Role of the ATM-checkpoint kinase 2 pathway in CDT-mediated apoptosis of gingival epithelial cells.
Role of the ATM-checkpoint kinase 2 pathway in CDT-mediated apoptosis of gingival epithelial cells.
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DOI：
10.1371/journal.pone.0011714
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发表时间：
2010-07-23
期刊：
影响因子：
3.7
通讯作者：
Handfield M
中科院分区：
文献类型：
--
作者：
Alaoui-El-Azher M;Mans JJ;Baker HV;Chen C;Progulske-Fox A;Lamont RJ;Handfield M
口腔病原菌伴放线杆菌的细胞致死性膨胀毒素（CDT）可诱导多种细胞类型的细胞周期阻滞和凋亡。Western分析，药理学抑制和siRNA沉默在人永生化牙龈角质形成细胞（HIGK）中进行，以剖析共济失调毛细血管扩张突变（ATM）通路在CDT触发的信号转导步骤中的功能作用。感染的HIGK与时间依赖性诱导细胞质组蛋白相关的DNA片段。然而，在没有CDT的情况下，感染的HIGK发生可逆的DNA链断裂，但不发生细胞凋亡，而半胱天冬酶3活性、p21水平和HIGK活力不受影响。与野生型感染的细胞相比，在CDT突变体感染的HIGK中胱天蛋白酶9活性减弱。ATM下游效应子蛋白激酶检查点激酶2（Chk 2）的药理学抑制和siRNA沉默显著影响了CDT介导的细胞凋亡。总之，这些发现提供了关于ATM-Chk 2途径响应于A.放线菌共生体在口腔上皮细胞中的作用，最终导致细胞凋亡。我们进一步提出存在一种与CDT不同的未知因子，该因子与不引发口腔上皮细胞末端凋亡的可逆DNA片段化有关。该模型可能解释了关于A.伴放线菌
The cytolethal distending toxin (CDT) of the oral pathogen Aggregatibacter actinomycetemcomitans induces cell cycle arrest and apoptosis in various cell types. Western analysis, pharmacological inhibition and siRNA silencing were performed in human immortalized gingival keratinocytes (HIGK) to dissect the functional role of the ataxia telangiectasia mutated (ATM) pathway in the signal transduction steps triggered by the CDT. Infection of HIGK was associated with a time-dependent induction of cytoplasmic histone-associated DNA fragmentation. However, in the absence of CDT, infected HIGK underwent reversible DNA strand breaks but not apoptosis, while caspase 3 activity, p21 levels, and HIGK viability were unaffected. Caspase 9 activity was attenuated in the CDT mutant-infected HIGK compared to wild-type infected cells. Pharmacological inhibition and siRNA-silencing of the ATM downstream effector, the protein kinase checkpoint kinase 2 (Chk2), significantly impacted CDT-mediated apoptosis. Together, these findings provide insight on the specificity of the ATM-Chk2 pathway in response to the CDT of A. actinomycetemcomitans in oral epithelial cells, which ultimately leads to apoptosis. We further propose the existence of an unidentified factor that is distinct from the CDT, and involved with a reversible DNA fragmentation that does not trigger terminal apoptosis in oral epithelial cells. This model potentially explains conflicting reports on the biological activity of the A. actinomycetemcomitans CDT.
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