Epithelial-derived gasdermin D mediates nonlytic IL-1β release during experimental colitis

Area of Science:

• Cell Biology
• Immunology
• Gastroenterology

Background:

• Gasdermin D (GSDMD) is known to induce pyroptosis, a form of programmed cell death, through caspase activation and IL-1β release.
• The precise mechanisms regulating IL-1β release, particularly in non-pyroptotic contexts, remain incompletely understood in intestinal epithelial cells (IECs).

Purpose of the Study:

• To investigate a non-pyroptotic role of full-length Gasdermin D (GSDMD) in the release of IL-1β from intestinal epithelial cells (IECs).
• To elucidate the molecular mechanisms by which GSDMD mediates IL-1β release via small extracellular vesicles (sEVs).
• To determine the contribution of GSDMD-mediated IL-1β sEV release to intestinal inflammation, such as in inflammatory bowel disease (IBD).

Main Methods:

• Investigated GSDMD's role in IL-1β release using cell culture models of IECs and colonic explants.
• Utilized co-immunoprecipitation and immunofluorescence to examine protein interactions and cellular localization (GSDMD, IL-1β, Cdc37/Hsp90, NEDD4, CD63, ALIX).
• Assessed the impact of GSDMD deficiency on disease severity in experimental colitis models and analyzed GSDMD expression in IBD patients.

Main Results:

• Identified a non-pyroptotic function of full-length GSDMD in promoting the release of IL-1β-containing small extracellular vesicles (sEVs) from IECs.
• Demonstrated that GSDMD, with Cdc37/Hsp90 and NEDD4, polyubiquitinates pro-IL-1β, signaling its packaging into secretory vesicles.
• Showed that GSDMD and NEDD4 are essential for the release of CD63+ sEVs containing IL-1β, GSDMD, NEDD4, and caspase-8.
• Observed increased epithelial GSDMD expression in IBD patients and experimental colitis, with GSDMD deficiency attenuating colitis severity.

Conclusions:

• Full-length GSDMD mediates IL-1β release through a non-pyroptotic pathway involving NEDD4-dependent polyubiquitination and packaging into sEVs.
• GSDMD-driven release of IL-1β-containing sEVs contributes to the pathogenesis of intestinal inflammation, including IBD.
• Targeting GSDMD-mediated sEV release may offer a therapeutic strategy for inflammatory bowel diseases.