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

• Published in: Mucosal immunology Vol. 7; no. 6; pp. 1312 - 1325
• Main Authors: Watanabe, T, Asano, N, Meng, G, Yamashita, K, Arai, Y, Sakurai, T, Kudo, M, Fuss, I J, Kitani, A, Shimosegawa, T, Chiba, T, Strober, W
• Format: Journal Article
• Language: English
• Published: New York Nature Publishing Group US 01.11.2014; Elsevier Limited
• Subjects: 631/250/256; 631/250/347; 631/80/86; 692/699/1503/1581/257/1402; Allergology; Animals; Antibodies; Biomedical and Life Sciences; Biomedicine; Colon - immunology; Colon - pathology; Crohn Disease - genetics; Crohn Disease - immunology; Crohn Disease - pathology; Dendritic Cells - immunology; Dendritic Cells - pathology; Down-Regulation - immunology; Gastroenterology; HEK293 Cells; Humans; Immunology; 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
• ISSN: 1933-0219; 1935-3456
• DOI: 10.1038/mi.2014.19

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.