The Enterohemorrhagic Escherichia coli Effector EspW Triggers Actin Remodeling in a Rac1-Dependent Manner.

Pamela Sandu,Andrew D Mcainsh,Hauke Drechsler,Gad Frankel,Cedric N Berger,Valerie F Crepin

doi:10.1128/iai.00244-17

Pamela Sandu, Andrew D Mcainsh + Show 4 more

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https://doi.org/10.1128/iai.00244-17

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Abstract

ABSTRACTEnterohemorrhagic Escherichia coli (EHEC) is a diarrheagenic pathogen that colonizes the gut mucosa and induces attaching-and-effacing lesions. EHEC employs a type III secretion system (T3SS) to translocate 50 effector proteins that hijack and manipulate host cell signaling pathways, which allow bacterial colonization and subversion of immune responses and disease progression. The aim of this study was to characterize the T3SS effector EspW. We found espW in the sequenced O157:H7 and non-O157 EHEC strains as well as in Shigella boydii. Furthermore, a truncated version of EspW, containing the first 206 residues, is present in EPEC strains belonging to serotype O55:H7. Screening a collection of clinical EPEC isolates revealed that espW is present in 52% of the tested strains. We report that EspW modulates actin dynamics in a Rac1-dependent manner. Ectopic expression of EspW results in formation of unique membrane protrusions. Infection of Swiss cells with an EHEC espW deletion mutant induces a cell shrinkage phenotype that could be rescued by Rac1 activation via expression of the bacterial guanine nucleotide exchange factor, EspT. Furthermore, using a yeast two-hybrid screen, we identified the motor protein Kif15 as a potential interacting partner of EspW. Kif15 and EspW colocalized in cotransfected cells, while ectopically expressed Kif15 localized to the actin pedestals following EHEC infection. The data suggest that Kif15 recruits EspW to the site of bacterial attachment, which in turn activates Rac1, resulting in modifications of the actin cytoskeleton that are essential to maintain cell shape during infection.

Highlights

Enterohemorrhagic Escherichia coli (EHEC) is a diarrheagenic pathogen that colonizes the gut mucosa and induces attaching-and-effacing lesions
In order to determine if either the long or short versions of espW are present in other enteropathogenic E. coli (EPEC) strains, we screened by PCR a collection of 132 clinical isolates available in our laboratory
Neither of the espW variants was found in C. rodentium and the prototype EPEC strain E2348/69, while the prototype atypical EPEC strain E110019 (O111:H9) contains the long version of espW

Summary

Introduction

Enterohemorrhagic Escherichia coli (EHEC) is a diarrheagenic pathogen that colonizes the gut mucosa and induces attaching-and-effacing lesions. The data suggest that Kif recruits EspW to the site of bacterial attachment, which in turn activates Rac, resulting in modifications of the actin cytoskeleton that are essential to maintain cell shape during infection. EPEC, EHEC, and C. rodentium employ a filamentous type III secretion system (T3SS) [4], located within the locus of enterocyte effacement (LEE) [5], to translocate a plethora of effector proteins directly from the bacterial cell into host cell cytoplasm [6]. The A/E pathogen effector Map induces filopodia via Cdc at the site of attachment [19, 20], EspM promotes stress fibers via RhoA activation [21], and EspT triggers ruffle and lamellipodia formation by Rac1 [22]. The aim of this study was to investigate the role of EspW during EHEC infection and its putative role as a Rho GTPase regulator

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