细胞因子改变气道细胞糖皮质激素受体磷酸化作用：磷酸化激酶的作用
2013/02/08
哮喘患者对糖皮质激素不敏感是治疗中的巨大挑战。我们最近证明，将气道平滑肌细胞短期暴露于前哮喘细胞因子将显著降低其对糖皮质激素反应。这种效应部分是由于干扰素调节因子-1作用，提示还有别的机制参与其中(Am J Respir Cell MolBiol 2008;38:463-472)。尽管糖皮质激素受体（GR）可以在氨基末端区域的多个丝氨酸位点发生磷酸化，但最主要的磷酸化位点在211位丝氨酸（Ser211）和226位丝氨酸（Ser226）.我们证明了新的假设，即细胞因子诱导的气道平滑肌细胞对糖皮质激素不敏感是由于GR磷酸化受损所致。当用TNF-α（10mg/ml）和IFN-γ(500UI/ml)处理气道平滑肌细胞6小时，以及同时或提前2小时加入氟替卡松（100nm）处理。GR磷酸化作用发生在Ser226而不是Ser211残基上。细胞因子能显著抑制糖皮质激素诱导的GR Ser211的磷酸化，而不是Ser226。同时，增加了Ser/Thr蛋白磷酸激酶PP5表达，而不是PP1或PP2A。通过内含糖皮质激素响应要素报告基因的转染研究，显示特异性siRNA可诱导PP5的mRNA敲除，而不是PP1或PP2A的mRNA敲除，可以部分阻断细胞因子对GR介导的交互作用的抑制。同样，当PP5表达受到抑制时，细胞因子无法抑制GC诱导的GR-Ser211磷酸化。我们推测前哮喘细胞因子诱导的气道平滑肌细胞对糖皮质激素低敏感的机制，可能部分缘于于PP5介导的GR-Ser211磷酸化受损。
Bouazza B, Krytska K, Debba-Pavard M, Amrani Y, Honkanen RE, Tran J, Tliba O.
Cytokines alter glucocorticoid receptor phosphorylation in airway cells: role of phosphatases.
Am J Respir Cell Mol Biol. 2012 Oct;47(4):464-73. doi: 10.1165/rcmb.2011-0364OC. Epub 2012 May 16.（附：影响因子：5.125）Bouazza B, Krytska K, Debba-Pavard M, Amrani Y, Honkanen RE, Tran J, Tliba O.
Source
Department of Pharmaceutical Sciences, Thomas Jefferson University, Jefferson School of Pharmacy, Philadelphia, PA 19107-5233, USA.Abstract
Corticosteroid insensitivity (CSI) represents a profound challenge in managing patients with asthma. We recently demonstrated that short exposure of airway smooth muscle cells (ASMCs) to proasthmatic cytokines drastically reduced their responsiveness to glucocorticoids (GCs), an effect that was partially mediated via interferon regulatory factor-1, suggesting the involvement of additional mechanisms (Am J Respir Cell MolBiol 2008;38:463-472). Although GC receptor (GR) can be phosphorylated at multiple serines in the N-terminal region, the major phosphorylation sites critical for GR transcriptional activity are serines 211 (Ser211) and 226 (Ser226). We tested the novel hypothesis that cytokine-induced CSI in ASMCs is due to an impaired GR phosphorylation. Cells were treated with TNF-α (10 ng/ml) and IFN-γ (500 UI/ml) for 6 hours and/or fluticasone (100 nm) added 2 hours before. GR was constitutively phosphorylated at Ser226 but not at Ser211 residues. Cytokines dramatically suppressed fluticasone-induced phosphorylation of GR on Ser211 but not on Ser226 residues while increasing the expression of Ser/Thr protein phosphatase (PP)5 but not that of PP1 or PP2A. Transfection studies using a reporter construct containing GC responsive elements showed that the specific small interfering RNA-induced mRNA knockdown of PP5, but not that of PP1 or PP2A, partially prevented the cytokine suppressive effects on GR-meditated transactivation activity. Similarly, cytokines failed to inhibit GC-induced GR-Ser211 phosphorylation when expression of PP5 was suppressed. We propose that the novel mechanism that proasthmatic cytokine-induced CSI in ASMCs is due, in part, to PP5-mediated impairment of GR-Ser211 phosphorylation.
（深圳市人民医院 王凌伟摘译 邱晨审校）
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布地奈德/福莫特罗治疗哮喘和慢性阻塞性肺疾病患者前后的肺功能变化比较
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严重哮喘患者气道平滑肌细胞趋化因子表达对糖皮质激素低敏感的机制研究
