An alternatively spliced STING isoform localizes in the cytoplasmic membrane and directly senses extracellular cGAMP.
An alternatively spliced STING isoform localizes in the cytoplasmic membrane and directly senses extracellular cGAMP.
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选择性剪接的 STING 异构体定位于细胞质膜并直接感知细胞外 cGAMP
DOI：
10.1172/jci144339
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发表时间：
2022-02-01
期刊：
影响因子：
--
通讯作者：
Zheng T
中科院分区：
文献类型：
--
作者：
Li X;Zhu Y;Zhang X;An X;Weng M;Shi J;Wang S;Liu C;Luo S;Zheng T
研究表明，2'3'-环状 GMP-AMP (cGAMP) 是激活 IFN 基因抗病毒刺激物 (STING) 的第二信使，可引发抗肿瘤免疫反应。由于 cGAMP 无法穿过细胞膜，因此尚不清楚细胞内 STING 如何被细胞外 cGAMP 激活，直到 SLC19A1 被确定为将细胞外 cGAMP 转运到细胞质中的输入者。然而，SLC19A1 缺陷细胞也能感知细胞外 cGAMP，这表明除了促进 STING 感知细胞外 cGAMP 的转运蛋白之外，还存在其他机制。在这里，我们使用免疫沉淀、免疫荧光和流式细胞术，鉴定了一种选择性剪接的 STING 亚型，即质膜 STING (pmSTING)，它位于质膜中，其 C 末端位于细胞外，因为与经典 STING 相比，其 N 末端缺少 1 个跨膜结构域。进一步的研究表明，细胞外cGAMP不仅促进pmSTING的二聚化以及pmSTING与TANK结合激酶1（TBK1）和IFN调节因子3（IRF3）的相互作用，而且还增强pmSTING转染细胞中TBK1和IRF3的磷酸化以及IFN的产生。此外，我们还在包括人类在内的其他物种中发现了类似的 pmSTING 亚型。这项研究表明 pmSTING 在感测细胞外 cGAMP 中发挥保守作用，并深入了解 cGAMP 作为免疫递质的作用。
It has been revealed that 2′3′-cyclic-GMP-AMP (cGAMP), a second messenger that activates the antiviral stimulator of IFN genes (STING), elicits an antitumoral immune response. Since cGAMP cannot cross the cell membrane, it is not clear how intracellular STING has been activated by extracellular cGAMP until SLC19A1 was identified as an importer to transport extracellular cGAMP into the cytosol. However, SLC19A1-deficient cells also sense extracellular cGAMP, suggesting the presence of mechanisms other than the facilitating transporters for STING sensing extracellular cGAMP. Here, using immunoprecipitation, immunofluorescence, and flow cytometry, we identified an alternatively spliced STING isoform, plasmatic membrane STING (pmSTING), that localized in the plasma membrane with its C-terminus outside the cell, due to a lack of 1 transmembrane domain in its N-terminus compared with canonical STING. Further studies showed that extracellular cGAMP not only promoted the dimerization of pmSTING and interaction of pmSTING with TANK-binding kinase 1 (TBK1) and IFN regulatory factor 3 (IRF3), but also enhanced the phosphorylation of TBK1 and IRF3 and the production of IFN in pmSTING-transfected cells. Additionally, we also identified similar pmSTING isoforms in other species including human. This study suggests a conserved role for pmSTING in sensing extracellular cGAMP and provides insight into the role of cGAMP as an immunotransmitter.