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

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.

Comparison of Tir from enterohemorrahgic and enteropathogenic Escherichia coli strains: two homologues with distinct intracellular properties

“…This tyrosine phosphorylation is required for the interaction of EPEC Tir with cytokeratin-18 [14] and for the localization of Grb2 and CrkII to the pedestals [15]. Nck, an adapter protein including Nck1 and Nck2, has the properties of binding to phosphorylated tyrosine in its Src homology 2 (SH2) domain and is involved in the activation of neural WiskottAldrich syndrome protein (N-WASP) in vitro to trigger actin polymerization [16].…”

Hierarchical Delivery of an Essential Host Colonization Factor in Enteropathogenic Escherichia coli

“…One of the best studied EPEC type III effectors is Tir (translocated intimin receptor), a protein that is injected into host cells, modified by host kinases, and localized to the host membrane (10,11). Furthermore, the amino-and carboxyl-terminal regions of Tir interact with a number of host proteins, causing dramatic host cytoskeletal rearrangements, which result in actin-rich lesions termed pedestals (12)(13)(14)(15)(16). Remarkably, host membrane-localized Tir also serves as a receptor for EPEC via intimin (10), a bacterial outer membrane adhesin also encoded by the LEE of A/E pathogens.…”

Enteropathogenic Escherichia coli , Shigella flexneri , and Listeria monocytogenes Recruit a Junctional Protein, Zonula Occludens-1, to Actin Tails and Pedestals

“…The actin-rich structures contain a variety of actin-binding and cytoskeletal proteins, as well as the F-actin filaments as a major structural component (for review, see reference 49). Some of the proteins are essential (8,9,29,51,58), while others are nonessential but affect the efficiency (3,12,35,45,47,52) of the formation and function of the structures. Thus, these proteins should participate in the coordinated regulation of actin dynamics to create the actin-rich structures, although a full understanding of their precise roles still requires further investigation.…”