All Publications

  • Phage anti-CBASS protein simultaneously sequesters cyclic trinucleotides and dinucleotides. Molecular cell Cao, X., Xiao, Y., Huiting, E., Cao, X., Li, D., Ren, J., Fedorova, I., Wang, H., Guan, L., Wang, Y., Li, L., Bondy-Denomy, J., Feng, Y. 2023

    Abstract

    Cyclic-oligonucleotide-based anti-phage signaling system (CBASS) is a common immune system that uses cyclic oligonucleotide signals to limit phage replication. In turn, phages encode anti-CBASS (Acb) proteins such as Acb2, which can sequester some cyclic dinucleotides (CDNs) and limit downstream effector activation. Here, we identified that Acb2 sequesters many CDNs produced by CBASS systems and inhibits stimulator of interferon genes (STING) activity in human cells. Surprisingly, the Acb2 hexamer also binds with high affinity to CBASS cyclic trinucleotides (CTNs) 3'3'3'-cyclic AMP-AMP-AMP and 3'3'3'-cAAG at a distinct site from CDNs. One Acb2 hexamer can simultaneously bind two CTNs and three CDNs. Phage-encoded Acb2 provides protection from type III-C CBASS that uses cA3 signaling molecules. Moreover, phylogenetic analysis of >2,000 Acb2 homologs encoded by diverse phages and prophages revealed that most are expected to bind both CTNs and CDNs. Altogether, Acb2 sequesters nearly all known CBASS signaling molecules through two distinct binding pockets and therefore serves as a broad-spectrum inhibitor of cGAS-based immunity.

    View details for DOI 10.1016/j.molcel.2023.11.026

    View details for PubMedID 38103556

  • Phage anti-CBASS protein simultaneously sequesters cyclic trinucleotides and dinucleotides. bioRxiv : the preprint server for biology Cao, X., Xiao, Y., Huiting, E., Cao, X., Li, D., Ren, J., Guan, L., Wang, Y., Li, L., Bondy-Denomy, J., Feng, Y. 2023

    Abstract

    CBASS is a common anti-phage immune system that uses cyclic oligonucleotide signals to activate effectors and limit phage replication. In turn, phages encode anti-CBASS (Acb) proteins. We recently uncovered a widespread phage anti-CBASS protein Acb2 that acts as a "sponge" by forming a hexamer complex with three cGAMP molecules. Here, we identified that Acb2 binds and sequesters many CBASS and cGAS-produced cyclic dinucleotides in vitro and inhibits cGAMP-mediated STING activity in human cells. Surprisingly, Acb2 also binds CBASS cyclic trinucleotides 3'3'3'-cyclic AMP-AMP-AMP (cA3) and 3'3'3'-cAAG with high affinity. Structural characterization identified a distinct binding pocket within the Acb2 hexamer that binds two cyclic trinucleotide molecules and another binding pocket that binds to cyclic dinucleotides. Binding in one pocket does not allosterically alter the other, such that one Acb2 hexamer can simultaneously bind two cyclic trinucleotides and three cyclic dinucleotides. Phage-encoded Acb2 provides protection from Type III-C CBASS that uses cA3 signaling molecules in vivo and blocks cA3-mediated activation of the endonuclease effector in vitro. Altogether, Acb2 sequesters nearly all known CBASS signaling molecules through two distinct binding pockets and therefore serves as a broad-spectrum inhibitor of cGAS-based immunity.

    View details for DOI 10.1101/2023.06.01.543220

    View details for PubMedID 37398474

    View details for PubMedCentralID PMC10312549

  • Nordihydroguaiaretic Acid (NDGA) Inhibits CsgA Polymerization, Bacterial Amyloid Biogenesis, and Biofilm Formation. Chembiochem : a European journal of chemical biology Visser, J. A., Yager, D., Chambers, S. A., Lim, J. Y., Cao, X., Cegelski, L. 2023: e202300266

    Abstract

    Escherichia coli and other Enterobacteriaceae thrive in robust biofilm communities through the coproduction of curli amyloid fibers and phosphoethanolamine cellulose. Curli promote adhesion to abiotic surfaces and plant and human host tissues and are associated with pathogenesis in urinary tract infection and foodborne illness. As amyloid, curli production in the host has also been implicated in the pathogenesis of neurodegenerative diseases. We report that the natural product nordihydroguaiaretic acid (NDGA) is effective as a curlicide in E. coli. NDGA prevents CsgA polymerization in vitro in a dose-dependent manner. NDGA selectively inhibits cellassociated curli assembly in E. coli and inhibits biofilm formation among uropathogenic E. coli in a curli-specific manner. More broadly, our work emphasizes the ability to evaluate and identify bioactive amyloid assembly inhibitors using the powerful gene-directed amyloid biogenesis machinery in E. coli.

    View details for DOI 10.1002/cbic.202300266

    View details for PubMedID 37195016

  • ENPP1's regulation of extracellular cGAMP is a ubiquitous mechanism of attenuating STING signaling. Proceedings of the National Academy of Sciences of the United States of America Carozza, J. A., Cordova, A. F., Brown, J. A., AlSaif, Y., Bohnert, V., Cao, X., Mardjuki, R. E., Skariah, G., Fernandez, D., Li, L. 2022; 119 (21): e2119189119

    Abstract

    SignificanceThe immune system strikes a careful balance between launching a robust response to threats and avoiding overactivation. The molecule cGAMP is an immunotransmitter that activates innate immunity and signals extracellularly, where it is subject to degradation by the enzyme ENPP1. Here, we engineer ENPP1 to lose activity toward cGAMP but not other substrates, thus creating a biochemically precise tool to understand how ENPP1 regulates extracellular cGAMP and thus innate immunity. We uncover that ENPP1's degradation of extracellular cGAMP has a long evolutionary history, and that this mechanism is critical for controlling diverse immune threats, including viral infection and inflammation.

    View details for DOI 10.1073/pnas.2119189119

    View details for PubMedID 35588451

  • Therapeutic Interventions Targeting Innate Immune Receptors: A Balancing Act CHEMICAL REVIEWS Cao, X., Cordova, A. F., Li, L. 2022; 122 (3): 3414-3458

    Abstract

    The innate immune system is an organism's first line of defense against an onslaught of internal and external threats. The downstream adaptive immune system has been a popular target for therapeutic intervention, while there is a relative paucity of therapeutics targeting the innate immune system. However, the innate immune system plays a critical role in many human diseases, such as microbial infection, cancer, and autoimmunity, highlighting the need for ongoing therapeutic research. In this review, we discuss the major innate immune pathways and detail the molecular strategies underpinning successful therapeutics targeting each pathway as well as previous and ongoing efforts. We will also discuss any recent discoveries that could inform the development of novel therapeutic strategies. As our understanding of the innate immune system continues to develop, we envision that therapies harnessing the power of the innate immune system will become the mainstay of treatment for a wide variety of human diseases.

    View details for DOI 10.1021/acs.chemrev.1c00716

    View details for Web of Science ID 000767145700008

    View details for PubMedID 34870969