Mechanism of internalization of the cytolethal distending toxin of Actinobacillus actinomycetemcomitans
Mechanism of internalization of the cytolethal distending toxin of Actinobacillus actinomycetemcomitans
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DOI：
10.1099/mic.0.27671-0
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发表时间：
2005-05-01
期刊：
影响因子：
2.8
通讯作者：
Henderson, B
中科院分区：
文献类型：
--
作者：
Akifusa, S;Heywood, W;Henderson, B
CDT由cdtA、cdtB和cdtC三个基因编码，目前被认为具有越来越多的生物学作用，包括抑制细胞周期进程、促进细胞凋亡和刺激细胞因子分泌。看来CDT的内化是必不可少的，至少对于细胞周期阻断是如此。利用从牙周病细菌放线菌中纯化的重组CDT蛋白，作者研究了哪种毒素蛋白组合产生细胞周期抑制，哪种结合和/或进入宿主细胞。未发现CdtB与HEp-2人上皮细胞结合的证据。相反，CdtA和CdtC都与这些细胞结合。细胞周期阻滞的诱导需要细胞同时暴露于CdtB和CdtC。细胞预暴露于CdtC；仅10分钟，然后去除游离CdtC并添加外源性CdtB，导致细胞周期进展受到抑制，这表明CdtB可以与细胞表面的CdtC结合。利用各种方法跟踪CDT蛋白的内化，我们得出结论，CdtC在细胞表面结合CdtB，并通过可被莫能菌素和brefeldin a阻断的内体途径将其作为复合物运输到细胞中。
Cytolethal distending toxin (CDT), which is encoded by three genes, cdtA, cdtB and cdtC, is now recognized to have a growing list of biological actions, including inhibition of cell cycle progression, promotion of apoptosis and stimulation of cytokine secretion. It appears that internalization of CDT is essential, at least for cell cycle blockade. Using purified recombinant CDT proteins from the periodontopathic bacterium Actinobacillus actinomycetemcomitans, the authors investigated which combination of toxin proteins produce cell cycle inhibition and which bound and/or entered into host cells. No evidence was found that CdtB bound to HEp-2 human epithelial cells. In contrast, both CdtA and CdtC bound to these cells. Induction of cell cycle arrest required that cells be exposed to both CdtB and CdtC. Pre-exposure of cells to CdtC; for as little as 10 min, followed by removal of the free CdtC and addition of exogenous CdtB, resulted in the inhibition of cell cycle progression, suggesting that CdtB could bind to cell-surface-located CdtC. Using various methods to follow internalization of the CDT proteins it was concluded that CdtC acts to bind CdtB at the cell surface and transports it into the cell as a complex via an endosomal pathway blockable by monensin and brefeldin A.