The RNFT2/IL-3Rα axis regulates IL-3 signaling and innate immunity
The RNFT2/IL-3Rα axis regulates IL-3 signaling and innate immunity
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RNFT2/IL-3R α 轴调节 IL-3 信号传导和先天免疫
DOI：
10.1172/jci.insight.133652
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发表时间：
2020-02-13
期刊：
影响因子：
8
通讯作者：
Chen, Bill B.
中科院分区：
文献类型：
--
作者：
Tong, Yao;Lear, Travis B.;Chen, Bill B.
白细胞介素3(IL-3)受体α(IL-3Rα)是配体特异性IL-3R的α亚基，启动细胞内对IL-3的反应信号。IL-3在小鼠脓毒症模型中增强促炎信号和细胞因子风暴。在这里，我们发现RNFT2(RINFING TMAN-DOMAIN CONTING Protein 2，也叫TMEM118)，一个以前未被描述的环指泛素E3连接酶，通过IL-3Rα泛素化和蛋白酶体中的降解，负向调节依赖IL-3的细胞反应。在体外，IL-3刺激促进依赖RNFT2的IL-3Rα蛋白酶体降解，我们发现IL-3Rα赖氨酸357是泛素受体位点。我们确定，内毒素刺激降低了RNFT2的丰度，延长了IL-3Rα的半衰期，并使细胞对IL-3的影响敏感，协同作用增加了促炎信号。在体内，IL-3与内毒素协同作用加重了内毒素和铜绿假单胞菌攻击小鼠的肺部炎症；相反，IL-3中和减轻了内毒素诱导的肺损伤。此外，在脂多糖诱导的小鼠肺损伤中，RNFT2过表达减少了肺部炎症和损伤，而Rnft2基因敲除则加剧了炎症反应。最后，我们检测了囊性纤维化患者的人肺组织中的RNFT2和IL-3Rα，也表明在有急性呼吸窘迫综合征风险的机械通气危重患者中，IL-3水平升高。这些结果证实RNFT2是IL-3Rα的负性调节因子，并表明RNFT2/IL-3Rα/IL-3轴在调节肺内的天然免疫反应中具有潜在的作用。
Interleukin-3 (IL-3) receptor alpha (IL-3R alpha) is the alpha subunit of the ligand-specific IL-3R and initiates intracellular signaling in response to IL-3. IL-3 amplifies proinflammatory signaling and cytokine storm in murine sepsis models. Here we found that RNFT2 (RING finger transmembrane-domain containing protein 2, also TMEM118), a previously uncharacterized RING finger ubiquitin E3 ligase, negatively regulated IL-3-dependent cellular responses through IL-3R alpha ubiquitination and degradation in the proteasome. In vitro, IL-3 stimulation promoted IL-3R alpha proteasomal degradation dependent on RNFT2, and we identified IL-3R alpha lysine 357 as a ubiquitin acceptor site. We determined that LPS priming reduces RNFT2 abundance, extends IL-3R alpha half-life, and sensitizes cells to the effects of IL-3, acting synergistically to increase proinflammatory signaling. In vivo, IL-3 synergized with LPS to exacerbate lung inflammation in LPS and Pseudomonas aeruginosa-challenged mice; conversely, IL-3 neutralization reduced LPS-induced lung injury. Further, RNFT2 overexpression reduced lung inflammation and injury, whereas Rnft2 knockdown exacerbated inflammatory responses in LPS-induced murine lung injury. Last, we examined RNFT2 and IL-3R alpha in human lung explants from patients with cystic fibrosis and also showed that IL-3 is elevated in mechanically ventilated critically ill humans at risk for acute respiratory distress syndrome. These results identify RNFT2 as a negative regulator of IL-3R alpha and show a potential role for the RNFT2/IL-3R alpha/IL-3 axis in regulating innate immune responses in the lung.