Format

Send to

Choose Destination
J Biol Chem. 2015 Aug 14;290(33):20167-84. doi: 10.1074/jbc.M115.652321. Epub 2015 Jun 22.

Caspase-8 as an Effector and Regulator of NLRP3 Inflammasome Signaling.

Author information

1
Pathology, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106.
2
From the Departments of Physiology and Biophysics and.
3
Pathology, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, the Department of Immunology, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195, and.
4
the Department of Immunology, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195, and.
5
the Department of Microbiology and Immunology, Emory Vaccine Center, Emory University School of Medicine, Atlanta, Georgia 30322.
6
Pathology, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, From the Departments of Physiology and Biophysics and george.dubyak@case.edu.

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-1β-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 pro-apoptotic 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.

KEYWORDS:

apoptosis; caspase 1 (CASP1); caspase 8; dendritic cell; inflammasome; inflammation; interleukin 1 (IL-1); pyroptosis

PMID:
26100631
PMCID:
PMC4536427
DOI:
10.1074/jbc.M115.652321
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for HighWire Icon for PubMed Central
Loading ...
Support Center