Enteropathogenic Escherichia coli (EPEC) infection causes a histopathological lesion including recruitment of F-actin beneath the attached bacteria and formation of actin-rich pedestal-like structures. Another important target of EPEC is the tight junction (TJ), and EspF induces displacement of TJ proteins and increased intestinal permeability. Previously, we determined that an EPEC strain lacking EspF did not cause TJ disruption; meanwhile, pedestals were located on the TJ and smaller than those induced by the wild-type strain. Therefore, EspF could be playing an important role in both phenotypes. Here, using different cell models, we found that EspF was essential for pedestal maturation through ZO-1 disassembly from TJ, leading to (a) ZO-1 recruitment to the pedestal structure; no other main TJ proteins were required. Recruited ZO-1 allowed the afadin recruitment. (b) Afadin recruitment caused an afadin-ZO-1 transient interaction, like during TJ formation. (c) Afadin and ZO-1 were segregated to the tip and the stem of pedestal, respectively, causing pedestal maturation. Initiation of these three discrete phases for pedestal maturation functionally and physically required EspF expression. Pedestal maturation process could help coordinate the epithelial actomyosin function by maintaining the actin-rich column composing the pedestal structure and could be important in the dynamics of the pedestal movement on epithelial cells.
Keywords: Enteropathogenic E. coli; EspF; TJ disassembly; ZO-1; actin polymerization; actin rearrangement; afadin; calcium switch; effector protein; tight junction.
© 2019 The Authors. MicrobiologyOpen published by John Wiley & Sons Ltd.