Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, USA.
Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, Massachusetts, USA.
Nat Chem Biol. 2014 Dec;10(12):1043-8. doi: 10.1038/nchembio.1661. Epub 2014 Oct 26.
Agonists of mouse STING (TMEM173) shrink and even cure solid tumors by activating innate immunity; human STING (hSTING) agonists are needed to test this therapeutic hypothesis in humans. The endogenous STING agonist is 2'3'-cGAMP, a second messenger that signals the presence of cytosolic double-stranded DNA. We report activity-guided partial purification and identification of ecto-nucleotide pyrophosphatase/phosphodiesterase (ENPP1) to be the dominant 2'3'-cGAMP hydrolyzing activity in cultured cells. The hydrolysis activity of ENPP1 was confirmed using recombinant protein and was depleted in tissue extracts and plasma from Enpp1(-/-) mice. We synthesized a hydrolysis-resistant bisphosphothioate analog of 2'3'-cGAMP (2'3'-cG(s)A(s)MP) that has similar affinity for hSTING in vitro and is ten times more potent at inducing IFN-β secretion from human THP1 monocytes. Studies in mouse Enpp1(-/-) lung fibroblasts indicate that resistance to hydrolysis contributes substantially to its higher potency. 2'3'-cG(s)A(s)MP is therefore improved over natural 2'3'-cGAMP as a model agonist and has potential as a vaccine adjuvant and cancer therapeutic.
激动剂的鼠标 STING（TMEM173）缩小，甚至通过激活先天免疫治愈实体瘤; 人类 STING（hSTING）激动剂需要测试这种治疗假说在人类中。内源性 STING 激动剂是 2'3'-cGAMP，一种第二信使，信号存在细胞质双链 DNA。我们报告活性指导的部分纯化和鉴定ecto-核苷酸焦磷酸酶/磷酸二酯酶（ENPP1）是培养细胞中主要的 2'3'-cGAMP 水解活性。使用重组蛋白证实了 ENPP1 的水解活性，并在 Enpp1（-/-）小鼠的组织提取物和血浆中耗尽。我们合成了一种水解抗性的双磷酸硫代酯类似物 2'3'-cGAMP（2'3'-cG（s）A（s）MP），它在体外对 hSTING 的亲和力相似，并且在诱导人 THP1 单核细胞 IFN-β分泌方面的效力是其 10 倍。在小鼠 Enpp1（-/-）肺成纤维细胞中的研究表明，对水解的抗性大大有助于其更高的效力。因此，2'3'-cG（s）A（s）MP 作为模型激动剂优于天然 2'3'-cGAMP，具有作为疫苗佐剂和癌症治疗剂的潜力。
