Dataset Information

Vacuolation Activity and Intracellular Trafficking of ArtB, the Binding Subunit of an AB5 Toxin Produced by Salmonella enterica Serovar Typhi.

ABSTRACT: Various Salmonella enterica serovars, including S. enterica serovar Typhi, encode an AB5 toxin (ArtAB), the A subunit of which is an ADP-ribosyltransferase related to the S1 subunit of pertussis toxin. However, although the A subunit is able to catalyze ADP-ribosylation of host G proteins, a cytotoxic phenotype has yet to be identified for the holotoxin. Here we show that its B subunit pentamer (ArtB) binds to receptors on the surface of Vero (African green monkey kidney) cell, CHO (Chinese hamster ovary) cell, U937 (human monocyte) cell, and HBMEC (human brain microvascular endothelial cell) lines. Moreover, ArtB induced marked vacuolation in all cell lines after 4 h of incubation. Further studies in Vero cells showed that vacuolation was inhibited by bafilomycin A1 and was dependent on the clathrin-mediated uptake of ArtB. Vacuolation was also inhibited by treatment of cells with neuraminidase, indicating that sialylated glycans are functional receptors for ArtB. Confocal colocalization studies indicated that after cell binding and internalization, ArtB undergoes retrograde transport via early endosomes, the trans-Golgi network, and the Golgi apparatus, reaching the endoplasmic reticulum (ER) after approximately 2 h. The onset of vacuolation also coincided with gross cytoskeletal reorganization. At later time points, ArtB colocalized with ER-Tracker Red in the vacuolar membrane, implying that vacuolation is a consequence of ER disorganization. Thus, the isolated B subunit of this cryptic AB5 toxin has significant effects on target cells with the potential to contribute directly to pathogenesis independently of the catalytic A subunit.

SUBMITTER: Herdman BP

PROVIDER: S-EPMC5520444 | biostudies-literature | 2017 Aug

REPOSITORIES: biostudies-literature

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Vacuolation Activity and Intracellular Trafficking of ArtB, the Binding Subunit of an AB5 Toxin Produced by Salmonella enterica Serovar Typhi.

Herdman Brock P BP Paton James C JC Wang Hui H Beddoe Travis T Paton Adrienne W AW

Infection and immunity 20170719 8

Various <i>Salmonella enterica</i> serovars, including <i>S. enterica</i> serovar Typhi, encode an AB5 toxin (ArtAB), the A subunit of which is an ADP-ribosyltransferase related to the S1 subunit of pertussis toxin. However, although the A subunit is able to catalyze ADP-ribosylation of host G proteins, a cytotoxic phenotype has yet to be identified for the holotoxin. Here we show that its B subunit pentamer (ArtB) binds to receptors on the surface of Vero (African green monkey kidney) cell, CHO ...[more]

PMID: 28533468

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Project description:BackgroundTyphoid fever is an acute systemic infection of humans caused by Salmonella enterica subspecies enterica serovar Typhi (S. Typhi). In chronic carriers, the bacteria survive the harsh environment of the gallbladder by producing biofilm. The phenotype of S. Typhi biofilm cells is significantly different from the free-swimming planktonic cells, and studies have shown that they are associated with antibiotic resistance, immune system evasion, and bacterial persistence. However, the mechanism of this transition and the events leading to biofilm formation are unknown. High throughput sequencing was performed to identify the genes involved in biofilm formation and to postulate the mechanism of action.ResultsPlanktonic S. Typhi cells were cultured using standard nutrient broth whereas biofilm cells were cultured in a stressful environment using high shearing-force and bile to mimic the gallbladder. Sequencing libraries were prepared from S. Typhi planktonic cells and mature biofilm cells using the Illumina HiSeq 2500 platform, and the transcriptome data obtained were processed using Cufflinks bioinformatics suite of programs to investigate differential gene expression between the two phenotypes. A total of 35 up-regulated and 29 down-regulated genes were identified. The identities of the differentially expressed genes were confirmed using NCBI BLAST and their functions were analyzed. The results showed that the genes associated with metabolic processes and biofilm regulations were down-regulated while those associated with the membrane matrix and antibiotic resistance were highly up-regulated.ConclusionsIt is proposed that the biofilm phenotype of S. Typhi allows the bacteria to increase production of the membrane matrix in order to serve as a physical shield and to adhere to surfaces, and enter an energy conservation state in response to the stressful environment. Conversely, the planktonic phenotype allows the bacteria to produce flagella and increase metabolic activity to enable the bacteria to migrate and form new colonies of infection. This data provide a basis for further studies to uncover the mechanism of biofilm formation in S. Typhi and to discover novel genes or pathways associated with the development of the typhoid carrier state.

Project description:Salmonella Typhi (S. Typhi) is the causative agent of typhoid fever; a systemic disease affecting ~20 million people per year globally. There are little data regarding the contemporary epidemiology of typhoid in Latin America. Consequently, we aimed to describe some recent epidemiological aspects of typhoid in Colombia using cases reported to the National Public Health Surveillance System (Sivigila) between 2012 and 2015. Over the four-year reporting period there were 836 culture confirmed cases of typhoid in Colombia, with the majority (676/836; 80.1%) of reported cases originated from only seven departments. We further characterized 402 S. Typhi isolates with available corresponding data recovered from various departments of Colombia through antimicrobial susceptibility testing and molecular subtyping. The majority (235/402; 58.5%) of these typhoid cases occurred in males and were most commonly reported in those aged between 10 and 29 years (218/402; 54.2%); there were three (0.74%) reported fatalities. The overwhelming preponderance (339/402; 84.3%) of S. Typhi were susceptible to all tested antimicrobials. The most common antimicrobial to which the organisms exhibited non-susceptibility was ampicillin (30/402;7.5%), followed by nalidixic acid (23/402, 5.7%). Molecular subtyping identified substantial genetic diversity, which was well distributed across the country. Despite the diffuse pattern of S. Typhi genotypes, we identified various geographical hotspots of disease associated with local dominant genotypes. Notably, we found limited overlap of Colombian genotypes with organisms reported in other Latin American countries. Our work highlights a substantial burden of typhoid in Colombia, characterized by sustained transmission in some regions and limited epidemics in other departments. The disease is widely distributed across the country and associated with multiple antimicrobial susceptible genotypes that appear to be restricted to Colombia. This study provides a current perspective for typhoid in Latin America and highlights the importance of pathogen-specific surveillance to add insight into the limited epidemiology of typhoid in this region.

Dataset Information

Vacuolation Activity and Intracellular Trafficking of ArtB, the Binding Subunit of an AB5 Toxin Produced by Salmonella enterica Serovar Typhi.

Publications

Vacuolation Activity and Intracellular Trafficking of ArtB, the Binding Subunit of an AB5 Toxin Produced by Salmonella enterica Serovar Typhi.

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