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Cell Rep. 2013 May 30;3(5):1355-61. doi: 10.1016/j.celrep.2013.05.009. Epub 2013 May 23.

The innate immune DNA sensor cGAS produces a noncanonical cyclic dinucleotide that activates human STING.

Author information

1
Division of Immunology and Pathogenesis, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.

Abstract

The presence of foreign DNA in the cytosol of mammalian cells elicits a potent antiviral interferon response. Recently, cytosolic DNA was proposed to induce the synthesis of cyclic GMP-AMP (cGAMP) upon binding to an enzyme called cGAMP synthase (cGAS). cGAMP activates an interferon response by binding to a downstream receptor called STING. Here, we identify natural variants of human STING (hSTING) that are poorly responsive to cGAMP yet, unexpectedly, are normally responsive to DNA and cGAS signaling. We explain this paradox by demonstrating that the cGAS product is actually a noncanonical cyclic dinucleotide, cyclic [G(2'-5')pA(3'-5')p], which contains a single 2'-5' phosphodiester bond. Cyclic [G(2'-5')pA(3'-5')p] potently activates diverse hSTING receptors and, therefore, may be a useful adjuvant or immunotherapeutic. Our results indicate that hSTING variants have evolved to distinguish conventional (3'-5') cyclic dinucleotides, known to be produced mainly by bacteria, from the noncanonical cyclic dinucleotide produced by mammalian cGAS.

PMID:
23707065
PMCID:
PMC3706192
DOI:
10.1016/j.celrep.2013.05.009
[Indexed for MEDLINE]
Free PMC Article

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