Cytoskeleton-modulating effectors of enteropathogenic and enterohemorrhagic Escherichia coli: role of EspL2 in adherence and an alternative pathway for modulating cytoskeleton through Annexin A2 function.

Enterohemorrhagic Escherichia coli (EHEC) and enteropathogenic Escherichia coli (EPEC) are attaching/effacing pathogens that possess a type III secretion system and deliver a variety of effectors into host cells for successful infection. EHEC produces at least 20 effector families with various functions. Reorganization of the cellular cytoskeleton at the adherent site is a hallmark of these pathogens. EspL2 of EHEC is a novel effector class that can modulate the cellular cytoskeleton. By interacting with and activating Annexin A2, EspL2 contributes to the formation of a condensed microcolony and may adhere to host cells in a translocated intimin receptor-independent manner. The interaction of EspL2 with Annexin A2 increases F-actin bundling activity and strengthens the membrane-cytoskeleton linkage, resulting in the condensation of actin fibers and the induction of a pseudopod-like structure. Membrane microdomains, namely the lipid raft, which is rich in Annexin A2, may be a platform by which EHEC/EPEC infection modulates cellular signaling and the cytoskeleton.