Descoteaux A, Matlashewski G
Institute of Parasitology, McGill University, Macdonald College, Ste-Anne de Bellevue, Québec, Canada.
J Immunol. 1990 Aug 1;145(3):846-53.
The effect of murine rTNF-alpha on c-fos and TNF mRNA accumulation and protein synthesis was investigated in bone marrow-derived macrophages to examine the mechanism(s) by which TNF modulates macrophage activity. A rapid and transient expression of the c-fos gene was induced by murine rTNF. This was blocked by 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine, an inhibitor of protein kinase C, suggesting that the murine rTNF stimulated a protein kinase C-dependent signal transduction pathway. Although LPS induced the accumulation of one TNF mRNA species, murine rTNF induced the synthesis of two distinct TNF mRNA species. Both LPS- and murine rTNF-induced TNF mRNA accumulation was equally enhanced by pretreatment with mouse rIFN-gamma. In contrast, cycloheximide pretreatment had little effect on murine rTNF-induced TNF mRNA accumulation, whereas this treatment increased LPS-induced TNF mRNA by sevenfold. These results argue that TNF mRNA accumulation can be modulated in macrophages by distinct mechanisms. As assessed by Western blot and immunoprecipitation analysis, LPS stimulated the synthesis of both cell-associated and secreted forms of TNF protein. In comparison, newly synthesized TNF protein was not detected when macrophages were treated with murine rTNF alone or in combination with murine rIFN-gamma. This demonstrates that although murine rTNF stimulated the synthesis of two distinct TNF mRNA species, additional signal(s) are necessary for their translation into protein and that such signals are present after LPS stimulation.
为研究肿瘤坏死因子（TNF）调节巨噬细胞活性的机制，我们在骨髓来源的巨噬细胞中研究了小鼠重组肿瘤坏死因子-α（rTNF-α）对c-fos和TNF信使核糖核酸（mRNA）积累及蛋白质合成的影响。小鼠rTNF诱导了c-fos基因的快速瞬时表达。这被蛋白激酶C抑制剂1-（5-异喹啉磺酰基）-2-甲基哌嗪阻断，提示小鼠rTNF刺激了一条依赖蛋白激酶C的信号转导途径。虽然脂多糖（LPS）诱导了一种TNF mRNA种类的积累，但小鼠rTNF诱导了两种不同的TNF mRNA种类的合成。用小鼠重组干扰素-γ（rIFN-γ）预处理可同等程度增强LPS和小鼠rTNF诱导的TNF mRNA积累。相比之下，放线菌酮预处理对小鼠rTNF诱导的TNF mRNA积累影响不大，而该处理使LPS诱导的TNF mRNA增加了7倍。这些结果表明，TNF mRNA积累在巨噬细胞中可通过不同机制进行调节。通过蛋白质印迹和免疫沉淀分析评估，LPS刺激了细胞相关和分泌形式的TNF蛋白的合成。相比之下，当巨噬细胞单独用小鼠rTNF或与小鼠rIFN-γ联合处理时，未检测到新合成的TNF蛋白。这表明，虽然小鼠rTNF刺激了两种不同的TNF mRNA种类的合成，但它们翻译成蛋白质还需要其他信号，且这种信号在LPS刺激后存在。
