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Anthrax lethal toxin triggers the formation of a membrane‐associated inflammasome complex in murine macrophages
Author(s) -
Nour Adel M,
Yeung YeeGuide,
Santambrogio Laura,
Stanley E. Richard,
Brojatsch Jürgen
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.650.4
Subject(s) - inflammasome , caspase 1 , pyroptosis , chemistry , inflammation , caspase , caspase 8 , toxin , biology , apoptosis , microbiology and biotechnology , programmed cell death , biochemistry , immunology
Multiple microbial toxins, including the anthrax lethal toxin (LT), trigger an inflammatory response by activating caspase‐1. The caspase‐1 activator Nalp1b protein controls the susceptibility of murine macrophages to LT‐mediated cell death. In this study, we generated antibodies against the murine inflammatory proteins Asc and Nalp1b to localize and identify the LT‐triggered inflammasome complex. Using subcellular fractionation, we found that caspase‐1 and Nalp1b in the triton X‐100 soluble post‐nuclear particulate fraction of murine macrophages. Furthermore, we used immunostaining to show that both proteins co‐localized to the trafficking motor protein dynamin‐2. Unlike caspase‐1 and Nalp1b, Asc and the caspase‐1 substrate interleukin (IL)‐18 were cytosolic. Using size exclusion chromatography (SEC), we discovered that procaspase‐1 preassembles as a 200 kDa complex in untreated macrophages, which shifts to an 800 kDa complex upon LT treatment. Then, we immunopurified caspase‐1 complexes from SEC fractions and identified the caspase‐1‐associated proteins using mass spectroscopy. Consistent with formation of the inflammasome complex, the 800 Kda complex contained proteins involved in inflammation including Nalp1b, enolase, caspase‐1, and caspase‐4. The identified proteins could serve as potential therapeutic targets for management of a variety of microbial and inflammatory diseases.