Involvement of the intermediate filament protein cytokeratin‐18 in actin pedestal formation during EPEC infection

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Abstract
While remaining extracellular, enteropathogenic Escherichia coli (EPEC) establish direct links with the cytoskeleton of the target epithelial cell leading to the formation of actin‐rich pedestals underneath attached bacteria. The translocated adaptor protein Tir forms the transmembrane bridge between the cytoskeleton and the bacterium; the extracellular domain of Tir functions as a receptor for the bacterial adhesin intimin, while the intracellular amino and carboxy termini interact with a number of focal adhesion and other cytoskeletal proteins; and recruitment of some is dependent on phosphorylation of Tyr 474. Using Tir as bait and HeLa cell cDNA library as prey in a yeast two‐hybrid screen, we identified cytokeratin 18 as a novel Tir partner protein. Cytokeratin 18 is recruited to the EPEC‐induced pedestal and has a direct role in actin accretion and cytoskeleton reorganization. This study is the first to implicate intermediate filaments in microfilament reorganization following EPEC infection.