10.1371/journal.ppat.1003400
Cierra N. Casson
Cierra
N. Casson
Alan M. Copenhaver
Alan
M. Copenhaver
Erin E. Zwack
Erin
E. Zwack
Hieu T. Nguyen
Hieu T.
Nguyen
Till Strowig
Till
Strowig
Bahar Javdan
Bahar
Javdan
William P. Bradley
William
P. Bradley
Thomas C. Fung
Thomas
C. Fung
Richard A. Flavell
Richard
A. Flavell
Igor E. Brodsky
Igor
E. Brodsky
Sunny Shin
Sunny
Shin
Caspase-11 Activation in Response to Bacterial Secretion Systems that Access the Host Cytosol
Public Library of Science
2013
immunology
Immune cells
monocytes
immunity
Immune activation
Immune defense
Immunity to infections
Innate immunity
microbiology
Bacterial pathogens
Gram negative
inflammation
Host-pathogen interaction
pathogenesis
activation
bacterial
secretion
systems
2013-06-06 01:04:19
Dataset
https://plos.figshare.com/articles/dataset/_Caspase_11_Activation_in_Response_to_Bacterial_Secretion_Systems_that_Access_the_Host_Cytosol_/713859
<div><p>Inflammasome activation is important for antimicrobial defense because it induces cell death and regulates the secretion of IL-1 family cytokines, which play a critical role in inflammatory responses. The inflammasome activates caspase-1 to process and secrete IL-1β. However, the mechanisms governing IL-1α release are less clear. Recently, a non-canonical inflammasome was described that activates caspase-11 and mediates pyroptosis and release of IL-1α and IL-1β. Caspase-11 activation in response to Gram-negative bacteria requires Toll-like receptor 4 (TLR4) and TIR-domain-containing adaptor-inducing interferon-β (TRIF)-dependent interferon production. Whether additional bacterial signals trigger caspase-11 activation is unknown. Many bacterial pathogens use specialized secretion systems to translocate effector proteins into the cytosol of host cells. These secretion systems can also deliver flagellin into the cytosol, which triggers caspase-1 activation and pyroptosis. However, even in the absence of flagellin, these secretion systems induce inflammasome activation and the release of IL-1α and IL-1β, but the inflammasome pathways that mediate this response are unclear. We observe rapid IL-1α and IL-1β release and cell death in response to the type IV or type III secretion systems of <i>Legionella pneumophila</i> and <i>Yersinia pseudotuberculosis</i>. Unlike IL-1β, IL-1α secretion does not require caspase-1. Instead, caspase-11 activation is required for both IL-1α secretion and cell death in response to the activity of these secretion systems. Interestingly, whereas caspase-11 promotes IL-1β release in response to the type IV secretion system through the NLRP3/ASC inflammasome, caspase-11-dependent release of IL-1α is independent of both the NAIP5/NLRC4 and NLRP3/ASC inflammasomes as well as TRIF and type I interferon signaling. Furthermore, we find both overlapping and non-redundant roles for IL-1α and IL-1β in mediating neutrophil recruitment and bacterial clearance in response to pulmonary infection by <i>L. pneumophila</i>. Our findings demonstrate that virulent, but not avirulent, bacteria trigger a rapid caspase-11-dependent innate immune response important for host defense.</p></div>