NLRC4 inflammasome activation is NLRP3- and phosphorylation-independent during infection and does not protect from melanoma

J Exp Med. 2020 Jul 6;217(7):e20191736. doi: 10.1084/jem.20191736.


The NAIP/NLRC4 inflammasome is a cytosolic sensor of bacteria that activates caspase-1 and initiates potent immune responses. Structural, biochemical, and genetic data demonstrate that NAIP proteins are receptors for bacterial ligands, while NLRC4 is a downstream adaptor that multimerizes with NAIPs to form an inflammasome. NLRC4 has also been proposed to suppress tumor growth, though the underlying mechanism is unknown. Further, NLRC4 is phosphorylated on serine 533, which was suggested to be critical for its function. In the absence of S533 phosphorylation, it was proposed that another inflammasome protein, NLRP3, can induce NLRC4 activation. We generated a new Nlrc4-deficient mouse line and mice with S533D phosphomimetic or S533A nonphosphorylatable NLRC4. Using these models in vivo and in vitro, we fail to observe a requirement for phosphorylation in NLRC4 inflammasome function. Furthermore, we find no role for NLRP3 in NLRC4 function, or for NLRC4 in a model of melanoma. These results clarify our understanding of the mechanism and biological functions of NAIP/NLRC4 activation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Apoptosis Regulatory Proteins / chemistry
  • Apoptosis Regulatory Proteins / metabolism*
  • Base Sequence
  • Calcium-Binding Proteins / chemistry
  • Calcium-Binding Proteins / metabolism*
  • Cytosol / metabolism
  • Disease Susceptibility
  • Flagellin / metabolism
  • Inflammasomes / metabolism*
  • Melanoma / metabolism*
  • Melanoma / pathology*
  • Mice, Inbred C57BL
  • Mice, Mutant Strains
  • NLR Family, Pyrin Domain-Containing 3 Protein / metabolism*
  • Phosphorylation
  • Salmonella Infections, Animal / metabolism*
  • Salmonella Infections, Animal / pathology
  • Signal Transduction


  • Apoptosis Regulatory Proteins
  • Calcium-Binding Proteins
  • Inflammasomes
  • Ipaf protein, mouse
  • NLR Family, Pyrin Domain-Containing 3 Protein
  • Flagellin