Yu Mingxia, Shi Wenfang, Zhang Jian, Niu Lin, Chen Qizheng, Yan Dan, Liu Tao, Jing Wang, Jiang Xiaodan, Wei Feng, Yin Bingjiao, Zhang Wenjie, Li Qingfen, Li Zhuoya
Department of Immunology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, PR China.
Eur J Cell Biol. 2009 Mar;88(3):181-91. doi: 10.1016/j.ejcb.2008.09.001. Epub 2008 Oct 23.
Membrane tumor necrosis factor-alpha (mTNF-alpha) serves as a receptor transducing signals into mTNF-alpha-bearing cells. Among human peripheral blood mononuclear cells, natural killer (NK) cells have been reported to be the only cell type constitutively expressing mTNF-alpha, which is involved in the cytotoxicity of resting NK cells. Using an IL-2-dependent human NK cell line, NK92, which constitutively expresses mTNF-alpha, we examined the effect of reverse signaling via mTNF-alpha on cellular activities. When the cells were prestimulated with soluble TNFR1 (sTNFR1) which activated mTNF-alpha-mediated reverse signaling, the cytotoxicity of NK92 cells was significantly increased. Further investigation demonstrated that prestimulation with sTNFR1 augmented exocytosis and mRNA transcription of two cytotoxic molecules, perforin and granzyme B, which could serve as underlying molecular mechanisms by which mTNF-alpha-mediated reverse signaling promoted cytotoxicity of NK cells toward K562 cells. On the other hand, pretreatment of NK92 with sTNFR1 boosted the expression of FasL and TNF-alpha, including both the secretory and membrane forms. These molecules also contribute to the NK-mediated cytotoxicity, although K562 cells are Fas-negative and sTNF-alpha-resistant. Interestingly, the mTNF-alpha reverse signaling was found to act synergistically with IL-2 on NK-mediated cytotoxicity. This synergy markedly promoted the production of secretory as well as membrane cytotoxic molecules which may be responsible for the enhanced NK92-mediated cytotoxicity. Our observations suggest that, via reverse signaling, constitutively expressed mTNF-alpha may sensitize NK cells to activating stimuli, such as IL-2, resulting in increased NK-mediated cytotoxicity through promoting the production of multiple cytotoxic effector molecules.
膜肿瘤坏死因子-α（mTNF-α）作为一种受体，将信号转导至表达mTNF-α的细胞中。在人类外周血单核细胞中，据报道自然杀伤（NK）细胞是唯一组成性表达mTNF-α的细胞类型，mTNF-α参与静息NK细胞的细胞毒性作用。我们使用组成性表达mTNF-α的IL-2依赖型人NK细胞系NK92，研究了通过mTNF-α的反向信号传导对细胞活性的影响。当用可溶性TNFR1（sTNFR1）预刺激细胞以激活mTNF-α介导的反向信号传导时，NK92细胞的细胞毒性显著增加。进一步研究表明，用sTNFR1预刺激可增强两种细胞毒性分子穿孔素和颗粒酶B的胞吐作用和mRNA转录，这可能是mTNF-α介导的反向信号传导促进NK细胞对K562细胞细胞毒性的潜在分子机制。另一方面，用sTNFR1预处理NK92可提高FasL和TNF-α的表达，包括分泌型和膜型。这些分子也有助于NK介导的细胞毒性，尽管K562细胞是Fas阴性且对sTNF-α耐药。有趣的是，发现mTNF-α反向信号传导与IL-2在NK介导的细胞毒性上具有协同作用。这种协同作用显著促进了分泌型和膜型细胞毒性分子的产生，这可能是NK92介导的细胞毒性增强的原因。我们的观察结果表明，通过反向信号传导，组成性表达的mTNF-α可能使NK细胞对诸如IL-2等激活刺激敏感，从而通过促进多种细胞毒性效应分子的产生增加NK介导的细胞毒性。
