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PubMed2023

Proteomics from compartment-specific APEX2 labeling in Mycobacterium tuberculosis reveals Type VII secretion substrates in the cell wall.

The cell wall of mycobacteria plays a key role in interactions with the environment. Its ability to act as a selective filter is crucial to bacterial survival. Proteins in the cell wall enable this function by mediating the import and export of diverse metabolites, from ions to lipids to proteins. Identifying cell wall proteins is an important step in assigning function, especially as many mycobacterial proteins lack functionally characterized homologues. Current methods for protein localization have inherent limitations that reduce accuracy. Here we showed that although chemical labeling of live cells did not exclusively label surface proteins, protein tagging by the engineered peroxidase APEX2 within live Mycobacterium tuberculosis accurately identified the cytosolic and cell wall proteomes. Our data indicate that substrates of the virulence-associated Type VII ESX secretion system are exposed to the periplasm, providing insight into the currently unknown mechanism by which these proteins cross the mycobacterial cell envelope.

Mycobacterium tuberculosis↗

PubMed2025

Type IV Pili-Associated Secretion of a Biofilm Matrix Protein From Clostridium perfringens That Forms Intermolecular Isopeptide Bonds.

Clostridium perfringens is a gram-positive, anaerobic, spore-forming bacterial pathogen of humans and animals. C. perfringens also produces type IV pili (T4P) and has two complete sets of T4P-associated genes, one of which has been shown to produce surface pili needed for cell adherence. One hypothesis about the second set of T4P genes is that they comprise a type II secretion system (TTSS) like those found in gram-negative bacteria, but for gram-positive bacteria, the TTSS would aid transit across the thick peptidoglycan (PG) layer. The secretome of mutants lacking type IV pilins was examined, and a single protein, BsaC (CPE0517), was identified as being dependent on pilin PilA3 for secretion. The bsaC gene is in an operon with genes encoding a SipW signal peptidase and two putative biofilm matrix proteins, BsaA and BsaB, both of which have remote homology to Bacillus subtilis biofilm protein TasA. Since BsaA forms long oligomers that are secreted, we analyzed BsaA monomer interactions with de novo modeling. These models projected that the monomers formed isopeptide bonds as part of a donor strand exchange process. Mutations in residues predicted to form the isopeptide bonds led to the loss of oligomerization, supporting an exchange and lock mechanism, and isopeptide bonds were detected by mass spectrometry methods. Phylogenetic analysis showed the BsaA family of proteins is widespread among bacteria and archaea, but only a subset is predicted to form isopeptide bonds.

Fimbriae, Bacterial↗

PubMed2005

Role of an in planta-expressed xylanase of Xanthomonas oryzae pv. oryzae in promoting virulence on rice.

Xanthomonas oryzae pv. oryzae is the causal agent of bacterial leaf blight, a serious disease of rice. We demonstrated earlier that the type II secretion system (T2S) is important for virulence of X. oryzae pv. oryzae and that several proteins, including a xylanase, are secreted through this system. In this study, the xynB gene encoding for the secreted xylanase was cloned as a 6.9-kb EcoRI fragment (pRR7) that also included a paralog called xynA. As in X. oryzae pv. oryzae, xynA and xynB are adjacent to each other in X. axonopodis pv. citri, whereas only the xynA homolog is present in X. campestris pv. campestris. Mutations in xynB but not xynA affect secreted xylanase activity. Western blot analysis using anti-XynB antibodies on exudates from infected rice leaves indicated that this xylanase is expressed during in planta growth. Another T2S-secreted protein was identified to be a lipase/esterase (LipA) based on the sequence tags obtained by tandem mass spectrometry analysis and biochemical assays. Mutations in either xynB or lipA partially affected virulence. However, a lipA-xynB double mutant was significantly reduced for virulence, and the pRR7 clone containing an intact xynB gene could complement the virulence-deficient phenotype of the lipA-xynB mutant. Our results suggest that there is functional redundancy among the T2S secreted proteins of X. oryzae pv. oryzae in promoting virulence on rice.

Amino Acid Sequence↗

PubMed1998

The Yersinia Yop virulon, a bacterial system to subvert cells of the primary host defense.

The Yop virulon enables yersinias (Yersinia pestis, Y. pseudotuberculosis and Y. enterocolitica) to survive and multiply in the lymphoid tissues of their host. It is an integrated system allowing extracellular bacteria to communicate with the host cell's cytosol by injection of effector proteins. It is composed of four elements: (1) a contact or type III secretion system called Ysc, devoted to the secretion of Yop proteins. This secretion apparatus, made of some 22 proteins, recognizes the Yops by a short N-terminal signal that is not cleaved off during secretion; (2) a system designed to deliver bacterial proteins into eukaryotic target cells. This system is made of YopB, YopD and LcrV; (3) a control element (YopN) and (4) a set of effector Yop proteins designed to disarm these cells or disrupt their communications (YopE, YopH, YopM, YpkA/YopO, YopP). The whole virulon is encoded by a 70-kb plasmid called pYV. Transcription of the genes is controlled both by temperature and by contact with a eukaryotic cell.

Animals↗

PubMed1991

Neuroendocrine control of prolactin secretion: the role of the serotonergic system.

The secretion of prolactin (PRL) falls into distinct patterns in mammals. Suckling, stress, cervical stimulation and estrogen all stimulate PRL secretion. The estrogen-induced afternoon PRL surge is circadian in nature and is regulated by the central serotonergic system. Interruption of the serotonergic system by all means blocks the PRL surge. As for the site and mechanism of 5-HT action, it has been shown that 5-HT has no direct effect on the anterior pituitary and its action on PRL secretion may be dissociated from its peripheral cardiovascular effect. Its action may not involve the central dopaminergic system or interaction with the central opioid system. However, it may be stimulating a yet unidentified PRL-releasing factor during specific time in the afternoon of estrogen-treated rats.

Animals↗

PubMed2001

The PDZ domain of OutC and the N-terminal region of OutD determine the secretion specificity of the type II out pathway of Erwinia chrysanthemi.

The plant pathogens Erwinia chrysanthemi and Erwinia carotovora secrete multiple exoproteins by a type II pathway, the Out system. Secretion in Erwinia is species-specific: exoproteins of one species cannot be secreted by the other. We analysed the role of two components of the Out system, the bitopic inner membrane protein OutC and the secretin OutD, in the specific recognition of secreted proteins. We demonstrated that the PDZ domain of OutC determines its secretion specificity towards certain exoproteins. The secretin is the major determinant of specificity of the Out system: OutD of E. carotovora changes the secretion specificity of E. chrysanthemi and enables it to secrete heterologous exoproteins. Construction of chimeric OutD showed that the N-terminal region is the specificity domain of the secretin. Thus, both the PDZ domain of OutC and the N-terminal region of OutD are required for specific recognition of secreted proteins. Systematic analysis of the secretion of several exoproteins demonstrated that different exoproteins secreted by the Out machinery have different requirement for their presumed targeting signals on OutC and OutD. This strongly indicates that diverse exoproteins possess a variable number of targeting signals which are recognised by different regions of OutC and OutD.

Amino Acid Motifs↗

PubMed1976

Stimulatory role for brain serotoninergic system on prolactin secretion in the male rat.

Systemic administration of parachlorophenylalanine (PCPA, 100 mg/kg sc on alternate days X two times), a blocker of serotonin (5-HT) synthesis, considerably decreased brain 5-HT and plasma prolactin (PRL) levels in young male rats. Intraventricular (IVT) administration of 5,7-dihydroxytryptamine (5,7-DHT, 200 mug/20 mul), a neurotoxic drug which destroys 5-HT nerve terminals, induced, 3, 12, and 30 days after treatment, a marked depletion of brain 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) and considerably reduced plasma PRL levels at each time interval. Feeding of rat for up to 4 days with a tryptophan (TP)-deficient diet, caused a depletion of brain 5-HT and 5-HIAA contents and did not modify plasma PRL levels. Addition of TP (2 g/kg of diet) to the TP-deficient diet resulted in increased brain 5-HT and 5-HIAA contents and significantly increased PRL levels. These data provide evidence for the role of the 5-HT system in the maintenance of tonic PRL secretion.

5,6-Dihydroxytryptamine↗

PubMed1997

The Yersinia Yop virulon: a bacterial system for subverting eukaryotic cells.

The Yop virulon enables Yersinia spp. (Y. pestis, Y. pseudotuberculosis and Y. enterocolitica) to survive and multiply in the lymphoid tissues of their host. It is an integrated system allowing extracellular bacteria to communicate with the host cell's cytosol by the injection of effector proteins. It is composed of the following four elements. (I) A contact or type III secretion system called Ysc, which is devoted to the secretion of Yop proteins. This secretion apparatus, comprising some 22 proteins recognizes the Yops by a short N-terminal signal that is not cleaved off during secretion. (II) A system designed to deliver bacterial proteins into eukaryotic target cells. This system is made of YopB, YopD and possibly other Yops such as LcrV. (III) A control element (YopN). (IV) A set of effector Yop proteins designed to disarm these cells or disrupt their communications (YopE, YopH, YpkA/YopO, and YopM). The whole virulon is encoded by a 70 kb plasmid designated pYV. Transcription of the genes is controlled both by temperature and by contact with a eukaryotic cell.

Bacterial Outer Membrane Proteins↗

PubMed2000

Prevalence and polymorphism of genes encoding translocated effector proteins among clinical isolates of Salmonella enterica.

Pathogenic Salmonella enterica strains are capable of causing local and/or systemic infections. They employ two type III secretion systems to translocate an array of virulence-associated proteins (effector proteins) directly into the cytosol of target cells of the host. Earlier data had shown that changes in the repertoire of translocated effector proteins may contribute to the adaptation of Salmonella strains to new hosts and to the emergence of epidemic strains. Using PCR and Southern blot techniques the presence of and the polymorphism among the genes encoding the translocated effector proteins SopB, SopD, SopE, SopE2, SipA, SipB, SipC, AvrA, and SptP was studied in 71 phylogenetically well characterised S. enterica subspecies I (subspecies enterica) strains of the SARB collection and in 209 clinical and epidemic isolates of S. enterica subspecies I belonging to various serovars, phage types, and genotypes. All these Salmonella strains harbour all these respective genes with the exception of sopE and avrA which have been identified in only some of them. Several of the studied genes display genetic polymorphisms (RFLP). These RFLP patterns did not show a strict correlation with the genetic distance, the grouping genes in order to understand their role in the evolution of Salmonella as a pathogen.

Actins↗

PubMed2003

Structural definition on the surface of Helicobacter pylori type IV secretion apparatus.

Genetic and functional studies have indicated that the type IV secretion system (TFSS) of Helicobacter pylori forms a secretion complex in the cell envelope that protrudes towards the outside in order to inject CagA protein into gastric epithelial cells. However, the proposed structural model is based on partial amino acid homology with the components of the Agrobacterium tumefaciens TFSS. Therefore, we undertook the identification of the structural features of the TFSS exposed on the surface of H. pylori and found that filamentous structures present on the bacterial surface are related to the secretion apparatus. Using immunofluorescence microscopy with antibodies directed to tyrosine-phosphorylated CagA (pY-CagA) and Hp0532 (VirB7) in the infection assay, pY-CagA signals were detected just below the host cell-attached bacteria, where Hp0532 (VirB7) signals were detected as co-localized, suggesting that the CagA injected into the host cell through the TFSS apparatus is still mostly confined to the areas just below the attached bacteria after being phosphorylated. Furthermore, the filamentous structures on bacterium were found to be associated with Hp0532 (VirB7) or Hp0528 (VirB9), the major components of TFSS, by immunogold electron microscopy. These results strongly suggest that the H. pylori TFSS apparatus is a filamentous macromolecular structure protruding from the bacterial envelope.

Antigens, Bacterial↗

PubMed2004

The major structural components of two cell surface filaments of Porphyromonas gingivalis are matured through lipoprotein precursors.

Bacterial cell surface filaments play significant roles in adherence to and invasion of host cells. They are generated by the chaperone/usher pathway system (class I fimbriae), the type II secretion system (type IV pili) and the nucleation-dependent polymerization system (Curli filaments) that are categorized by their modes of expression and assembly. In this study, we found that the periodontal pathogen Porphyromonas gingivalis expressed the major structural components of two cell surface filaments (fimbrilin and the 75 kDa protein) that had extremely long prosequences in their primary gene products. N-terminal amino acid sequencing of the prosequences, treatment of P. gingivalis cells with globomycin, an inhibitor for lipoprotein-specific signal peptidase, amino acid substitution of the cysteine residue of the prosequence of fimbrilin and [(3)H]-palmitic acid labelling implied that fimbrilin and the 75 kDa protein were matured through their lipoprotein precursor forms. Accumulation of precursor forms of fimbrilin and the 75 kDa protein on the cell surface of the gingipain-null mutant revealed that Arg-gingipain processed these precursors on the surface to yield their mature forms, which subsequently assembled into the filamentous structures, suggesting that the transport and assembly of the major component proteins appear to be novel.

Adhesins, Bacterial↗

PubMed2006

Proteomic and microarray characterization of the AggR regulon identifies a pheU pathogenicity island in enteroaggregative Escherichia coli.

Enteroaggregative Escherichia coli (EAEC) is defined by aggregative adherence (AA) to HEp-2 cells, where bacteria display adherence to cell surfaces and also to the intervening substratum in a stacked-brick configuration. We previously showed that an AraC homologue designated AggR is required for the expression of plasmid-encoded genes that mediate AA of EAEC strain 042. In this study, we hypothesized that AggR also controls the expression of other virulence determinants in EAEC 042. Using proteomic and microarray analysis, we identified for the first time that AggR activates the expression of chromosomal genes, including 25 contiguous genes (aaiA-Y), which are localized to a 117 kb pathogenicity island (PAI) inserted at pheU. Many of these genes have homologues in other Gram-negative bacteria and were recently proposed to constitute a type VI secretion system (T6SS). AaiC was identified as a secreted protein that has no apparent homologues within GenBank. EAEC strains carrying in-frame deletions of aaiB, aaiG, aaiO or aaiP still synthesized AaiC; however, AaiC secretion was abolished. Cloning of aai genes into E. coli HB101 suggested that aaiA-P are sufficient for AaiC secretion. A second T6SS was identified within the pheU PAI that secretes a protein unrelated by sequence identity to AaiC. Distribution studies indicated that aaiA and aaiC are commonly found in EAEC isolates worldwide, particularly in strains defined as typical EAEC. These data support the hypothesis that AggR is a global regulator of EAEC virulence determinants, and builds on the hypothesis that T6SS is an importance mediator of pathogenesis.

Algorithms↗

PubMed2026

Serotypic and Genomic Diversity of Vibrio anguillarum in Rainbow Trout Farms in Turkey: Implications for Vibriosis Control and Vaccine Candidate Selection.

Outbreaks of vibriosis caused by Vibrio anguillarum are a persistent constraint on rainbow trout (Oncorhynchus mykiss) aquaculture. However, information on the population structure of field strains in Turkey has been lacking. Here, we report the first systematic serotypic, proteomic, and genomic characterization of 23 V. anguillarum isolates collected over 10 years from rainbow trout farms located in six major aquaculture regions of Turkey. Serological analyses based on microagglutination, supported by ELISA characterization of hyperimmune sera, identified a clear predominance of serotype O1, whereas isolate V12 exhibited a non-agglutinating, atypical O-antigen profile. Protein profiling (SDS-PAGE) and immunoblotting showed largely conserved whole-cell protein patterns among the isolates, but distinct immunogenic bands at 14, 18, and 40 kDa were detected in isolates V18 and V21. Long-read whole-genome sequencing revealed that most Turkish isolates grouped within the global O1 clade, while V12, V25, and V28 isolates occupied more distant branches. Comparative genomics demonstrated a conserved core virulence gene set (RTX toxins, siderophore and iron-uptake systems, motility and adhesion factors, Type VI secretion system), with strain-dependent variation in accessory loci such as anguibactin and T6SS-I. Experimental infections of rainbow trout demonstrated significant differences in virulence among isolates (p < 0.05), with the V18 isolate showing high, the V15 intermediate, and the V12 low-mortality rates. By elucidating the relationship among the serotype, immunogenic protein profiles, virulence gene repertoires, and in vivo pathogenicity, this study provides a comprehensive overview of the antigenic and genomic diversity of Vibrio anguillarum isolates from Turkey. Notably, the identification of V18 and V21 as promising candidate strains for further vaccine evaluation, characterized by high virulence and unique immunogenic features, provides a scientific foundation for the development of serotype-specific vaccination strategies to mitigate vibriosis-associated losses in aquaculture.

Animals↗

PubMed1998

External loops at the C terminus of Erwinia chrysanthemi pectate lyase C are required for species-specific secretion through the out type II pathway.

The type II secretion system (main terminal branch of the general secretion pathway) is used by diverse gram-negative bacteria to secrete extracellular proteins. Proteins secreted by this pathway are synthesized with an N-terminal signal peptide which is removed upon translocation across the inner membrane, but the signals which target the mature proteins for secretion across the outer membrane are unknown. The plant pathogens Erwinia chrysanthemi and Erwinia carotovora secrete several isozymes of pectate lyase (Pel) by the out-encoded type II pathway. However, these two bacteria cannot secrete Pels encoded by heterologously expressed pel genes from the other species, suggesting the existence of species-specific secretion signals within these proteins. The functional cluster of E. chrysanthemi out genes carried on cosmid pCPP2006 enables Escherichia coli to secrete E. chrysanthemi, but not E. carotovora, Pels. We exploited the high sequence similarity between E. chrysanthemi PelC and E. carotovora Pel1 to construct 15 hybrid proteins in which different regions of PelC were replaced with homologous sequences from Pell. The differential secretion of these hybrid proteins by E. coli(pCPP2006) revealed M118 to D175 and V215 to C329 as regions required for species-specific secretion of PelC. We propose that the primary targeting signal is contained within the external loops formed by G274 to C329 but is dependent on residues in M118 to D170 and V215 to G274 for proper positioning.

Amino Acid Sequence↗

PubMed2004

Type III secretion phenotypes of Pseudomonas aeruginosa strains change during infection of individuals with cystic fibrosis.

Pseudomonas aeruginosa is a frequent cause of respiratory exacerbations in individuals with cystic fibrosis. An important virulence determinant of this pathogen is its type III protein secretion system. In this study, the type III secretion properties of 435 P. aeruginosa respiratory isolates from 56 chronically infected individuals with cystic fibrosis were investigated. Although it had been previously reported that 75 to 90% of P. aeruginosa isolates from patients with hospital-acquired pneumonia secreted type III proteins, only 12% of isolates from cystic fibrosis patients did so, with nearly all of these isolates secreting ExoS and ExoT but not ExoU. Despite the low overall prevalence of type III protein-secreting isolates, at least one secreting isolate was cultured from one-third of cystic fibrosis patients. Interestingly, the fraction of cystic fibrosis patient isolates capable of secreting type III proteins decreased with duration of infection. Although 90% of isolates from the environment, the presumed reservoir for the majority of P. aeruginosa strains that infect patients with cystic fibrosis, secreted type III proteins, only 49% of isolates from newly infected children, 18% of isolates from chronically infected children, and 4% of isolates from chronically infected adults with cystic fibrosis secreted these proteins. Within individual patients, isolates of clonal origin differed in their secretion phenotypes, indicating that as strains persisted in cystic fibrosis patient airways, their type III protein secretion properties changed. Together, these findings indicate that following infection of cystic fibrosis patient airways, P. aeruginosa strains gradually change from a type III protein secretion-positive phenotype to a secretion-negative phenotype.

Adolescent↗

PubMed2005

[Cardiac failure in children].

The understanding of cardiac failure pathophysiology in children has advanced greatly in recent years. Whilst cardiac failure secondary to left ventricular dysfunction with viral or metabolic cardiomyopathy is comparable in pathophysiological terms with adults, other aetiological mechanisms are also implicated, linked both to anatomical anomalies in congenital cardiopathy and their surgical repair. The role of the neuroendocrine system with adrenergic activation of the renin-angiotensin system, secretion of natriuretic peptides and the inflammatory system, before and during surgical repair procedures, have been proven both experimentally and clinically. Understanding these pathophysiological mechanisms opens new therapeutic perspectives for improving the management of children with congenital cardiopathy in cardiac failure and reducing postoperative mortality and morbidity.

Child↗

PubMed1978

[Demonstration of a 2d LH-RH neurosecretory system in the duck hypothalamus].

Using immunocytochemical techniques with an anti-LH-RH immuneserum, evidence of two neuronal systems secreting LH-RH has been shown in the Duck hypothalamus. In addition to the previously described system, located in the preoptic nucleus, a second system could be demonstrated in the infundibular nucleus. The perikarya of the infundibular LH-RH producing neurons were significantly smaller than those of the preoptic neurons. On the other hand, under the experimental conditions used, the infundibular system had approximately five times less LH-RH secreting neurons than the preoptic system, and its perikarya appeared less heavily loaded in IR LH-RH. The LH-RH containing axons from both neuronal populations ran down to the external layer of the median eminence, where they ended in close contact with the capillaries of the hypophysial portal system.

Animals↗

PubMed2006

Comparison of the genome sequence of the poultry pathogen Bordetella avium with those of B. bronchiseptica, B. pertussis, and B. parapertussis reveals extensive diversity in surface structures associated with host interaction.

Bordetella avium is a pathogen of poultry and is phylogenetically distinct from Bordetella bronchiseptica, Bordetella pertussis, and Bordetella parapertussis, which are other species in the Bordetella genus that infect mammals. In order to understand the evolutionary relatedness of Bordetella species and further the understanding of pathogenesis, we obtained the complete genome sequence of B. avium strain 197N, a pathogenic strain that has been extensively studied. With 3,732,255 base pairs of DNA and 3,417 predicted coding sequences, it has the smallest genome and gene complement of the sequenced bordetellae. In this study, the presence or absence of previously reported virulence factors from B. avium was confirmed, and the genetic bases for growth characteristics were elucidated. Over 1,100 genes present in B. avium but not in B. bronchiseptica were identified, and most were predicted to encode surface or secreted proteins that are likely to define an organism adapted to the avian rather than the mammalian respiratory tracts. These include genes coding for the synthesis of a polysaccharide capsule, hemagglutinins, a type I secretion system adjacent to two very large genes for secreted proteins, and unique genes for both lipopolysaccharide and fimbrial biogenesis. Three apparently complete prophages are also present. The BvgAS virulence regulatory system appears to have polymorphisms at a poly(C) tract that is involved in phase variation in other bordetellae. A number of putative iron-regulated outer membrane proteins were predicted from the sequence, and this regulation was confirmed experimentally for five of these.

Animals↗