RT Journal Article SR Electronic T1 The STING ligand 2’3’-cGAMP induces an NF-κB-dependent anti-bacterial innate immune response in the starlet sea anemone Nematostella vectensis JF bioRxiv FD Cold Spring Harbor Laboratory SP 2021.05.13.443009 DO 10.1101/2021.05.13.443009 A1 Shally R. Margolis A1 Peter A. Dietzen A1 Beth M. Hayes A1 Stephen C. Wilson A1 Brenna C. Remick A1 Seemay Chou A1 Russell E. Vance YR 2021 UL http://biorxiv.org/content/early/2021/05/14/2021.05.13.443009.abstract AB In mammals, the cGAS-cGAMP-STING pathway is crucial for sensing viral infection and initiating an anti-viral type I interferon response. cGAS and STING are highly conserved genes that originated in bacteria and are present in most animals. By contrast, interferons only emerged in vertebrates; thus, the function of STING in invertebrates is unclear. Here, we use the STING ligand 2’3’-cGAMP to activate immune responses in a model cnidarian invertebrate, the starlet sea anemone Nematostella vectensis. Using RNA-Seq, we found that 2’3’-cGAMP induces robust transcription of both anti-viral and anti-bacterial genes, including the conserved transcription factor NF-κB. Knockdown experiments identified a role for NF-κB in specifically inducing anti-bacterial genes downstream of 2’3’-cGAMP, and some of these genes were also found to be induced during Pseudomonas aeruginosa infection. Furthermore, we characterized the protein product of one of the putative anti-bacterial genes, the N. vectensis homolog of Dae4, and found that it has conserved anti-bacterial activity. This work describes an unexpected role of a cGAMP sensing pathway in anti-bacterial immunity and suggests that a broad transcriptional response is an evolutionarily ancestral output of 2’3’-cGAMP signaling in animals.Significance statement Anti-viral immune responses are initiated via signaling pathways such as the STING pathway. In mammals, activation of this pathway results in the production of anti-viral molecules called interferons. Surprisingly, the STING pathway is present in organisms such as sea anemones that lack interferons; the function of this pathway in these organisms is thus unclear. Here we report that in the anemone Nematostella vectensis, a small molecule activator of the STING pathway, cGAMP, not only induces an anti-viral response, but also stimulates an anti-bacterial immune response. These results provide insights into the evolutionary origins of innate immunity, and suggest a broader ancestral role for cGAMP-STING signaling that evolved toward more specialized anti-viral functions in mammals.Competing Interest StatementR.E.V. consults for Ventus Therapeutics. The other authors declare no competing interests.