SEARCH · Search PubMed

Results for “effector”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources

PubMed2025

In silico prediction method for plant Nucleotide-binding leucine-rich repeat- and pathogen effector interactions.

Plant Nucleotide-binding leucine-rich repeat (NLR) proteins play a crucial role in effector recognition and activation of Effector triggered immunity following pathogen infection. Genome sequencing advancements have led to the identification of a myriad of NLRs in numerous agriculturally important plant species. However, deciphering which NLRs recognize specific pathogen effectors remains challenging. Predicting NLR-effector interactions in silico will provide a more targeted approach for experimental validation, critical for elucidating function, and advancing our understanding of NLR-triggered immunity. In this study, NLR-effector protein complex structures were predicted using AlphaFold2-Multimer for all experimentally validated NLR-effector interactions reported in literature. Binding affinities- and energies were predicted using 97 machine learning models from Area-Affinity. We show that AlphaFold2-Multimer predicted structures have acceptable accuracy and can be used to investigate NLR-effector interactions in silico. Binding affinities for 58 NLR-effector complexes ranged between -8.5 and -10.6 log(K), and binding energies between -11.8 and -14.4 kcal/mol-1, depending on the Area-Affinity model used. For 2427 "forced" NLR-effector complexes, these estimates showed larger variability, enabling identification of novel NLR-effector interactions with 99% accuracy using an Ensemble machine learning model. The narrow range of binding energies- and affinities for "true" interactions suggest a specific change in Gibbs free energy, and thus conformational change, is required for NLR activation. This is the first study to provide a method for predicting NLR-effector interactions, applicable to all pathosystems. Finally, the NLR-Effector Interaction Classification (NEIC) resource can streamline research efforts by identifying NLRs important for plant-pathogen resistance, advancing our understanding of plant immunity.

Plant Proteins↗

PubMed2005

New concept of spare receptors and effectors.

The present study provides a new concept of the spare receptor. Model [A]: 1) Several receptors connect with an effector; 2) if an agonist occupies one of the receptors connecting with one effector, the effector fully functions. When the number of receptors connecting with one effector is "m", the relationship between the functional effectors (E) and the concentration of agonists ([a]) is as follows: [formula: see text] where Rt is the total number of receptors and Kd is the agonist dissociation constant from the receptor. Model [B]: 1) Several receptors connect with an effector; 2) only when agonists occupy all of the receptors connecting with one effector, the effector functions. The relationship between E and [a] is as follows: [formula: see text] If m=1, equations (I) and (II) are exactly the same as the Michaelis-Menten equation. If m is larger than 1, the apparent saturation in the effector efficiency becomes larger in Model [A], and smaller in Model [B], respectively. The dissociation of the fractional efficiency of effectors from the fractional binding of agonists to receptors becomes larger as m becomes larger in both models. Further, we propose a variable model, including the concept of agonist-occupancy-dependent stability in the functional conformation change of the effector; only when more than j pieces of receptors connecting with one effector are occupied by agonists, the effector functions (Model [M]). The relationship between E and [a] is as follows: [formula: see text]

Mathematics↗

PubMed1994

Generation of polarized antigen-specific CD8 effector populations: reciprocal action of interleukin (IL)-4 and IL-12 in promoting type 2 versus type 1 cytokine profiles.

We have generated primary effector populations from naive CD8 T cells in response to antigen and determined their patterns of cytokine secretion upon restimulation. The effect of exogenous factors on the effector generation was examined and compared with responses of antigen-specific CD4 effectors generated under comparable conditions. CD8 cells from bm1 mice were stimulated with C57BL/6 (B6) antigen presenting cells (APCs) bearing allogeneic class I and CD8 cells from female severe combined immunodeficiency (SCID) B6 mice, transgenic for a T cell receptor alpha/beta (TCR-alpha/beta) that recognizes H-Y on Db, were stimulated with APCs from male mice. In parallel, CD4 cells from bm12 mice were stimulated with alloantigen and CD4 cells from V beta 3/V alpha 11 TCR transgenics were stimulated with a peptide of pigeon cytochrome c on IEk. T cells from both transgenic mice were of naive phenotype whereas normal mice contained 10-20% memory cells. Effector CD8 populations generated were L-selectin low, CD45RB high, and CD44 high. Naive CD8 cells from SCID anti-H-Y mice made little or no cytokine immediately upon stimulation in contrast to naive CD4 which produced large amounts of interleukin 2 (IL-2). Both populations, however, generated primary effectors over 4-5 d that made substantial quantities of many cytokines upon restimulation. Both CD8 and CD4 effectors produced similar patterns of cytokines with alloantigen or specific antigen. Cytokines present during naive CD8 stimulation influenced the cytokine secretion profile of the effectors, as previously shown for CD4 cells, although secretion by CD8 effectors was generally lower than that of CD4 effectors. CD8 cells cultured with IL-2 alone made predominantly interferon gamma (IFN-gamma) and no IL-4 or IL-5, similar to CD4 cells. Priming with IFN-gamma increased IFN-gamma secretion from CD4 effectors, but had little if any effect on CD8 cells. In contrast, priming with IL-12 generated CD8 effectors, as well as CD4 effectors, producing elevated quantities of IFN-gamma, with similar levels from both the CD4 and CD8 populations. The presence of IL-4 during effector cell generation promoted synthesis of IL-4 and IL-5 from both CD8 and CD4 cells while downregulating IFN-gamma secretion. CD8 cells made only small amounts of IL-4, more than 100-fold less than CD4 cells, whereas significant levels of IL-5 were induced, only 3-10-fold lower than from CD4.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed2004

Evaluating the cytotoxicity of innate immune effector cells using the GrB ELISPOT assay.

BACKGROUND: This study assessed the Granzyme B (GrB) ELISPOT as a viable alternative to the 51Cr-release assay for measuring cytotoxic activity of innate immune effector cells. We strategically selected the GrB ELISPOT assay because GrB is a hallmark effector molecule of cell-mediated destruction of target cells. METHODS: We optimized the GrB ELISPOT assay using the human-derived TALL-104 cytotoxic cell line as effectors against K562 target cells. Titration studies were performed to assess whether the ELISPOT assay could accurately enumerate the number of GrB-secreting effector cells. TALL-104 were treated with various secretion inhibitors and utilized in the GrB ELISPOT to determine if GrB measured in the ELISPOT was due to degranulation of effector cells. Additionally, CD107a expression on effector cells after effector-target interaction was utilized to further confirm the mechanism of GrB release by TALL-104 and lymphokine-activated killer (LAK) cells. Direct comparisons between the GrB ELISPOT, the IFN-gamma ELISPOT and the standard 51Cr-release assays were made using human LAK cells. RESULTS: Titration studies demonstrated a strong correlation between the number of TALL-104 and LAK effector cells and the number of GrB spots per well. GrB secretion was detectable within 10 min of effector-target contact with optimal secretion observed at 3-4 h; in contrast, optimal IFN-gamma secretion was not observed until 24 h. The protein secretion inhibitor, brefeldin A, did not inhibit the release of GrB but did abrogate IFN-gamma production by TALL-104 cells. GrB secretion was abrogated by BAPTA-AM (1,2-bis-(2-aminophenoxy)ethane-N,N,N', N'-tetraacetic acid tetra(acetoxymethyl) ester), which sequesters intracellular Ca2+, thereby preventing degranulation. The number of effector cells expressing the degranulation associated glycoprotein CD107a increased after interaction with target cells and correlated with the stimulated release of GrB measured in the ELISPOT assay. CONCLUSIONS: Because of its high sensitivity and ability to estimate cytotoxic effector cell frequency, the GrB ELISPOT assay is a viable alternative to the 51Cr-release assay to measure MHC non-restricted cytotoxic activity of innate immune cells. Compared to the IFN-gamma ELISPOT assay, the GrB ELISPOT may be a more direct measure of cytotoxic cell activity. Because GrB is one of the primary effector molecules in natural killer (NK) cell-mediated killing, detection and enumeration of GrB secreting effector cells can provide valuable insight with regards to innate immunological responses.

Journal Article↗

PubMed2025

Transposable elements create distinct genomic niches for effector evolution among Magnaporthe oryzae lineages.

BACKGROUND: Plant-pathogen interactions are characterized by evolutionary arms races. At the molecular level, fungal effectors can target important plant functions, while plants evolve to improve effector recognition. Rapid evolution in genes encoding effectors can be facilitated by transposable elements (TEs). In Magnaporthe oryzae, the causal agent of blast disease in several cereals and grasses, TEs play important roles in chromosomal evolution as well as the gain or loss of effector genes in host specialized lineages. However, a global understanding of TE dynamics driving effector evolution at population scale and across lineages is lacking. RESULTS: Here, we focus on 16 AVR effector loci assessed across a global sampling of 11 reference genomes and 447 newly generated draft genome assemblies from publicly available short-read sequencing data across all major M. oryzae lineages and outgroups. We classified each effector based on evidence for duplication, deletion and translocation processes among lineages. Next, we determined AVR gain and loss dynamics across lineages allowing for a broad categorization of effector dynamics. Each AVR was integrated in a distinct genomic niche determined by the TE activity profile contributing to the diversification at the locus. We quantified TE contributions to effector niches and found that TE identity helped diversify AVR loci. We used the large genomic dataset to recapitulate the evolution of the rice blast AVR1-CO39 locus. CONCLUSIONS: Taken together, our work demonstrates how TE dynamics are an integral component of M. oryzae effector evolution, likely facilitating escape from host recognition. In-depth tracking of effector loci is a valuable tool to predict the durability of host resistance.

Ascomycota↗

PubMed2000

The effector loop and prenylation site of R-Ras are involved in the regulation of integrin function.

The closely related small GTP-binding proteins H-Ras and R-Ras have opposing effects on the regulation of integrin cell adhesion receptors. To gain insight into the properties of R-Ras with respect to the regulation of integrin function and interactions with downstream effectors we performed an analysis of R-Ras variants containing mutations in the effector binding domain and C-terminal prenylation site. We found that the activation of the downstream effector PI 3-kinase was sensitive to mutations in the effector binding domain, as was the binding to the effectors, Ral-GDS, Raf-1 and the novel effector Nore1. Furthermore, specific mutations in the effector binding loop and C-terminal prenylation motif impaired the ability of R-Ras to regulate integrin function in CHO cells. However, the ability of the R-Ras effector loop mutants to bind, and activate known effectors did not correlate with their ability to regulate integrin function. Thus, the known R-Ras effectors are not critical for regulating integrin activation, at least in CHO cells. Consequently, these studies provide insight into the structural basis of the interactions between R-Ras and its candidate effectors and suggest the existence of novel mechanisms through which this GTPase could regulate cell adhesion.

Amino Acid Sequence↗

PubMed2006

Closing the circle on the discovery of genes encoding Hrp regulon members and type III secretion system effectors in the genomes of three model Pseudomonas syringae strains.

Pseudomonas syringae strains translocate large and distinct collections of effector proteins into plant cells via the type III secretion system (T3SS). Mutations in T3SS-encoding hrp genes are unable to elicit the hypersensitive response or pathogenesis in nonhost and host plants, respectively. Mutations in individual effectors lack strong phenotypes, which has impeded their discovery. P. syringae effectors are designated Hop (Hrp outer protein) or Avr (avirulence) proteins. Some Hop proteins are considered to be extracellular T3SS helpers acting at the plant-bacterium interface. Identification of complete sets of effectors and related proteins has been enabled by the application of bioinformatic and high-throughput experimental techniques to the complete genome sequences of three model strains: P. syringae pv. tomato DC3000, P. syringae pv. phaseolicola 1448A, and P. syringae pv. syringae B728a. Several recent papers, including three in this issue of Molecular Plant-Microbe Interactions, address the effector inventories of these strains. These studies establish that active effector genes in P. syringae are expressed by the HrpL alternative sigma factor and can be predicted on the basis of cis Hrp promoter sequences and N-terminal amino-acid patterns. Among the three strains analyzed, P. syringae pv. tomato DC3000 has the largest effector inventory and P. syringae pv. syringae B728a has the smallest. Each strain has several effector genes that appear inactive. Only five of the 46 effector families that are represented in these three strains have an active member in all of the strains. Web-based community resources for managing and sharing growing information on these complex effector arsenals should help future efforts to understand how effectors promote P. syringae virulence.

Bacterial Outer Membrane Proteins↗

PubMed1985

Restricted effector cell function in ADCC.

Human effector cell function in ADCC reactions was studied as a result of observations showing discrepant ADCC reactivities among different effector cell populations. Effector cells prepared from ten blood donors were tested individually and as a pool against a battery of nine antisera-target cell combinations in an 11-x-9 matrix. The results identified individuals with weak, intermediate, and strong effector cell functions; however, there was a wide range of ADCC reactivity by each person's effector cells against the nine targets. No single antibody-target cell combination was consistently subjected to the least kill or greatest kill by the different effector cell preparations. Pooled effector cell responses were found to be weaker than expected. There was no relationship of age or sex with effector cell function, but a trend was noted for strong and weak reactions to be associated with HLA-DR7 and DR1, respectively. Neither the sharing of HLA antigens between effector and target cells nor self ADCC reactivity could account for the variations in effector cell function. Exploratory principal components factor analysis suggested that recognition of antibody-target cell combinations by effector cells was represented by three major groupings. These data collectively indicate the existence of an allorestrictive Fc receptor recognition step in ADCC responses.

Adult↗

PubMed1994

Binding units (BU) and the area under binding isotherms (AUI). New indices of effector-target conjugation.

New methods for simplified quantitation of effector-target conjugation have been developed. The binding unit (BU) is defined as the number of target cells required to bind a specified percentage of effector cells. The number of binding units is determined from binding isotherms in which effector conjugate frequencies are measured by holding constant the number of effector cells and by varying the number of target cells. Alternately, a binding unit can be defined as the number of effector cells required to bind a specified percentage of target cells. In this case, BU is computed from binding isotherms in which target conjugate frequencies are measured at different values of effector cells by holding constant the number of target cells. Also, the area under the curve (AUI) of these isotherms is another index that can be used as an overall measure of the binding capacity in an effector-target system. The experimental values of BU and AUI determined from effector and target isotherms agree well with theoretical predictions based on our previously developed binding model (J. Immunol. Methods (1992) 155, 133-147). The relationship between BU and AUI, and procedures to determine these parameters are shown. The value of these indices to express effector-target conjugation quantitatively has been confirmed by determining the values of BU and AUI for the NK-K562 effector-target system.

Adult↗

PubMed2001

Increased cytotoxic T cells with effector phenotype in aplastic anemia and myelodysplasia.

OBJECTIVE: We hypothesized that an active autoimmune process in aplastic anemia (AA) corresponds to the expansion of cytotoxic lymphocytes (CTLs) displaying mature effector phenotype. We determined whether the numbers of effector CTLs in blood of patients with bone marrow failure syndromes are elevated and correlate with the disease activity and responsiveness to immunosuppression. PATIENTS AND METHODS: We analyzed samples from patients with AA, myelodysplastic syndrome (MDS), polytransfused patients with nonimmune-mediated hematologic disease, and normal controls for the presence of effector T lymphocytes using four-color flow cytometry. Expression of CD57 and loss of CD28 on CD8+CD3+ CTL were used as markers for the terminal effector phenotype. In addition, intracellular staining for perforin and granzyme B was preformed. The numbers of effector CTL did not differ between healthy individuals and hematologic controls and the two groups were pooled. RESULTS: The percentages of CD8+CD28- and CD8+CD28-CD57+ cells were significantly higher in AA and MDS patients than in controls. There was a trend toward a gradual decrease in the effector CTLs from the high values observed in untreated new patients and patients who did not respond to immunosuppression, intermediate levels for partial responders and complete responders, to the lowest levels seen in controls. However, severity of pancytopenia did not correlate with the size of the effector cell population. In contrast to CD57+ CTLs, expression of perforin or granzyme B in the cytotoxic effector cells did not differ in AA patients from those of controls. CONCLUSIONS: Our results indicate that phenotypically defined effector CTLs are increased in AA and MDS and the effector phenotype may be useful to isolate and characterize antigen-specific T cells in AA in order to delineate the possible inciting or driving agents in AA.

Anemia, Aplastic↗

PubMed2006

An extensive repertoire of type III secretion effectors in Escherichia coli O157 and the role of lambdoid phages in their dissemination.

Several pathogenic strains of Escherichia coli exploit type III secretion to inject "effector proteins" into human cells, which then subvert eukaryotic cell biology to the bacterium's advantage. We have exploited bioinformatics and experimental approaches to establish that the effector repertoire in the Sakai strain of enterohemorrhagic E. coli (EHEC) O157:H7 is much larger than previously thought. Homology searches led to the identification of >60 putative effector genes. Thirteen of these were judged to be likely pseudogenes, whereas 49 were judged to be potentially functional. In total, 39 proteins were confirmed experimentally as effectors: 31 through proteomics and 28 through translocation assays. At the protein level, the EHEC effector sequences fall into >20 families. The largest family, the NleG family, contains 14 members in the Sakai strain alone. EHEC also harbors functional homologs of effectors from plant pathogens (HopPtoH, HopW, AvrA) and from Shigella (OspD, OspE, OspG), and two additional members of the Map/IpgB family. Genes encoding proven or predicted effectors occur in >20 exchangeable effector loci scattered throughout the chromosome. Crucially, the majority of functional effector genes are encoded by nine exchangeable effector loci that lie within lambdoid prophages. Thus, type III secretion in E. coli is linked to a vast phage "metagenome," acting as a crucible for the evolution of pathogenicity.

Bacteriophage lambda↗

PubMed2006

TIP47 is a key effector for Rab9 localization.

The human genome encodes approximately 70 Rab GTPases that localize to the surfaces of distinct membrane compartments. To investigate the mechanism of Rab localization, chimeras containing heterologous Rab hypervariable domains were generated, and their ability to bind seven Rab effectors was quantified. Two chimeras could bind effectors for two distinctly localized Rabs; a Rab5/9 hybrid bound both Rab5 and Rab9 effectors, and a Rab1/9 hybrid bound to certain Rab1 and Rab9 effectors. These unusual chimeras permitted a test of the importance of effector binding for Rab localization. In both cases, changing the cellular concentration of a key Rab9 effector, which is called tail-interacting protein of 47 kD, moved a fraction of the proteins from their parental Rab localization to that of Rab9. Thus, relative concentrations of certain competing effectors could determine a chimera's localization. These data confirm the importance of effector interactions for Rab9 localization, and support a model in which effector proteins rely on Rabs as much as Rabs rely on effectors to achieve their correct steady state localizations.

Binding, Competitive↗

PubMed1976

Cell-mediated lympholysis of N-(3-nitro-4-hydroxy-5-iodophenylacetyl)-beta-anaylglycylglycyl-modified autologous lymphocytes. Effector cell specificity to modified cell surface components controlled by the H-2K and H-2D serological regions of the murine major histocompatibility complex.

Splenic lymphocytes from four C57BL/10 congenic mouse strains were sensitized in vitro to N(-3-nitro-4-hydroxy-5-iodophenylacetyl)-beta-alanylglycylglycyl-(N) modified autologous lymphocytes. The effector cells generated after 5 days of culture were assayed on a series of either N-modified phytohemagglutinin-stimulated spleen cells or N-modified tumor cells. The results indicated in all cases that both N modification of the targets and H-2 homology between the modified stimulating and target cells are required for lysis to occur. In each case the effector cells were found to lyse N-modified target cells only when there was homology at either or both ends of the major histocompatibility complex (MHC) between the stimulator and target cells. B10.BR lysed targets sharing alleles at K (or K plus I-A) and/or at D. B10.A effector cell specificity was mapped to K (or K plus I-A) and/or the D half of the MHC (D or D plus I-C and/or S). The two regions of specificity determined for B10.D2 effector cells were D (or D plus S plus I-C) and a region not including D of the MHC. C57BL/10 effector cells lysed N-modified targets only if there was target cell H-2 homology at K, I-A, and I-B or at the D serological region. As in the trinitrophenyl (TNP) system (6) B10.BR and B10.A effector cells lysed targets sharing K end H-2 serological regions greater than target cells sharing D-end serological regions. The C57BL/10 effector cells were shown to react to the K end greater than the D end, which differed from the equal reactivity seen in the TNP system for this strain. The data are consistent with the hypothesis that the antigen recognized by the effector cell includes an altered H-2 serological cell surface product. That the reaction is not "hapten specific" and the H-2 homology is required only for effector:target cell interaction was excluded by the use of two F1 combinations in which lysis of only N-modified target cells sharing the H-2 haplotype with the stimulating parental strain was obtained. Finally, it was demonstrated that N and TNP modification create distinct new antigenic determinants, since an effector cell sensitized to one modifying agent will lyse only H-2 matched target modified with that same modifying agent.

Animals↗

PubMed2003

Effector T cells have a lower ligand affinity threshold for activation than naive T cells.

It has been previously established that effector and memory T cells are more sensitive to antigen stimulation than naive T cells. In this study, we compared the effect of ligand affinity on the activation of naive and effector T cells derived from pigeon cytochrome c (PCC)-specific TCR transgenic mice by stimulating these cells with a variety of ligands with widely differing antigenicity. The data obtained indicated the following. (i) The differences in antigen dose requirements for activation of naive and effector cells widened as the affinity of the antigen decreased. Most dramatically, peptides that were TCR antagonists for naive T cells were recognized as agonists by effector T cells. (ii) While both naive and effector T cells were activated by the bacterial superantigen staphylococcal enterotoxin A, specific for the transgenic TCR V(beta)3 chain, effector, but not naive, T cells were stimulated to proliferate by toxic shock syndrome toxin-1, a superantigen not previously described to be stimulatory for V(beta)3 T cells. (iii) Effector T cells, but not naive cells, proliferated in response to endogenous self-peptides presented by antigen-presenting cells in a syngeneic mixed lymphocyte reaction. Taken together these data indicate that effector T cells have a lower affinity threshold for activation than naive T cells. Further studies demonstrated that the heightened reactivity of effector T cells to low-affinity ligands declined progressively with repeated stimulations by antigen such that after repeated stimulation effector T cells were no longer stimulated by low-affinity ligands but recognized them as TCR antagonists similar to naive T cells.

Animals↗

PubMed2001

Generation and biochemical analysis of human effector CD4 T cells: alterations in tyrosine phosphorylation and loss of CD3zeta expression.

Human effector T cells have been difficult to isolate and characterize due to their phenotypic and functional similarity to the memory subset. In this study, a biochemical approach was used to analyze human effector CD4 T cells generated in vitro by activation with anti-CD3 and autologous monocytes for 3 to 5 days. The resultant effector cells expressed the appropriate activation/differentiation markers and secreted high levels of interferon gamma (IFN-gamma) when restimulated. Biochemically, effector CD4 T cells exhibited increases in total intracellular tyrosine phosphorylation and effector-associated phosphorylated species. Paradoxically, these alterations in tyrosine phosphorylation were concomitant with greatly reduced expression of CD3zeta and CD3epsilon signaling subunits coincident with a reduction in surface T-cell receptor (TCR) expression. Because loss of CD3zeta has also been detected in T cells isolated ex vivo from individuals with cancer, chronic viral infection, and autoimmune diseases, the requirements and kinetics of CD3zeta down-regulation were examined. The loss of CD3zeta expression persisted throughout the course of effector T-cell differentiation, was reversible on removal from the activating stimulus, and was modulated by activation conditions. These biochemical changes occurred in effector T cells generated from naive or memory CD4 T-cell precursors and distinguished effector from memory T cells. The results suggest that human effector T-cell differentiation is accompanied by alterations in the TCR signal transduction and that loss of CD3zeta expression may be a feature of chronic T-cell activation and effector generation in vivo. (Blood. 2001;97:3851-3859)

CD3 Complex↗

PubMed2004

Subversion of effector CD8+ T cell differentiation in acute hepatitis C virus infection: the role of the virus.

In a companion study, we showed a dichotomy between the expansion of central memory (CCR7(+)) hepatitis C virus (HCV)-specific CTL and the incomplete memory effector differentiation in patients with acute HCV infection. Indeed, effector cells were unable to perform immediate functions, despite expressing the tissue-homing phenotype of effector memory cells (CCR7(-); semi-effectors). However, since they promptly differentiated into full-effectors upon IL-2 contact, we suggested that the inhibitory effect by environmental (possibly viral) factors on IL-2 production may have a pivotal role in generating the large population of semi-effector CCR7(-)/IFN-gamma(-) CTL. In accord with this view, we report here strong evidence in support of circulating HCVcore protein (HCVcore) playing a central role in inhibiting effector CTL differentiation, but not memory CTL expansion. The regulatory HCVcore effect is related to inhibition of the signal transduction pathway instrumental for IL-2 production, supporting the evidence that IL-2 was capable both of pushing semi-effector CTL to complete their effector cell program and of restoring the HCVcore-dependent inhibitory effect. Therefore, the strength of CTL activation is dependent on the balance between the threshold of stimulatory signals and the viral interference capacities provided during priming.

Acute Disease↗

PubMed2001

Transfer of the Salmonella type III effector sopE between unrelated phage families.

Salmonella spp. are pathogenic enterobacteria that employ type III secretion systems to translocate effector proteins and modulate responses of host cells. The repertoire of translocated effector proteins is thought to define host specificity and epidemic virulence, and varies even between closely related Salmonella strains. Therefore, horizontal transfer of effector protein genes between Salmonella strains plays a key role in shaping the Salmonella-host interaction. Several effector protein genes are located in temperate phages. The P2-like phage SopE Phi encodes SopE and the lambda-like GIFSY phages encode several effector proteins of the YopM/IpaH-family. Lysogenic conversion with these phages is responsible for much of the diversity of the effector protein repertoires observed among Salmonella spp. However, free exchange of effector proteins by lysogenic conversion can be restricted by superinfection immunity. To identify genetic mechanisms that may further enhance horizontal transfer of effector genes, we have analyzed sopE loci from Salmonella spp. that do not harbor P2-like sequences of SopE Phi. In two novel sopE loci that were identified, the 723 nt sopE gene is located in a conserved 1.2 kb cassette present also in SopE Phi. Most strikingly, in Salmonella enterica subspecies I serovars Gallinarum, Enteritidis, Hadar and Dublin, the sopE-cassette is located in a cryptic lambda-like prophage with similarity to the GIFSY phages. This provides the first evidence for transfer of virulence genes between different phage families. We show that such a mechanism can circumvent restrictions to phage-mediated gene transfer and thereby enhances reassortment of the effector protein repertoires in Salmonella spp.

Amino Acid Sequence↗

PubMed1998

Four hydrophobic amino acid residues in the C-terminal effector domain of the yeast Mig1p repressor are important for its in vivo activity.

The Mig1 repressor is a zinc finger protein that mediates glucose repression in yeast. Previous work in Saccharomyces cerevisiae has shown that two domains in Miglp are required for repression: the N-terminal zinc finger region and a C-terminal effector domain. Both domains are also conserved in Miglp homologs from the distantly related yeasts Kluyveromyces lactis and K. marxianus, and these Mig1 proteins can fully replace the endogenous Mig1p in S. cerevisiae. We have now made a detailed analysis of the conserved C-terminal effector domain in Mig1p from K. marxianus, using expression in S. cerevisiae to monitor its function. First, a series of small deletions were made within the effector domain. Second, an alanine scan mutagenesis was carried out across the effector domain. Third, double, triple and quadruple mutants were made that affect certain residues within the effector domain. Our results show that four conserved residues within the effector domain, three leucines and one isoleucine, are particularly important for its function in vivo. The analysis further revealed that while the C-terminal effector domain of KmMig1p mediates a seven- to nine-fold repression of the reporter gene, a five- to sixfold residual effect also exists that is independent of the C-terminal effector domain. Similar results were obtained when the corresponding mutations were made in ScMig1p. Moreover, we found that mutations in these residues affect the interaction between Mig1p and the general corepressor subunit Cyc8p (Ssn6p). Modeling of the C-terminal effector domain using a protein of known structure suggests that it may be folded into an alpha-helix.

Alanine↗