The Experts below are selected from a list of 132 Experts worldwide ranked by ideXlab platform
Jorge E. Galán - One of the best experts on this subject based on the ideXlab platform.
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Structure and function of the Salmonella Typhi chimaeric A_2B_5 typhoid Toxin
Nature, 2013Co-Authors: Jeongmin Song, Jorge E. GalánAbstract:The biological basis for the pathogenic properties of Salmonella enterica serovar Typhi ( S . Typhi) is largely unknown. S . Typhi causes life-threatening systemic infections known as typhoid fever, whereas most other Salmonella enterica serotypes are either harmless or associated with less-serious gastric infections or food poisoning. This study shows that administration of typhoid Toxin, a novel AB Toxin composed of two A subunits unique to S . Typhi, reproduces many of the acute symptoms of typhoid fever. The authors go on to identify carbohydrates on cell-surface glycoproteins as receptors for typhoid Toxin and determine the Toxin's crystal structure, providing insights into these interactions. Theses advances suggest that antiToxin-based therapeutics may be effective in treating typhoid. Unlike most salmonellae, Salmonella enterica serovar Typhi causes life-threatening systemic infections known as typhoid fever, for which the molecular basis is unknown; here administration of typhoid Toxin produced by S. Typhi reproduces many of the acute symptoms of typhoid fever, carbohydrates on cell surface glycoproteins are identified as receptors for typhoid Toxin and the Toxin’s crystal structure is determined, providing insights into these interactions. Salmonella enterica serovar Typhi ( S. Typhi) differs from most other salmonellae in that it causes a life-threatening systemic infection known as typhoid fever^ 1 . The molecular bases for its unique clinical presentation are unknown^ 2 . Here we find that the systemic administration of typhoid Toxin, a unique virulence factor of S. Typhi, reproduces many of the acute symptoms of typhoid fever in an animal model. We identify specific carbohydrate moieties on specific surface glycoproteins that serve as receptors for typhoid Toxin, which explains its broad cell target specificity. We present the atomic structure of typhoid Toxin, which shows an unprecedented A_2B_5 organization with two covalently linked A subunits non-covalently associated to a pentameric B subunit. The structure provides insight into the Toxin’s receptor-binding specificity and delivery mechanisms and reveals how the activities of two powerful Toxins have been co-opted into a single, unique Toxin that can induce many of the symptoms characteristic of typhoid fever. These findings may lead to the development of potentially life-saving therapeutics against typhoid fever.
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Cytolethal distending Toxin: limited damage as a strategy to modulate cellular functions
Trends in Microbiology, 2002Co-Authors: Maria Lara-tejero, Jorge E. GalánAbstract:ABstract The coevolution of bacterial pathogens and their hosts has contributed to the development of very complex and sophisticated functional pathogen–host interfaces. Thus, well-adapted pathogens have evolved a variety of strategies to manipulate host cell functions precisely. For example, a group of unrelated Gram-negative pathogenic bacteria have evolved a Toxin, known as cytolethal distending Toxin (CDT), that has the ABility to control cell cycle progression in eukaryotic cells. Recent studies have identified CdtB as the active subunit of the CDT holoToxin. Through its nuclease activity, CdtB causes limited DNA damage, thereby triggering the DNA-damage response that ultimately results in the observed arrest of the cell cycle. In addition, it has been estABlished that CDT is a tripartite AB Toxin in which CdtB is the active ‘A' subunit and CdtA and CdtC constitute the heterodimeric ‘B' subunit required for the delivery of CdtB into the target cell. The mechanism of action of CDT suggests that the infliction of limited damage could be a strategy used by pathogenic bacteria to modulate host cell functions.
Hiroshi Otani - One of the best experts on this subject based on the ideXlab platform.
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host specific AB Toxin production by germinating spores of alternaria brassicicola is induced by a host derived oligosaccharide
Physiological and Molecular Plant Pathology, 2005Co-Authors: Hajime Akamatsu, Motoichiro Kodama, Hiromitsu Nakajima, Toshinari Kawada, Hiroshi OtaniAbstract:ABstract The phytopathogenic fungus Alternaria brassicicola is the causal agent of black spot disease of Brassica plants and produces a host-specific protein Toxin named AB-Toxin. AB-Toxin is released from spores germinating only on host leaves. In this study, we found a factor for inducing AB-Toxin production that is released from host leaves after spore germination has begun. GC and GC–MS analyses of the compound purified by gel filtration chromatography demonstrated that it is an oligosaccharide of 1.3 kDa. This is the first evidence that host-specific Toxin production by germinating spores of a fungal pathogen is induced by recognition of host-derived factors.
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Specific inhibition of spore germination of Alternaria brassicicola by fistupyrone from Streptomyces sp. TP-A0569
Journal of General Plant Pathology, 2003Co-Authors: Evelyn Aigho Aremu, Hajime Akamatsu, Motoichiro Kodama, Tamotsu Furumai, Yasuhiro Igarashi, Yukio Sato, Hiroshi OtaniAbstract:Fistupyrone (FP), a metABolite from Streptomyces sp. TP-A0569, inhibited the in vivo infection of Chinese cABbage seedlings by Alternaria brassicicola. To detect the possible action sites of FP, the effect of FP on the infection behavior of A. brassicicola and A. alternata was investigated. When spores of A. brassicicola were suspended in FP solution and inoculated on host leaves, FP at 0.1 ppm significantly inhibited spore germination, appressorial formation, and infection hypha formation of A. brassicicola . Host-specific AB-Toxin production and lesion formation by A. brassicicola spores were also reduced significantly by treatment with FP 1 ppm. The effect of FP seemed to be irreversible because significant washing of FP-treated spores with distilled water (DW) did not change the inhibitory effects. In contrast, A. alternata isolates such as Japanese pear pathotype, apple pathotype, and saprophyte behaved almost equally in both FP- and DW-treated spores. Mycelial dry weight in potato dextrose broth and mycelial diameters on potato dextrose agar, gelatin glucose agar, and Czapek solution agar of both A. brassicicola and A. alternata were not different with or without addition of FP. These results indicate that FP at low concentrations has a fungicidal effect on spores of A. brassicicola but not on spores of A. alternata ; FP also does not affect the vegetative phase of these fungi.
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Production of a host-specific Toxin by germinating spores ofAlternaria brassicicola☆
Physiological and Molecular Plant Pathology, 1998Co-Authors: Hiroshi Otani, Motoichiro Kodama, A. Kohnobe, Keisuke KohmotoAbstract:ABstract Spore suspensions ofAlternaria brassicicolapathogenic toBrassicaspp. were incubated on the surface ofBrassicaleaves. The spore germination fluid was collected and examined for biological activity. In a detached leaf assay, the fluid induced water-soaking symptoms followed by brown necrotic lesions onBrassicaleaves susceptible to the pathogen but did not cause visible symptoms on non-host leaves. When spores of the non-pathogenic speciesAlternaria alternatawere combined with the fluid and inoculated on the leaves, the spores could invadeBrassicaleaves, just as the pathogen did. These results indicate thatA. brassicicolaproduces a host-specific Toxin(s) and releases it during spore germination on the leaves. Toxin activity of the fluid was retained by an ultrafiltration membrane with a 5 kDa cut off. The Toxin was purified by ion exchange chromatography and gel filtration HPLC. The molecular weight of the Toxin was estimated to be 35 kDa by SDS-polyacrylamide gel electrophoresis. The activity of the Toxin was heat lABile and was also lost after treatment with proteinase K. Thus, the Toxin named AB-Toxin is probABly a protein, the first described among the many host-specific Toxins produced byAlternariaspecies.
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Involvement of Host Factors in the Production of a Protein Host-Specific Toxin Produced by Alternaria Brassicicola
Molecular Genetics of Host-Specific Toxins in Plant Disease, 1998Co-Authors: Hiroshi Otani, Motoichiro Kodama, A. Kohnobe, Keisuke KohmotoAbstract:Alternaria brassicicola, the cause of black leaf spot of Brassica spp., produces a host-specific Toxin named AB-Toxin during spore germination at the infection site on host plants. Unlike other Alternaria host-specific Toxins which are low-molecular-weight secondary metABolites, AB-Toxin is a protein and estimated to be 35 kDa by SDS-polyacrylamide gel electrophoresis. AB-Toxin was not detected in the culture filtrates of the pathogen. When the spores (5×105 – 106 spores/ml) suspended in water were dropped on host leaves, non-host leaves and plastic plates, the spores germinated only on host leaves and released AB-Toxin in the spore germination fluid. Spores suspended in Czapek-Dox and PDB solutions germinated on plastic plates, but only trace of AB-Toxin was detected. These results indicate that AB-Toxin production by A. brassicicola is induced by host-related factors during early stages of host-parasite interactions.
Jeongmin Song - One of the best experts on this subject based on the ideXlab platform.
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Structure and function of the Salmonella Typhi chimaeric A_2B_5 typhoid Toxin
Nature, 2013Co-Authors: Jeongmin Song, Jorge E. GalánAbstract:The biological basis for the pathogenic properties of Salmonella enterica serovar Typhi ( S . Typhi) is largely unknown. S . Typhi causes life-threatening systemic infections known as typhoid fever, whereas most other Salmonella enterica serotypes are either harmless or associated with less-serious gastric infections or food poisoning. This study shows that administration of typhoid Toxin, a novel AB Toxin composed of two A subunits unique to S . Typhi, reproduces many of the acute symptoms of typhoid fever. The authors go on to identify carbohydrates on cell-surface glycoproteins as receptors for typhoid Toxin and determine the Toxin's crystal structure, providing insights into these interactions. Theses advances suggest that antiToxin-based therapeutics may be effective in treating typhoid. Unlike most salmonellae, Salmonella enterica serovar Typhi causes life-threatening systemic infections known as typhoid fever, for which the molecular basis is unknown; here administration of typhoid Toxin produced by S. Typhi reproduces many of the acute symptoms of typhoid fever, carbohydrates on cell surface glycoproteins are identified as receptors for typhoid Toxin and the Toxin’s crystal structure is determined, providing insights into these interactions. Salmonella enterica serovar Typhi ( S. Typhi) differs from most other salmonellae in that it causes a life-threatening systemic infection known as typhoid fever^ 1 . The molecular bases for its unique clinical presentation are unknown^ 2 . Here we find that the systemic administration of typhoid Toxin, a unique virulence factor of S. Typhi, reproduces many of the acute symptoms of typhoid fever in an animal model. We identify specific carbohydrate moieties on specific surface glycoproteins that serve as receptors for typhoid Toxin, which explains its broad cell target specificity. We present the atomic structure of typhoid Toxin, which shows an unprecedented A_2B_5 organization with two covalently linked A subunits non-covalently associated to a pentameric B subunit. The structure provides insight into the Toxin’s receptor-binding specificity and delivery mechanisms and reveals how the activities of two powerful Toxins have been co-opted into a single, unique Toxin that can induce many of the symptoms characteristic of typhoid fever. These findings may lead to the development of potentially life-saving therapeutics against typhoid fever.
Nuno M.s. Dos Santos - One of the best experts on this subject based on the ideXlab platform.
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Role of AIP56 disulphide bond and its reduction by cytosolic redox systems for efficient intoxication
Cellular Microbiology, 2019Co-Authors: Cassilda Pereira, Nuno M.s. Dos Santos, Inês S. Rodrigues, Liliana M. G. Pereira, Johnny Lisboa, Rute D. Pinto, Leonor Araújo, Pedro Oliveira, Roland Benz, Ana Do ValeAbstract:Apoptosis-inducing protein of 56 kDa (AIP56) is a major virulence factor of Photobacterium damselae subsp. piscicida, a gram-negative pathogen that infects warm water fish species worldwide and causes serious economic losses in aquacultures. AIP56 is a single-chain AB Toxin composed by two domains connected by an unstructured linker peptide flanked by two cysteine residues that form a disulphide bond. The A domain comprises a zinc-metalloprotease moiety that cleaves the NF-kB p65, and the B domain is involved in binding and internalisation of the Toxin into susceptible cells. Previous experiments suggested that disruption of AIP56 disulphide bond partially compromised toxicity, but conclusive evidences supporting the importance of that bond in intoxication were lacking. Here, we show that although the disulphide bond of AIP56 is dispensABle for receptor recognition, endocytosis, and membrane interaction, it needs to be intact for efficient translocation of the Toxin into the cytosol. We also show that the host cell thioredoxin reductase-thioredoxin system is involved in AIP56 intoxication by reducing the disulphide bond of the Toxin at the cytosol. The present study contributes to a better understanding of the molecular mechanisms operating during AIP56 intoxication and reveals common features shared with other AB Toxins.
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The Apoptogenic Toxin AIP56 Is Secreted by the Type II Secretion System of Photobacterium damselae subsp. piscicida
Toxins, 2017Co-Authors: Ana Do Vale, Cassilda Pereira, Carlos R. Osorio, Nuno M.s. Dos SantosAbstract:AIP56 (apoptosis-inducing protein of 56 kDa) is a key virulence factor of Photobacterium damselae subsp. piscicida (Phdp), the causative agent of a septicaemia affecting warm water marine fish species. Phdp-associated pathology is triggered by AIP56, a short trip AB Toxin with a metalloprotease A domain that cleaves the p65 subunit of NF-κB, an evolutionarily conserved transcription factor that regulates the expression of inflammatory and anti-apoptotic genes and plays a central role in host responses to infection. During infection by Phdp, AIP56 is systemically disseminated and induces apoptosis of macrophages and neutrophils, compromising the host phagocytic defence and contributing to the genesis of pathology. Although it is well estABlished that the secretion of AIP56 is crucial for Phdp pathogenicity, the protein secretion systems operating in Phdp and the mechanism responsible for the extracellular release of the Toxin remain unknown. Here, we report that Phdp encodes a type II secretion system (T2SS) and show that mutation of the EpsL component of this system impairs AIP56 secretion. This work demonstrates that Phdp has a functional T2SS that mediates secretion of its key virulence factor AIP56.
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Intracellular trafficking of AIP56, an NF-κB-cleaving Toxin from Photobacterium damselae subsp. piscicida.
Infection and Immunity, 2014Co-Authors: Liliana M. G. Pereira, Rute D. Pinto, Pedro Oliveira, Roland Benz, Daniela S Medeiros Da Silva, Ana R. Moreira, Christoph Beitzinger, Paula Sampaio, Jorge E. Azevedo, Nuno M.s. Dos SantosAbstract:ABSTRACT AIP56 (apoptosis-inducing protein of 56 kDa) is a metalloprotease AB Toxin secreted by Photobacterium damselae subsp. piscicida that acts by cleaving NF-κB. During infection, AIP56 spreads systemically and depletes phagocytes by postapoptotic secondary necrosis, impairing the host phagocytic defense and contributing to the genesis of infection-associated necrotic lesions. Here we show that mouse bone marrow-derived macrophages (mBMDM) intoxicated by AIP56 undergo NF-κB p65 depletion and apoptosis. Similarly to what was reported for sea bass phagocytes, intoxication of mBMDM involves interaction of AIP56 C-terminal region with cell surface components, suggesting the existence of a conserved receptor. Biochemical approaches and confocal microscopy revealed that AIP56 undergoes clathrin-dependent endocytosis, reaches early endosomes, and follows the recycling pathway. Translocation of AIP56 into the cytosol requires endosome acidification, and an acidic pulse triggers translocation of cell surface-bound AIP56 into the cytosol. Accordingly, at acidic pH, AIP56 becomes more hydrophobic, interacting with artificial lipid bilayer membranes. Altogether, these data indicate that AIP56 is a short-trip Toxin that reaches the cytosol using an acidic-pH-dependent mechanism, probABly from early endosomes. Usually, for short-trip AB Toxins, a minor pool reaches the cytosol by translocating from endosomes, whereas the rest is routed to lysosomes for degradation. Here we demonstrate that part of endocytosed AIP56 is recycled back and released extracellularly through a mechanism requiring phosphoinositide 3-kinase (PI3K) activity but independent of endosome acidification. So far, we have been unABle to detect biological activity of recycled AIP56, thereby bringing into question its biological relevance as well as the importance of the recycling pathway.
Keisuke Kohmoto - One of the best experts on this subject based on the ideXlab platform.
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Production of a host-specific Toxin by germinating spores ofAlternaria brassicicola☆
Physiological and Molecular Plant Pathology, 1998Co-Authors: Hiroshi Otani, Motoichiro Kodama, A. Kohnobe, Keisuke KohmotoAbstract:ABstract Spore suspensions ofAlternaria brassicicolapathogenic toBrassicaspp. were incubated on the surface ofBrassicaleaves. The spore germination fluid was collected and examined for biological activity. In a detached leaf assay, the fluid induced water-soaking symptoms followed by brown necrotic lesions onBrassicaleaves susceptible to the pathogen but did not cause visible symptoms on non-host leaves. When spores of the non-pathogenic speciesAlternaria alternatawere combined with the fluid and inoculated on the leaves, the spores could invadeBrassicaleaves, just as the pathogen did. These results indicate thatA. brassicicolaproduces a host-specific Toxin(s) and releases it during spore germination on the leaves. Toxin activity of the fluid was retained by an ultrafiltration membrane with a 5 kDa cut off. The Toxin was purified by ion exchange chromatography and gel filtration HPLC. The molecular weight of the Toxin was estimated to be 35 kDa by SDS-polyacrylamide gel electrophoresis. The activity of the Toxin was heat lABile and was also lost after treatment with proteinase K. Thus, the Toxin named AB-Toxin is probABly a protein, the first described among the many host-specific Toxins produced byAlternariaspecies.
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Involvement of Host Factors in the Production of a Protein Host-Specific Toxin Produced by Alternaria Brassicicola
Molecular Genetics of Host-Specific Toxins in Plant Disease, 1998Co-Authors: Hiroshi Otani, Motoichiro Kodama, A. Kohnobe, Keisuke KohmotoAbstract:Alternaria brassicicola, the cause of black leaf spot of Brassica spp., produces a host-specific Toxin named AB-Toxin during spore germination at the infection site on host plants. Unlike other Alternaria host-specific Toxins which are low-molecular-weight secondary metABolites, AB-Toxin is a protein and estimated to be 35 kDa by SDS-polyacrylamide gel electrophoresis. AB-Toxin was not detected in the culture filtrates of the pathogen. When the spores (5×105 – 106 spores/ml) suspended in water were dropped on host leaves, non-host leaves and plastic plates, the spores germinated only on host leaves and released AB-Toxin in the spore germination fluid. Spores suspended in Czapek-Dox and PDB solutions germinated on plastic plates, but only trace of AB-Toxin was detected. These results indicate that AB-Toxin production by A. brassicicola is induced by host-related factors during early stages of host-parasite interactions.
