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Dynamic control of bacterial antiphage defense through the CdnG-Cap5 cyclic oligonucleotide-based antiphage pathway

Feng Ye1, Jiaao Gong1, Yao Ge1

  • 1School of Life Science, Beijing Institute of Technology, Beijing, China.

The Journal of Biological Chemistry
|December 8, 2025
PubMed

Insights

The cyclic oligonucleotide-based antiphage signaling system (CBASS) in Vibrio cholerae uses VcCdnG to produce a cyclic di-AMP second messenger. This molecule activates the VcCap5 effector, leading to bacterial cell death and defense against phages.

Area of Science:

  • Bacterial immunology
  • Molecular biology
  • Virology

Background:

  • The cyclic oligonucleotide-based antiphage signaling system (CBASS) is a crucial bacterial defense against viral infections.
  • CBASS shares functional similarities with the human innate immune pathway.
  • Vibrio cholerae, a human pathogen, possesses a CBASS system that presents a therapeutic target.

Purpose of the Study:

  • To biochemically and structurally characterize the CdnG-Cap5 CBASS system in Vibrio cholerae.
  • To elucidate the molecular mechanisms of CBASS-mediated bacterial immunity.
  • To understand the synthesis of second messengers and activation of effectors in this system.

Main Methods:

  • Biochemical assays to determine enzyme activity and product formation.
  • X-ray crystallography for structural determination of CdnG and Cap5.
  • Binding assays to study the interaction between the second messenger and effector.
  • In vitro assays to assess effector activation and downstream consequences.

Main Results:

  • VcCdnG synthesizes 3'2'-cyclic GMP-AMP (cGAMP) as the bacterial second messenger.
  • VcCdnG is a representative clade G system, abundant in bacteria.
  • The second messenger cGAMP specifically binds and triggers the tetramerization of the VcCap5 effector.
  • VcCap5 activation leads to bacterial cell death, demonstrating an antiphage mechanism.
  • VcCap5 displays multiligand sensitivity and dose-dependent responses.

Conclusions:

  • This study reveals the molecular basis of CBASS immunity in Vibrio cholerae.
  • The findings provide insights into the widespread clade G CBASS systems.
  • Understanding this bacterial defense mechanism enhances knowledge of phage-bacteria interactions and potential therapeutic strategies.
Keywords:
3'2'-cGAMPCap5CdnGmolecular mechanismprotein structuresecond messenger

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