No abstract

Constant exposure of intestinal epithelial cells (IEC) to potentially damaging stimuli makes mucosal repair programs essential for gut homeostasis, immunological quiescence and resistance to colitis. Trefoil factor 2 (TFF2) is a mucus associated protein that promotes epithelial barrier integrity in the lung and intestine, but whether a bona-fide TFF2 receptor exists remains controversial. Herein, we provide evidence that leucine rich repeat nogo interacting protein 3 (LINGO3) is a transmembrane component of TFF2 signaling and proliferation within IEC. TFF2 requires LINGO3 for barrier recovery in scratch-wound assays and mice lacking LINGO3 (LINGO3KO) have impaired intestinal barrier function under steady state conditions. Interestingly, LINGO3KO mice phenocopy TFF2KO mice, with both having a significant accumulation of mucosal CD4+TH1 cells expressing IFNg+ TNFa+ under steady-state conditions and impaired recovery from DSS-induced colitis. Impaired recovery in LINGO3KO animals was marked by reduced intestinal crypt regeneration and reduced expression of the stem cell marker LGR5 compared to WT counterparts. Additionally, TFF2 agonist administration (TFF2-Fc) promoted enhanced recovery and limited inflammatory cell recruitment in WT mice during DSS-induced colitis whereas TFF2-Fc treatment was ineffective in LINGO3KO animals. Combined, these data support our contention that a TFF2-LINGO3 ligand/receptor axis regulates tissue repair and inflammation within the gastrointestinal tract through regulation of IEC function.

Mucosal epithelia are constantly exposed to damaging stimuli from mechanical, chemical, or biologic entities, and depend on rapid repair mechanisms to maintain tissue homeostasis and immunological quiescence. The reparative cytokine Trefoil factor 2 (TFF2) serves to enforce mucosal barrier integrity, but whether TFF2 receptor(s) exist is controversial. Herein, we demonstrate leucine rich repeat and immunoglobulin like domain containing nogo receptor interacting protein 3 (LINGO3) is a necessary transmembrane component for TFF2-mediated ERK signaling, proliferation, and recovery of trans-epithelial resistance of primary epithelia during wound healing. Human respiratory and intestinal epithelia express LINGO3 and mice lacking Lingo3 have impaired intestinal barrier function and fail to recover from DSSinduced colitis. Compared to wild-type controls, LINGO3 deficiency impairs both crypt regeneration and expression of the intestinal stem cell marker Lgr5. Importantly, Lingo3 -/mice display a phenotype similar to that previously reported for Tff2 deficiency, with increased paracellular permeability, and significant accumulation of mucosal CD4 + T H 1 cells expressing IFNγ + TNF + even under steady-state conditions. Combined, these data reveal a previously unrecognized role for LINGO3 as a putative TFF2 receptor that regulates mucosal barrier integrity and GI inflammation. Significance:Intestinal epithelial cells (IEC) are necessary for maintenance of homeostasis, resistance to infectious organisms, and overall organismal health. When injured the IEC and the underlying stroma and progenitor cell pool undergo restitutive and regenerative processes driven by the reparative cytokine Trefoil factor 2 (TFF2).This report identifies a novel receptor component for TFF2 signaling expressed on both human and mouse epithelial cells that is necessary for barrier integrity at the steady state and during colitic disease. The discovery of a novel TFF2-LINGO3 axis sheds new light on the processes controlling tissue repair, restitution, and regeneration at the mucosal interface.