scholarly journals Activation of the Cpx Envelope Stress Response Down-Regulates Expression of Several Locus of Enterocyte Effacement-Encoded Genes in Enteropathogenic Escherichia coli

2008 ◽  
Vol 76 (4) ◽  
pp. 1465-1475 ◽  
Author(s):  
Dawn M. MacRitchie ◽  
Jordan D. Ward ◽  
Anna Z. Nevesinjac ◽  
Tracy L. Raivio
Keyword(s):  
Escherichia Coli ◽  
Stress Response ◽  
Two Component System ◽  
Down Regulation ◽  
Cellular Processes ◽  
Pathway Activation ◽  
Envelope Stress ◽  
Cpx Pathway ◽  
Enterocyte Effacement ◽  
First Time

ABSTRACT The Cpx two-component system regulates an extracytoplasmic stress response that functions to rid the envelope of misfolded and mislocalized proteins that may interfere with normal cellular processes. The Cpx pathway is also involved in pathogenesis. This study investigated the role of the Cpx response in enteropathogenic Escherichia coli (EPEC) type III secretion (T3S). It was determined that a functional Cpx pathway is not required for T3S but that pathway activation inhibits secretion by reducing the cellular pools of T3S substrates. The EPEC T3S system structural components, as well as a number of its substrates, are encoded on the locus of enterocyte effacement (LEE) pathogenicity island. Transcriptional fusions to the five major operons of the LEE were constructed and examined under Cpx pathway-activating conditions. Induction of the Cpx response caused a decrease in the transcription of several LEE operons, with the most pronounced effect on LEE4 and LEE5. Collectively, these two operons encode components of the T3S translocation apparatus, the bacterial adhesin intimin, and the translocated bacterial receptor Tir. These data show for the first time that activation of the Cpx envelope stress response in EPEC inhibits T3S of both translocators and effectors, likely through down regulation of LEE transcription. Coupled with recent findings, our results suggest that Cpx-mediated down regulation of virulence is a conserved theme in a number of bacterial pathogens.

scholarly journals Dephosphorylated NPr is involved in an envelope stress response of Escherichia coli

Microbiology ◽  
2015 ◽  
Vol 161 (5) ◽  
pp. 1113-1123 ◽  
Author(s):  
Jaeseop Lee ◽  
Young-Ha Park ◽  
Yeon-Ran Kim ◽  
Yeong-Jae Seok ◽  
Chang-Ro Lee
Keyword(s):  
Escherichia Coli ◽  
Stress Response ◽  
Envelope Stress

Microarray analysis of gene regulation by oxygen, nitrate, nitrite, FNR, NarL and NarP during anaerobic growth of Escherichia coli: new insights into microbial physiology

2006 ◽  
Vol 34 (1) ◽  
pp. 104-107 ◽  
Author(s):  
T.W. Overton ◽  
L. Griffiths ◽  
M.D. Patel ◽  
J.L. Hobman ◽  
C.W. Penn ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Coli Strain ◽  
Anaerobic Growth ◽  
Aerobic Growth ◽  
Two Component System ◽  
Strain Mg1655 ◽  
Microbial Physiology ◽  
Two Component ◽  
Nitrate And Nitrite ◽  
First Time

RNA was isolated from cultures of Escherichia coli strain MG1655 and derivatives defective in fnr, narXL, or narXL with narP, during aerobic growth, or anaerobic growth in the presence or absence of nitrate or nitrite, in non-repressing media in which both strain MG1655 and an fnr deletion mutant grew at similar rates. Glycerol was used as the non-repressing carbon source and both trimethylamine-N-oxide and fumarate were added as terminal electron acceptors. Microarray data supplemented with bioinformatic data revealed that the FNR (fumarate and nitrate reductase regulator) regulon includes at least 104, and possibly as many as 115, operons, 68 of which are activated and 36 are repressed during anaerobic growth. A total of 51 operons were directly or indirectly activated by NarL in response to nitrate; a further 41 operons were repressed. Four subgroups of genes implicated in management of reactive nitrogen compounds, NO and products of NO metabolism, were identified; they included proteins of previously unknown function. Global repression by the nitrate- and nitrite-responsive two-component system, NarQ-NarP, was shown for the first time. In contrast with the frdABCD, aspA and ansB operons that are repressed only by NarL, the dcuB-fumB operon was among 37 operons that are repressed by NarP.

scholarly journals Reduction of Turgor Is Not the Stimulus for the Sensor Kinase KdpD of Escherichia coli

2008 ◽  
Vol 190 (7) ◽  
pp. 2360-2367 ◽  
Author(s):  
Knut Hamann ◽  
Petra Zimmann ◽  
Karlheinz Altendorf
Keyword(s):  
Escherichia Coli ◽  
Cytoplasmic Membrane ◽  
Current View ◽  
Sensor Kinase ◽  
Two Component System ◽  
Intracellular Atp ◽  
Two Component ◽  
Stimulus Perception ◽  
First Time

ABSTRACT Stimulus perception by the KdpD/KdpE two-component system of Escherichia coli is still controversial with respect to the nature of the stimulus that is perceived by the sensor kinase KdpD. Limiting potassium concentrations in the medium or high osmolality leads to KdpD/KdpE signal transduction, resulting in kdpFABC expression. It has been hypothesized that changes in turgor are sensed by KdpD through alterations in the physical state of the cytoplasmic membrane. However, in this study the quantitative determination of expression levels of the kdpFABC operon revealed that the system responds very effectively to K+-limiting conditions in the medium but barely and to various degrees to salt and sugar stress. Since the current view of stimulus perception calls for mainly intracellular parameters, which might be sensed by KdpD, we set out to test the cytoplasmic concentrations of ATP, K+, Na+, glutamate, proline, glycine, trehalose, putrescine, and spermidine under K+-limiting conditions. As a first result, the determination of the cytoplasmic volume, which is a prerequisite for such measurements, revealed that a transient shrinkage of the cytoplasmic volume, which is indicative of a reduction in turgor, occurred only under osmotic upshift but not under K+-limiting conditions. Furthermore, the intracellular ATP concentration significantly increased under osmotic upshift, whereas only a slight increase occurred after a potassium downshift. Finally, the cytoplasmic K+ concentration rose severalfold only after an osmotic upshock. For the first time, these data indicate that stimulus perception by KdpD correlates neither with changes in the cytoplasmic volume nor with changes in the intracellular ATP or K+ concentration or those of the other solutes tested. In conclusion, we propose that a reduction in turgor cannot be the stimulus for KdpD.

scholarly journals Cpx Signal Transduction Is Influenced by a Conserved N-Terminal Domain in the Novel Inhibitor CpxP and the Periplasmic Protease DegP

2005 ◽  
Vol 187 (19) ◽  
pp. 6622-6630 ◽  
Author(s):  
Daelynn R. Buelow ◽  
Tracy L. Raivio
Keyword(s):  
Stress Response ◽  
Stress Responses ◽  
Feedback Inhibition ◽  
Functional Domain ◽  
The Novel ◽  
Loss Of Function ◽  
Terminal Domain ◽  
Envelope Stress ◽  
Cpx Pathway ◽  
Α Helix

ABSTRACT In Escherichia coli, envelope stress can be overcome by three different envelope stress responses: the σE stress response and the Bae and Cpx two-component systems. The Cpx envelope stress response is controlled by the sensor kinase CpxA, the response regulator CpxR, and the novel periplasmic protein CpxP. CpxP mediates feedback inhibition of the Cpx pathway through a hypothetical interaction with the sensing domain of CpxA. No informative homologues of CpxP are known, and thus it is unclear how CpxP exerts this inhibition. Here, we identified six cpxP loss-of-function mutations using a CpxP-β-lactamase (CpxP′-′Bla) translational fusion construct. These loss-of-function mutations identified a highly conserved, predicted α-helix in the N-terminal domain of CpxP that affects both the function and the stability of the protein. In the course of this study, we also found that CpxP′-′Bla stability is differentially controlled by the periplasmic protease DegP in response to inducing cues and that mutation of degP diminishes Cpx pathway activity. We propose that the N-terminal α-helix is an important functional domain for inhibition of the Cpx pathway and that CpxP is subject to DegP-dependent proteolysis.

scholarly journals The Cpx Envelope Stress Response Is Controlled by Amplification and Feedback Inhibition

1999 ◽  
Vol 181 (17) ◽  
pp. 5263-5272 ◽  
Author(s):  
Tracy L. Raivio ◽  
Daniel L. Popkin ◽  
Thomas J. Silhavy
Keyword(s):  
Escherichia Coli ◽  
Stress Response ◽  
Virulence Factors ◽  
Histidine Kinase ◽  
Feedback Inhibition ◽  
Response Regulator ◽  
Regulatory System ◽  
Concomitant Increase ◽  
Envelope Stress ◽  
Two Component

ABSTRACT In Escherichia coli, the Cpx two-component regulatory system activates expression of protein folding and degrading factors in response to misfolded proteins in the bacterial envelope (inner membrane, periplasm, and outer membrane). It is comprised of the histidine kinase CpxA and the response regulator CpxR. This response plays a role in protection from stresses, such as elevated pH, as well as in the biogenesis of virulence factors. Here, we show that the Cpx periplasmic stress response is subject to amplification and repression through positive and negative autofeedback mechanisms. Western blot and operon fusion analyses demonstrated that the cpxRA operon is autoactivated. Conditions that lead to elevated levels of phosphorylated CpxR cause a concomitant increase in transcription ofcpxRA. Conversely, overproduction of CpxP, a small, Cpx-regulated protein of previously unknown function, represses the regulon and can block activation of the pathway. This repression is dependent on an intact CpxA sensing domain. The ability to autoactivate and then subsequently repress allows for a temporary amplification of the Cpx response that may be important in rescuing cells from transitory stresses and cueing the appropriately timed elaboration of virulence factors.

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