Lack of Tir Ubiquitylation Contributes to Enteropathogenic E. coli Remaining Extracellular During Nonphagocytic Cell Infections

Abstract

Enteropathogenic Escherichia coli (EPEC) is an extracellular pathogen that alters many host subcellular components during its infectious processes. We have previously shown that EPEC hijacks a large assortment of host cell endocytic components and uses these proteins to form protruding structures called ''pedestals'' rather than triggering internalization of the bacteria. Other invasive pathogens that also recruit similar endocytic components have been shown to enter their host cells on the ubiquitylation of their host cell receptors. Therefore, we hypothesize that EPEC remains extracellular by maintaining its receptor, translocated intimin receptor (Tir), in an unubiquitylated state. Using immunoprecipitation-Western blots, we demonstrate no association of ubiquitin with Tir. To further elucidate the effect Tir ubiquitylation would have on EPEC during their infections, we engineered Tir-ubiquitin fusion constructs, expressed them in host epithelial cells, and infected them with Dtir EPEC. We found these cells induced a significant increase in EPEC invasion as compared with cells that expressed the Tir construct that lacked ubiquitin conjugation. Our results indicate that the lack of EPEC receptor ubiquitylation is a contributing factor that these microbes use to prevent their internalization into epithelial cells.

A genome‐wide transposon mutagenesis screening identifies LppB as a key factor associated with Mycoplasma bovis colonization and invasion into host cells

“…Many pathogenic microorganisms have been identified for using the clathrin-mediated endocytic pathways to invade host cells. [72][73][74] A lipid raft-mediated endocytosis pathway was exploited by some pathogenic microorganisms, such as Chlamydia, for cell entry. Nishi K et al 50 reported that M. bovis can be internalized through a clathrin-dependent pathway or a clathrin-independent, lipid raft-mediated pathway, but the virulence factors responsible the mediated internalization process reunknown.…”

“…The colocalization of rLppB with clathrin and caveolin was found by confocal microscopy. Many pathogenic microorganisms have been identified for using the clathrin‐mediated endocytic pathways to invade host cells 72–74 . A lipid raft‐mediated endocytosis pathway was exploited by some pathogenic microorganisms, such as Chlamydia, for cell entry.…”