Endocytosis, cytotoxicity and translocation of Shiga toxin-2 are stimulated by infection of human intestinal (HCT-8) monolayers with an hypervirulent E. coli O157:H7 lacking stx2 gene

AMARAL MM; GARIMANO NICOLAS EZEQUIEL; IBARRA C

Frontiers in Cellular and Infection Microbiology

Frontiers Media S.A.

Año: 2019

2235-2988

Shiga toxin-producing Escherichia coli (STEC) strains are responsible for multiple clinical syndromes, including hemolytic uremicsyndrome (HUS). E. coli O157:H7 is the most prevalent serotype associated with HUS and produces a variety of virulence factorsbeing Stx2 the responsible of the most HUS severe cases. After intestinal colonization by STEC, Stx2 is released into the intestinallumen, translocated to the circulatory system and then binds to its receptor, globotriaosylceramide (Gb3), in target cells. Thus,Stx2 passage through the colonic epithelial barrier is a key step in order to produce disease, being its mechanisms still poorlyunderstood. We have previously reported that STEC interaction with the human colonic mucosa enhanced Stx2 production. In thepresent work, we have demonstrated that infection with O157:H7∆stx2, a mutant unable to produce Stx2, enhanced either Stx2cytotoxicity on an intestinal cell line (HCT-8) or translocation across HCT-8 monolayers. Moreover, we found that translocation wasenhanced by both paracellular and transcellular pathways. Using specific endocytosis inhibitors, we have further demonstratedthat the main mechanisms implicated on Stx2 endocytosis and translocation, either when O157:H7∆stx2 was present or not, wereGb3-dependent, but dynamin-independent. On the other hand, dynamin dependent endocytosis and macropinocytosis became morerelevant only when O157:H7∆stx2 infection was present. Overall, this study highlights the effects of STEC infection on the intestinalepithelial cell host and the mechanisms underlying Stx2 endocytosis, cytotoxic activity and translocation, in the aim of finding newtools towards a therapeutic approach.