Flagellar Cap Protein FliD Mediates Adherence of Atypical Enteropathogenic Escherichia coli to Enterocyte Microvilli

Abstract

The expression of flagella correlates with different aspects of bacterial pathogenicity, ranging from adherence to host cells to activation of inflammatory responses by the innate immune system. In the present study, we investigated the role of flagella in the adherence of an atypical enteropathogenic Escherichia coli (aEPEC) strain (serotype O51:H40) to human enterocytes. Accordingly, isogenic mutants deficient in flagellin (FliC), the flagellar structural subunit; the flagellar cap protein (FliD); or the MotAB proteins, involved in the control of flagellar motion, were generated and tested for binding to differentiated Caco-2 cells. Binding of the aEPEC strain to enterocytes was significantly impaired in strains with the fliC and fliD genes deleted, both of which could not form flagella on the bacterial surface. A nonmotile but flagellated MotAB mutant also showed impaired adhesion to Caco-2 cells. In accordance with these observations, adhesion of aEPEC strain 1711-4 to Caco-2 cells was drastically reduced after the treatment of Caco-2 cells with purified FliD. In addition, incubation of aEPEC bacteria with specific anti-FliD serum impaired binding to Caco-2 cells. Finally, incubation of Caco-2 cells with purified FliD, followed by immunolabeling, showed that the protein was specifically bound to the microvillus tips of differentiated Caco-2 cells. The aEPEC FliD or anti-FliD serum also reduced the adherence of prototype typical enteropathogenic, enterohemorrhagic, and enterotoxigenic E. coli strains to Caco-2 cells. In conclusion, our findings further strengthened the role of flagella in the adherence of aEPEC to human enterocytes and disclosed the relevant structural and functional involvement of FliD in the adhesion process.

Association of Atypical Enteropathogenic Escherichia coli with Diarrhea and Related Mortality in Kittens

“…The H type of E. coli refers to the flagellin component of the flagella (55). The presence of flagellin is important for adherence and stimulation of cytokines by aEPEC in in vitro studies (56)(57)(58), and mutations in the fliC gene of O113:H21 Shiga-toxin producing E. coli lead to a decreased association with the colonic epithelium in experimentally infected mice (59). However, in that study, it is unclear if the impaired epithelial association in the mutated H21 was specific to that H type (H21).…”

Diarrheagenic Escherichia coli

“…Moreover, it has been recently shown that the flagellar cap protein FliD of an aEPEC strain (serotype O51:H40) binds to unknown receptors on intestinal Caco-2 cell microvilli 92 . Interestingly, an anti-FliD serum and purified FliD reduced adherence of the aEPEC as well as that of tEPEC, EHEC and ETEC prototype strains to the same cell line 92 .…”

“…Interestingly, an anti-FliD serum and purified FliD reduced adherence of the aEPEC as well as that of tEPEC, EHEC and ETEC prototype strains to the same cell line 92 . Furthermore, it has been suggested that adherence of aEPEC of serotype O26:H11 may be mediated by binding of the flagellin protein FliC (the subunit of the flagella shaft) to cellular fibronectin 93 .…”

Proteomics Profile of Cronobacter sakazakii and fliF Mutant: Adherence and Invasion to Mouse Neuroblastoma Cells

“…Chemotaxis and motility by flagella are pathogenic attributes that contribute to biofilm formation, adherence, and invasion in several pathogens; in addition, flagella stimulate the secretion of effector molecules and modulation of the immune system [18][19][20]. Flagellar motility plays an important role in the pathogenesis of Helicobacter pylori, Pseudomonas aeruginosa, Vibrio cholerae, Salmonella species, and E. coli [18,[21][22]. The main advantage of bacterial flagella is the ability to direct bacterial movement to a specific colonization site in the host [23].…”