Chitin-Binding Domains of Escherichia Coli ChiA Mediate Interactions With Intestinal Epithelial Cells in Mice With Colitis

Abstract

Background & Aims Inducible chitinase 3-like-1 (CHI3L1) is expressed by intestinal epithelial cells (IECs) and adheres to bacteria under conditions of inflammation. We performed a structure–function analysis of the chitin-binding domains (CBDs) encoded by the chiA gene, which mediates the pathogenic effects of adherent invasive Escherichia coli (AIEC). Methods We created AIEC (strain LF82) with deletion of chiA (LF82-ΔchiA) or that expressed chiA with specific mutations. We investigated the effects of infecting different IEC lines with these bacteria, compared with non-pathogenic E coli; chitinase activities were measured using the colloidal chitin-azure method. Colitis was induced in C57/Bl6 mice by administration of dextran sodium sulfate (DSS), and mice were given 108 bacteria for 15 consecutive days by gavage. Stool/tissue samples were collected and analyzed. Results LF82-ΔchiA had significantly less adhesion to IEC lines than LF82. Complementation of LF82-ΔchiA with the LF82 chiA gene, but not chiA from non-pathogenic (K12) E coli, increased adhesion. We identified 5 specific polymorphisms in the CBD of LF82 ChiA (at amino acids 362, 370, 378, 388, and 548) that differ from chiA of K12 and were required for LF82 to interact directly with IECs. This interaction was mediated by an N-glycosylated asparagine in CHI3L1 (amino acid 68) on IECs. Mice infected with LF82, or LF82-ΔchiA complemented with LF82 chiA, developed more severe colitis following administration of DSS than mice infected with LF82-ΔchiA or LF82 that expressed mutant forms of chiA. Conclusion AIEC adhere to an N-glycosylated CHI3L1 on IEC via the CBD of chiA. This mechanism of promotes pathogenic effects of AIEC in mice with colitis.

Chitinase 3-like 1 Synergistically Activates IL6-mediated STAT3 Phosphorylation in Intestinal Epithelial Cells in Murine Models of Infectious Colitis

“…9). During the onset of inflammation by specific type of pathogen, CHI3L1 expression is induced on the IECs and facilitates the adhesion and invasion of these bacteria through the N-glycosylated residue on CHI3L1 [28]. The bacteria then invade into the lamina proprial compartment, where it activates macrophages to produce TNFα.…”

Siderophore-mediated iron acquisition and modulation of host-bacterial interactions

“…Interestingly, the yersiniabactin siderophore system is overrepresented in the genomes of resident E. coli isolates recovered more frequently from Crohn’s disease patients compared to healthy controls [101] [78]. These resident E. coli strains exhibit unique functional characteristics, such as increased epithelial invasiveness and the ability to induce colitis in numerous rodent models [102] [103] [104] [105] [106] [107], and may therefore contribute to the maintenance of a proinflammatory intestinal environment in Crohn’s disease. Thus features of the inflamed environment, such as elevated Lcn2 secretion, may provide selection pressure for the retention of members of the intestinal microbiota that harbor Lcn2-resistant siderophore systems.…”

The Intestinal Microbiota in Inflammatory Bowel Diseases

“…Induction of colitis correlates with the ability of E. coli strains to adhere to the mucosa, persist within macrophages and translocate across the mucosal barrier. Mechanisms of these pathogenic functions are being elucidated, with an example of a relevant virulence gene being the chitin-binding domain of chiA, which binds to N-glycosylated chitinase 3-like-1 on intestinal epithelial cells [32]. Multiple other bacterial species, including Enterococci and Bacteroides exhibit fundamental variations that affect protective versus pathogenic properties.…”