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 Rcs System in Enterobacteriaceae: Envelope Stress Responses and Virulence Regulation

2021 ◽  
Vol 12 ◽  
Author(s):  
Jiao Meng ◽  
Glenn Young ◽  
Jingyu Chen
Keyword(s):  
Stress Response ◽  
Stress Responses ◽  
Bacterial Infections ◽  
Pathogenic Bacteria ◽  
Cell Envelope ◽  
Regulatory System ◽  
Virulence Regulation ◽  
Bacterial Interaction ◽  
Envelope Stress

The bacterial cell envelope is a protective barrier at the frontline of bacterial interaction with the environment, and its integrity is regulated by various stress response systems. The Rcs (regulator of capsule synthesis) system, a non-orthodox two-component regulatory system (TCS) found in many members of the Enterobacteriaceae family, is one of the envelope stress response pathways. The Rcs system can sense envelope damage or defects and regulate the transcriptome to counteract stress, which is particularly important for the survival and virulence of pathogenic bacteria. In this review, we summarize the roles of the Rcs system in envelope stress responses (ESRs) and virulence regulation. We discuss the environmental and intrinsic sources of envelope stress that cause activation of the Rcs system with an emphasis on the role of RcsF in detection of envelope stress and signal transduction. Finally, the different regulation mechanisms governing the Rcs system’s control of virulence in several common pathogens are introduced. This review highlights the important role of the Rcs system in the environmental adaptation of bacteria and provides a theoretical basis for the development of new strategies for control, prevention, and treatment of bacterial infections.

scholarly journals A Suppressor Mutation That Creates a Faster and More Robust σE Envelope Stress Response

2016 ◽  
Vol 198 (17) ◽  
pp. 2345-2351 ◽  
Author(s):  
Anna Konovalova ◽  
Jaclyn A. Schwalm ◽  
Thomas J. Silhavy
Keyword(s):  
Stress Response ◽  
Stress Responses ◽  
Novel Mutation ◽  
Signal Transduction Pathway ◽  
Normal Growth ◽  
Internal Stresses ◽  
Content Type ◽  
Envelope Stress ◽  
Genetic Perturbations ◽  
Periplasmic Stress

ABSTRACTThe σE envelope stress response is an essential signal transduction pathway which detects and removes mistargeted outer membrane (OM) β-barrel proteins (OMPs) in the periplasm ofEscherichia coli. It relies on σE, an alternative sigma factor encoded by therpoEgene. Here we report a novel mutation, a nucleotide change of C to A in the third base of the second codon, which increases levels of σE (rpoE_S2R). TherpoE_S2Rmutation does not lead to the induction of the stress response during normal growth but instead changes the dynamics of induction upon periplasmic stress, resulting in a faster and more robust response. This allows cells to adapt faster to the periplasmic stress, avoiding lethal accumulation of unfolded OMPs in the periplasm caused by severe defects in the OMP assembly pathway.IMPORTANCESurvival of bacteria under conditions of external or internal stresses depends on timely induction of stress response signaling pathways to regulate expression of appropriate genes that function to maintain cellular homeostasis. Previous studies have shown that strong preinduction of envelope stress responses can allow bacteria to survive a number of lethal genetic perturbations. In our paper, we describe a unique mutation that enhances kinetics of the σE envelope stress response pathway rather than preinducing the response. This allows bacteria to quickly adapt to sudden and severe periplasmic stress.

scholarly journals Signal Detection and Target Gene Induction by the CpxRA Two-Component System

2003 ◽  
Vol 185 (8) ◽  
pp. 2432-2440 ◽  
Author(s):  
Patricia A. DiGiuseppe ◽  
Thomas J. Silhavy
Keyword(s):  
Signal Transduction ◽  
Feedback Inhibition ◽  
Response Regulator ◽  
Negative Regulator ◽  
Outer Membrane Lipoprotein ◽  
Envelope Stress ◽  
Two Component ◽  
Two Component Signal Transduction ◽  
Cpx Pathway ◽  
Target Gene Induction

ABSTRACT The Cpx pathway is a two-component signal transduction system that senses a variety of envelope stresses, including misfolded proteins, and responds by upregulating periplasmic folding and trafficking factors. CpxA resides in the inner membrane and has both kinase and phosphatase activities. CpxR, the response regulator, mediates a response by activating transcription of stress-combative genes. Signal transduction is subject to feedback inhibition via regulon member CpxP and autoamplification. Recently, it was shown that the Cpx pathway is also upregulated when cells adhere to hydrophobic surfaces and that this response is dependent on the outer membrane lipoprotein NlpE. Here we show that while NlpE is required for induction of the Cpx pathway by adhesion, induction by envelope stress and during growth is NlpE independent. We show that while all of the envelope stresses tested induce the Cpx pathway in a manner that is dependent on the periplasmic domain of CpxA, induction during growth is independent of CpxA. Therefore, we propose that the Cpx pathway can sense inducing cues that enter the signaling pathway at three distinct points. Although CpxP is not required for induction of the Cpx pathway, we show that its activity as a negative regulator of CpxA is inactivated by envelope stress. Moreover, the cpxP promoter is more inducible than any other regulon member tested. Consistent with these results, we suggest that CpxP performs a second function, most likely that of a chaperone. Finally, we show that two Cpx-regulated genes are differentially upregulated in response to different envelope stresses, suggesting the existence of three stress-responsive systems.

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.

scholarly journals The Vibrio cholerae Cpx Envelope Stress Response Senses and Mediates Adaptation to Low Iron

2014 ◽  
Vol 197 (2) ◽  
pp. 262-276 ◽  
Author(s):  
Nicole Acosta ◽  
Stefan Pukatzki ◽  
Tracy L. Raivio
Keyword(s):  
Vibrio Cholerae ◽  
Stress Responses ◽  
Bacterial Species ◽  
Membrane Pore ◽  
Toxic Compounds ◽  
Content Type ◽  
Major Function ◽  
Pathway Activation ◽  
Envelope Stress ◽  
Cpx Pathway

The Cpx pathway, a two-component system that employs the sensor histidine kinase CpxA and the response regulator CpxR, regulates crucial envelope stress responses across bacterial species and affects antibiotic resistance. To characterize the CpxR regulon inVibrio cholerae, the transcriptional profile of the pandemicV. choleraeEl Tor C6706 strain was examined upon overexpression ofcpxR. Our data show that the Cpx regulon ofV. choleraeis enriched in genes encoding membrane-localized and transport proteins, including a large number of genes known or predicted to be iron regulated. Activation of the Cpx pathway further led to the expression of TolC, the major outer membrane pore, and of components of two RND efflux systems inV. cholerae. We show that iron chelation, toxic compounds, or deletion of specific RND efflux components leads to Cpx pathway activation. Furthermore, mutations that eliminate the Cpx response or members of its regulon result in growth phenotypes in the presence of these inducers that, together with Cpx pathway activation, are partially suppressed by iron. Cumulatively, our results suggest that a major function of the Cpx response inV. choleraeis to mediate adaptation to envelope perturbations caused by toxic compounds and the depletion of iron.

scholarly journals A lipoprotein/β-barrel complex monitors lipopolysaccharide integrity transducing information across the outer membrane

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Anna Konovalova ◽  
Angela M Mitchell ◽  
Thomas J Silhavy
Keyword(s):  
Stress Response ◽  
Cell Surface ◽  
Charged Surface ◽  
Lateral Interactions ◽  
Terminal Domain ◽  
Outer Leaflet ◽  
Envelope Stress ◽  
Signaling Domain ◽  
Phosphate Groups ◽  
Positively Charged

Lipoprotein RcsF is the OM component of the Rcs envelope stress response. RcsF exists in complexes with β-barrel proteins (OMPs) allowing it to adopt a transmembrane orientation with a lipidated N-terminal domain on the cell surface and a periplasmic C-terminal domain. Here we report that mutations that remove BamE or alter a residue in the RcsF trans-lumen domain specifically prevent assembly of the interlocked complexes without inactivating either RcsF or the OMP. Using these mutations we demonstrate that these RcsF/OMP complexes are required for sensing OM outer leaflet stress. Using mutations that alter the positively charged surface-exposed domain, we show that RcsF monitors lateral interactions between lipopolysaccharide (LPS) molecules. When these interactions are disrupted by cationic antimicrobial peptides, or by the loss of negatively charged phosphate groups on the LPS molecule, this information is transduced to the RcsF C-terminal signaling domain located in the periplasm to activate the stress response.

scholarly journals Fine-Tuning of σEActivation Suppresses Multiple Assembly-Defective Mutations inEscherichia coli

2019 ◽  
Vol 201 (11) ◽  
Author(s):  
Elizabeth M. Hart ◽  
Aileen O’Connell ◽  
Kimberly Tang ◽  
Joseph S. Wzorek ◽  
Marcin Grabowicz ◽  
...  
Keyword(s):  
Stress Response ◽  
Cell Viability ◽  
Outer Membrane ◽  
Stress Responses ◽  
Expression Profiles ◽  
Outer Membrane Proteins ◽  
Fine Tuning ◽  
Permeability Barrier ◽  
Gram Negative ◽  
Envelope Stress

ABSTRACTThe Gram-negative outer membrane (OM) is a selectively permeable asymmetric bilayer that allows vital nutrients to diffuse into the cell but prevents toxins and hydrophobic molecules from entering. Functionally and structurally diverse β-barrel outer membrane proteins (OMPs) build and maintain the permeability barrier, making the assembly of OMPs crucial for cell viability. In this work, we characterize an assembly-defective mutant of the maltoporin LamB, LamBG439D. We show that the folding defect of LamBG439Dresults in an accumulation of unfolded substrate that is toxic to the cell when the periplasmic protease DegP is removed. Selection for suppressors of this toxicity identified the novel mutantdegSA323Eallele. The mutant DegSA323Eprotein contains an amino acid substitution at the PDZ/protease domain interface that results in a partially activated conformation of this protein. This activation increases basal levels of downstream σEstress response signaling. Furthermore, the enhanced σEactivity of DegSA323Esuppresses a number of other assembly-defective conditions without exhibiting the toxicity associated with high levels of σEactivity. We propose that the increased basal levels of σEsignaling primes the cell to respond to envelope stress before OMP assembly defects threaten cell viability. This finding addresses the importance of envelope stress responses in monitoring the OMP assembly process and underpins the critical balance between envelope defects and stress response activation.IMPORTANCEGram-negative bacteria, such asEscherichia coli, inhabit a natural environment that is prone to flux. In order to cope with shifting growth conditions and the changing availability of nutrients, cells must be capable of quickly responding to stress. Stress response pathways allow cells to rapidly shift gene expression profiles to ensure survival in this unpredictable environment. Here we describe a mutant that partially activates the σEstress response pathway. The elevated basal level of this stress response allows the cell to quickly respond to overwhelming stress to ensure cell survival.

scholarly journals Impact of bacterial sRNAs in stress responses

2017 ◽  
Vol 45 (6) ◽  
pp. 1203-1212 ◽  
Author(s):  
Erik Holmqvist ◽  
E. Gerhart H. Wagner
Keyword(s):  
Dna Damage ◽  
Stress Response ◽  
Stress Responses ◽  
Transcriptional Control ◽  
Iron Homeostasis ◽  
Stress Relief ◽  
Regulatory Circuits ◽  
Envelope Stress ◽  
Key Players ◽  
Non Coding Rnas

Bacterial life is harsh and involves numerous environmental and internal challenges that are perceived as stresses. Consequently, adequate responses to survive, cope with, and counteract stress conditions have evolved. In the last few decades, a class of small, non-coding RNAs (sRNAs) has been shown to be involved as key players in stress responses. This review will discuss — primarily from an enterobacterial perspective — selected stress response pathways that involve antisense-type sRNAs. These include themes of how bacteria deal with severe envelope stress, threats of DNA damage, problems with poisoning due to toxic sugar intermediates, issues of iron homeostasis, and nutrient limitation/starvation. The examples discussed highlight how stress relief can be achieved, and how sRNAs act mechanistically in regulatory circuits. For some cases, we will propose scenarios that may suggest why contributions from post-transcriptional control by sRNAs, rather than transcriptional control alone, appear to be a beneficial and universally selected feature.

scholarly journals Hfq Modulates the σE-Mediated Envelope Stress Response and the σ32-Mediated Cytoplasmic Stress Response in Escherichia coli

2006 ◽  
Vol 189 (5) ◽  
pp. 1963-1973 ◽  
Author(s):  
Eric Guisbert ◽  
Virgil A. Rhodius ◽  
Nidhi Ahuja ◽  
Emily Witkin ◽  
Carol A. Gross
Keyword(s):  
Escherichia Coli ◽  
Stress Response ◽  
Membrane Proteins ◽  
Outer Membrane ◽  
Stress Responses ◽  
Outer Membrane Proteins ◽  
Sugar Uptake ◽  
Acid Uptake ◽  
General Role ◽  
Envelope Stress

ABSTRACT Hfq, a chaperone for small noncoding RNAs, regulates many processes in Escherichia coli, including the σS-mediated general stress response. Here we used microarray analysis to identify the changes in gene expression resulting from lack of Hfq. We identify several potential new targets for Hfq regulation, including genes encoding outer membrane proteins, enzymes, factors, and transporters. Many of these genes are involved in amino acid uptake and biosynthesis, sugar uptake and metabolism, and cell energetics. In addition, we find altered regulation of the σE- and σ32-mediated stress responses, which we analyze further. We show that cells lacking Hfq induce the σE-mediated envelope stress response and are defective in σE-mediated repression of outer membrane proteins. We also show that the σ32-mediated cytoplasmic stress response is repressed in cells lacking Hfq due to increased expression of DnaK. Furthermore, we show that cells lacking Hfq are defective in the “long-term adaptation” of σ32 to chronic chaperone overexpression. Together, our results indicate that Hfq may play a general role in stress response regulation in E. coli.

scholarly journals Dual Regulation of Phosphatidylserine Decarboxylase Expression by Envelope Stress Responses

2021 ◽  
Vol 8 ◽  
Author(s):  
Yasmine Hassoun ◽  
Julia Bartoli ◽  
Astrid Wahl ◽  
Julie Pamela Viala ◽  
Emmanuelle Bouveret
Keyword(s):  
Stress Response ◽  
Stress Responses ◽  
Response Regulators ◽  
Two Component System ◽  
Component System ◽  
Basal Expression ◽  
Gene Coding ◽  
Envelope Stress ◽  
Two Component ◽  
Artificial Activation

Bacteria adapt to versatile environments by modulating gene expression through a set of stress response regulators, alternative Sigma factors, or two-component systems. Among the central processes that must be finely tuned is membrane homeostasis, including synthesis of phospholipids (PL). However, few genetic regulations of this process have been reported. We have previously shown that the gene coding the first step of PL synthesis is regulated by σE and ppGpp, and that the BasRS (PmrAB) two component system controls the expression of the DgkA PL recycling enzyme. The gene coding for phosphatidylserine decarboxylase, the last step in phosphatidylethanolamine synthesis is another gene in the PL synthesis pathway susceptible of stress response regulation. Indeed, psd appears in transcriptome studies of the σE envelope stress Sigma factor and of the CpxAR two component system. Interestingly, this gene is presumably in operon with mscM coding for a miniconductance mechanosensitive channel. In this study, we dissected the promoter region of the psd-mscM operon and studied its regulation by σE and CpxR. By artificial activation of σE and CpxRA stress response pathways, using GFP transcriptional fusion and western-blot analysis of Psd and MscM enzyme production, we showed that the operon is under the control of two distinct promoters. One is activated by σE, the second is activated by CpxRA and also responsible for basal expression of the operon. The fact that the phosphatidylethanolamine synthesis pathway is controlled by envelope stress responses at both its first and last steps might be important for adaptation of the membrane to envelope perturbations.

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