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Updated: May 12, 2025
PIP-on-a-chip: A Label-free Study of Protein-phosphoinositide Interactions
Published on: July 27, 2017
Cyclic-dinucleotide-induced filamentous assembly of phospholipases governs broad CBASS immunity
Jingge Wang1, Zhao Li1, Hao Lang2
1Department of Radiology, Zhuhai People's Hospital, The Affiliated Hospital of Beijing Institute of Technology, School of Life Science, Beijing Institute of Technology, Beijing 100081, China.
Abstract:
Cyclic-oligonucleotide-based antiphage signaling systems (CBASS), a widespread antiviral bacterial immune system homologous to the mammalian cGAS-STING pathway, synthesizes cyclic nucleotide signals and triggers effector proteins to induce cell death and prevent viral propagation. Among various CBASS effectors, phospholipase effectors are the first to be discovered and are one of the most widespread families that sense cyclic dinucleotides to degrade cell membrane phospholipids. Here, we report that CBASS phospholipases assemble from a dimeric inactive state into active higher-order filamentous oligomers upon sensing cyclic dinucleotides. Using a combined approach of cryo-electron microscopy and X-ray crystallography, we have determined the structures of CBASS phospholipase in the inactive dimeric state, the cyclic-dinucleotide-bound active higher-order state, and the substrate-analog-bound catalytic mimicry state, thereby visualizing the complete conformational reorganization process. Complemented by functional assays of intermolecular binding, phospholipase enzymatic activity, in vitro membrane disruption, and in vivo antiphage efficiency, our work elucidates the mechanisms of assembly and activation of CBASS phospholipases.
Insights
Cyclic-oligonucleotide-based antiphage signaling systems (CBASS) phospholipases assemble into active filaments when sensing cyclic dinucleotides. This structural study reveals their activation mechanism, crucial for bacterial antiviral defense.
Area of Science:
- Molecular Biology
- Structural Biology
- Bacterial Immunology
Background:
- Cyclic-oligonucleotide-based antiphage signaling systems (CBASS) are key bacterial antiviral mechanisms.
- CBASS pathways utilize cyclic nucleotide signals to activate effector proteins, inducing cell death.
- Phospholipase effectors are a widespread CBASS family that degrade cell membranes.
Purpose of the Study:
- To elucidate the structural mechanisms of CBASS phospholipase activation.
- To visualize the conformational changes from inactive dimers to active oligomers.
- To understand the assembly and activation process of these bacterial defense proteins.
Main Methods:
- Cryo-electron microscopy (cryo-EM) and X-ray crystallography.
- Determination of structures in inactive, cyclic-dinucleotide-bound, and substrate-analog-bound states.
- Functional assays including binding, enzymatic activity, membrane disruption, and antiphage efficiency.
Main Results:
- CBASS phospholipases transition from inactive dimers to active filamentous oligomers upon cyclic dinucleotide binding.
- Structures captured the complete conformational reorganization process.
- Functional assays confirmed the role of assembly in membrane disruption and antiphage activity.
Conclusions:
- CBASS phospholipase activation is driven by assembly into higher-order structures.
- This mechanism is essential for bacterial defense against viral infection.
- The findings provide insights into a conserved antiviral pathway homologous to mammalian cGAS-STING.
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