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1.
Commun Biol ; 7(1): 162, 2024 Feb 09.
Artigo em Inglês | MEDLINE | ID: mdl-38332126

RESUMO

Modulation of cell death is a powerful strategy employed by pathogenic bacteria to evade host immune clearance and occupy profitable replication niches during infection. Intracellular pathogens employ the type III secretion system (T3SS) to deliver effectors, which interfere with regulated cell death pathways to evade immune defenses. Here, we reveal that poly(ADP-ribose) polymerase-1 (PARP1)-dependent cell death restrains Edwardsiella piscicida's proliferation in mouse monocyte macrophages J774A.1, of which PARP1 activation results in the accumulation of poly(ADP-ribose) (PAR) and enhanced inflammatory response. Moreover, E. piscicida, an important intracellular pathogen, leverages a T3SS effector YfiD to impair PARP1's activity and inhibit PAR accumulation. Once translocated into the host nucleus, YfiD binds to the ADP-ribosyl transferase (ART) domain of PARP1 to suppress its PARylation ability as the pharmacological inhibitor of PARP1 behaves. Furthermore, the interaction between YfiD and ART mainly relies on the complete unfolding of the helical domain, which releases the inhibitory effect on ART. In addition, YfiD impairs the inflammatory response and cell death in macrophages and promotes in vivo colonization and virulence of E. piscicida. Collectively, our results establish the functional mechanism of YfiD as a potential PARP1 inhibitor and provide more insights into host defense against bacterial infection.


Assuntos
Edwardsiella , Infecções por Enterobacteriaceae , Animais , Camundongos , Sistemas de Secreção Tipo III/metabolismo , Poli Adenosina Difosfato Ribose , Virulência , Edwardsiella/metabolismo
2.
mBio ; 15(3): e0306723, 2024 Mar 13.
Artigo em Inglês | MEDLINE | ID: mdl-38376149

RESUMO

Type III secretion systems (T3SSs) are essential for motility and virulence in many bacterial pathogens. Proteins destined for the flagellar T3SS contain at least two export signals in their N-terminal D0 domain. Here, we describe a third carboxy (C)-terminal signal in early flagellar subunits that facilitates subunit targeting to the export machinery. Mutational analysis identified critical residues within the flagellar hook subunit C-terminal export signal. The flagellar ATPase and cytoplasmic ring components were not required for this targeting, indicating that core export machinery components facilitate substrate targeting via the C-terminal export signal. More broadly, these results demonstrate that multiple distinct export signals within type III secretion substrates facilitate distinct export events at the T3SS export machinery. Our data establish key events in the export mechanism of type III secretion systems: targeting of subunits to and their sequential interactions with key components of the export machinery. IMPORTANCE: Many bacterial pathogens utilize T3SS to inject virulence proteins (effectors) into host cells or to assemble flagella on the bacterial cell surface. Bacterial flagella present a paradigm for how cells build and operate complex cell-surface "nanomachines." Efficient subunit targeting from the bacterial cytosol to type III secretion systems is essential for rapid assembly and secretion by T3SSs. Subunits are thought to dock at the export machinery before being unfolded and translocated into the export channel. However, little is known about how subunits dock at the export machinery and the events that occur post docking. Here, we identified a new export signal within the C-termini of subunits that is essential for targeting of subunits to the type III export machinery. We show that this new export signal and previously identified export signals are recognized separately and sequentially, revealing a pathway for subunit transit through the type III export machinery in which sequential recognition events carry out different roles at major steps in the export pathway.


Assuntos
Proteínas de Bactérias , Sistemas de Secreção Tipo III , Proteínas de Bactérias/metabolismo , Sistemas de Secreção Tipo III/metabolismo , Bactérias/metabolismo , Flagelos/metabolismo , Membrana Celular/metabolismo , Transporte Proteico
3.
Protein Sci ; 33(3): e4930, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38380768

RESUMO

Bacteria express lytic enzymes such as glycosidases, which have potentially self-destructive peptidoglycan (PG)-degrading activity and, therefore, require careful regulation in bacteria. The PG glycosidase EtgA is regulated by localization to the assembling type III secretion system (T3SS), generating a hole in the PG layer for the T3SS to reach the outer membrane. The EtgA localization was found to be mediated via EtgA interacting with the T3SS inner rod protein EscI. To gain structural insights into the EtgA recognition of EscI, we determined the 2.01 Å resolution structure of an EscI (51-87)-linker-EtgA fusion protein designed based on AlphaFold2 predictions. The structure revealed EscI residues 72-87 forming an α-helix interacting with the backside of EtgA, distant from the active site. EscI residues 56-71 also were found to interact with EtgA, with these residues stretching across the EtgA surface. The ability of the EscI to interact with EtgA was also probed using an EscI peptide. The EscI peptide comprising residues 66-87, slightly larger than the observed EscI α-helix, was shown to bind to EtgA using microscale thermophoresis and thermal shift differential scanning fluorimetry. The EscI peptide also had a two-fold activity-enhancing effect on EtgA, whereas the EscI-EtgA fusion protein enhanced activity over four-fold compared to EtgA. Our studies suggest that EtgA regulation by EscI could be trifold involving protein localization, protein activation, and protein stabilization components. Analysis of the sequence conservation of the EscI EtgA interface residues suggested a possible conservation of such regulation for related proteins from different bacteria.


Assuntos
Proteínas de Escherichia coli , Sistemas de Secreção Tipo III , Sistemas de Secreção Tipo III/metabolismo , Glicosídeo Hidrolases/metabolismo , Proteínas de Escherichia coli/química , Peptidoglicano/metabolismo , Transporte Proteico , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo
4.
Int J Mol Sci ; 25(4)2024 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-38396724

RESUMO

The development of new approaches and drugs for effective control of the chronic and complicated forms of urogenital chlamydia caused by Chlamydia trachomatis, which is suspected to be one of the main causes of infertility in both women and men, is an urgent task. We used the technology of single-domain antibody (nanobody) generation both for the production of targeting anti-chlamydia molecules and for the subsequent acquisition of anti-idiotypic nanobodies (ai-Nbs) mimicking the structure of a given epitope of the pathogen (the epitope of the Chlamydial Type III Secretion System Needle Protein). In a mouse model, we have shown that the obtained ai-Nbs are able to induce a narrowly specific humoral immune response in the host, leading to the generation of intrinsic anti-Chlamydia antibodies, potentially therapeutic, specifically recognizing a given antigenic epitope of Chlamydia. The immune sera derived from mice immunized with ai-Nbs are able to suppress chlamydial infection in vitro. We hypothesize that the proposed method of the creation and use of ai-Nbs, which mimic and present to the host immune system exactly the desired region of the antigen, create a fundamentally new universal approach to generating molecular structures as a part of specific vaccine for the targeted induction of immune response, especially useful in cases where it is difficult to prepare an antigen preserving the desired epitope in its native conformation.


Assuntos
Infecções por Chlamydia , Anticorpos de Domínio Único , Humanos , Camundongos , Animais , Feminino , Epitopos , Sistemas de Secreção Tipo III , Chlamydia trachomatis , Anticorpos Antibacterianos
5.
PLoS Pathog ; 20(1): e1011280, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-38271464

RESUMO

Subverting the host immune response to inhibit inflammation is a key virulence strategy of Yersinia pestis. The inflammatory cascade is tightly controlled via the sequential action of lipid and protein mediators of inflammation. Because delayed inflammation is essential for Y. pestis to cause lethal infection, defining the Y. pestis mechanisms to manipulate the inflammatory cascade is necessary to understand this pathogen's virulence. While previous studies have established that Y. pestis actively inhibits the expression of host proteins that mediate inflammation, there is currently a gap in our understanding of the inflammatory lipid mediator response during plague. Here we used the murine model to define the kinetics of the synthesis of leukotriene B4 (LTB4), a pro-inflammatory lipid chemoattractant and immune cell activator, within the lungs during pneumonic plague. Furthermore, we demonstrated that exogenous administration of LTB4 prior to infection limited bacterial proliferation, suggesting that the absence of LTB4 synthesis during plague contributes to Y. pestis immune evasion. Using primary leukocytes from mice and humans further revealed that Y. pestis actively inhibits the synthesis of LTB4. Finally, using Y. pestis mutants in the Ysc type 3 secretion system (T3SS) and Yersinia outer protein (Yop) effectors, we demonstrate that leukocytes recognize the T3SS to initiate the rapid synthesis of LTB4. However, several Yop effectors secreted through the T3SS effectively inhibit this host response. Together, these data demonstrate that Y. pestis actively inhibits the synthesis of the inflammatory lipid LTB4 contributing to the delay in the inflammatory cascade required for rapid recruitment of leukocytes to sites of infection.


Assuntos
Peste , Yersinia pestis , Humanos , Animais , Camundongos , Yersinia pestis/metabolismo , Peste/microbiologia , Sistemas de Secreção Tipo III/metabolismo , Leucotrieno B4/metabolismo , Leucócitos/metabolismo , Inflamação , Proteínas de Bactérias/metabolismo
6.
Nat Microbiol ; 9(1): 185-199, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-38172622

RESUMO

Bacteria use type III secretion injectisomes to inject effector proteins into eukaryotic target cells. Recruitment of effectors to the machinery and the resulting export hierarchy involve the sorting platform. These conserved proteins form pod structures at the cytosolic interface of the injectisome but are also mobile in the cytosol. Photoactivated localization microscopy in Yersinia enterocolitica revealed a direct interaction of the sorting platform proteins SctQ and SctL with effectors in the cytosol of live bacteria. These proteins form larger cytosolic protein complexes involving the ATPase SctN and the membrane connector SctK. The mobility and composition of these mobile pod structures are modulated in the presence of effectors and their chaperones, and upon initiation of secretion, which also increases the number of injectisomes from ~5 to ~18 per bacterium. Our quantitative data support an effector shuttling mechanism, in which sorting platform proteins bind to effectors in the cytosol and deliver the cargo to the export gate at the membrane-bound injectisome.


Assuntos
Sistemas de Secreção Tipo III , Yersinia enterocolitica , Sistemas de Secreção Tipo III/genética , Sistemas de Secreção Tipo III/metabolismo , Yersinia enterocolitica/genética , Yersinia enterocolitica/metabolismo , Citosol/metabolismo , Transporte Proteico , Microscopia de Fluorescência
7.
Mol Microbiol ; 121(2): 304-323, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-38178634

RESUMO

In animal pathogens, assembly of the type III secretion system injectisome requires the presence of so-called pilotins, small lipoproteins that assist the formation of the secretin ring in the outer membrane. Using a combination of functional assays, interaction studies, proteomics, and live-cell microscopy, we determined the contribution of the pilotin to the assembly, function, and substrate selectivity of the T3SS and identified potential new downstream roles of pilotin proteins. In absence of its pilotin SctG, Yersinia enterocolitica forms few, largely polar injectisome sorting platforms and needles. Accordingly, most export apparatus subcomplexes are mobile in these strains, suggesting the absence of fully assembled injectisomes. Remarkably, while absence of the pilotin all but prevents export of early T3SS substrates, such as the needle subunits, it has little effect on secretion of late T3SS substrates, including the virulence effectors. We found that although pilotins interact with other injectisome components such as the secretin in the outer membrane, they mostly localize in transient mobile clusters in the bacterial membrane. Together, these findings provide a new view on the role of pilotins in the assembly and function of type III secretion injectisomes.


Assuntos
Sistemas de Secreção Tipo III , Yersinia enterocolitica , Animais , Sistemas de Secreção Tipo III/genética , Sistemas de Secreção Tipo III/metabolismo , Secretina/metabolismo , Especificidade por Substrato , Yersinia enterocolitica/genética , Ligação Proteica , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo
8.
Microbiol Spectr ; 12(3): e0062623, 2024 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-38289930

RESUMO

Pseudomonas aeruginosa is an opportunistic pathogen that causes acute and chronic infections in immunocompromised individuals. Small regulatory RNAs (sRNAs) regulate multiple bacterial adaptations to environmental changes, especially virulence. Our previous study showed that sRNA PrrH negatively regulates the expression of a number of virulence factors, such as pyocyanin, rhamnolipid, biofilm, and elastase in the P. aeruginosa strain PAO1. However, previous studies have shown that the prrH-deficient mutant attenuates virulence in an acute murine lung infection model. All ΔprrH-infected mice survived the entire 28-day course of the experiment, whereas all mice inoculated with the wild-type or the complemented mutant succumbed to lung infection within 4 days of injection, but the specific mechanism is unclear. Herein, we explored how PrrH mediates severe lung injury by regulating the expression of virulence factors. In vivo mouse and in vitro cellular assays demonstrated that PrrH enhanced the pathogenicity of PAO1, causing severe lung injury. Mechanistically, PrrH binds to the coding sequence region of the mRNA of exsA, which encodes the type III secretion system master regulatory protein. We further demonstrated that PrrH mediates a severe inflammatory response and exacerbates the apoptosis of A549 cells. Overall, our results revealed that PrrH positively regulates ExsA, enhances the pathogenicity of P. aeruginosa, and causes severe lung injury. IMPORTANCE: Pseudomonas aeruginosa is a Gram-negative bacterium and the leading cause of nosocomial pneumonia. The pathogenicity of P. aeruginosa is due to the secretion of many virulence factors. Small regulatory RNAs (sRNAs) regulate various bacterial adaptations, especially virulence. Therefore, understanding the mechanism by which sRNAs regulate virulence is necessary for understanding the pathogenicity of P. aeruginosa and the treatment of the related disease. In this study, we demonstrated that PrrH enhances the pathogenicity of P. aeruginosa by binding to the coding sequence regions of the ExsA, the master regulatory protein of type III secretion system, causing severe lung injury and exacerbating the inflammatory response and apoptosis. These findings revealed that PrrH is a crucial molecule that positively regulates ExsA. Type III-positive strains are often associated with a high mortality rate in P. aeruginosa infections in clinical practice. Therefore, this discovery may provide a new target for treating P. aeruginosa infections, especially type III-positive strains.


Assuntos
Lesão Pulmonar Aguda , Infecções por Pseudomonas , Animais , Camundongos , Sistemas de Secreção Tipo III/metabolismo , Pseudomonas aeruginosa/metabolismo , RNA/metabolismo , Fatores de Virulência/genética , Fatores de Virulência/metabolismo , Fatores de Transcrição/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Regulação Bacteriana da Expressão Gênica , Infecções por Pseudomonas/microbiologia
9.
PLoS Pathog ; 20(1): e1011946, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-38198506

RESUMO

Pseudomonas aeruginosa is a highly pathogenic bacterium known for its ability to sense and coordinate the production of virulence factors in response to host immune responses. However, the regulatory mechanisms underlying this process have remained largely elusive. In this study, we investigate the two-component system CprRS in P. aeruginosa and unveil the crucial role of the sensor protein CprS in sensing the human host defense peptide LL-37, thereby modulating bacterial virulence. We demonstrate that CprS acts as a phosphatase in the presence of LL-37, leading to the phosphorylation and activation of the response regulator CprR. The results prove that CprR directly recognizes a specific sequence within the promoter region of the HigBA toxin-antitoxin system, resulting in enhanced expression of the toxin HigB. Importantly, LL-37-induced HigB expression promotes the production of type III secretion system effectors, leading to reduced expression of proinflammatory cytokines and increased cytotoxicity towards macrophages. Moreover, mutations in cprS or cprR significantly impair bacterial survival in both macrophage and insect infection models. This study uncovers the regulatory mechanism of the CprRS system, enabling P. aeruginosa to detect and respond to human innate immune responses while maintaining a balanced virulence gene expression profile. Additionally, this study provides new evidence and insights into the complex regulatory system of T3SS in P. aeruginosa within the host environment, contributing to a better understanding of host-microbe communication and the development of novel strategies to combat bacterial infections.


Assuntos
Infecções por Pseudomonas , Pseudomonas aeruginosa , Humanos , Pseudomonas aeruginosa/metabolismo , Infecções por Pseudomonas/genética , Infecções por Pseudomonas/microbiologia , Fatores de Virulência/genética , Fatores de Virulência/metabolismo , Virulência , Sistemas de Secreção Tipo III/metabolismo , Proteínas de Bactérias/metabolismo , Regulação Bacteriana da Expressão Gênica
10.
Nat Struct Mol Biol ; 31(1): 82-91, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-38177670

RESUMO

The NLR family caspase activation and recruitment domain-containing 4 (NLRC4) inflammasome is a critical cytosolic innate immune machine formed upon the direct sensing of bacterial infection and in response to cell stress during sterile chronic inflammation. Despite its major role in instigating the subsequent host immune response, a more complete understanding of the molecular events in the formation of the NLRC4 inflammasome in humans is lacking. Here we identify Bacillus thailandensis type III secretion system needle protein (Needle) as a potent trigger of the human NLR family apoptosis inhibitory protein (NAIP)/NLRC4 inflammasome complex formation and determine its structural features by cryogenic electron microscopy. We also provide a detailed understanding of how type III secretion system pathogen components are sensed by human NAIP to form a cascade of NLRC4 protomer through a critical lasso-like motif, a 'lock-key' activation model and large structural rearrangement, ultimately forming the full human NLRC4 inflammasome. These results shed light on key regulatory mechanisms specific to the NLRC4 inflammasome assembly, and the innate immune modalities of pathogen sensing in humans.


Assuntos
Inflamassomos , Sistemas de Secreção Tipo III , Humanos , Macrófagos/metabolismo , Macrófagos/microbiologia , Flagelina/metabolismo , Proteínas de Ligação ao Cálcio/metabolismo , Proteínas Adaptadoras de Sinalização CARD , Proteína Inibidora de Apoptose Neuronal/metabolismo
11.
Mol Plant Pathol ; 25(1): e13398, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-37877898

RESUMO

Ralstonia solanacearum PhcB and PhcA control a quorum-sensing (QS) system that globally regulates expression of about one third of all genes, including pathogenesis genes. The PhcB-PhcA QS system positively regulates the production of exopolysaccharide (EPS) and negatively regulates hrp gene expression, which is crucial for the type III secretion system (T3SS). Both EPS and the T3SS are essential for pathogenicity. The gene rsc2734 is located upstream of a phcBSR operon and annotated as a response regulator of a two-component system. Here, we demonstrated that RSc2734, hereafter named PrhX, positively regulated hrp gene expression via a PrhA-PrhIR-PrhJ-HrpG signalling cascade. Moreover, PrhX was crucial for R. solanacearum to invade host roots and grow in planta naturally. prhX expression was independent of the PhcB-PhcA QS system. PrhX did not affect the expression of phcB and phcA and the QS-dependent phenotypes, such as EPS production and biofilm formation. Our results provide novel insights into the complex regulatory network of the T3SS and pathogenesis in R. solanacearum.


Assuntos
Ralstonia solanacearum , Sistemas de Secreção Tipo III/genética , Sistemas de Secreção Tipo III/metabolismo , Cianoacrilatos/metabolismo , Virulência/genética , Proteínas de Bactérias/metabolismo , Regulação Bacteriana da Expressão Gênica
12.
Phytopathology ; 114(1): 47-60, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-37505057

RESUMO

Xanthomonas spp. infect a wide range of annual and perennial plants. Bacterial blight in young seedlings of Eucalyptus spp. in Indonesia was originally identified as X. perforans. However, these strains failed to elicit a hypersensitive response (HR) on either tomatoes or peppers. Two of the strains, EPK43 and BCC 972, when infiltrated into tomato and pepper leaves, failed to grow to significant levels in comparison with well-characterized X. euvesicatoria pv. perforans (Xp) strains. Furthermore, spray inoculation of 'Bonny Best' tomato plants with a bacterial suspension of the Eucalyptus strains resulted in no obvious symptoms. We sequenced the whole genomes of eight strains isolated from two Eucalyptus species between 2007 and 2015. The strains had average nucleotide identities (ANIs) of at least 97.8 with Xp and X. euvesicatoria pv. euvesicatoria (Xeu) strains, both of which are causal agents of bacterial spot of tomatoes and peppers. A comparison of the Eucalyptus strains revealed that the ANI values were >99.99% with each other. Core genome phylogeny clustered all Eucalyptus strains with X. euvesicatoria pv. rosa. They formed separate clades, which included X. euvesicatoria pv. alangii, X. euvesicatoria pv. citrumelonis, and X. euvesicatoria pv. alfalfae. Based on ANI, phylogenetic relationships, and pathogenicity, we designated these Eucalyptus strains as X. euvesicatoria pv. eucalypti (Xee). Comparative analysis of sequenced strains provided unique profiles of type III secretion effectors. Core effector XopD, present in all pathogenic Xp and Xeu strains, was absent in the Xee strains. Comparison of the hrp clusters of Xee, Xp, and Xeu genomes revealed that HrpE in Xee strains was very different from that in Xp and Xeu. To determine if it was functional, we deleted the gene and complemented with the Xee hrpE, confirming it was essential for secretion of type III effectors. HrpE has a hypervariable N-terminus in Xanthomonas spp., in which the N-terminus of Xee strains differs significantly from those of Xeu and Xp strains.


Assuntos
Eucalyptus , Xanthomonas , Sistemas de Secreção Tipo III , Filogenia , Doenças das Plantas/microbiologia
13.
Microbiol Spectr ; 12(1): e0240623, 2024 Jan 11.
Artigo em Inglês | MEDLINE | ID: mdl-38078719

RESUMO

IMPORTANCE: Salmonella spp. remains a major worldwide health concern that causes significant morbidity and mortality in both humans and animals. The spread of antimicrobial resistant strains has declined the efficacy of conventional chemotherapy. Thus, novel anti-infection drugs or strategies are needed. Anti-virulence strategy represents one of the promising means for the treatment of bacterial infections. In this study, we found that the natural compound fisetin could inhibit Salmonella invasion of host cells by targeting SPI-1 regulation. Fisetin treatment impaired the interaction of the regulatory protein HilD with the promoters of its target genes, thereby suppressing the expression of T3SS-1 effectors as well as structural proteins. Moreover, fisetin treatment could reduce pathology in the Salmonella murine infection model. Collectively, our results suggest that fisetin may serve as a promising lead compound for the development of anti-Salmonella drugs.


Assuntos
Flavonóis , Infecções por Salmonella , Salmonella typhimurium , Humanos , Animais , Camundongos , Salmonella typhimurium/genética , Sistemas de Secreção Tipo III/metabolismo , Infecções por Salmonella/tratamento farmacológico , Infecções por Salmonella/microbiologia , Fatores de Transcrição/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Regulação Bacteriana da Expressão Gênica
14.
Microbiol Spectr ; 12(1): e0222423, 2024 Jan 11.
Artigo em Inglês | MEDLINE | ID: mdl-38088541

RESUMO

IMPORTANCE: The identification of decisive virulence-associated genes in highly pathogenic P. aeruginosa isolates in the clinic is essential for diagnosis and the start of appropriate treatment. Over the past decades, P. aeruginosa ST463 has spread rapidly in East China and is highly resistant to ß-lactams. Given the poor clinical outcome caused by this phenotype, detailed information regarding its decisive virulence genes and factors affecting virulence expression needs to be deciphered. Here, we demonstrate that the T3SS effector ExoU has toxic effects on mammalian cells and is required for virulence in the murine bloodstream infection model. Moreover, a functional downstream SpcU is required for ExoU secretion and cytotoxicity. This work highlights the potential role of ExoU in the pathogenesis of disease and provides a new perspective for further research on the development of new antimicrobials with antivirulence ability.


Assuntos
Infecções por Pseudomonas , Sepse , Animais , Camundongos , Sistemas de Secreção Tipo III/genética , Sistemas de Secreção Tipo III/metabolismo , Pseudomonas aeruginosa/metabolismo , Fatores de Virulência/genética , Fatores de Virulência/metabolismo , Infecções por Pseudomonas/tratamento farmacológico , Sepse/tratamento farmacológico , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Antibacterianos/farmacologia , Antibacterianos/uso terapêutico , Antibacterianos/metabolismo , Mamíferos
15.
Infect Immun ; 92(1): e0032923, 2024 Jan 16.
Artigo em Inglês | MEDLINE | ID: mdl-38084951

RESUMO

Engineering pathogens is a useful method for discovering new details of microbial pathogenesis and host defense. However, engineering can result in off-target effects. We previously engineered Salmonella enterica serovar Typhimurium to overexpress the secretion signal of the type 3 secretion system effector SspH1 fused with domains of other proteins as cargo. Such engineering had no virulence cost to the bacteria for the first 48 hours post infection in mice. Here, we show that after 48 hours, the engineered bacteria manifest an attenuation that correlates with the quantity of the SspH1 translocation signal expressed. In IFN-γ-deficient mice, this attenuation was weakened. Conversely, the attenuation was accelerated in the context of a pre-existing infection. We speculate that inflammatory signals change aspects of the target cell's physiology, which makes host cells less permissive to S. Typhimurium infection. This increased degree of difficulty requires the bacteria to utilize its T3SS at peak efficiency, which can be disrupted by engineered effectors.


Assuntos
Salmonella typhimurium , Sistemas de Secreção Tipo III , Animais , Camundongos , Virulência , Sistemas de Secreção Tipo III/genética , Fatores de Virulência/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo
16.
Chemosphere ; 350: 140997, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-38128737

RESUMO

S. enterica, S. flexneri, and V. parahaemolyticus bacteria are globally recognized to cause severe diarrheal diseases, consisting of Type III Secretion System (T3SS) effectors that help in bacterial infection and virulence in host cells. This study investigates the properties of multi-electrode cylindrical DBD plasma-generated nitric oxide water (MCDBD-PG-NOW) treatment on the survival and virulence of S. enterica, S. flexneri, and V. parahaemolyticus bacteria. The Colony Forming Unit (CFU) assay, live/dead cell staining, lipid peroxidation assay, and bacteria morphological analysis showed substantial growth inhibition of bacteria. Moreover, to confirm the interaction of reactive nitrogen species (RNS) with bacterial membrane biotin switch assay, DAF-FM, and FTIR analysis were carried out, which established the formation of S-nitrosothiols in the cell membrane, intracellular accumulation of RNS, and changes in the cell composition post-PG-NOW treatment. Furthermore, the conventional culture-based method and a quantitative PCR using propidium monoazide showed minimal VBNC induction under similar condition. The efficiency of bacteria to adhere to mammalian colon cells was significantly reduced. In addition, the infection rate was also controlled by disrupting the virulent genes, leading to the collapse of the infection mechanism. This study provides insights into whether RNS generated from PG-NOW might be beneficial for preventing diarrheal infections.


Assuntos
Bactérias , Óxido Nítrico , Animais , Virulência , Bactérias/metabolismo , Sistemas de Secreção Tipo III/genética , Sistemas de Secreção Tipo III/metabolismo , Diarreia , Proteínas de Bactérias/metabolismo , Mamíferos/metabolismo
17.
Front Cell Infect Microbiol ; 13: 1255852, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-38089815

RESUMO

Many pathogens use Type III and Type IV protein secretion systems to secrete virulence factors from the bacterial cytosol into host cells. These systems operate through a one-step mechanism. The secreted substrates (protein or nucleo-protein complexes in the case of Type IV conjugative systems) are guided to the base of the secretion channel, where they are directly delivered into the host cell in an ATP-dependent unfolded state. Despite the numerous disparities between these secretion systems, here we have focused on the structural and functional similarities between both systems. In particular, on the structural similarity shared by one of the main ATPases (EscN and VirD4 in Type III and Type IV secretion systems, respectively). Interestingly, these ATPases also exhibit a structural resemblance to F1-ATPases, which suggests a common mechanism for substrate secretion. The correlation between structure and function of essential components in both systems can provide significant insights into the molecular mechanisms involved. This approach is of great interest in the pursuit of identifying inhibitors that can effectively target these systems.


Assuntos
Proteínas de Bactérias , Sistemas de Secreção Tipo IV , Sistemas de Secreção Tipo IV/metabolismo , Proteínas de Bactérias/metabolismo , Bactérias/metabolismo , Transporte Proteico , Adenosina Trifosfatases , Sistemas de Secreção Tipo III/metabolismo
18.
Vet Res ; 54(1): 108, 2023 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-37993950

RESUMO

Lawsonia intracellularis, the etiologic agent of proliferative enteropathy (PE), is an obligate intracellular Gram-negative bacterium possessing a type III secretion system (T3SS), which enables the pathogen to translocate effector proteins into targeted host cells to modulate their functions. T3SS is a syringe-like apparatus consisting of a base, an extracellular needle, a tip, and a translocon. The translocon proteins assembled by two hydrophobic membrane proteins can form pores in the host-cell membrane, and therefore play an essential role in the function of T3SS. To date, little is known about the T3SS and translocon proteins of L. intracellularis. In this study, we first analyzed the conservation of the T3S apparatus between L. intracellularis and Yersinia, and characterized the putative T3S hydrophobic major translocon protein LI1158 and minor translocon protein LI1159 in the L. intracellularis genome. Then, by using Yersinia pseudotuberculosis as a surrogate system, we found that the full-length LI1158 and LI1159 proteins, but not the putative class II chaperone LI1157, were secreted in a - Ca2+ and T3SS-dependent manner and the secretion signal was located at the N terminus (aa 1-40). Furthermore, yeast-two hybrid experiments revealed that LI1158 and LI1159 could self-interact, and LI1159 could interact with LI1157. However, unlike CPn0809 and YopB, which are the major hydrophobic translocon proteins of the T3SS of C. pneumoniae and Yersinia, respectively, full-length LI1158 was non-toxic to both yeast and Escherichia coli cells, but full-length LI1159 showed certain toxicity to E. coli cells. Taken together, despite some differences from the findings in other bacteria, our results demonstrate that LI1158 and LI1159 may be the translocon proteins of L. intracellularis T3SS, and probably play important roles in the translocation of effector proteins at the early pathogen infection stage.


Assuntos
Lawsonia (Bactéria) , Animais , Sistemas de Secreção Tipo III/genética , Sistemas de Secreção Tipo III/metabolismo , Escherichia coli/metabolismo , Saccharomyces cerevisiae , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo
19.
ACS Infect Dis ; 9(12): 2652-2664, 2023 Dec 08.
Artigo em Inglês | MEDLINE | ID: mdl-37978950

RESUMO

Multi-drug-resistant Pseudomonas aeruginosa poses a serious threat to hospitalized patients. This organism expresses an arsenal of virulence factors that enables it to readily establish infections and disseminate in the host. The Type 3 secretion system (T3SS) and its associated effectors play a crucial role in the pathogenesis of P. aeruginosa, making them attractive targets for the development of novel therapeutic agents. The T3SS translocon, composed of PopD and PopB, is an essential component of the T3SS secretion apparatus. In the properly assembled translocon, the N-terminus of PopD protrudes into the cytoplasm of the target mammalian cell, which can be exploited as a molecular indicator of functional translocon assembly. In this article, we describe a novel whole-cell-based assay that employs the split NanoLuc luciferase detection system to provide a readout for translocon assembly. The assay demonstrates a favorable signal/noise ratio (13.6) and robustness (Z' = 0.67), making it highly suitable for high-throughput screening of small-molecule inhibitors targeting T3SS translocon assembly.


Assuntos
Infecções por Pseudomonas , Pseudomonas aeruginosa , Animais , Humanos , Pseudomonas aeruginosa/fisiologia , Proteínas de Bactérias/genética , Sistemas de Secreção Tipo III , Mamíferos
20.
Front Cell Infect Microbiol ; 13: 1267748, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-38029243

RESUMO

Pseudomonas aeruginosa is an opportunistic human pathogen capable of causing a variety of acute and chronic infections. Its type III secretion system (T3SS) plays a critical role in pathogenesis during acute infection. ExsA is a master regulator that activates the expression of all T3SS genes. Transcription of exsA is driven by two distinct promoters, its own promoter PexsA and its operon promoter PexsC. Here, in combination with a DNA pull-down assay and mass spectrometric analysis, we found that a histone-like nucleoid-structuring (H-NS) family protein MvaT can bind to the PexsC promoter. Using EMSA and reporter assays, we further found that MvaT directly binds to the PexsC promoter to repress the expression of T3SS genes. The repression of MvaT on PexsC is independent of ExsA, with MvaT binding to the -429 to -380 bp region relative to the transcription start site of the exsC gene. The presented work further reveals the complex regulatory network of the T3SS in P. aeruginosa.


Assuntos
Transativadores , Sistemas de Secreção Tipo III , Humanos , Sistemas de Secreção Tipo III/genética , Sistemas de Secreção Tipo III/metabolismo , Transativadores/genética , Pseudomonas aeruginosa/genética , Pseudomonas aeruginosa/metabolismo , Proteínas de Bactérias/metabolismo , Regiões Promotoras Genéticas , Regulação Bacteriana da Expressão Gênica
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