The colonic pathogen Entamoeba histolytica activates caspase-4/1 that cleaves the pore-forming protein gasdermin D to regulate IL-1β secretion

PLoS Pathog. 2022 Mar 18;18(3):e1010415. doi: 10.1371/journal.ppat.1010415. eCollection 2022 Mar.

Abstract

A hallmark of Entamoeba histolytica (Eh) invasion in the gut is acute inflammation dominated by the secretion of pro-inflammatory cytokines TNF-α and IL-1β. This is initiated when Eh in contact with macrophages in the lamina propria activates caspase-1 by recruiting the NLRP3 inflammasome complex in a Gal-lectin and EhCP-A5-dependent manner resulting in the maturation and secretion of IL-1β and IL-18. Here, we interrogated the requirements and mechanisms for Eh-induced caspase-4/1 activation in the cleavage of gasdermin D (GSDMD) to regulate bioactive IL-1β release in the absence of cell death in human macrophages. Unlike caspase-1, caspase-4 activation occurred as early as 10 min that was dependent on Eh Gal-lectin and EhCP-A5 binding to macrophages. By utilizing CRISPR-Cas9 gene edited CASP4/1, NLRP3 KO and ASC-def cells, caspase-4 activation was found to be independent of the canonical NLRP3 inflammasomes. In CRISPR-Cas9 gene edited CASP1 macrophages, caspase-4 activation was significantly up regulated that enhanced the enzymatic cleavage of GSDMD at the same cleavage site as caspase-1 to induce GSDMD pore formation and sustained bioactive IL-1β secretion. Eh-induced IL-1β secretion was independent of pyroptosis as revealed by pharmacological blockade of GSDMD pore formation and in CRISPR-Cas9 gene edited GSDMD KO macrophages. This was in marked contrast to the potent positive control, lipopolysaccharide + Nigericin that induced high expression of predominantly caspase-1 that efficiently cleaved GSDMD with high IL-1β secretion/release associated with massive cell pyroptosis. These results reveal that Eh triggered "hyperactivated macrophages" allowed caspase-4 dependent cleavage of GSDMD and IL-1β secretion to occur in the absence of pyroptosis that may play an important role in disease pathogenesis.

MeSH terms

  • Caspase 1 / genetics
  • Caspase 1 / metabolism
  • Caspases, Initiator / metabolism
  • Entamoeba histolytica* / metabolism
  • Humans
  • Interleukin-1beta
  • Intracellular Signaling Peptides and Proteins / genetics
  • Intracellular Signaling Peptides and Proteins / metabolism
  • Phosphate-Binding Proteins / genetics
  • Phosphate-Binding Proteins / metabolism
  • Pore Forming Cytotoxic Proteins / metabolism
  • Pyroptosis

Substances

  • GSDMD protein, human
  • IL1B protein, human
  • Interleukin-1beta
  • Intracellular Signaling Peptides and Proteins
  • Phosphate-Binding Proteins
  • Pore Forming Cytotoxic Proteins
  • CASP4 protein, human
  • Caspases, Initiator
  • Caspase 1