锌指蛋白36(ZFP36)对肿瘤坏死因子(TNF)的负反馈控制受丝裂原活化蛋白激酶磷酸酶双特异性磷酸酶1(DUSP1)的限制:糖皮质激素调节的意义

Negative Feed-forward Control of Tumor Necrosis Factor (TNF) by Tristetraprolin (ZFP36) Is Limited by the Mitogen-activated Protein Kinase Phosphatase, Dual-specificity Phosphatase 1 (DUSP1): IMPLICATIONS FOR REGULATION BY GLUCOCORTICOIDS.

作者信息

Shah Suharsh, Mostafa Mahmoud M, McWhae Andrew, Traves Suzanne L, Newton Robert

机构信息

From the Airways Inflammation Research Group, Snyder Institute for Chronic Diseases, University of Calgary, Calgary, Alberta T2N 4Z6, Canada.

From the Airways Inflammation Research Group, Snyder Institute for Chronic Diseases, University of Calgary, Calgary, Alberta T2N 4Z6, Canada

出版信息

J Biol Chem. 2016 Jan 1;291(1):110-25. doi: 10.1074/jbc.M115.697599. Epub 2015 Nov 6.

Abstract

TNF is central to inflammation and may play a role in the pathogenesis of asthma. The 3'-untranslated region of the TNF transcript contains AU-rich elements (AREs) that are targeted by the RNA-binding protein, tristetraprolin (also known as zinc finger protein 36 (ZFP36)), which is itself up-regulated by inflammatory stimuli, to promote mRNA degradation. Using primary human bronchial epithelial and pulmonary epithelial A549 cells, we confirm that interleukin-1β (IL1B) induces expression of dual-specificity phosphatase 1 (DUSP1), ZFP36, and TNF. Whereas IL1B-induced DUSP1 is involved in feedback control of MAPK pathways, ZFP36 exerts negative (incoherent) feed-forward control of TNF mRNA and protein expression. DUSP1 silencing increased IL1B-induced ZFP36 expression at 2 h and profoundly repressed TNF mRNA at 6 h. This was partly due to increased TNF mRNA degradation, an effect that was reduced by ZFP36 silencing. This confirms a regulatory network, whereby DUSP1-dependent negative feedback control reduces feed-forward control by ZFP36. Conversely, whereas DUSP1 overexpression and inhibition of MAPKs prevented IL1B-induced expression of ZFP36, this was associated with increased TNF mRNA expression at 6 h, an effect that was predominantly due to elevated transcription. This points to MAPK-dependent feed-forward control of TNF involving ZFP36-dependent and -independent mechanisms. In terms of repression by dexamethasone, neither silencing of DUSP1, silencing of ZFP36, nor silencing of both together prevented the repression of IL1B-induced TNF expression, thereby demonstrating the need for further repressive mechanisms by anti-inflammatory glucocorticoids. In summary, these data illustrate why understanding the competing effects of feedback and feed-forward control is relevant to the development of novel anti-inflammatory therapies.

摘要

肿瘤坏死因子(TNF)是炎症的核心因素,可能在哮喘的发病机制中起作用。TNF转录本的3'非翻译区包含富含AU元件(AREs),这些元件是RNA结合蛋白Tristetraprolin(也称为锌指蛋白36(ZFP36))的作用靶点,该蛋白本身会因炎症刺激而上调,以促进mRNA降解。我们使用原代人支气管上皮细胞和肺上皮A549细胞证实,白细胞介素-1β(IL1B)可诱导双特异性磷酸酶1(DUSP1)、ZFP36和TNF的表达。虽然IL1B诱导的DUSP1参与丝裂原活化蛋白激酶(MAPK)途径的反馈控制,但ZFP36对TNF mRNA和蛋白表达发挥负向(非相干)前馈控制作用。DUSP1沉默在2小时时增加了IL1B诱导的ZFP36表达,并在6小时时显著抑制了TNF mRNA。这部分是由于TNF mRNA降解增加,而ZFP36沉默可减弱这种效应。这证实了一个调节网络,即依赖DUSP1的负反馈控制降低了ZFP36的前馈控制。相反,虽然DUSP1过表达和MAPK抑制可阻止IL1B诱导的ZFP36表达,但这与6小时时TNF mRNA表达增加有关,这种效应主要是由于转录升高。这表明MAPK对TNF的前馈控制涉及ZFP36依赖和非依赖机制。就地塞米松的抑制作用而言,DUSP1沉默、ZFP36沉默或两者同时沉默均不能阻止地塞米松对IL1B诱导的TNF表达的抑制,从而表明抗炎糖皮质激素需要进一步的抑制机制。总之,这些数据说明了为什么理解反馈和前馈控制的竞争效应与新型抗炎疗法的开发相关。

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