The secreted autotransporter toxin, Sat, functions as a virulence factor in Afa/Dr diffusely adhering Escherichia coli by promoting lesions in tight junction of polarized epithelial cells

Abstract

SummaryAfa/Dr diffusely adhering Escherichia coli (DAEC) strains are responsible for urinary tract and intestinal infections. Both in intestine and kidney, the epithelial cells forming epithelium are sealed by junctional domains. We provide evidence that the Secreted autotransporter toxin, Sat, belonging to the subfamily of serine protease autotransporters of Enterobacteriaceae (SPATEs), acts as a virulence factor in Afa/Dr DAEC by promoting lesions in the tight junctions (TJs) of polarized epithelial Caco-2/TC7 cells. Southern blot analysis reveals that the prototype strains of the subclass-1 and subclass-2 typical Afa/Dr DAEC strains, hybridize with a sat probe. Using the wildtype IH11128 strain, the recombinant E. coli AAEC185 strain that expresses Sat, the recombinant E. coli that expresses both Dr adhesin and Sat, we report that Sat in monolayers of cultured enterocyte-like Caco-2/TC7 cells, induces rearrangements of the TJs-associated proteins ZO-1, ZO-3 and occludin, and increases the formation of domes as the result of an increase in the paracellular permeability without affecting the transepithelial electrical resistance of the cell monolayers. Moreover, we observe that Sat-induced disassembly of TJs-associated proteins is dependent on the serine protease motif. Finally, an analysis of the prevalence of the sat gene in three collections of Afa/Dr DAEC strains collected from the stools of children with and without diarrhoea, and from the urine of patients with urinary tract infection (UTI) shows that: (i) the sat gene is highly prevalent in UTI-associated Afa/Dr DAEC strains (88% positive), (ii) the sat gene is generally absent from Afa/Dr DAEC strains collected from the stools of children without diarrhoea (16% positive); whereas (iii) it is present in about half of the strains collected from the stools of children with diarrhoea (46% positive).

Infection strategies of enteric pathogenic Escherichia coli

“…77 The only documented secreted factor associated with DAEC infection is the SPATE Sat. Sat can induce rearrangement of the tight junction proteins ZO-1, ZO-3 and occludin increasing paracellular permeability but not transepithelial resistance 78 and can also bind spectrin, 79 rearrange focal adhesion associated proteins vinculin and paxillin, and cause cell detachment and caspase-independent cell death.…”

Diarrheagenic Escherichia coli in sub-Saharan Africa: Status, Uncertainties and Necessities

“…In one study, afa, sfa and pap were detected among DAEC isolates from Bangui but none of them, nor DAEC as a whole, were associated with chronic diarrhea in HIV-positive patients [68]. Recently, Guignot et al have identified an autotransporter toxin, Sat, in UPEC and many diarrhea-associated DAEC [229]. Importantly, they showed that sat was significantly more commonly found in DAEC from children with diarrhea and UPEC than in DAEC from healthy children [229].…”

“…Recently, Guignot et al have identified an autotransporter toxin, Sat, in UPEC and many diarrhea-associated DAEC [229]. Importantly, they showed that sat was significantly more commonly found in DAEC from children with diarrhea and UPEC than in DAEC from healthy children [229]. sat may represent a true DAEC virulence marker that future epidemiological studies, including those in Africa, may want to investigate.…”

Animal models of enteroaggregativeEscherichia coliinfection

“…Having hemagglutinin and mucinolytic activity, Pic is able to penetrate the intestinal mucus cytoskeletal damage to tight junctions between intestinal epithelial cells. 64 Likewise, SigA, a SPATE largely associated with Shigella flexneri pathogenesis, is capable of inducing fodrin degradation causing catastrophic morphological changes in cells. 65 Interestingly, although only moderately prevalent in EAEC strains, SepA is the SPATE most strongly associated with severe diarrheal illness 63 though its role in EAEC pathogenesis remains largely uncharacterized.…”