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Crystallization and preliminary crystallographic analysis of an Ig-domain-encompassing fragment of the giant adhesion protein SiiE from Salmonella enterica.

ABSTRACT: Salmonella infections can be life-threatening. SiiE is a giant adhesion molecule of 5559 amino acids that is encoded in Salmonella pathogenicity island 4 (SPI4) and that promotes the initial contact between the pathogen and polarized epithelial cells in the intestine of the host. Starting from an engineered deletion version of SiiE (mini-SiiE; 97 kDa), limited proteolysis was used to reproducibly generate a 30 kDa fragment that readily crystallized. Mass spectrometry hints that this fragment spans the predicted Ig domains 50-52 of SiiE. Crystals of both native and selenomethionine-labelled protein could be obtained in space group C2 and diffraction data were recorded to a resolution of 1.85 Å.

PROVIDER: S-EPMC3212453 | BioStudies |

REPOSITORIES: biostudies

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The giant adhesin SiiE of Salmonella enterica.

Project description:Salmonella enterica is a Gram-negative, food-borne pathogen, which colonizes the intestinal tract and invades enterocytes. Invasion of polarized cells depends on the SPI1-encoded type III secretion system (T3SS) and the SPI4-encoded type I secretion system (T1SS). The substrate of this T1SS is the non-fimbrial giant adhesin SiiE. With a size of 595 kDa, SiiE is the largest protein of the Salmonella proteome and consists of 53 repetitive bacterial immunoglobulin (BIg) domains, each containing several conserved residues. As known for other T1SS substrates, such as E. coli HlyA, Ca2+ ions bound by conserved D residues within the BIg domains stabilize the protein and facilitate secretion. The adhesin SiiE mediates the first contact to the host cell and thereby positions the SPI1-T3SS to initiate the translocation of a cocktail of effector proteins. This leads to actin remodeling, membrane ruffle formation and bacterial internalization. SiiE binds to host cell apical membranes in a lectin-like manner. GlcNAc and ?2-3 linked sialic acid-containing structures are ligands of SiiE. Since SiiE shows repetitive domain architecture, we propose a zipper-like binding mediated by each individual BIg domain. In this review, we discuss the characteristics of the SPI4-T1SS and the giant adhesin SiiE.

| S-EPMC6272769 | BioStudies

Structural and functional dissection reveals distinct roles of Ca2+-binding sites in the giant adhesin SiiE of Salmonella enterica.

Project description:The giant non-fimbrial adhesin SiiE of Salmonella enterica mediates the first contact to the apical site of epithelial cells and enables subsequent invasion. SiiE is a 595 kDa protein composed of 53 repetitive bacterial immunoglobulin (BIg) domains and the only known substrate of the SPI4-encoded type 1 secretion system (T1SS). The crystal structure of BIg50-52 of SiiE revealed two distinct Ca2+-binding sites per BIg domain formed by conserved aspartate or glutamate residues. In a mutational analysis Ca2+-binding sites were disrupted by aspartate to serine exchange at various positions in the BIg domains of SiiE. Amounts of secreted SiiE diminish with a decreasing number of intact Ca2+-binding sites. BIg domains of SiiE contain distinct Ca2+-binding sites, with type I sites being similar to other T1SS-secreted proteins and type II sites newly identified in SiiE. We functionally and structurally dissected the roles of type I and type II Ca2+-binding sites in SiiE, as well as the importance of Ca2+-binding sites in various positions of SiiE. Type I Ca2+-binding sites were critical for efficient secretion of SiiE and a decreasing number of type I sites correlated with reduced secretion. Type II sites were less important for secretion, stability and surface expression of SiiE, however integrity of type II sites in the C-terminal portion was required for the function of SiiE in mediating adhesion and invasion.

| S-EPMC5466336 | BioStudies

MUC1 is a receptor for the Salmonella SiiE adhesin that enables apical invasion into enterocytes.

Project description:The cellular invasion machinery of the enteric pathogen Salmonella consists of a type III secretion system (T3SS) with injectable virulence factors that induce uptake by macropinocytosis. Salmonella invasion at the apical surface of intestinal epithelial cells is inefficient, presumably because of a glycosylated barrier formed by transmembrane mucins that prevents T3SS contact with host cells. We observed that Salmonella is capable of apical invasion of intestinal epithelial cells that express the transmembrane mucin MUC1. Knockout of MUC1 in HT29-MTX cells or removal of MUC1 sialic acids by neuraminidase treatment reduced Salmonella apical invasion but did not affect lateral invasion that is not hampered by a defensive barrier. A Salmonella deletion strain lacking the SiiE giant adhesin was unable to invade intestinal epithelial cells through MUC1. SiiE-positive Salmonella closely associated with the MUC1 layer at the apical surface, but invaded Salmonella were negative for the adhesin. Our findings uncover that the transmembrane mucin MUC1 is required for Salmonella SiiE-mediated entry of enterocytes via the apical route.

2019-01-01 | S-EPMC6375660 | BioStudies

Salmonella SiiE prevents an efficient humoral immune memory by interfering with IgG+ plasma cell persistence in the bone marrow.

Project description:Serum IgG, which is mainly generated from IgG-secreting plasma cells in the bone marrow (BM), protects our body against various pathogens. We show here that the protein SiiE of Salmonella is both required and sufficient to prevent an efficient humoral immune memory against the pathogen by selectively reducing the number of IgG-secreting plasma cells in the BM. Attenuated SiiE-deficient Salmonella induces high and lasting titers of specific and protective Salmonella-specific IgG and qualifies as an efficient vaccine against Salmonella A SiiE-derived peptide with homology to laminin ?1 is sufficient to ablate IgG-secreting plasma cells from the BM, identifying laminin ?1 as a component of niches for IgG-secreting plasma cells in the BM, and furthermore, qualifies it as a unique therapeutic option to selectively ablate IgG-secreting plasma cells in autoimmune diseases and multiple myeloma.

| S-EPMC6462062 | BioStudies

Salmonella enterica invasion of polarized epithelial cells is a highly cooperative effort.

Project description:The invasion of polarized epithelial cells by Salmonella enterica requires the cooperative activity of the Salmonella pathogenicity island 1 (SPI1)-encoded type III secretion system (T3SS) and the SPI4-encoded adhesin SiiE. The invasion of polarized cells is more efficient than that of nonpolarized cells, and we observed the formation of clusters of bacteria on infected cells. Here we demonstrate that the invasion of polarized cells is a highly cooperative activity. Using a novel live-cell imaging approach, we visualized the cooperative entry of multiple bacteria into ruffles induced on the apical surfaces of polarized cells. The induction of membrane ruffles by activity of Salmonella enables otherwise noninvasive mutant strains to enter polarized host cells. Bacterial motility and chemotaxis were of lower importance for cooperativity in polarized-cell invasion. We propose that cooperative invasion is a key factor for the very efficient entry into polarized cells and a factor contributing to epithelial damage and intestinal inflammation.

| S-EPMC4019164 | BioStudies

SprB is the molecular link between Salmonella pathogenicity island 1 (SPI1) and SPI4.

Project description:Salmonella pathogenicity island 1 (SPI1) and SPI4 have previously been shown to be jointly regulated. We report that SPI1 and SPI4 gene expression is linked through a transcriptional activator, SprB, encoded within SPI1 and regulated by HilA. SprB directly activates SPI4 gene expression and weakly represses SPI1 gene expression through HilD.

| S-EPMC2863475 | BioStudies

Gaussia princeps luciferase as a reporter for transcriptional activity, protein secretion, and protein-protein interactions in Salmonella enterica serovar typhimurium.

Project description:Gaussia princeps luciferase (Gluc) is widely used as a reporter in eukaryotes, but data about its applicability in bacteria are very limited. Here we show that a codon-optimized Gluc gene can be efficiently expressed in Salmonella enterica serovar Typhimurium. To test different Gluc variants as transcriptional reporters, we used the siiA promoter of Salmonella pathogenicity island 4 (SPI-4) driving expression of either an episomal or a chromosomally integrated Gluc gene. Most reliable results were obtained from lysates of single-copy Gluc reporter strains. Given the small size, high activity, and cofactor independence of Gluc, it might be especially suited to monitor secretion of bacterial proteins. We demonstrate its usefulness by luminescence detection of fusion proteins of Gluc and C-terminal portions of the SPI-4-encoded, type I-secreted adhesin SiiE in supernatants. The SiiE C-terminal moiety including immunoglobulin (Ig) domain 53 is essential and sufficient for mediating type I-dependent secretion of Gluc. In eukaryotes, protein-protein interaction studies based on split-Gluc protein complementation assays (PCA) could be established. We adapted these methods for use in Salmonella, demonstrating the interaction between the SPI-1-encoded effector SipA and its cognate secretion chaperone InvB. In conclusion, the versatile Gluc can be used to address a variety of biological questions, thus representing a valuable addition to the toolbox of modern molecular biology and microbiology.

| S-EPMC3255616 | BioStudies

Gene expression analysis of Salmonella enterica SPI in macrophages indicates differences between serovars that induce systemic disease from those normally causing enteritis.

Project description:Global gene expression of the invasive Salmonella serovars S. Enteritidis and S. Typhimurium, and the less-invasive S. Infantis and S. Hadar was studied during infection of a chicken macrophage cell line. Major functional gene groups responsible for intracellular physiological changes were regulated similarly in all four serovars. However, SPI1 and SPI4 genes of S. Enteritidis and S. Typhimurium were strongly repressed in the macrophages whereas S. Infantis, S. Hadar and other similar serovars maintained up-regulation of these gene sets. This phenomenon may explain some of the biological differences between invasive and non-invasive Salmonella serovars.

| S-EPMC3878769 | BioStudies

The Seed Development Factors TT2 and MYB5 Regulate Heat Stress Response in Arabidopsis.

Project description:HEAT SHOCK FACTOR A2 (HSFA2) is a regulator of multiple environmental stress responses required for stress acclimation. We analyzed HSFA2 co-regulated genes and identified 43 genes strongly co-regulated with HSFA2 during multiple stresses. Motif enrichment analysis revealed an over-representation of the site II element (SIIE) in the promoters of these genes. In a yeast 1-hybrid screen with the SIIE, we identified the closely related R2R3-MYB transcription factors TT2 and MYB5. We found overexpression of MYB5 or TT2 rendered plants heat stress tolerant. In contrast, tt2, myb5, and tt2/myb5 loss of function mutants showed heat stress hypersensitivity. Transient expression assays confirmed that MYB5 and TT2 can regulate the HSFA2 promoter together with the other members of the MBW complex, TT8 and TRANSPARENT TESTA GLABRA 1 (TTG1) and that the SIIE was involved in this regulation. Transcriptomic analysis revealed that TT2/MYB5 target promoters were enriched in SIIE. Overall, we report a new function of TT2 and MYB5 in stress resistance and a role in SIIE-mediated HSFA2 regulation.

| S-EPMC8156827 | BioStudies

Cloning and sequencing of the gene encoding a 31-kilodalton antigen of Haemophilus somnus.

Project description:Immunoblots using bovine antibody against Haemophilus somnus as the primary antibody consistently identified 31-, 40- and 78-kDa proteins in Sarkosyl-insoluble extracts of H. somnus. A genomic library of H. somnus 8025 DNA was constructed in plasmid pUC19, and 45 recombinants expressed proteins which were recognized by bovine antiserum in Western blots (immunoblots). Ten of the recombinants expressing a 31-kDa protein caused the lysis of bovine erythrocytes. Restriction endonuclease mapping indicated that the hemolytic recombinants shared an approximately 1.7-kb BglII fragment. Southern blot analysis using the BglII fragment as a probe revealed homology among the recombinants and the presence of an identically sized BglII fragment in the chromosome of all H. somnus isolates tested. Sequence analysis indicated the presence of an 822-bp open reading frame within the 1.7-kb BglII fragment. Deletion of this open reading frame resulted in the loss of hemolytic activity and protein expression in recombinant Escherichia coli, suggesting the possible role of the 31-kDa protein as a hemolysin. An amino acid sequence deduced from the DNA sequence shared homology with outer membrane protein A of E. coli, Salmonella typhimurium, and Shigella dysenteriae, with P6 of Haemophilus influenzae, and with PIII of Neisseria gonorrhoeae. An amino acid analysis of the recombinant 31-kDa protein agreed with the amino acid composition deduced from the DNA sequence.

1993-01-01 | S-EPMC280925 | BioStudies

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