Hannigan G, Williams B R
EMBO J. 1986 Jul;5(7):1607-13. doi: 10.1002/j.1460-2075.1986.tb04403.x.
We show that human glioblastoma cells, moving from exponential growth into a state of density-dependent growth arrest, demonstrate a 7-fold drop in the total number of alpha-IFN-receptors expressed per cell. This loss of receptor activity was not seen when cells were grown in the presence of anti-alpha-IFN-monoclonal antibody. The active binding sites expressed on the arrested cell population were of reduced affinity for IFN, relative to the high-affinity sites expressed on the growing cells, resulting in a 3-fold lower initial rate of IFN-binding to the arrested cells. We exploited this difference to investigate the relationship between IFN receptor binding and induced gene transcription. As determined by nuclear run-off assays, the transcriptional response of both the gene family 1-8 and 2-5A synthetase to IFN treatment also showed a 3-fold reduction in density-arrested cells. Longer-term (0-8 h) induction and down-regulation of gene transcription in IFN-treated cells closely followed the binding to, and down-regulation of, cell surface-localized IFN receptors. Furthermore, inhibition of the intracellular breakdown of IFN did not affect transcriptional responses to IFN. Thus transcription of these IFN-induced genes is closely linked to surface receptor occupancy and is most likely mediated by transmembrane signals alone.
我们发现，人类胶质母细胞瘤细胞从指数生长期进入密度依赖性生长停滞状态时，每个细胞表达的α-干扰素受体总数下降了7倍。当细胞在抗α-干扰素单克隆抗体存在的情况下生长时，未观察到受体活性的这种丧失。相对于生长细胞上表达的高亲和力位点，停滞细胞群体上表达的活性结合位点对干扰素的亲和力降低，导致干扰素与停滞细胞结合的初始速率降低3倍。我们利用这种差异来研究干扰素受体结合与诱导基因转录之间的关系。通过核转录分析确定，基因家族1-8和2-5A合成酶对干扰素治疗的转录反应在密度停滞细胞中也降低了3倍。在干扰素处理的细胞中，基因转录的长期（0-8小时）诱导和下调与细胞表面定位的干扰素受体的结合和下调密切相关。此外，抑制干扰素的细胞内分解并不影响对干扰素的转录反应。因此，这些干扰素诱导基因的转录与表面受体占据密切相关，最有可能仅由跨膜信号介导。
