Mundschau L J, Faller D V
Division of Pediatric Hematology and Oncology, Dana Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115.
Mol Cell Biol. 1991 Jun;11(6):3148-54. doi: 10.1128/mcb.11.6.3148-3154.1991.
Several lines of evidence now exist to suggest an interaction between the platelet-derived growth factor (PDGF) growth-stimulatory signal transduction pathway and the beta interferon (IFN-beta) growth-inhibitory signal transduction pathway. The most direct examples are inhibition of PDGF-mediated gene induction and mitogenesis by IFN-beta and the effects of activators and inhibitors of the IFN-inducible double-stranded RNA-dependent eIF2 kinase on expression of PDGF-inducible genes. To further investigate the nature of this PDGF/IFN-beta interaction, we selected BALB/c-3T3 cells for resistance to growth inhibition by IFN-beta and analyzed the phenotypes of resulting clonal lines (called IRB cells) with respect to PDGF signal transduction. Although selected only for IFN resistance, the IRB cells were found to be defective for induction of growth-related genes c-fos, c-myc and JE in response to PDGF. This block to signal transduction was not due to loss or inactivation of PDGF receptors, as immunoprecipitation of PDGF receptors with antiphosphotyrosine antibodies showed them to be present at equal levels in the BALB/c-3T3 and IRB cells and to be autophosphorylated normally in response to PDGF. Furthermore, treatment with other peptide growth factors (PDGF-AA, fibroblast growth factor, and epidermal growth factor) also failed to induce c-fos, c-myc, or JE expression in IRB cells. All of these growth factors, however, were able to induce another early growth-related gene, Egr-1. The block to signaling was not due to a defect in inositol phosphate metabolism, as PDGF treatment induced normal calcium mobilization and phosphotidylinositol-3-kinase activation in these cells. Activation of protein kinase C by phorbol esters did induce c-fos, c-myc, and JE in IRB cells, indicating that signalling pathways distal to this enzyme remained intact. We have previously shown that IFN-inducible enzyme activities, including double-stranded RNA-dependent eIF2 kinase and 2',5'-oligoadenylate synthetase, are normal in IRB cells. The finding that the induction of multiple growth-related genes by several independent growth factors is inhibited in these IFN-resistant cells suggests that there is a second messenger common to both growth factor and IFN signaling pathways and that this messenger is defective in these cells.
目前有几条证据表明血小板衍生生长因子（PDGF）的生长刺激信号转导途径与β干扰素（IFN-β）的生长抑制信号转导途径之间存在相互作用。最直接的例子是IFN-β对PDGF介导的基因诱导和有丝分裂的抑制作用，以及IFN诱导的双链RNA依赖性eIF2激酶的激活剂和抑制剂对PDGF诱导基因表达的影响。为了进一步研究这种PDGF/IFN-β相互作用的本质，我们选择对IFN-β生长抑制具有抗性的BALB/c-3T3细胞，并分析所得克隆系（称为IRB细胞）在PDGF信号转导方面的表型。尽管仅选择了对IFN具有抗性的细胞，但发现IRB细胞在响应PDGF时诱导生长相关基因c-fos、c-myc和JE方面存在缺陷。这种信号转导阻滞并非由于PDGF受体的丢失或失活，因为用抗磷酸酪氨酸抗体对PDGF受体进行免疫沉淀显示，它们在BALB/c-3T3细胞和IRB细胞中的水平相等，并且在响应PDGF时能正常自磷酸化。此外，用其他肽生长因子（PDGF-AA、成纤维细胞生长因子和表皮生长因子）处理也未能在IRB细胞中诱导c-fos、c-myc或JE的表达。然而，所有这些生长因子都能够诱导另一个早期生长相关基因Egr-1。信号转导阻滞并非由于肌醇磷酸代谢缺陷，因为PDGF处理在这些细胞中诱导了正常的钙动员和磷脂酰肌醇-3-激酶激活。佛波酯激活蛋白激酶C确实在IRB细胞中诱导了c-fos、c-myc和JE，这表明该酶下游的信号通路仍然完整。我们之前已经表明，IRB细胞中IFN诱导的酶活性，包括双链RNA依赖性eIF2激酶和2',5'-寡腺苷酸合成酶，是正常的。在这些对IFN具有抗性的细胞中，几种独立生长因子对多个生长相关基因的诱导受到抑制，这一发现表明生长因子和IFN信号通路存在一个共同的第二信使，并且该信使在这些细胞中存在缺陷。
