Centaurin β1 (CENTB1), a GTPase-activating protein, is a member of the ADP-ribosylation factor family encoded by a gene located on the short arm of human chromosome 17. A yeast two-hybrid screen first suggested a direct interaction between CENTB1 and NOD2. Co-immunoprecipitation experiments confirmed direct interaction between CENTB1 and NOD2 and demonstrated similar interaction between CENTB1 and NOD1. We also demonstrate that endogenous CENTB1 interacts with endogenous NOD2 and NOD1 in SW480 and HT-29 intestinal epithelial cells. CENTB1 partially co-localized with NOD2 and NOD1 proteins in the cytoplasm of mammalian cells. CENTB1 expression in epithelial cells was highly induced by tumor necrosis factor α, interleukin 1β, and the NOD1 and NOD2 ligands (γ-D-glutamyl-meso-diaminopimelic acid and muramyl dipeptide, respectively). In addition, CENTB1 mRNA level is increased in the inflamed mucosa of patients with inflammatory bowel disease. Functionally, CENTB1 overexpression inhibited NOD1- and NOD2-dependent activation of NF-κB, whereas small inhibitory RNA against CENTB1 increased NF-κB activation following NOD1- or NOD2-mediated recognition of the bacterial components γ-D-glutamyl-meso-diaminopimelic acid and muramyl dipeptide, respectively. In contrast, CENTB1 had no effect on NF-κB activation induced by Toll-like receptors. In conclusion, CENTB1 selectively down-regulates NF-κB activation via NODs pathways, creating a "feedback" loop and suggesting a novel role of CENTB1 in innate immune responses to bacteria and inflammatory responses.
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