Guanylate-Binding Protein-Dependent Noncanonical Inflammasome Activation Prevents Burkholderia thailandensis-Induced Multinucleated Giant Cell Formation.

Marisa Dilucca,Kateryna Shkarina,Petr Broz,Saray Ramos,José Carlos Santos,Dominique Soldati-Favre

doi:10.1128/mbio.02054-21

Abstract

ABSTRACTInflammasomes are cytosolic multiprotein signaling complexes that are activated upon pattern recognition receptor-mediated recognition of pathogen-derived ligands or endogenous danger signals. Their assembly activates the downstream inflammatory caspase-1 and caspase-4/5 (human) or caspase-11 (mouse), which induces cytokine release and pyroptotic cell death through the cleavage of the pore-forming effector gasdermin D. Pathogen detection by host cells also results in the production and release of interferons (IFNs), which fine-tune inflammasome-mediated responses. IFN-induced guanylate-binding proteins (GBPs) have been shown to control the activation of the noncanonical inflammasome by recruiting caspase-4 on the surface of cytosolic Gram-negative bacteria and promoting its interaction with lipopolysaccharide (LPS). The Gram-negative opportunistic bacterial pathogen Burkholderia thailandensis infects epithelial cells and macrophages and hijacks the host actin polymerization machinery to spread into neighboring cells. This process causes host cell fusion and the formation of so-called multinucleated giant cells (MNGCs). Caspase-1- and IFN-regulated caspase-11-mediated inflammasome pathways play an important protective role against B. thailandensis in mice, but little is known about the role of IFNs and inflammasomes during B. thailandensis infection of human cells, particularly epithelial cells. Here, we report that IFN-γ priming of human epithelial cells restricts B. thailandensis-induced MNGC formation in a GBP1-dependent manner. Mechanistically, GBP1 does not promote bacteriolysis or impair actin-based bacterial motility but acts by inducing caspase-4-dependent pyroptosis of the infected cell. In addition, we show that IFN-γ priming of human primary macrophages confers a more efficient antimicrobial effect through inflammasome activation, further confirming the important role that interferon signaling plays in restricting Burkholderia replication and spread.

Highlights

Inflammasomes are cytosolic multiprotein signaling complexes that are activated upon pattern recognition receptor-mediated recognition of pathogenderived ligands or endogenous danger signals
To gain more insights into the role of IFN priming in protecting human epithelial cells against B. thailandensis infection, we infected HeLa cells with B. thailandensis and monitored the formation of multinucleated giant cells (MNGCs), a hallmark of B. thailandensis spread and replication
Our results suggest that GBP1 impairs B. thailandensis cell-to-cell spread by triggering caspase-4-dependent pyroptosis of infected cells

Summary

Introduction

Inflammasomes are cytosolic multiprotein signaling complexes that are activated upon pattern recognition receptor-mediated recognition of pathogenderived ligands or endogenous danger signals. The Gram-negative opportunistic bacterial pathogen Burkholderia thailandensis infects epithelial cells and macrophages and hijacks the host actin polymerization machinery to spread into neighboring cells This process causes host cell fusion and the formation of so-called multinucleated giant cells (MNGCs). By functioning as a bona fide LPS sensor, human GBP1 (hGBP1) assembles a platform that recruits other GBP family members (hGBP2 to -4 [hGPB2-4]) [16] and caspase-4 directly on the surface of cytosolic Salmonella enterica serovar Typhimurium or Shigella flexneri cells [17,18,19,20,21] This in turn allows the activation of the so-called noncanonical inflammasome via LPS-induced caspase-4 oligomerization and activation, which cleaves the pore-forming cell death effector gasdermin D (GSDMD) to induce proinflammatory pyroptosis and interleukin-18 (IL-18) release [22, 23].

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Results

Conclusion