Bacterial 2',3'-cGAMP activates a SAVED effector to form membrane-disrupting filaments and restrict phage replication

Aaron Whiteley — Fri, 27 Mar 2026 15:00:00 +0000

Bacterial 2',3'-cGAMP activates a SAVED effector to form membrane-disrupting filaments and restrict phage replication Aaron Whiteley Fri, 03/27/2026 - 09:00

Uday Tak , Kate Schinkel , Peace Walth , Jian Wei Tay , Erik Hartwick , Aaron Whiteley

Cell Host Microbe (2026). PubMed PMID: 41903528

Abstract

Mammalian cells initiate antiviral signaling when cyclic GMP-AMP synthase (cGAS) detects cytoplasmic DNA and synthesizes 2',3'-cyclic GMP-AMP (2',3'-cGAMP), which activates stimulator of interferon genes (STING). Similarly, bacteria use cyclic oligonucleotide-based antiphage signaling systems (CBASS) to detect phage using ancestral cGAS/DncV-like nucleotidyltransferases (CD-NTases), but they are not known to use 2',3'-cGAMP. Here, we discover a bacterial CD-NTase that produces 2',3'-cGAMP to activate a Saf-2TM-SMODS-associated fused to various effector domains (SAVED) effector (CD-NTase-associated protein 14 [Cap14]), which initiates membrane disruption to restrict phage replication. Cryo-electron microscopy (cryo-EM) reveals that Cap14 binds 2',3'-cGAMP to form a filament, while electrophysiology suggests that cGAMP activates membrane disruption. Swapping the Cap14 transmembrane domain with a nuclease domain yields a functional chimera that exclusively responds to 2',3'-cGAMP. We hypothesize that other predicted transmembrane effectors in CBASS operons disrupt membranes, and we confirm this by showing that bacterial STING homologs with transmembrane domains restrict phage through membrane disruption. These findings expand our understanding of cGAS-STING-like pathways in bacterial immunity.

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Tak U, Schinkel K, Walth P, Tay JW, Hartwick EW, Whiteley AT. Bacterial 2',3'-cGAMP activates a SAVED effector to form membrane-disrupting filaments and restrict phage replication.Cell Host Microbe. 2026 Mar 27;. doi: 10.1016/j.chom.2026.03.004. [Epub ahead of print] PubMed PMID: 41903528; NIHMSID:NIHMS2161427.

Tak U, Schinkel K, Walth P, Tay JW, Hartwick EW, ➤Whiteley AT | Cell Host Microbe 2026

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Bacterial cGAS-like enzymes produce 2′,3′-cGAMP to activate an ion channel that restricts phage replication

Anonymous — Wed, 26 Jul 2023 16:44:22 +0000

Bacterial cGAS-like enzymes produce 2′,3′-cGAMP to activate an ion channel that restricts phage replication Anonymous (not verified) Wed, 07/26/2023 - 10:44

Uday Tak , Peace Holguin-Walth , Aaron Whiteley

BioRxiv (2023) PubMed PMID: 37546940; PubMed Central PMCID: PMC10402079.

Abstract

The mammalian innate immune system uses cyclic GMP–AMP synthase (cGAS) to synthesize the cyclic dinucleotide 2′,3′-cGAMP during antiviral and antitumor immune responses. 2′,3′-cGAMP is a nucleotide second messenger that initiates inflammatory signaling by binding to and activating the stimulator of interferon genes (STING) receptor. Bacteria also encode cGAS/DncV-like nucleotidyltransferases (CD-NTases) that produce nucleotide second messengers to initiate antiviral (antiphage) signaling. Bacterial CD-NTases produce a wide range of cyclic oligonucleotides but have not been documented to produce 2′,3′-cGAMP. Here we discovered bacterial CD-NTases that produce 2′,3′-cGAMP to restrict phage replication. Bacterial 2′,3′-cGAMP binds to CD-NTase associated protein 14 (Cap14), a transmembrane protein of unknown function. Using electrophysiology, we show that Cap14 is a chloride-selective ion channel that is activated by 2′,3′-cGAMP binding. Cap14 adopts a modular architecture, with an N-terminal transmembrane domain and a C-terminal nucleotide-binding SAVED domain. Domain-swapping experiments demonstrated the Cap14 transmembrane region could be substituted with a nuclease, thereby generating a biosensor that is selective for 2′,3′-cGAMP. This study reveals that 2′,3′-cGAMP signaling extends beyond metazoa to bacteria. Further, our findings suggest that transmembrane proteins of unknown function in bacterial immune pathways may broadly function as nucleotide-gated ion channels.

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Tak U, Walth P, Whiteley AT. Bacterial cGAS-like enzymes produce 2',3'-cGAMP to activate an ion channel that restricts phage replication.bioRxiv. 2023 Jul 24;. doi: 10.1101/2023.07.24.550367. PubMed PMID: 37546940; PubMed Central PMCID: PMC10402079.

Tak U, Walth P, ➤Whiteley AT | BioRxiv 2023

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Bacterial 2',3'-cGAMP activates a SAVED effector to form membrane-disrupting filaments and restrict phage replication

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Bacterial cGAS-like enzymes produce 2′,3′-cGAMP to activate an ion channel that restricts phage replication

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