The Rel family member p50 mediates cytokine-induced C-reactive protein expression by a novel mechanism
The Rel family member p50 mediates cytokine-induced C-reactive protein expression by a novel mechanism
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DOI：
10.4049/jimmunol.165.8.4592
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发表时间：
2000-10-15
影响因子：
4.4
通讯作者：
Kushner, I
中科院分区：
文献类型：
--
作者：
Cha-Molstad, H;Agrawal, A;Kushner, I
Hep 3B细胞中C反应蛋白（CRP）的转录由IL-6诱导，通过C/EBP亚型和STAT 3起作用。IL-1 β单独没有作用，但通过未知机制大大增强IL-6诱导的转录。由于IL-1 β激活NF-κ B B系统，我探索了过表达的Rel家族成员对CRP表达的影响。出乎意料的是，瞬时转染的Hep 3 B细胞中的反式激活测定显示p50过表达显著诱导CRP转录，作用于3'至-86区域。在过表达的p50存在下，IL-1 β诱导CRP表达增加3倍，对IL-6和IL-6加IL-1 β的反应比在没有p50过表达的细胞中观察到的高4倍。相反，过表达的p65消除了p50和细胞因子对CRP的诱导作用，EMSA研究表明重组p50与CRP启动子上的非共有κ B位点结合，该位点与近端C/EBP结合位点重叠。突变的p50结合位点的多聚嘧啶道抑制细胞因子的反式激活作用。当C/EBP β在IL-6存在或不存在的情况下被极大激活时，在IL-1 β刺激后18小时，在Hep 3B细胞核中发现含有P50的二聚体，而不是含有p65的二聚体。这些结果表明IL-1 β诱导含有p50的二聚体的核转位，并且p50与由IL-6和IL-1 β激活的C/EBP β相互作用以诱导CRP表达。
Transcription of C-reactive protein (CRP) in Hep 3B cells is induced by IL-6, acting through C/EBP isoforms and STAT3. IL-1 beta, which alone has no effect, greatly enhances IL-6-induced transcription by unknown mechanisms. Because IL-1 beta activates the NF-kappa B system, me explored the effects of overexpressed Rel family members on CRP expression, Unexpectedly, transactivation assays in transiently transfected Hep 3B cells showed p50 overexpression to markedly induce CRP transcription, acting in a region 3' to -86, In the presence of overexpressed p50, IL-1 beta induced a 3-fold increase in CRP expression, and responses to IL-6 and to IL-6 plus IL-1 beta were 4-fold greater than seen in cells without p50 overexpression. In contrast, overexpressed p65 abolished CRP induction by p50 and by cytokines, EMSA studies demonstrated that recombinant p50 bound to a nonconsensus kappa B site over-lapping the proximal C/EBP binding site on the CRP promoter. Mutation of a polypyrimidine tract in the p50-binding site inhibited the transactivating effect of cytokines. P50- but not p65-containing dimers were found in nuclei of Hep 3B cells 18 h after stimulation with IL-1 beta, when C/EBP beta is greatly activated, in the presence or absence of IL-6, These findings suggest that IL-1 beta induces nuclear translocation of p50-containing dimers and that p50 interacts with C/EBP beta activated by both IL-6 and IL-1 beta to induce CRP expression.