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In response to infections and tissue damage, ASC-containing inflammasome protein complexes are assembled that promote caspase-1 activation, IL-1β and IL-18 processing and release, pyroptosis, and the release of ASC particles. However, excessive or persistent activation of the inflammasome causes inflammatory diseases. Therefore, a well-balanced inflammasome response is crucial for the maintenance of homeostasis. We show that the PYD-only protein POP1 inhibited ASC-dependent inflammasome assembly by preventing inflammasome nucleation, and consequently interfered with caspase-1 activation, IL-1β and IL-18 release, pyroptosis, and the release of ASC particles. There is no mouse ortholog for POP1, but transgenic expression of human POP1 in monocytes, macrophages, and dendritic cells protected mice from systemic inflammation triggered by molecular PAMPs, inflammasome component NLRP3 mutation, and ASC danger particles. POP1 expression was regulated by TLR and IL-1R signaling, and we propose that POP1 provides a regulatory feedback loop that shuts down excessive inflammatory responses and thereby prevents systemic inflammation.

Original publication

DOI

10.1016/j.immuni.2015.07.018

Type

Journal article

Journal

Immunity

Publication Date

18/08/2015

Volume

43

Pages

264 - 276

Keywords

Animals, Apoptosis, Carrier Proteins, Caspase 1, Cell Line, Cryopyrin-Associated Periodic Syndromes, Dendritic Cells, Female, Gene Expression Regulation, Homeostasis, Humans, Inflammasomes, Interleukin-18, Interleukin-1beta, Lipopolysaccharides, Macrophages, Peritoneal, Mice, Mice, Inbred C57BL, Mice, Knockout, Mice, Transgenic, Monocytes, NLR Family, Pyrin Domain-Containing 3 Protein, Peritonitis, Protein Multimerization, RNA, Small Interfering, Ribonucleoproteins