Weiss T, Grell M, Hessabi B, Bourteele S, Müller G, Scheurich P, Wajant H
Institute of Cell Biology and Immunology, University of Stuttgart, Germany.
J Immunol. 1997 Mar 1;158(5):2398-404.
TNFR p60 (TNFR60) is the main mediator of TNF-induced apoptosis, although in some cells TNFR80 is also involved. TNFR80-dependent induction or enhancement of cytotoxicity has been explained by intracellular signaling, "ligand passing," or induction of endogenous TNF. Using HeLa transfectants expressing wild-type TNFR80 and deletion mutants derived from them, we have investigated the mechanism of TNFR80-mediated cytotoxicity. TNFR80 induces no cytotoxicity on its own, but is functional in these transfectants, as selective stimulation activates nuclear factor-kappaB (NF-kappaB) and induces NF-kappaB-dependent cellular responses (IL-6 and manganese superoxide dismutase). TNFR60-induced cytotoxicity, however, is enhanced about 1000-fold by costimulation of TNFR80, whereas only additive responses are observed with regard to NF-kappaB-dependent responses. Ligand passing is not critically involved, because a similar potentiation of TNFR60-mediated cytotoxicity was observed when agonistic Abs were used for stimulation of both receptors. In addition, in HeLa cells overexpressing a truncated form of TNFR80 lacking the cytoplasmic domain, no TNFR80-dependent potentiation of TNFR60-mediated cytotoxicity was detectable, emphasizing that intracellular signaling of TNFR80 is required for synergistic activity. The involvement of endogenously produced TNF can be ruled out by the use of TNF-neutralizing Abs. The ability of TNFR80 to cooperate with TNFR60 could be mapped to the binding site for the TNF receptor-associated factor-2. These results are in agreement with a differential cooperation of both TNFR; an additive effect is obtained in those responses that are initiated by both receptors via identical pathways, i.e., activation of NF-kappaB, whereas induction of cytotoxicity is most likely mediated by distinct signaling pathways, allowing positive cooperativity.
肿瘤坏死因子受体p60（TNFR60）是肿瘤坏死因子（TNF）诱导细胞凋亡的主要介质，不过在某些细胞中，TNFR80也参与其中。TNFR80依赖性细胞毒性的诱导或增强已通过细胞内信号传导、“配体传递”或内源性TNF的诱导来解释。利用表达野生型TNFR80及其缺失突变体的HeLa转染细胞，我们研究了TNFR80介导细胞毒性的机制。TNFR80自身不诱导细胞毒性，但在这些转染细胞中具有功能，因为选择性刺激可激活核因子-κB（NF-κB）并诱导NF-κB依赖性细胞反应（白细胞介素-6和锰超氧化物歧化酶）。然而，通过TNFR80的共刺激，TNFR60诱导的细胞毒性增强了约1000倍，而对于NF-κB依赖性反应仅观察到相加效应。配体传递并非关键因素，因为当使用激动性抗体刺激两种受体时，观察到了类似的TNFR60介导的细胞毒性增强。此外，在过表达缺乏细胞质结构域的截短形式TNFR80的HeLa细胞中，未检测到TNFR80依赖性的TNFR60介导的细胞毒性增强，这强调了TNFR80的细胞内信号传导对于协同活性是必需的。使用TNF中和抗体可以排除内源性产生的TNF的参与。TNFR80与TNFR60协同作用的能力可定位到TNF受体相关因子-2的结合位点。这些结果与两种TNFR的差异协同作用一致；在两种受体通过相同途径启动的反应中，即NF-κB的激活，获得相加效应，而细胞毒性的诱导很可能由不同的信号传导途径介导，从而允许正协同作用。
