Distinct Roles for CdtA and CdtC during Intoxication by Cytolethal Distending Toxins.
Distinct Roles for CdtA and CdtC during Intoxication by Cytolethal Distending Toxins.
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DOI：
10.1371/journal.pone.0143977
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发表时间：
2015
期刊：
影响因子：
3.7
通讯作者：
Bradley KA
中科院分区：
文献类型：
--
作者：
Dixon SD;Huynh MM;Tamilselvam B;Spiegelman LM;Son SB;Eshraghi A;Blanke SR;Bradley KA
细胞致死性膨胀毒素（CDTs）是由多种革兰氏阴性病原体产生的异源三聚体蛋白外毒素。酶亚基CdtB具有DNA酶和磷脂酰肌醇3-4-5三磷酸酶活性，其诱导宿主细胞周期停滞、细胞膨胀和凋亡。为了发挥细胞周期调节和细胞毒性作用，CDTs必须从宿主细胞表面摄取并以最终导致CdtB定位于细胞核的方式在细胞内转运。然而，CDTs与宿主细胞结合并利用现有的摄取和转运途径进入细胞核的分子细节和机制知之甚少。本文报道了杜克雷嗜血杆菌和肠致病性大肠杆菌CDTs的CdtA和CdtC亚基。大肠杆菌（Ec-CDT）中的CdtB亚基足以独立地支持它们各自的CdtB亚基的中毒。CdtA支持CdtB介导的T细胞和上皮细胞的杀伤，其几乎与用全毒素观察到的一样有效。相反，CdtC支持中毒的效率取决于毒素的来源以及靶细胞类型。此外，CdtC被发现改变Ec-CDT的亚细胞运输，如通过对EGA（内体运输的抑制剂）的敏感性、与早期和晚期内体的标记物的共定位以及DNA损伤响应的动力学所确定的。最后，宿主细胞胆固醇被发现影响由Ec-CdtA介导的中毒的敏感性，揭示了胆固醇或富含胆固醇的膜结构域在由该亚基介导的中毒中的作用。总之，本文提供的数据支持CdtA和CdtC各自结合宿主细胞表面上的不同受体的模型，所述受体指导交替的细胞内摄取和/或运输途径。
Cytolethal distending toxins (CDTs) are heterotrimeric protein exotoxins produced by a diverse array of Gram-negative pathogens. The enzymatic subunit, CdtB, possesses DNase and phosphatidylinositol 3-4-5 trisphosphate phosphatase activities that induce host cell cycle arrest, cellular distension and apoptosis. To exert cyclomodulatory and cytotoxic effects CDTs must be taken up from the host cell surface and transported intracellularly in a manner that ultimately results in localization of CdtB to the nucleus. However, the molecular details and mechanism by which CDTs bind to host cells and exploit existing uptake and transport pathways to gain access to the nucleus are poorly understood. Here, we report that CdtA and CdtC subunits of CDTs derived from Haemophilus ducreyi (Hd-CDT) and enteropathogenic E. coli (Ec-CDT) are independently sufficient to support intoxication by their respective CdtB subunits. CdtA supported CdtB-mediated killing of T-cells and epithelial cells that was nearly as efficient as that observed with holotoxin. In contrast, the efficiency by which CdtC supported intoxication was dependent on the source of the toxin as well as the target cell type. Further, CdtC was found to alter the subcellular trafficking of Ec-CDT as determined by sensitivity to EGA, an inhibitor of endosomal trafficking, colocalization with markers of early and late endosomes, and the kinetics of DNA damage response. Finally, host cellular cholesterol was found to influence sensitivity to intoxication mediated by Ec-CdtA, revealing a role for cholesterol or cholesterol-rich membrane domains in intoxication mediated by this subunit. In summary, data presented here support a model in which CdtA and CdtC each bind distinct receptors on host cell surfaces that direct alternate intracellular uptake and/or trafficking pathways.