NOD2 downregulates colonic inflammation by IRF4-mediated inhibition of K63-linked polyubiquitination of RICK and TRAF6

Mucosal Immunol. 2014 Nov;7(6):1312-25. doi: 10.1038/mi.2014.19. Epub 2014 Mar 26.


It is well established that polymorphisms of the caspase activation and recruitment domain 15 (CARD15) gene, a major risk factor in Crohn's disease (CD), lead to loss of nucleotide-binding oligomerization domain 2 (NOD2) function. However, a molecular explanation of how such loss of function leads to increased susceptibility to CD has remained unclear. In a previous study exploring this question, we reported that activation of NOD2 in human dendritic cells by its ligand, muramyl dipeptide (MDP), negatively regulates Toll-like receptor (TLR)-mediated inflammatory responses. Here we show that NOD2 activation results in increased interferon regulatory factor 4 (IRF4) expression and binding to tumor necrosis factor receptor associated factor 6 (TRAF6) and RICK (receptor interacting serine-threonine kinase). We then show that such binding leads to IRF4-mediated inhibition of Lys63-linked polyubiquitination of TRAF6 and RICK and thus to downregulation of nuclear factor (NF)-κB activation. Finally, we demonstrate that protection of mice from the development of experimental colitis by MDP or IRF4 administration is accompanied by similar IRF4-mediated effects on polyubiquitination of TRAF6 and RICK in colonic lamina propria mononuclear cells. These findings thus define a mechanism of NOD2-mediated regulation of innate immune responses to intestinal microflora that could explain the relation of CARD15 polymorphisms and resultant NOD2 dysfunction to CD.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Colon / immunology*
  • Colon / pathology
  • Crohn Disease / genetics
  • Crohn Disease / immunology*
  • Crohn Disease / pathology
  • Dendritic Cells / immunology
  • Dendritic Cells / pathology
  • Down-Regulation / immunology*
  • HEK293 Cells
  • Humans
  • Inflammation / genetics
  • Inflammation / immunology
  • Inflammation / pathology
  • Interferon Regulatory Factors / genetics
  • Interferon Regulatory Factors / immunology*
  • Mice
  • Nod2 Signaling Adaptor Protein / genetics
  • Nod2 Signaling Adaptor Protein / immunology*
  • Receptor-Interacting Protein Serine-Threonine Kinase 2
  • Receptor-Interacting Protein Serine-Threonine Kinases / genetics
  • Receptor-Interacting Protein Serine-Threonine Kinases / immunology*
  • TNF Receptor-Associated Factor 6 / genetics
  • TNF Receptor-Associated Factor 6 / immunology*
  • Ubiquitination / genetics
  • Ubiquitination / immunology*


  • Interferon Regulatory Factors
  • NOD2 protein, human
  • Nod2 Signaling Adaptor Protein
  • Nod2 protein, mouse
  • TNF Receptor-Associated Factor 6
  • interferon regulatory factor-4
  • Receptor-Interacting Protein Serine-Threonine Kinase 2
  • Receptor-Interacting Protein Serine-Threonine Kinases
  • Ripk2 protein, mouse