Galectin-3 promotes noncanonical inflammasome activation through intracellular binding to lipopolysaccharide glycans

Tzu Han Lo, Hung Lin Chen, Cheng I. Yao, I. Chun Weng, Chi Shan Li, Chi Chun Huang, Nien Jung Chen, Chun Hung Lin, Fu Tong Liu*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

Cytosolic lipopolysaccharides (LPSs) bind directly to caspase-4/5/11 through their lipid A moiety, inducing inflammatory caspase oligomerization and activation, which is identified as the noncanonical inflammasome pathway. Galectins, β-galactoside–binding proteins, bind to various gram-negative bacterial LPS, which display β-galactoside–containing polysaccharide chains. Galectins are mainly present intracellularly, but their interactions with cytosolic microbial glycans have not been investigated. We report that in cell-free systems, galectin-3 augments the LPS-induced assembly of caspase-4/11 oligomers, leading to increased caspase-4/11 activation. Its carboxyl-terminal carbohydrate-recognition domain is essential for this effect, and its N-terminal domain, which contributes to the self-association property of the protein, is also critical, suggesting that this promoting effect is dependent on the functional multivalency of galectin-3. Moreover, galectin-3 enhances intracellular LPS-induced caspase-4/11 oligomerization and activation, as well as gasdermin D cleavage in human embryonic kidney (HEK) 293T cells, and it additionally promotes interleukin-1β production and pyroptotic death in macrophages. Galectin-3 also promotes caspase-11 activation and gasdermin D cleavage in macrophages treated with outer membrane vesicles, which are known to be taken up by cells and release LPSs into the cytosol. Coimmunoprecipitation confirmed that galectin-3 associates with caspase-11 after intracellular delivery of LPSs. Immunofluorescence staining revealed colocalization of LPSs, galectin-3, and caspase-11 independent of host N-glycans. Thus, we conclude that galectin-3 amplifies caspase-4/ 11 oligomerization and activation through LPS glycan binding, resulting in more intense pyroptosis—a critical mechanism of host resistance against bacterial infection that may provide opportunities for new therapeutic interventions.

Original languageEnglish
Article numbere2026246118
JournalProceedings of the National Academy of Sciences of the United States of America
Volume118
Issue number30
DOIs
StatePublished - 27 Jul 2021

Keywords

  • Caspase-4/11
  • Galectin-3
  • Lipopolysaccharide
  • Noncanonical inflammasome

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