lymphocytes were protected from Cdt holotoxin-induced G, arrest by pre-exposure to CdtA and CdtC. Finally, we have used optical biosensor technology to show that CdtA and CdtC have a strong affinity for one another (10(-7) M). Furthermore, although CdtB is unable to bind to either CdtA or CdtC alone, it is capable of forming a stable complex with CdtA/CdtC. The implications of our results with respect to the function and structure of the Cdt holotoxin are discussed.