Abstract
We recently described the induction of noncanonical IL-1β processing via caspase-8 recruited to ripoptosome signaling platforms in myeloid leukocytes. Here, we demonstrate that activated NLRP3·ASC inflammasomes recruit caspase-8 to drive IL-1β processing in murine bone marrow-derived dendritic cells (BMDC) independent of caspase-1 and -11. Sustained stimulation (>2 h) of LPS-primed caspase-1-deficient (Casp1/11 -/-) BMDC with the canonical NLRP3 inflammasome agonist nigericin results in release of bioactive IL-1β in conjunction with robust caspase-8 activation. This IL-1β processing and caspase-8 activation do not proceed in Nlrp3 -/- or Asc -/- BMDC and are suppressed by pharmacological inhibition of caspase-8, indicating that caspase-8 can act as a direct IL-1oβ-converting enzyme during NLRP3 inflammasome activation. In contrast to the rapid caspase-1-mediated death of wild type (WT) BMDC via NLRP3-dependent pyroptosis, nigericin-stimulated Casp1/11 -/- BMDC exhibit markedly delayed cell death via NLRP3-dependent apoptosis. Biochemical analyses of WT and Casp1/11 -/- BMDC indicated that caspase-8 is proteolytically processed within detergent-insoluble ASC-enriched protein complexes prior to extracellular export during nigericin treatment. Although nigericin-stimulated caspase-1 activation and activity are only modestly attenuated in caspase-8-deficient (Casp8 -/- Rip3 -/-) BMDC, these cells do not exhibit the rapid loss of viability of WT cells. These results support a contribution of caspase-8 to both IL-1β production and regulated death signaling via NLRP3 inflammasomes. In the absence of caspase-1, NLRP3 inflammasomes directly utilize caspase-8 as both a proapoptotic initiator and major IL-1β-converting protease. In the presence of caspase-1, caspase-8 acts as a positive modulator of the NLRP3-dependent caspase-1 signaling cascades that drive both IL-1β production and pyroptotic death.
Original language | English (US) |
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Pages (from-to) | 20167-20184 |
Number of pages | 18 |
Journal | Journal of Biological Chemistry |
Volume | 290 |
Issue number | 33 |
DOIs | |
State | Published - Aug 14 2015 |
ASJC Scopus subject areas
- Biochemistry
- Molecular Biology
- Cell Biology