scholarly journals Edwardsiella tarda MliC, a Lysozyme Inhibitor That Participates in Pathogenesis in a Manner That Parallels Ivy

2014 ◽  
Vol 83 (2) ◽  
pp. 583-590 ◽  
Author(s):  
Mo-Fei Li ◽  
Chong Wang ◽  
Li Sun
Keyword(s):  
Bacterial Pathogen ◽  
Structural Features ◽  
Edwardsiella Tarda ◽  
Fish Tissues ◽  
Farmed Fish ◽  
Double Knockout ◽  
Content Type ◽  
Bacterial Dissemination ◽  
Lysozyme Inhibitor ◽  
Single Knockout

Edwardsiella tarda, a bacterial pathogen to farmed fish as well as humans, possesses the genes of two lysozyme inhibitors,ivyandmliC(ivyEtandmliCEt). We recently studied IvyEtand found it to be implicated inE. tardavirulence. In the present study, we characterized MliCEtin comparison with IvyEtin a turbot model. MliCEtcontains the FWSKG motif and two cysteines (C33 and C98) that are highly conserved in subgroup 1 MliCs but are of unknown functional importance. To examine the essentialness of these conserved structural features, recombinant MliCEt(rMliC) and its mutants bearing C33S and W79A (of the FWSKG motif) substitutions were prepared. Subsequent analysis showed that rMliC (i) inhibited lysozyme-induced lysis of a Gram-positive bacterium, (ii) reduced serum-facilitated lysozyme killing ofE. tarda, and (iii) when introduced into turbot, promoted bacterial dissemination in fish tissues. The C33S mutation had no influence on the activity of rMliC, while the W79A mutation slightly but significantly enhanced the activity of rMliC. Knockout strains of eithermliCEtorivyEtwere severely attenuated for the ability of tissue invasion, host lethality, serum survival, and intracellular replication. The lost virulence of themliCtransformant (TXΔmliC) was restored by complementation with an introducedmliCEtgene. Compared to the ΔivyEtor ΔmliCEtsingle-knockout strains, the ΔmliCEtΔivyEtdouble-knockout strain was significantly impaired in most of the virulence features. Together, these results provide the first evidence that the conserved cysteine is functionally dispensable to a subgroup 1 MliC and that as a virulence factor, MliCEtmost likely works in a concerted and parallel manner with Ivy.

scholarly journals Edwardsiella tarda Ivy, a Lysozyme Inhibitor That Blocks the Lytic Effect of Lysozyme and Facilitates Host Infection in a Manner That Is Dependent on the Conserved Cysteine Residue

2013 ◽  
Vol 81 (10) ◽  
pp. 3527-3533 ◽  
Author(s):  
Chong Wang ◽  
Yong-hua Hu ◽  
Bo-guang Sun ◽  
Jun Li ◽  
Li Sun
Keyword(s):  
Bacterial Pathogen ◽  
Scophthalmus Maximus ◽  
Cysteine Residue ◽  
Edwardsiella Tarda ◽  
Broad Host Range ◽  
Content Type ◽  
Lytic Effect ◽  
Lysozyme Inhibitor

ABSTRACTEdwardsiella tardais a Gram-negative bacterial pathogen with a broad host range that includes fish and humans. In this study, we examined the activity and function of the lysozyme inhibitor Ivy (named IvyEt) identified in the pathogenicE. tardastrain TX01. IvyEtpossesses the Ivy signature motif CKPHDC in the form of82CQPHNC87and contains several highly conserved residues, including a tryptophan (W55). For the purpose of virulence analysis, an isogenic TX01 mutant, TXivy, was created. TXivy bears an in-frame deletion of theivyEtgene. A live infection study in a turbot (Scophthalmus maximus) model showed that, compared to TX01, TXivy exhibited attenuated overall virulence, reduced tissue dissemination and colonization capacity, an impaired ability to replicate in host macrophages, and decreased resistance against the bactericidal effect of host serum. To facilitate functional analysis, recombinant IvyEt(rIvy) and three mutant proteins, i.e., rIvyW55A, rIvyC82S, and rIvyH85D, which bear Ala, Ser, and Asp substitutions at W55, C82, and H85, respectively, were prepared.In vitrostudies showed that rIvy, rIvyW55A, and rIvyH85D were able to block the lytic effect of lysozyme on a Gram-positive bacterium, whereas rIvyC82S could not do so. Likewise, rIvy, but not rIvyC82S, inhibited the serum-facilitated killing effect of lysozyme onE. tarda.In vivoanalysis showed that rIvy, but not rIvyC82S, restored the lost pathogenicity of TXivy and enhanced the infectivity of TX01. Together these results indicate that IvyEtis a lysozyme inhibitor and a virulence factor that depends on the conserved C82 for biological activity.

scholarly journals Two DHH Subfamily 1 Proteins Contribute to Pneumococcal Virulence and Confer Protection against Pneumococcal Disease

2011 ◽  
Vol 79 (9) ◽  
pp. 3697-3710 ◽  
Author(s):  
L. E. Cron ◽  
K. Stol ◽  
P. Burghout ◽  
S. van Selm ◽  
E. R. Simonetti ◽  
...  
Keyword(s):  
Otitis Media ◽  
Pneumococcal Disease ◽  
Capsular Polysaccharide ◽  
Pneumococcal Infection ◽  
Bacterial Pathogen ◽  
Protein Vaccine ◽  
Double Knockout ◽  
Content Type ◽  
Knockout Mutants ◽  
Different Strains

ABSTRACTStreptococcus pneumoniaeis an important human bacterial pathogen, causing such infections as pneumonia, meningitis, septicemia, and otitis media. Current capsular polysaccharide-based conjugate vaccines protect against a fraction of the over 90 serotypes known, whereas vaccines based on conserved pneumococcal proteins are considered promising broad-range alternatives. The pneumococcal genome encodes two conserved proteins of an as yet unknown function, SP1298 and SP2205, classified as DHH (Asp-His-His) subfamily 1 proteins. Here we examined their contribution to pneumococcal pathogenesis using single and double knockout mutants in three different strains: D39, TIGR4, and BHN100. Mutants lacking both SP1298 and SP2205 were severely impaired in adherence to human epithelial Detroit 562 cells. Importantly, the attenuated phenotypes were restored upon genetic complementation of the deleted genes. Single and mixed mouse models of colonization, otitis media, pneumonia, and bacteremia showed that bacterial loads in the nasopharynx, middle ears, lungs, and blood of mice infected with the mutants were significantly reduced from those of wild-type-infected mice, with an apparent additive effect upon deletion of both genes. Minor strain-specific phenotypes were observed, i.e., deletion of SP1298 affected host-cell adherence in BHN100 only, and deletion of SP2205 significantly attenuated virulence in lungs and blood in D39 and BHN100 but not TIGR4. Finally, subcutaneous vaccination with a combination of both DHH subfamily 1 proteins conferred protection to nasopharynx, lungs, and blood of mice infected with TIGR4. We conclude that SP1298 and SP2205 play a significant role at several stages of pneumococcal infection, and importantly, these proteins are potential candidates for a multicomponent protein vaccine.

scholarly journals Agent-Based Modeling Demonstrates How Local Chemotactic Behavior Can Shape Biofilm Architecture

mSphere ◽  
2019 ◽  
Vol 4 (3) ◽  
Author(s):  
Emily G. Sweeney ◽  
Andrew Nishida ◽  
Alexandra Weston ◽  
Maria S. Bañuelos ◽  
Kristin Potter ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Three Dimensional ◽  
Structural Features ◽  
Agent Based Modeling ◽  
Emergent Properties ◽  
Cellular Interactions ◽  
Biofilm Growth ◽  
Content Type ◽  
Agent Based ◽  
H Pylori

ABSTRACTBacteria are often found living in aggregated multicellular communities known as biofilms. Biofilms are three-dimensional structures that confer distinct physical and biological properties to the collective of cells living within them. We used agent-based modeling to explore whether local cellular interactions were sufficient to give rise to global structural features of biofilms. Specifically, we asked whether chemorepulsion from a self-produced quorum-sensing molecule, autoinducer-2 (AI-2), was sufficient to recapitulate biofilm growth and cellular organization observed for biofilms ofHelicobacter pylori, a common bacterial resident of human stomachs. To carry out this modeling, we modified an existing platform, Individual-based Dynamics of Microbial Communities Simulator (iDynoMiCS), to incorporate three-dimensional chemotaxis, planktonic cells that could join or leave the biofilm structure, and cellular production of AI-2. We simulated biofilm growth of previously characterizedH. pyloristrains with various AI-2 production and sensing capacities. Using biologically plausible parameters, we were able to recapitulate both the variation in biofilm mass and cellular distributions observed with these strains. Specifically, the strains that were competent to chemotax away from AI-2 produced smaller and more heterogeneously spaced biofilms, whereas the AI-2 chemotaxis-defective strains produced larger and more homogeneously spaced biofilms. The model also provided new insights into the cellular demographics contributing to the biofilm patterning of each strain. Our analysis supports the idea that cellular interactions at small spatial and temporal scales are sufficient to give rise to larger-scale emergent properties of biofilms.IMPORTANCEMost bacteria exist in aggregated, three-dimensional structures called biofilms. Although biofilms play important ecological roles in natural and engineered settings, they can also pose societal problems, for example, when they grow in plumbing systems or on medical implants. Understanding the processes that promote the growth and disassembly of biofilms could lead to better strategies to manage these structures. We had previously shown thatHelicobacter pyloribacteria are repulsed by high concentrations of a self-produced molecule, AI-2, and thatH. pylorimutants deficient in AI-2 sensing form larger and more homogeneously spaced biofilms. Here, we used computer simulations of biofilm formation to show that localH. pyloribehavior of repulsion from high AI-2 could explain the overall architecture ofH. pyloribiofilms. Our findings demonstrate that it is possible to change global biofilm organization by manipulating local cell behaviors, which suggests that simple strategies targeting cells at local scales could be useful for controlling biofilms in industrial and medical settings.

scholarly journals Playing for fun or gambling for money: a qualitative longitudinal study of digitally simulated gambling among young Danes

2018 ◽  
Vol 19 (3) ◽  
pp. 251-266
Author(s):  
Søren Kristiansen ◽  
Maria Camilla Trabjerg ◽  
Nanna Reventlov Lauth ◽  
Anders Malling
Keyword(s):  
Young People ◽  
Panel Study ◽  
Structural Features ◽  
Geographic Region ◽  
Content Type ◽  
Individual Interviews ◽  
Regulatory Policies ◽  
And Behaviors ◽  
Gambling Market ◽  
Simulated Gambling

Purpose The study aims to explore the types of simulated games and gambling platforms used by adolescents, adolescent’s experiences, motivations and behaviors vis-à-vis simulated gambling and the potential interrelationships between simulated and monetary forms gambling. Design/methodology/approach Data was obtained from a qualitative longitudinal panel study with three waves of individual interviews. A cohort of 51 young Danes, with varying levels of gambling involvement, were interviewed three times, with a 10-12 frequency from 2011 to 2014. In total, 149 interviews were conducted over the 4-year period. Findings Enjoying social interactional effects appeared to be the main reasons young people engage in simulated gambling games. The study documented characteristics of both a catalyst pathway and a containment pathway emphasizing that for some young people simulated gambling may increase the likelihood of involvement in real money gambling while it may decrease it for others. Research limitations/implications The sample was relatively limited and it involved participants from only one of the five Danish regions. The sample reflects the culture, rural/urban configuration and gambling market of a specific geographic region. Practical implications Some forms of simulated digital gambling may provide players with excitement and unrealistic conceptions of winning chances, which, in turn, may encourage participation in real forms of gambling. This may call for regulatory policies aiming at the structural features of simulated gambling products and their rapid global spread. Consumer campaigns aimed at both young people themselves and their parents may be considered. Originality/value Few studies have provided insights into the meanings and motivations of young people engaged in simulated gambling. The current study is among the first to explore adolescent’s experiences, motivations and behaviors vis-à-vis simulated gambling and the potential interrelationships between simulated and monetary forms gambling.

scholarly journals CK1α ablation in keratinocytes induces p53-dependent, sunburn-protective skin hyperpigmentation

2017 ◽  
Vol 114 (38) ◽  
pp. E8035-E8044 ◽  
Author(s):  
Chung-Hsing Chang ◽  
Che-Jung Kuo ◽  
Takamichi Ito ◽  
Yu-Ya Su ◽  
Si-Tse Jiang ◽  
...  
Keyword(s):  
Target Genes ◽  
Neutralizing Antibody ◽  
Double Knockout ◽  
Melanocyte Stimulating Hormone ◽  
Kit Ligand ◽  
Skin Physiology ◽  
P53 Activation ◽  
P53 Target Genes ◽  
Single Knockout

Casein kinase 1α (CK1α), a component of the β-catenin destruction complex, is a critical regulator of Wnt signaling; its ablation induces both Wnt and p53 activation. To characterize the role of CK1α (encoded byCsnk1a1) in skin physiology, we crossed mice harboring floxedCsnk1a1with mice expressing K14–Cre–ERT2to generate mice in which tamoxifen induces the deletion ofCsnk1a1exclusively in keratinocytes [single-knockout (SKO) mice]. As expected, CK1α loss was accompanied by β-catenin and p53 stabilization, with the preferential induction of p53 target genes, but phenotypically most striking was hyperpigmentation of the skin, importantly without tumorigenesis, for at least 9 mo afterCsnk1a1ablation. The number of epidermal melanocytes and eumelanin levels were dramatically increased in SKO mice. To clarify the putative role of p53 in epidermal hyperpigmentation, we established K14–Cre–ERT2CK1α/p53 double-knockout (DKO) mice and found that coablation failed to induce epidermal hyperpigmentation, demonstrating that it was p53-dependent. Transcriptome analysis of the epidermis revealed p53-dependent up-regulation of Kit ligand (KitL). SKO mice treated with ACK2 (a Kit-neutralizing antibody) or imatinib (a Kit inhibitor) abrogated the CK1α ablation-induced hyperpigmentation, demonstrating that it requires the KitL/Kit pathway. Pro-opiomelanocortin (POMC), a precursor of α-melanocyte–stimulating hormone (α-MSH), was not activated in the CK1α ablation-induced hyperpigmentation, which is in contrast to the mechanism of p53-dependent UV tanning. Nevertheless, acute sunburn effects were successfully prevented in the hyperpigmented skin of SKO mice. CK1α inhibition induces skin-protective eumelanin but no carcinogenic pheomelanin and may therefore constitute an effective strategy for safely increasing eumelanin via UV-independent pathways, protecting against acute sunburn.

scholarly journals Cooperative effects of genes controlling the G2/M checkpoint

2000 ◽  
Vol 14 (13) ◽  
pp. 1584-1588
Author(s):  
Timothy A. Chan ◽  
Paul M. Hwang ◽  
Heiko Hermeking ◽  
Kenneth W. Kinzler ◽  
Bert Vogelstein
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Mammalian Cells ◽  
Growth Arrest ◽  
Double Knockout ◽  
Specific Test ◽  
Cooperative Effects ◽  
Exogenous Expression ◽  
Induced Genes ◽  
Single Knockout

It is believed that multiple effectors independently control the checkpoints permitting transitions between cell cycle phases. However, this has not been rigorously demonstrated in mammalian cells. The p53-induced genes p21 and 14-3-3ς are each required for the G2 arrest and allow a specific test of this fundamental tenet. We generated human cells deficient in bothp21 and 14-3-3ς and determined whether the double knockout was more sensitive to DNA damage than either single knockout.p21−/−14-3-3ς−/− cells were significantly more sensitive to DNA damage or to the exogenous expression of p53 than cells lacking only p21 or only 14-3-3ς. Thus, p21 and 14-3-3ς play distinct but complementary roles in the G2/M checkpoint, and help explain why genes at the nodal points of growth arrest pathways, like p53, are the targets of mutation in cancer cells.

scholarly journals Structural Similarities and Differences between Two Functionally Distinct SecA Proteins, Mycobacterium tuberculosis SecA1 and SecA2

2015 ◽  
Vol 198 (4) ◽  
pp. 720-730 ◽  
Author(s):  
Stephanie Swanson ◽  
Thomas R. Ioerger ◽  
Nathan W. Rigel ◽  
Brittany K. Miller ◽  
Miriam Braunstein ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Signal Peptide ◽  
Protein A ◽  
Structural Difference ◽  
Structural Similarity ◽  
Structural Features ◽  
Dominant Negative ◽  
Content Type ◽  
Functional Regions ◽  
Suppressor Mutations

ABSTRACTWhile SecA is the ATPase component of the major bacterial secretory (Sec) system, mycobacteria and some Gram-positive pathogens have a second paralog, SecA2. In bacteria with two SecA paralogs, each SecA is functionally distinct, and they cannot compensate for one another. Compared to SecA1, SecA2 exports a distinct and smaller set of substrates, some of which have roles in virulence. In the mycobacterial system, some SecA2-dependent substrates lack a signal peptide, while others contain a signal peptide but possess features in the mature protein that necessitate a role for SecA2 in their export. It is unclear how SecA2 functions in protein export, and one open question is whether SecA2 works with the canonical SecYEG channel to export proteins. In this study, we report the structure ofMycobacterium tuberculosisSecA2 (MtbSecA2), which is the first structure of any SecA2 protein. A high level of structural similarity is observed between SecA2 and SecA1. The major structural difference is the absence of the helical wing domain, which is likely to play a role in howMtbSecA2 recognizes its unique substrates. Importantly, structural features critical to the interaction between SecA1 and SecYEG are preserved in SecA2. Furthermore, suppressor mutations of a dominant-negativesecA2mutant map to the surface of SecA2 and help identify functional regions of SecA2 that may promote interactions with SecYEG or the translocating polypeptide substrate. These results support a model in which the mycobacterial SecA2 works with SecYEG.IMPORTANCESecA2 is a paralog of SecA1, which is the ATPase of the canonical bacterial Sec secretion system. SecA2 has a nonredundant function with SecA1, and SecA2 exports a distinct and smaller set of substrates than SecA1. This work reports the crystal structure of SecA2 ofMycobacterium tuberculosis(the first SecA2 structure reported for any organism). Many of the structural features of SecA1 are conserved in the SecA2 structure, including putative contacts with the SecYEG channel. Several structural differences are also identified that could relate to the unique function and selectivity of SecA2. Suppressor mutations of asecA2mutant map to the surface of SecA2 and help identify functional regions of SecA2 that may promote interactions with SecYEG.

Modeling and simulation analysis of the hybrid excitation synchronous machine system utilizing tooth harmonic for excitation

2016 ◽  
Vol 35 (2) ◽  
pp. 540-555 ◽  
Author(s):  
Yonghong Xia ◽  
Junbo Liu ◽  
Bo Xu ◽  
Hongjian Wu
Keyword(s):  
Permanent Magnet ◽  
Operation Mode ◽  
Structural Features ◽  
Current Waveform ◽  
Standard State ◽  
State Equations ◽  
Permanent Magnet Machine ◽  
Content Type ◽  
Machine System ◽  
Hybrid Excitation

Purpose – The purpose of this paper is to propose a novel hybrid excitation permanent magnet synchronous generator (HEPMSG) utilizing tooth harmonic for excitation, the structural features and operation principle of which are also described. Design/methodology/approach – To obtain the operation performance quickly, this paper derives the mathematical model of the machine system represented by circuit, and analyzes the operation mode of rectifier circuit in the tooth harmonic excitation system, then the standard state equations for each operation mode are obtained. Combining the inductance parameter of this machine with the load resistance and inductance, the armature current waveform, the field current waveform and tooth harmonic winding current waveform are obtained by using the numerical method to solve the standard state equation. Findings – Comparing with the experimental results, the availability of the principle and the validity of the model of the machine system are verified. Practical implications – This HEPMSG is a new brushless self-excited and self-regulated generator, which is suitable for an independent power source. Originality/value – Unlike the existing hybrid excitation permanent magnet machine, this HEPMSG utilized the inherent tooth harmonic EMF of the rotor to adjust the air-gap magnetic field of the permanent magnet machine.

scholarly journals Contributions of A2A and A2B adenosine receptors in coronary flow responses in relation to the KATP channel using A2B and A2A/2B double-knockout mice

2011 ◽  
Vol 301 (6) ◽  
pp. H2322-H2333 ◽  
Author(s):  
Maryam Sharifi Sanjani ◽  
Bunyen Teng ◽  
Thomas Krahn ◽  
Stephen Tilley ◽  
Catherine Ledent ◽  
...  
Keyword(s):  
Coronary Flow ◽  
Channel Blocker ◽  
Cardiovascular Disorders ◽  
Therapeutic Approaches ◽  
Double Knockout ◽  
Cgs 21680 ◽  
Pathological Conditions ◽  
Sch 58261 ◽  
Single Knockout

Adenosine plays a role in physiological and pathological conditions, and A2 adenosine receptor (AR) expression is modified in many cardiovascular disorders. In this study, we elucidated the role of the A2BAR and its relationship to the A2AAR in coronary flow (CF) changes using A2B single-knockout (KO) and A2A/2B double-KO (DKO) mice in a Langendorff setup. We used two approaches: 1) selective and nonselective AR agonists and antagonists and 2) A2AKO and A2BKO and A2A/2BDKO mice. BAY 60-6583 (a selective A2B agonist) had no effect on CF in A2BKO mice, whereas it significantly increased CF in wild-type (WT) mice (maximum of 23.3 ± 9 ml·min−1·g−1). 5′- N-ethylcarboxamido adenosine (NECA; a nonselective AR agonist) increased CF in A2BKO mice (maximum of 34.6 ± 4.7 ml·min−1·g−1) to a significantly higher degree compared with WT mice (maximum of 23.1 ± 2.1 ml·min−1·g−1). Also, CGS-21680 (a selective A2A agonist) increased CF in A2BKO mice (maximum of 29 ± 1.9 ml·min−1·g−1) to a significantly higher degree compared with WT mice (maximum of 25.1 ± 2.3 ml·min−1·g−1). SCH-58261 (an A2A-selective antagonist) inhibited the NECA-induced increase in CF to a significantly higher degree in A2BKO mice (19.3 ± 1.6 vs. 0.5 ± 0.4 ml·min−1·g−1) compared with WT mice (19 ± 3.5 vs. 3.6 ± 0.5 ml·min−1·g−1). NECA did not induce any increase in CF in A2A/2BDKO mice, whereas a significant increase was observed in WT mice (maximum of 23.1 ± 2.1 ml·min−1·g−1). Furthermore, the mitochondrial ATP-sensitive K+ (KATP) channel blocker 5-hydroxydecanoate had no effect on the NECA-induced increase in CF in WT mice, whereas the NECA-induced increase in CF in WT (17.6 ± 2 ml·min−1·g−1), A2AKO (12.5 ± 2.3 ml·min−1·g−1), and A2BKO (16.2 ± 0.8 ml·min−1·g−1) mice was significantly blunted by the KATP channel blocker glibenclamide (to 0.7 ± 0.7, 2.3 ± 1.1, and 0.9 ± 0.4 ml·min−1·g−1, respectively). Also, the CGS-21680-induced (22 ± 2.3 ml·min−1·g−1) and BAY 60-6583-induced (16.4 ± 1.60 ml·min−1·g−1) increase in CF in WT mice was significantly blunted by glibenclamide (to 1.2 ± 0.4 and 1.8 ± 1.2 ml·min−1·g−1, respectively). In conclusion, this is the first evidence supporting the compensatory upregulation of A2AARs in A2BKO mice and demonstrates that both A2AARs and A2BARs induce CF changes through KATP channels. These results identify AR-mediated CF responses that may lead to better therapeutic approaches for the treatment of cardiovascular disorders.

scholarly journals Perforin-2 Protects Host Cells and Mice by Restricting the Vacuole to Cytosol Transitioning of a Bacterial Pathogen

2016 ◽  
Vol 84 (4) ◽  
pp. 1083-1091 ◽  
Author(s):  
Ryan McCormack ◽  
Wael Bahnan ◽  
Niraj Shrestha ◽  
Justin Boucher ◽  
Marcella Barreto ◽  
...  
Keyword(s):  
Bacterial Pathogen ◽  
Virulence Gene ◽  
Systemic Infection ◽  
Protective Role ◽  
Host Cells ◽  
Content Type ◽  
Virulence Gene Expression ◽  
Membrane Bound ◽  
High Level ◽  
Macpf Domain

The host-encoded Perforin-2 (encoded by the macrophage-expressed gene 1,Mpeg1), which possesses a pore-forming MACPF domain, reduces the viability of bacterial pathogens that reside within membrane-bound compartments. Here, it is shown that Perforin-2 also restricts the proliferation of the intracytosolic pathogenListeria monocytogenes. Within a few hours of systemic infection, the massive proliferation ofL. monocytogenesinPerforin-2−/−mice leads to a rapid appearance of acute disease symptoms. We go on to show in culturedPerforin-2−/−cells that the vacuole-to-cytosol transitioning ofL. monocytogenesis greatly accelerated. Unexpectedly, we found that inPerforin-2−/−macrophages,Listeria-containing vacuoles quickly (≤15 min) acidify, and that this was coincident with greater virulence gene expression, likely accounting for the more rapid translocation ofL. monocytogenesto its replicative niche in the cytosol. This hypothesis was supported by our finding that aL. monocytogenesstrain expressing virulence factors at a constitutively high level replicated equally well inPerforin-2+/+andPerforin-2−/−macrophages. Our findings suggest that the protective role of Perforin-2 against listeriosis is based on it limiting the intracellular replication of the pathogen. This cellular activity of Perforin-2 may derive from it regulating the acidification ofListeria-containing vacuoles, thereby depriving the pathogen of favorable intracellular conditions that promote its virulence gene activity.

Sign in / Sign up

Export Citation Format

Share Document