Human non-canonical inflammasomes activate CASP3 to limit intracellular <i>Salmonella</i> replication in macrophages.

ABSTRACT: Inflammasomes are multiprotein signaling platforms that activate inflammatory caspases to initiate innate immune signaling. In humans, canonical inflammasomes activate CASP1, which cleaves the pore-forming protein gasdermin D (GSDMD) and the cytokines IL-1β and IL-18. In contrast, the non-canonical inflammasome detects bacterial lipopolysaccharide (LPS) through CASP4/5, which cleave GSDMD to drive pyroptosis. While CASP1 substrates are well characterized, CASP4/5 substrates remain less defined. Here, we show that in response to intracellular LPS and gram-negative bacterial infection, CASP4/5 directly cleave and activate the executioner caspases CASP3/7. CASP3 in turn cleaves and activates gasdermin E (GSDME). Surprisingly, CASP3, but not GSDME, was required for restricting intracellular Salmonella replication, suggesting that CASP4/5-induced apoptosis contributes to host defense. We further show that most GSDMD cleavage during non-canonical inflammasome activation is mediated by CASP1, and that GSDMD is the primary driver of pyroptosis. Finally, we confirm that CASP4/5 activate CASP3/7 and GSDME in human primary macrophages. These findings establish CASP4/5 as dual apoptotic initiator and inflammatory caspases and reveal a central role for the apoptotic signaling cascade in non-canonical inflammasome-mediated immunity.

SUBMITTER: Kulkarni M 

PROVIDER: S-EPMC12637516 | biostudies-literature | 2025 Nov

REPOSITORIES: biostudies-literature