A Novel Two-Component Signaling System That Activates Transcription of an Enterohemorrhagic Escherichia coli Effector Involved in Remodeling of Host Actin

Abstract

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is responsible for worldwide outbreaks of bloody diarrhea, hemorrhagic colitis, and life-threatening hemolytic uremic syndrome. After colonizing the large intestine, EHEC forms attaching and effacing (AE) lesions on intestinal epithelial cells. These lesions cause destruction of the microvilli and elicit actin rearrangement to form pedestals that cup each bacterium individually. EHEC responds to a signal produced by the intestinal microbial flora, autoinducer-3 (AI-3), and the host hormones epinephrine and norepinephrine to activate transcription of the genes involved in AE lesion formation. These three signals, involved in interkingdom communication, are sensed by bacterial sensor kinases. Here we describe a novel two-component system, QseEF (quorum-sensing E. coli regulators E and F), which is part of the AI-3/epinephrine/norepinephrine signaling system. QseE is the sensor kinase and QseF the response regulator. The qseEF genes are cotranscribed, and transcription of qseEF is activated by epinephrine through the QseC sensor. A qseF mutant does not form AE lesions. QseF activates transcription of the gene encoding EspFu, an effector protein translocated to the host cell by the EHEC, which mimics a eukaryotic SH2/SH3 adapter protein to engender actin polymerization during pedestal formation. Expression of the espFu gene from a plasmid restored AE lesion formation to the qseF mutant, suggesting that lack of espFu expression in this mutant was responsible for the loss of pedestal formation. These findings suggest the QseEF is a two-component system involved in the regulation of AE lesion formation by EHEC.

A transcriptome study of the QseEF two-component system and the QseG membrane protein in enterohaemorrhagic Escherichia coli O157 : H7

“…Conversely, transcription of rcsBC, a two-component system that regulates flagella (Clemmer & Rather, 2007), and the LEE genes (Tobe et al, 2005) is repressed by QseEFG. RcsBC play a modulatory role in the expression of the LEE genes (Tobe et al, 2005), while QseEFG are involved in activation of espFu/tccP (Reading et al, 2007), transcription, and translocation of type III secretion effectors to host cells (Reading et al, 2009). QseEFG regulation of the RcsBC system ties together type III secretion and effector expression with effector transloca- The qseE and qseG mutants grew slightly more slowly than the WT, and this was complemented by the addition of the gene expressed on a plasmid.…”

“…We have previously shown that QseEFG in EHEC is involved in AE lesion formation (Reading et al, 2007(Reading et al, , 2009. To identify additional targets of QseEFG, we performed transcriptome studies utilizing the Affymetrix GeneChip E. coli Genome 2.0 arrays to compare the transcripts of WT EHEC with those of DqseE, DqseF and DqseG single mutants.…”

“…QseE autophosphorylates and then transfers a phosphate to QseF (Yamamoto et al, 2005), which in turn activates transcription of espFu/tccP in EHEC (Reading et al, 2007). The QseG outer membrane protein is involved in Tir translocation by the type III secretion system (Reading et al, 2009).…”

“…QseF (GrlR) is a two-component response regulator protein containing a response regulator domain with a key aspartate residue, a s 54 -interaction domain including the GAFTGA motif, and a helix-turn-helix DNA-binding domain. QseG is an outer membrane protein and shares homology with many a-helical proteins (Reading et al, 2007(Reading et al, , 2009Reichenbach et al, 2009). The glnB gene encodes the PII protein.…”

“…QseE (GrlK) is a sensor kinase that responds to the host hormone epinephrine, phosphate and sulfate. It contains two transmembrane domains, a signal histidine kinase domain and an ATPase domain (Reading et al, 2007(Reading et al, , 2009Reichenbach et al, 2009). QseF (GrlR) is a two-component response regulator protein containing a response regulator domain with a key aspartate residue, a s 54 -interaction domain including the GAFTGA motif, and a helix-turn-helix DNA-binding domain.…”