Two distinct NFkB pathways triggered by TLR5 or LTbR signaling induces CCL20 expression on intestinal epithelial cells acting on the same NFkB binding site.

RUMBO M.,; SIERRO F.,; DIDIERLAURENT A.; SIRARD J.C.

Praga, Republica Checa

Congreso; VI European meeting of the mucosal immunology group; 2006

The chemokine CCL20 is permanently produced in epithelium associated to Peyer’s patches (PP). Epithelial CCL20 expression is also triggered by Toll-like receptor (TLR) signals. CCL20 promotes recruitment of CCR6+ dendritic cells to the sub-epithelial compartment and thus orchestrates the adaptive immunity either constitutively in PP via Lymphotoxin beta receptor (LTbR) signaling or transiently in intestinal epithelium upon TLR stimulation. We further characterized epithelial CCL20 expression upon stimulation of LTbR or the flagellin-specific TLR5. Transcriptional luciferase fusions with human CCL20 promoter were constructed and the NF-kappaB (NF-kb) proximal to transcription start was mutated. In human intestinal epithelial cells, both LTbR- and TLR5-dependent activation required the NF-kb binding site. The molecules involved in signaling were analyzed using ELISA assays specific for binding of nuclear extracts on duplex DNA. While TLR signaling promotes a transient translocation of p50 and p65 subunits, a late and sustained activation of RelB and p52 was observed upon LTbR stimulation. Moreover, all NF-kb members interact with CCL20-specific NF-kb sites. Finally, similar patterns of NF-kb activation were found in mouse intestinal epithelium treated with flagellin or anti-LTbR agonist. Therefore, different NF-kb pathways control CCL20 expression in intestinal epithelium by targeting the same NF-kb binding site. These results support the concept that the constitutive/inducible control of CCL20 chemokine relies on temporal regulation via different sets of NF-kB molecules.