Intracellular trafficking of SepA

Abstract

Enteroaggregative Escherichia coli (EAEC) is an emerging enteropathogen, associated with acute and persistent diarrhea in children and adults in developed and developing countries. In 2011 a massive outbreak of diarrhea affected many European countries, leading to several deaths due to the development of hemolytic uremic syndrome. This outbreak was caused by a Shiga toxin-producing E. coli strain of serotype O104:H4. The genome sequence indicated that the O104:H4 strain was in fact an EAEC that received the Shiga toxin 2 (Stx2) encoding-phage, which is the main feature of Shiga toxin-producing E. coli (STEC). This hybrid strain presents several virulence factors, including the SPATE (Serine Proteases Autotransporters of Enterobacteriaceae) proteins that are secreted by the type V secretion system, also known as autotransporters. SPATEs are present in all members of Enterobacteriaceae and are defined as important virulence factors in several pathogens. The Shigella extracellular protein A (SepA) is one SPATE that was originally described in Shigella flexneri 2a, and later in EAEC. This protein is classified as a class II SPATE, a group that includes the proteases with immunomodulatory activities. SepA apparently participates in the epithelial tissue destruction induced by Shigella flexneri; however, does not present cytotoxic effect on HEp-2 cells and its cellular traffic and target are unknown. EAEC strains that produce SepA are epidemiologically associated with diarrhea, but its role in the pathogenesis of EAEC diarrhea remains unknown. The PhD project linked to this BEPE proposal aims to determine if SepA is involved in the cytotoxic and inflammatory effects caused by EAEC. So far, SepA has been purified and its cytotoxic effect on HeLa and Y1 cells has been demonstrated. Antibodies against SepA have been obtained and a SepA-producing EAEC strain has been selected from our EAEC collection. Therefore, the present BEPE proposal aims to study the cellular traffic of SepA in intestinal cells.