19:10 - 21:00
Room: Ishikawa Ongakudō Interchange Hall
Poster Session
Caspase-1 serves as an apoptosis-initiating caspase in the absence of Gasdermin D (GSDMD)
Kohsuke Tsuchiya, Muhammad Mamunur Rashid Mahib, Takashi Suda
Division of Immunology and Molecular Biology, Cancer Research Institute, Kanazawa University, Kanazawa, Japan

Inflammasomes activate caspase-1 in response to various inflammatory stimuli, including the microbial pathogen Salmonella Typhimurium. Active caspase-1 then processes the pro-forms of IL-1β and IL-18 into their mature forms. Active caspase-1 also induces regulated necrosis called pyroptosis accompanied by rapid cell membrane rupture and release of IL-1β, IL-18, and DAMPs. Recent studies have revealed that GSDMD is a critical mediator of pyroptosis. Namely, caspase-1 cleaves GSDMD, and in turn, its N-terminal fragment forms pores in the plasma membrane, which cause osmotic cell swelling and necrotic death. However, the lack of GSDMD only delays but not abolishes inflammasome-mediated cell death of macrophages. Thus, it remains possible that caspase-1 is able to induce cell death in a GSDMD-independent manner. Here, we show that in the absence of GSDMD, caspase-1 induces apoptosis in different types of cells. After Salmonella infection, macrophages (BMM, RAW264.7) deficient in GSDMD underwent apoptosis accompanied by caspase-3 activation, phosphatidylserine exposure, and plasma membrane blebbing in a caspase-1-dependent manner. Besides, we established Colon-26 cells expressing iCasp1 (a caspase-1 derivative that can be polymerized with a small compound, AP20187), which died by pyroptosis during AP20187 treatment, and the Gsdmd gene in this cell line was disrupted using the CRISPR-Cas9 system. Importantly, GSDMD-null Colon-26-iCasp1 cells exhibited apoptosis upon AP20187 treatment, indicating that caspase-1 has a potential to induce apoptosis. It appears that the caspase-1-induced apoptosis depends on caspase-3, as it was significantly attenuated by genetic ablation of this caspase. Moreover, we found that Bid is required for caspase-1-induced caspase-3 activation and apoptosis in macrophages and Colon-26-iCasp1 cells. Taken together, these results suggest that caspase-1 induces not only GSDMD-dependent pyroptosis, but also apoptosis through the Bid-caspase-3 axis, which would occur after inflammasome formation in cell types that do not express GSDMD.


Reference:
Mo-P7-4
Session:
Poster Session 7 “Signal transduction and metabolic regulation”
Presenter/s:
Kohsuke Tsuchiya
Presentation type:
Poster Presentation
Room:
Ishikawa Ongakudō Interchange Hall
Date:
Monday, 30 October 2017
Time:
19:10 - 21:00
Session times:
19:10 - 21:00