Internalization of NK cells into tumor cells requires ezrin and leads to programmed cell-in-cell death
Internalization of NK cells into tumor cells requires ezrin and leads to programmed cell-in-cell death
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NK 细胞内化为肿瘤细胞需要埃兹蛋白并导致细胞内程序性死亡
DOI：
10.1038/cr.2009.114
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发表时间：
2009-12-01
期刊：
影响因子：
44.1
通讯作者：
Yao, Xuebiao
中科院分区：
文献类型：
--
作者：
Wang, Shan;Guo, Zhen;Yao, Xuebiao
细胞毒性淋巴细胞在协调免疫反应和消除缺陷细胞方面起着关键作用。我们先前已经报道，自然杀伤(NK)细胞进入靶肿瘤细胞，导致靶细胞死亡或在肿瘤细胞内自毁。然而，关于NK细胞内化后的命运以及异型细胞间过程是否与最近被称为齿状突的同型细胞内事件不同，目前仍不清楚。在这里，我们展示了NK细胞经历了一个细胞内的细胞过程，最终导致肿瘤细胞内的凋亡，并揭示了内化过程需要肌动蛋白细胞骨架调节因子Ezrin。为了可视化NK细胞如何进入肿瘤细胞，我们进行了NK细胞内化到肿瘤细胞的实时双色成像分析。令人惊讶的是，大多数NK细胞在进入肿瘤细胞后都会发生程序性死亡，这与在细胞内同型细胞过程中观察到的突起明显不同。内化的NK细胞发生明显的细胞死亡，表现为caspase3的激活和DNA片段化。此外，NK细胞内化后的死亡被caspase抑制剂Z-VAD-FMK减弱，证实了凋亡是肿瘤细胞内NK细胞的死亡方式。为了确定NK细胞进入肿瘤细胞所必需的蛋白因子，我们进行了基于siRNA的基因敲除分析，发现Ezrin在NK细胞内化中起着关键作用。重要的是，PKA介导的Ezrin磷酸化促进了NK细胞的内化过程。我们的发现提示了一种新的调控机制，通过该机制，Ezrin控制NK细胞内化到肿瘤细胞。
Cytotoxic lymphocytes are key players in the orchestration of immune response and elimination of defective cells. We have previously reported that natural killer (NK) cells enter target tumor cells, leading to either target cell death or self-destruction within tumor cells. However, it has remained elusive as to the fate of NK cells after internalization and whether the heterotypic cell-in-cell process is different from that of the homotypic cell-in-cell event recently named entosis. Here, we show that NK cells undergo a cell-in-cell process with the ultimate fate of apoptosis within tumor cells and reveal that the internalization process requires the actin cytoskeletal regulator, ezrin. To visualize how NK cells enter into tumor cells, we carried out real-time dual color imaging analyses of NK cell internalization into tumor cells. Surprisingly, most NK cells commit to programmed cell death after their entry into tumor cells, which is distinctively different from entosis observed in the homotypic cell-in-cell process. The apoptotic cell death of the internalized NK cells was evident by activation of caspase 3 and DNA fragmentation. Furthermore, NK cell death after internalization is attenuated by the caspase inhibitor, Z-VAD-FMK, confirming apoptosis as the mode of NK cell death within tumor cells. To determine protein factors essential for the entry of NK cells into tumor cells, we carried out siRNA-based knockdown analysis and discovered a critical role of ezrin in NK cell internalization. Importantly, PKA-mediated phosphorylation of ezrin promotes the NK cell internalization process. Our findings suggest a novel regulatory mechanism by which ezrin governs NK cell internalization into tumor cells.