The human papillomavirus type 16 E5 protein impairs TRAIL- and FasL-mediated apoptosis in HaCaT cells by different mechanisms
The human papillomavirus type 16 E5 protein impairs TRAIL- and FasL-mediated apoptosis in HaCaT cells by different mechanisms
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DOI：
10.1128/jvi.76.23.12162-12172.2002
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发表时间：
2002-12-01
影响因子：
5.4
通讯作者：
Alonso, A
中科院分区：
文献类型：
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作者：
Kabsch, K;Alonso, A
通过使用稳定转染 E5 (HaCaT/E5) 或空载体 (HaCaT/pMSG) 的多克隆 HaCaT 细胞系作为参考，研究人乳头瘤病毒 16 型 (HPV-16) E5 蛋白对细胞凋亡的影响。细胞凋亡由 Fas 配体 (FasL) 或肿瘤坏死因子相关凋亡诱导配体 (TRAIL) 触发，并通过检测 procaspase-8 和 procaspase-3 及其底物聚 (ADP-核糖) 聚合酶 (PARP) 的裂解来监测细胞凋亡。与 HaCaT/pMSG 对照细胞相反，我们发现在表达 E5 的角质形成细胞中，两种配体中任一种诱导的细胞凋亡均受到强烈抑制。 HaCaT/E5 细胞中 Fas 表达减少约两倍，这可能是保护细胞免受 FasL 诱导的细胞凋亡的机制的一部分。对于 TRAIL 受体，没有观察到这种下调。在这里，E5 损害了 TRAIL 触发的死亡诱导信号复合物的形成。显然，E5 采用不同的机制来抑制死亡受体信号传导。这种效应不仅限于 HaCaT/E5 细胞，因为我们发现小鼠成纤维细胞系 A31-E5 也受到保护，免受 TRAIL 诱导的细胞凋亡，但缺乏 E5 的对照细胞 A31-Neo 则不然。然而，在 FasL 诱导的细胞凋亡中没有观察到这种保护作用。据推测，人类致病性 HPV-16 E5 采用的一些抗凋亡机制是细胞类型特异性的。我们认为，抑制人角质形成细胞中配体介导的细胞凋亡是 HPV-16 E5 蛋白的主要功能，它需要在病毒感染的早期阶段预防细胞凋亡。
The effect of the human papillomavirus type 16 (HPV-16) E5 protein on apoptosis was investigated by using the polyclonal HaCaT-cell lines stably transfected either with E5 (HaCaT/E5) or the empty vector (HaCaT/pMSG) as reference. Apoptosis was triggered either by Fas ligand (FasL) or by tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and was monitored by detection of cleavage of procaspase-8 and procaspase-3, as well as their substrate poly(ADP-ribose) polymerase (PARP). In contrast to the HaCaT/pMSG control cells we found that apoptosis induced by either of the two ligands is strongly suppressed in the E5-expressing keratinocytes. Fas expression is reduced by about a factor of two in HaCaT/E5 cells, which could be part of the mechanisms that protect the cells from FasL-induced apoptosis. For the TRAIL receptors, no such downregulation was observed. Here, E5 impairs the formation of the death-inducing signaling complex triggered by TRAIL. Apparently, E5 employs different mechanisms to inhibit death receptor signaling. This effect is not restricted to HaCaT/E5 cells since we found that the mouse fibroblast cell line A31-E5 is protected from TRAIL-induced apoptosis, as well but not the E5-lacking control cells A31-Neo. However, no such protection was observed upon FasL-induced apoptosis. Presumably, some of the antiapoptotic mechanisms employed by E5 of the human pathogenic HPV-16 are cell type specific. We propose that inhibition of ligand-mediated apoptosis in human keratinocytes is a primary function of the HPV-16 E5 protein needed to prevent apoptosis at early stages of viral infection.