Sensor component of the NLRC4 inflammasome that specifically recognizes and binds flagellin from pathogenic bacteria such as Legionella or Salmonella (PubMed:12526741, PubMed:21874021, PubMed:21918512, PubMed:29146805, PubMed:29182158). Association of pathogenic bacteria proteins drives in turn drive assembly and activation of the NLRC4 inflammasome, promoting caspase-1 activation, cytokine production and macrophage pyroptosis (PubMed:21874021, PubMed:21918512, PubMed:29146805, PubMed:29182158). The NLRC4 inflammasome is activated as part of the innate immune response to a range of intracellular bacteria. The NLRC4 inflammasome senses Gram-negative bacteria such as L.pneumophila and P.aeruginosa, enteric pathogens S.typhimurium (Salmonella) and S.flexneri (PubMed:21874021, PubMed:21918512, PubMed:29146805, PubMed:29182158). May contribute to prevent motor-neuron apoptosis induced by a variety of signals (By similarity). Component of the NLRC4 inflammasome, at least composed of NLRC4, caspase-1 (CASP1) and some NAIP protein. Flagellin binding by NAIP5 triggers assembly of the inflammasome, a huge complex that contains a single NAIP5 chain and multiple copies of NLRC4 (PubMed:29182158). (Microbial infection) Interacts with S.typhimurium (Salmonella) flagellin. (Microbial infection) Interacts with L.pneumophila flagellin. Detected in macrophages (at protein level). Part of the Lgn1 locus that determines susceptibility to the intracellular pathogen L.pneumophila. Susceptibility differs between inbred mouse strains. Strain C57BL/6J is not permissive, i.e. L.pneumophila cannot multiply in C57BL/6J macrophages, contrary to the situation in mouse strain A/J. Strain FVB/NJ macrophages display intermediate permissiveness for intracellular proliferation of L.pneumophila.