Critical function for Naip5 in inflammasome activation by a conserved carboxy-terminal domain of flagellin


Inflammasomes are cytosolic multiprotein complexes that sense microbial infection and trigger cytokine production and cell death. However, the molecular components of inflammasomes and what they sense remain poorly defined. Here we demonstrate that 35 amino acids of the carboxyl terminus of flagellin triggered inflammasome activation in the absence of bacterial contaminants or secretion systems. To further elucidate the host flagellin-sensing pathway, we generated mice deficient in the intracellular sensor Naip5. These mice failed to activate the inflammasome in response to the 35 amino acids of flagellin or in response to Legionella pneumophila infection. Our data clarify the molecular basis for the cytosolic response to flagellin.

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Figure 1: The C terminus of flagellin is necessary and sufficient to trigger Ipaf- and caspase-1-dependent macrophage death.
Figure 2: The cytotoxic C terminus of flagellin is highly conserved and is distinct from the region sensed by TLR5.
Figure 3: Leucine residues in the C terminus of L. pneumophila flagellin are critical for inflammasome activation.
Figure 4: Naip5 is required for the activation of caspase-1 and release of IL-1β induced by L. pneumophila.
Figure 5: Naip5 is required for the restriction of L. pneumophila replication in macrophages.
Figure 6: Function of Naip5 in the recognition of L. pneumophila, S. typhimurium and P. aeruginosa.


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We thank S. Goodart and M. Michelman for help in generating Naip5-deficient mice; V. Dixit and S. Mariathasan (Genentech) for Ipaf-deficient mice; K. Fitzgerald and D. Golenbock (University of Massachusetts) for immortalized B6 macrophages; C. Roy and C. Case (Yale University) for caspase-3-deficient femurs; A. Van der Velden (Stony Brook University) and M. Starnbach (Harvard Medical School) for caspase-1-deficient mice and S. typhimurium LT2 and isogenic mutants; T. Machen (University of California, Berkeley) for P. aeruginosa strain PAK; G. Barton (University of California, Berkeley) for Pam3CSK4; and D. Raulet, G. Barton, and the Barton and Vance laboratories for discussions. Supported by the Cancer Research Institute (R.E.V.), the National Institutes of Health (AI075039 and AI070739 to R.E.V.) and the Stiftelsen Olle Engkvist Byggmästare through the Swedish Research Council (J.P.).

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K.L.L., J.P., S.W.B., C.E.W., J.v.M., E.A.D., T.H., Y.-H.S., W.F.D., R.M.T. and R.E.V. conceived the experiments; K.L.L., J.P., S.W.B., C.E.W., J.v.M., E.A.D., T.H., Y.-H.S. and D.C. did the experiments; and all authors analyzed data and wrote or edited the manuscript.

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Correspondence to Russell E Vance.

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Lightfield, K., Persson, J., Brubaker, S. et al. Critical function for Naip5 in inflammasome activation by a conserved carboxy-terminal domain of flagellin. Nat Immunol 9, 1171–1178 (2008).

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