Strain-specific transcriptional and posttranscriptional regulation of heat-labile toxin expression by enterotoxigenic Escherichia coli

Abstract

Enterotoxigenic Escherichia coli (ETEC) represents one of the most important etiological agents of diarrhea in developing countries and characteristically produces at least one of two enterotoxins: heat-labile toxin (LT) and heat-stable toxin (ST). It has been previously shown that the production and release of LT by human-derived ETEC strains are variable. Although the natural genetic polymorphisms of regulatory sequences of LT-encoding (eltAB) genes may explain the variable production of LT, the knowledge of the transcriptional and posttranscriptional aspects affecting LT expression among ETEC strains is not clear. To further understand the factors affecting LT expression, we evaluated the impact of the natural polymorphism in noncoding regulatory sequences of eltAB among clinically derived ETEC strains. Sequence analyses of seven clinically derived strains and the reference strain H10407 revealed polymorphic sites at both the promoter and upstream regions of the eltAB operon. Operon fusion assays with GFP revealed that specific nucleotide changes in the Pribnow box reduce eltAB transcription. Nonetheless, the total amounts of LT produced by the tested ETEC strains did not strictly correspond to the detected LTspecific mRNA levels. Indeed, the stability of LT varied according to the tested strain, indicating the presence of posttranscriptional mechanisms affecting LT expression. Taken together, our results indicate that the production of LT is a strain-specific process and involves transcriptional and posttranscriptional mechanisms that regulate the final amount of toxin produced and released by specific strains.

Virulence Factors of Enteric Pathogenic Escherichia coli: A Review

“…ETEC mainly secretes LT through the OMV system. ST and LT toxins are composed of a single A subunit with enzymatic activity and a pentameric B subunit binding to the GM1 ganglioside receptor on the host cell surface [ 68 ]. The structure and pathogenesis mechanism of LT is identical to that (about 80%) of the cholera toxin secreted by Vibrio cells.…”

Characteristics of Pathogenic Escherichia coli Associated with Diarrhea in Children under Five Years in Northwestern Ethiopia

“…The invasion of EIEC is mediated by a gene on a large invasion plasmid ( plnv ) and bacterial chromosome [ 7 ]. ETEC produces heat-labile (LT) and heat-stable (ST) toxins encoded by the eltAB and estAB genes [ 8 , 9 ]. In the pathogenesis of EAHC, aggregative adherence fimbriae ( AAFs ) play a role in adherence and epithelial damage.…”

Preparation of novel trivalent vaccine against enterotoxigenic Escherichia coli for preventing newborn piglet diarrhea

“…26 LT is composed of toxic subunit LT A and binding subunit LT B . [27][28][29] LT or LT B has good immunogenicity. LT A can change permeability of cell membranes and lead to diarrhea.…”