Open AccessEspT triggers formation of lamellipodia and membrane ruffles through activation of Rac‐1 and Cdc42
Author(s) -
Bulgin Richard R.,
Arbeloa Ana,
Chung Jade C. S.,
Frankel Gad
Publication year - 2009
Publication title -
cellular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.542
H-Index - 138
eISSN - 1462-5822
pISSN - 1462-5814
DOI - 10.1111/j.1462-5822.2008.01248.x
Subject(s) - cdc42 , lamellipodium , microbiology and biotechnology , biology , effector , guanine nucleotide exchange factor , gtpase , actin cytoskeleton , type three secretion system , secretion , shigella flexneri , rac gtp binding proteins , cytoskeleton , rac1 , cell , virulence , signal transduction , biochemistry , escherichia coli , gene
Summary Subversion of the eukaryotic cell cytoskeleton is a virulence strategy employed by many bacterial pathogens. Due to the pivotal role of Rho GTPases in actin dynamics they are common targets of bacterial effector proteins and toxins. IpgB1, IpgB2 ( Shigella ), SifA, SifB ( Salmonella ) and Map and EspM (attaching and effacing pathogens) constitute a family of type III secretion system effectors that subverts small GTPase signalling pathways. In this study we identified and characterized EspT from Citrobacter rodentium that triggers formation of lamellipodia on Swiss 3T3 and membrane ruffles on HeLa cells, which are reminiscent of the membrane ruffles induced by IpgB1. Ectopic expression of EspT and IpgB1, but not EspM, resulted in a mitochondrial localization. Using dominant negative constructs we found that EspT‐induced actin remodelling is dependent on GTP‐bound Rac‐1 and Cdc42 but not ELMO or Dock180, which are hijacked by IpgB1 in order to form a Rac‐1 specific guanine nucleotide exchange factor. Using pull‐down assays with the Rac‐1 and Cdc42 binding domains of Pak and WASP we demonstrate that EspT is capable of activating both Rac‐1 and Cdc42. These results suggest that EspT modulates the host cell cytoskeleton through coactivation of Rac‐1 and Cdc42 by a distinct mechanism.