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      Cytoplasmic flagellin activates caspase-1 and secretion of interleukin 1beta via Ipaf.

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          Abstract

          Macrophages respond to Salmonella typhimurium infection via Ipaf, a NACHT-leucine-rich repeat family member that activates caspase-1 and secretion of interleukin 1beta. However, the specific microbial salmonella-derived agonist responsible for activating Ipaf is unknown. We show here that cytosolic bacterial flagellin activated caspase-1 through Ipaf but was independent of Toll-like receptor 5, a known flagellin sensor. Stimulation of the Ipaf pathway in macrophages after infection required a functional salmonella pathogenicity island 1 type III secretion system but not the flagellar type III secretion system; furthermore, Ipaf activation could be recapitulated by the introduction of purified flagellin directly into the cytoplasm. These observations raise the possibility that the salmonella pathogenicity island 1 type III secretion system cannot completely exclude 'promiscuous' secretion of flagellin and that the host capitalizes on this 'error' by activating a potent host-defense pathway.

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          Author and article information

          Journal
          Nat Immunol
          Nature immunology
          Springer Science and Business Media LLC
          1529-2908
          1529-2908
          Jun 2006
          : 7
          : 6
          Affiliations
          [1 ] Institute for Systems Biology, Seattle, Washington 98103, USA.
          Article
          ni1344
          10.1038/ni1344
          16648853
          d897fa41-4583-44f7-bf86-d96f9e0aa0c4
          History

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