cGAS produces a 2′-5′-linked cyclic dinucleotide second messenger that activates STING


Detection of cytoplasmic DNA represents one of the most fundamental mechanisms of the innate immune system to sense the presence of microbial pathogens1. Moreover, erroneous detection of endogenous DNA by the same sensing mechanisms has an important pathophysiological role in certain sterile inflammatory conditions2,3. The endoplasmic-reticulum-resident protein STING is critically required for the initiation of type I interferon signalling upon detection of cytosolic DNA of both exogenous and endogenous origin4,5,6,7,8. Next to its pivotal role in DNA sensing, STING also serves as a direct receptor for the detection of cyclic dinucleotides, which function as second messenger molecules in bacteria9,10,11,12,13. DNA recognition, however, is triggered in an indirect fashion that depends on a recently characterized cytoplasmic nucleotidyl transferase, termed cGAMP synthase (cGAS), which upon interaction with DNA synthesizes a dinucleotide molecule that in turn binds to and activates STING14,15. We here show in vivo and in vitro that the cGAS-catalysed reaction product is distinct from previously characterized cyclic dinucleotides. Using a combinatorial approach based on mass spectrometry, enzymatic digestion, NMR analysis and chemical synthesis we demonstrate that cGAS produces a cyclic GMP-AMP dinucleotide, which comprises a 2′-5′ and a 3′-5′ phosphodiester linkage >Gp(2′-5′)Ap(3′-5′)>. We found that the presence of this 2′-5′ linkage was required to exert potent activation of human STING. Moreover, we show that cGAS first catalyses the synthesis of a linear 2′-5′-linked dinucleotide, which is then subject to cGAS-dependent cyclization in a second step through a 3′-5′ phosphodiester linkage. This 13-membered ring structure defines a novel class of second messenger molecules, extending the family of 2′-5′-linked antiviral biomolecules.

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Figure 1: The R231A STING mutant uncouples cyclic di-GMP sensing from cGAS-induced activation.
Figure 2: The cGAS reaction product is distinct from cGAMP(3′-5′).
Figure 3: The second messenger produced by cGAS is >Gp(2′-5′)Ap(3′-5′)>.
Figure 4: cGAMP(2′-5′) is a potent activator of human and murine STING.
Figure 5: >Gp(2′-5′)Ap(3′-5′)> is synthesized in a two-step process.


  1. 1

    Hornung, V. & Latz, E. Intracellular DNA recognition. Nature Rev. Immunol. 10, 123–130 (2010)

  2. 2

    Gall, A. et al. Autoimmunity initiates in nonhematopoietic cells and progresses via lymphocytes in an interferon-dependent autoimmune disease. Immunity 36, 120–131 (2012)

  3. 3

    Ahn, J., Gutman, D., Saijo, S. & Barber, G. N. STING manifests self DNA-dependent inflammatory disease. Proc. Natl Acad. Sci. USA 109, 19386–19391 (2012)

  4. 4

    Ishikawa, H. & Barber, G. N. STING is an endoplasmic reticulum adaptor that facilitates innate immune signalling. Nature 455, 674–678 (2008)

  5. 5

    Zhong, B. et al. The adaptor protein MITA links virus-sensing receptors to IRF3 transcription factor activation. Immunity 29, 538–550 (2008)

  6. 6

    Jin, L. et al. MPYS, a novel membrane tetraspanner, is associated with major histocompatibility complex class II and mediates transduction of apoptotic signals. Mol. Cell. Biol. 28, 5014–5026 (2008)

  7. 7

    Sun, W. et al. ERIS, an endoplasmic reticulum IFN stimulator, activates innate immune signaling through dimerization. Proc. Natl Acad. Sci. USA 106, 8653–8658 (2009)

  8. 8

    Ishikawa, H., Ma, Z. & Barber, G. N. STING regulates intracellular DNA-mediated, type I interferon-dependent innate immunity. Nature 461, 788–792 (2009)

  9. 9

    Burdette, D. L. et al. STING is a direct innate immune sensor of cyclic di-GMP. Nature 478, 515–518 (2011)

  10. 10

    Huang, Y. H., Liu, X. Y., Du, X. X., Jiang, Z. F. & Su, X. D. The structural basis for the sensing and binding of cyclic di-GMP by STING. Nature Struct. Mol. Biol. 19, 728–730 (2012)

  11. 11

    Ouyang, S. et al. Structural analysis of the STING adaptor protein reveals a hydrophobic dimer interface and mode of cyclic di-GMP binding. Immunity 36, 1073–1086 (2012)

  12. 12

    Shang, G. et al. Crystal structures of STING protein reveal basis for recognition of cyclic di-GMP. Nature Struct. Mol. Biol. 19, 725–727 (2012)

  13. 13

    Shu, C., Yi, G., Watts, T., Kao, C. C. & Li, P. Structure of STING bound to cyclic di-GMP reveals the mechanism of cyclic dinucleotide recognition by the immune system. Nature Struct. Mol. Biol. 19, 722–724 (2012)

  14. 14

    Wu, J. et al. Cyclic GMP-AMP is an endogenous second messenger in innate immune signaling by cytosolic DNA. Science 339, 826–830 (2013)

  15. 15

    Sun, L., Wu, J., Du, F., Chen, X. & Chen, Z. J. Cyclic GMP-AMP synthase is a cytosolic DNA sensor that activates the type I interferon pathway. Science 339, 786–791 (2013)

  16. 16

    Cavlar, T., Deimling, T., Ablasser, A., Hopfner, K. P. & Hornung, V. Species-specific detection of the antiviral small-molecule compound CMA by STING. EMBO J. 32, 1440–1450 (2013)

  17. 17

    Rao, F. et al. Enzymatic synthesis of c-di-GMP using a thermophilic diguanylate cyclase. Anal. Biochem. 389, 138–142 (2009)

  18. 18

    Davies, B. W., Bogard, R. W., Young, T. S. & Mekalanos, J. J. Coordinated regulation of accessory genetic elements produces cyclic di-nucleotides for V. cholerae virulence. Cell 149, 358–370 (2012)

  19. 19

    Conlon, J. et al. Mouse, but not human STING, binds and signals in response to the vascular disrupting agent 5,6-dimethylxanthenone-4-acetic acid. J. Immunol. 190, 5216–5225 (2013)

  20. 20

    Kristiansen, H., Gad, H. H., Eskildsen-Larsen, S., Despres, P. & Hartmann, R. The oligoadenylate synthetase family: an ancient protein family with multiple antiviral activities. J. Interferon Cytokine Res. 31, 41–47 (2011)

  21. 21

    Gao, P. et al. Cyclic [G(2′,5′)pA(3′,5′)p] is the metazoan second messenger produced by DNA-activated cyclic GMP-AMP synthase. Cell 153, 1094–1107 (2013)

  22. 22

    Diner, E. J. The innate immune DNA sensory cGAS produces a noncanonical cyclic dinucleotide that activates human STING. Cell Rep. 3, 1355–1361 (2013)

  23. 23

    Mizushima, S. & Nagata, S. pEF-BOS, a powerful mammalian expression vector. Nucleic Acids Res. 18, 5322 (1990)

  24. 24

    Gaffney, B. L., Veliath, E., Zhao, J. & Jones, R. A. One-flask syntheses of c-di-GMP and the [Rp,Rp] and [Rp,Sp] thiophosphate analogues. Org. Lett. 12, 3269–3271 (2010)

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We thank M. Pelegrin for providing us with LL171 cells. K.-P.H. is supported by the National Institutes of Health (U19AI083025), the European Research Council Advanced Grant 322869, and the Center for Integrated Protein Science Munich (CIPSM). A.A. and V.H. are members of the excellence cluster ImmunoSensation. V.H. is supported by grants from the German Research Foundation (SFB670) and the European Research Council (ERC 243046).

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A.A., M.G., T.C., G.W., T.D., I.R., J.L., K.-P.H. and V.H. designed experiments and analysed the data. A.A., M.G., T.C., G.W., T.D. and I.R. performed experiments. A.A. and V.H. wrote the manuscript. V.H. supervised the project.

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Correspondence to Andrea Ablasser or Veit Hornung.

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Ablasser, A., Goldeck, M., Cavlar, T. et al. cGAS produces a 2′-5′-linked cyclic dinucleotide second messenger that activates STING. Nature 498, 380–384 (2013).

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