B. Begue and C. Dumant contributed equally to this study.
Microbial induction of CARD15 expression in intestinal epithelial cells via toll-like receptor 5 triggers an antibacterial response loop†
Article first published online: 8 AUG 2006
Copyright © 2006 Wiley-Liss, Inc.
Journal of Cellular Physiology
Volume 209, Issue 2, pages 241–252, November 2006
How to Cite
Begue, B., Dumant, C., Bambou, J.C., Beaulieu, J.F., Chamaillard, M., Hugot, J.P., Goulet, O., Schmitz, J., Philpott, D.J., Cerf-Bensussan, N. and Ruemmele, F.M. (2006), Microbial induction of CARD15 expression in intestinal epithelial cells via toll-like receptor 5 triggers an antibacterial response loop. J. Cell. Physiol., 209: 241–252. doi: 10.1002/jcp.20739
- Issue published online: 29 AUG 2006
- Article first published online: 8 AUG 2006
- Manuscript Accepted: 7 JUN 2006
- Manuscript Received: 19 APR 2006
- Institut National de le Santé et de la Recherche médicale INSERM
- Fondation pour la Recherche medicale
With the discovery of CARD15 as susceptibility gene for Crohn's disease (CD) a first link to a potential defect in the innate immune system was made. In this work we aimed to analyze enterocyte NOD2/CARD15 expression and regulation in response to bacterial motifs and the consequences of the most common CD-specific CARD15 mutation on antibacterial responses of normal intestinal epithelial cells (IEC). Under normal conditions, IEC lines and ileal enterocytes did not express NOD2/CARD15 mRNA or protein, contrary to IEC derived from inflammatory CD sections. In vitro analyses revealed that the simple contact with non-pathogenic commensal E. Coli K12 was sufficient to induced NOD2/CARD15 mRNA and protein in human IEC (HIEC). We identified bacterial flagellin interacting with TLR5 as major motif in this regulation of NOD2/CARD15. E. Coli mutants not expressing flagellin (ΔFliC) failed to induce CARD15. Similarly, in HIEC transfected with a plasmid encoding dominant negative TLR5, no CARD15 induction was observed after K12 contact. Isolated TLR2 or TLR4 stimulation had no or only a marginal effect on NOD2/CARD15 expression. NOD2/CARD15 negative HIEC were unresponsive to muramyl dipeptide (MDP), but once NOD2/CARD15 was induced, HIEC and Caco2 cells responded to intra or extracellular MDP presentation with the activation of the NFkB pathway. IEC transfected with the Crohn-specific CARD15 mutant (F3020insC, FS) failed to activate NFkB after MDP-challenge, in contrast to CARD15WT IEC. In response to MDP, IEC induced a massive antibacterial peptide (ABP) response, seen in the apical release of CCL20. This was completely abolished in IEC carrying CARD15FS. These data suggest a critical role of NOD2/CARD15 in the bacterial clearance of the intestinal epithelium while CD-specific mutated NOD2/CARD15 causes an impaired epithelial barrier. J. Cell. Physiol. 209: 241–252, 2006. © 2006 Wiley-Liss, Inc.