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Itaconic acid, a missing link in macrophage activation, is produced by IRG1
Author(s) -
Cheng Jiongjia,
Jewel Delilah,
Chiles Thomas C.,
Stec Boguslaw,
Roberts Mary Fedarko
Publication year - 2013
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.27.1_supplement.789.13
Subject(s) - gene knockdown , cell culture , immune system , biology , stimulation , biochemistry , chemistry , microbiology and biotechnology , gene , immunology , neuroscience , genetics
Itaconic acid (ITA) is a metabolite produced by primary macrophages and cell lines derived from macrophages that is dramatically increased upon activation. ITA is synthesized by a cis‐aconitate decarboxylase (cADC). Sequence searches with a known fungal cADC show little homology to ORFs in mammalian cells. Studies with the macrophage cell line RAW246.7 show that cADC activity upon stimulation is dependent on de novo protein synthesis. MS analyses of partially purified RAW 246.7 protein extracts from stimulated cells show a very large increase for immune‐responsive gene 1 protein (IRG1). IRG1 synthesis follows the time course of ITA generation (measured by 1 H NMR) and siRNA knockdown of the IRG1 reduces cADC activity upon stimulation. Finally, expression of murine IRG1 in E. coli introduces cADC activity into protein extracts of the transformed bacterium. IRG1 previously was suggested to be a 2‐methylcitrate dehydratase. However, both the partially purified protein fraction from RAW246.7 cells containing cADC activity and recombinant IRG1 can not catalyze 2‐methylcitrate dehydration. This identifies IRG1 as the first mammalian cADC. Ongoing experiments seek a role for ITA in macrophages and in the mammalian immune system. This work has been supported by the U.S. Department of Energy, Office of Science, Energy Biosciences DE‐FG02–91ER20025.