F4⁺enterotoxigenicEscherichia coli(ETEC) adhesion mediated by the major fimbrial subunit FaeG

Abstract

The FaeG subunit is the major constituent of F4(+) fimbriae, associated with glycoprotein and/or glycolipid receptor recognition and majorly contributes to the pathogen attachment to the host cells. To investigate the key factor involved in the fimbrial binding of F4(+) Escherichia coli, both the recombinant E. coli SE5000 strains carrying the fae operon gene clusters that express the different types of fimbriae in vitro, named as rF4ab, rF4ac, and rF4ad, respectively, corresponding to the fimbrial types F4ab, F4ac, and F4ad, and the three isogenic in-frame faeG gene deletion mutants were constructed. The adhesion assays and adhesion inhibition assays showed that ΔfaeG mutants had a significant reduction in the binding to porcine brush border as well as the intestinal epithelial cell lines, while the complemented strain ΔfaeG/pfaeG restored the adhesion function. The recombinant bacterial strains rF4ab, rF4ac, and rF4ad have the same binding property as wild-type F4(+) E. coli strains do and improvement in terms of binding to porcine brush border and the intestinal epithelial cells, and the adherence was blocked by the monoclonal antibody anti-F4 fimbriae. These data demonstrate that the fimbrial binding of F4(+) E. coli is directly mediated by the major FaeG subunit.

Comparative genomics of Salmonella enterica serovar Montevideo reveals lineage-specific gene differences that may influence ecological niche association

“…In clade III, the peh operon has diverged considerably from other Montevideo clades ( Table 2 ) and closely resembles the peg fimbriae from Paratyphi A instead (97.2 % nucleotide similarity). Clade III faeG , encoding the major subunit of the K88 fimbriae [ 73, 74 ], has diverged considerably in comparison to other Montevideo clades ( Table 2 ). In addition, the safA of clade III shares higher nucleotide identity to the Typhimurium LT2 safA (94.4 %) as opposed to ~76 % nucleotide identity in the other Montevideo clades (data not shown).…”

ITGB5 Plays a Key Role in Escherichia coli F4ac-Induced Diarrhea in Piglets

“…In the complementary experiment, overexpression of ITGB5 in IPEC-J2 cells increased significantly ETEC F4ac adhesion ( Figure 5C). The fimbrial subunit FaeG is the most prominent part for F4ac adherence and is directly involved in the binding of the F4ac fimbriae to the receptors (19). Results from GST pull-down assay with purified FaeG and ITGB5 also showed that FaeG binds directly to ITGB5 (Figure 5D).…”

“…Previous studies have demonstrated that the fimbrial subunit FaeG is the most prominent part for F4 adherence and is directly involved in the binding of the F4 fimbriae to the host cells (19). To further verify the interaction between FaeG and ITGB5, a GST pull-down assay was conducted.…”

Porcine aminopeptidase N binds to F4+ enterotoxigenic Escherichia coli fimbriae

“…F4 + ETEC infections cause diarrhea in newborn and weaned piglets and fimbriae-mediated adherence to porcine intestinal cells is an initial step in the infection process [ 39 ]. The major fimbrial subunit FaeG directly mediates the binding of the three F4 variants to different host receptors [ 8 , 23 , 41 ]. The functional site of the F4ab FaeG subunit is contained within amino acids (AAs) 140-145 and 151-156, while AAs 147-160 dictate binding capacity for F4ac FaeG [ 40 , 41 ].…”

“…F4 + E. coli (C83901, O8:K87:F4ab; C83902, O8:K87:F4ac; C83903, O141:K85:F4ad) strains and their respective faeG deletion mutants were cultivated in Luria–Bertani (LB) media [ 8 , 22 ]. Recombinant E. coli SE5000 strains carrying the fae operon gene clusters, designated as rF4ab, rF4ac, and rF4ad, respectively, were cultivated in LB medium supplemented with ampicillin (100 μg/mL) [ 23 ]. Bacteria harboring the pcDNA TM 6.2-GW/miR-APN-top10 plasmid were cultivated in SOB medium supplemented with 50 µg/mL spectinomycin.…”