Superinduction of CYP1A1 gene expression -: Regulation of 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced degradation of Ah receptor by cycloheximide
Superinduction of CYP1A1 gene expression -: Regulation of 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced degradation of Ah receptor by cycloheximide
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DOI：
10.1074/jbc.275.17.12676
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发表时间：
2000-04-28
影响因子：
4.8
通讯作者：
Antonini, JM
中科院分区：
文献类型：
--
作者：
Ma, Q;Renzelli, AJ;Antonini, JM
环己亚胺在Ah受体（AhR）激动剂存在的情况下超诱导CYP1A1的转录。为了研究“超诱导”的分子靶标，我们分析了激动剂诱导的AhR降解。2,3,7,8-四氯二苯并-对二恶英（TCDD）是一种有效的AhR激动剂，可诱导AhR蛋白的快速减少，而环己亚胺可阻断稳态AhR的下调。对AhR周转率的分析表明，环己亚胺阻断了TCDD对AhR半衰期的缩短，阻断TCDD诱导的AhR降解需要抑制蛋白质合成，这是因为(a)环己亚胺在其引起AhR超诱导和降解抑制的浓度下抑制蛋白质合成；(b) purromycin，一种通过模拟氨基酰基trna合成蛋白质的抑制剂，也阻断了tcdd诱导的AhR降解。阻断tcdd诱导的AhR降解与CYP1A1基因表达的超诱导相关，并呈时间和剂量依赖性。此外，环己亚胺增加了tcdd活化的AhR和功能性AhR Amt复合物在细胞核中的积累。总的来说，我们的研究结果揭示了环己亚胺通过增强激动剂激活的AhR的稳定性来超诱导的机制，发现抑制蛋白质合成阻断了tcdd诱导的AhR的转换，这意味着环己亚胺敏感的、不稳定的因子(在bar hR下称为(a)，在bar降解下称为（d)，在bar促进下称为(p)，在bar actor下称为ADPF）控制激动剂激活的AhR在细胞核中的去除。
Cycloheximide superinduces the transcription of CYP1A1 in the presence of an agonist for the Ah receptor (AhR). To investigate the molecular target for "superinduction," we analyzed the agonist-induced degradation of AhR. Whereas 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a potent agonist of AhR, induces a rapid reduction of the AhR protein, cycloheximide blocks the downregulation of steady state AhR. Analyses of the turnover of AhR reveal that cycloheximide blocks the shortening of the half-life of AhR by TCDD, Blocking of the TCDD-induced AhR degradation requires inhibition of protein synthesis, because (a) cycloheximide inhibits protein synthesis at the concentration at which it causes superinduction and inhibition of AhR degradation; and (b) puromycin, an inhibitor of protein synthesis by mimicking aminoacyl-tRNA, also blocks the TCDD-induced AhR degradation. The blocking of the TCDD-induced AhR degradation correlates with the superinduction of CYP1A1 gene expression in a time- and dose-dependent manner. Furthermore, cycloheximide is shown to increase the accumulation of the TCDD-activated AhR and the functional AhR Amt complex in nucleus. Collectively, our results reveal a mechanism of superinduction by cycloheximide by enhancing the stability of agonist-activated AhR, The finding that inhibition of protein synthesis blocks the TCDD-induced AhR turnover implicates a cycloheximide-sensitive, labile factor (designated as (A) under bar hR (d) under bar egradation (p) under bar romoting (f) under bar actor, or ADPF) in controlling the removal of agonist-activated AhR in nucleus.