Search results for "toxin"
showing 10 items of 1434 documents
Interferons increase cell resistance to Staphylococcal alpha-toxin.
2007
ABSTRACTMany bacterial pathogens, includingStaphylococcus aureus, use a variety of pore-forming toxins as important virulence factors. Staphylococcal alpha-toxin, a prototype β-barrel pore-forming toxin, triggers the release of proinflammatory mediators and induces primarily necrotic death in susceptible cells. However, whether host factors released in response to staphylococcal infections may increase cell resistance to alpha-toxin is not known. Here we show that prior exposure to interferons (IFNs) prevents alpha-toxin-induced membrane permeabilization, the depletion of ATP, and cell death. Moreover, pretreatment with IFN-α decreases alpha-toxin-induced secretion of interleukin 1β (IL-1β)…
Coffee Silverskin and Spent Coffee Suitable as Neuroprotectors against Cell Death by Beauvericin and α-Zearalenol: Evaluating Strategies of Treatment
2021
Coffee silverskin and spent coffee have been evaluated in a neuroblastoma cell line (SH-SY5Y cells) against beauvericin (BEA) and α-zearalenol (α-ZEL)-induced cytotoxicity with different strategies of treatment. First, the direct treatment of mycotoxins and coffee by-products extracts in SH-SY5Y cells was assayed. IC50 values for α-ZEL were 20.8 and 14.0 µM for 48 h and 72 h, respectively and, for BEA only at 72 h, it was 2.5 µM. Afterwards, the pre-treatment with spent coffee obtained by boiling water increased cell viability for α-ZEL at 24 h and 48 h from 10% to 16% and from 25% to 30%, respectively
Botulinum A and the light chain of tetanus toxins inhibit distinct stages of Mg.ATP-dependent catecholamine exocytosis from permeabilised chromaffin …
1994
Susceptibilities of Mg.ATP-independent and Mg.ATP-requiring components of catecholamine secretion from digitonin-permeabilised chromaffin cells to inhibition by Clostridial botulinum type A and tetanus toxins were investigated. These toxins are Zn(2+)-dependent proteases which specifically cleave the 25-kDa synaptosomal-associated protein (SNAP-25) and vesicle-associated membrane protein (VAMP) II, respectively. When applied to permeabilised chromaffin cells they rapidly inhibited secretion in the presence of Mg.ATP but the catecholamine released in the absence of Mg.ATP, thought to represent fusion of primed granules, was not perturbed. The toxins can exert their effects per se in the abse…
Processing of tetanus and botulinum A neurotoxins in isolated chromaffin cells.
1995
Tetanus and botulinum A neurotoxins were introduced into the cytosol of chromaffin cells by means of an electric field in which the plasma membrane is forced to form pores of approximately 1 micron at the sites facing the electrodes. As demonstrated by electron microscopy, both [125I] and gold-labelled tetanus toxin (TeTx) diffuse through these transient openings. Dichain-TeTx, with its light chain linked to the heavy chain by means of a disulfide bond, causes the block of exocytosis to develop more slowly than does the purified light chain. The disulfide bonds, which in both toxins hold the subunits together, were cleaved by the intrinsic thioredoxin-reductase system. Single chain TeTx, in…
Role of toxin activation on binding and pore formation activity of the Bacillus thuringiensis Cry3 toxins in membranes of Leptinotarsa decemlineata (…
2004
AbstractBinding and pore formation constitute key steps in the mode of action of Bacillus thuringiensis δ-endotoxins.In this work, we present a comparative analysis of toxin-binding capacities of proteolytically processed Cry3A, Cry3B and Cry3C toxins to brush border membranes (BBMV) of the Colorado potato beetle Leptinotarsa decemlineata (CPB), a major potato coleopteran-insect pest. Competition experiments showed that the three Cry3 proteolytically activated toxins share a common binding site. Also heterologous competition experiments showed that Cry3Aa and Cry3Ca toxins have an extra binding site that is not shared with Cry3Ba toxin. The pore formation activity of the three different Cry…
A membrane associated metalloprotease cleaves Cry3Aa Bacillus thuringiensis toxin reducing pore formation in Colorado potato beetle brush border memb…
2007
AbstractInsect proteases are implicated in Bacillus thuringiensis insecticidal proteins mode of action determining toxin specificity and sensitivity. Few data are available on the involvement of proteases in the later steps of toxicity such as protease interaction with toxin–receptor complexes and the pore formation process. In this study, a Colorado potato beetle (CPB) midgut membrane metalloprotease was found to be involved in the proteolytic processing of Cry3Aa. Interaction of Cry3Aa with BBMV membrane proteases resulted in a distinct pattern of proteolysis. Cleavage was demonstrated to occur in protease accessible regions of domain III and was specifically inhibited by the metalloprote…
A cellular metalloproteinase activates Vibrio cholerae pro-cytolysin.
2004
Many strains of Vibrio cholerae produce a cytolysin (VCC) that forms oligomeric transmembrane pores in animal cells. The molecule is secreted as a procytolysin (pro-VCC) of 79 kDa that must be cleaved at the N terminus to generate the active 65-kDa toxin. Processing can occur in solution, and previous studies have described the action of mature VCC thus generated. However, little is known about the properties of pro-VCC itself. In this study, it is shown that pro-VCC exist as a monomer in solution and binds as a monomer to eukaryotic cells. Bound pro-VCC can then be activated either by exogenous, extracellular, or by endogenous, cell-bound proteases. In both cases, cleavage generates the 65…
Functional significance of membrane associated proteolysis in the toxicity of Bacillus thuringiensis Cry3Aa toxin against Colorado potato beetle.
2012
Abstract Bacillus thuringiensis Cry toxins are widely used as biocontrol agents in bioinsecticides and transgenic plants. In the three domain-Cry toxins, domain II has been identified as an important determinant of their highly specific activity against insects. In this work, we assessed the role in membrane associated proteolysis and toxicity in Colorado potato beetle (CPB) of a previously reported ADAM recognition motif present in Cry3Aa toxin domain II. We used site-directed mutagenesis to modify the Bacillus thuringiensis cry3A gene in amino acid residues 344, 346, 347, 351 and 353 of the ADAM recognition motif in Cry3Aa toxin. Cry3Aa toxin mutants displayed decreased toxicity when comp…
Prohibitin, an essential protein for Colorado potato beetle larval viability, is relevant to Bacillus thuringiensis Cry3Aa toxicity
2013
Bacillus thuringienesis (Bt) Cry toxins constitute the most extensively used environmentally safe biopesticide and their mode of action relies on the interaction of the toxins with membrane proteins in the midgut of susceptible insects that mediate toxicity and insect specificity. Therefore, identification of Bt Cry toxin interacting proteins in the midgut of target insects and understanding their role in toxicity is of great interest to exploit their insecticidal action. Using ligand blot, we demonstrated that Bt Cry3Aa toxin bound to a 30kDa protein in Colorado potato beetle (CPB) larval midgut membrane, identified by sequence homology as prohibitin-1 protein. Prohibitins comprise a highl…
Investigation of the steps involved in the difference of susceptibility of Ephestia kuehniella and Spodoptera littoralis to the Bacillus thuringiensi…
2011
BUPM95 is a Bacillus thuringiensis subsp. kurstaki strain producing the Vip3Aa16 toxin with an interesting insecticidal activity against the Lepidopteran larvae Ephestia kuehniella. Study of different steps in the mode of action of this Vegetative Insecticidal Protein on the Mediterranean flour moth (E. kuehniella) was carried out in the aim to investigate the origin of the higher susceptibility of this insect to Vip3Aa16 toxin compared to that of the Egyptian cotton leaf worm Spodoptera littoralis. Using E. kuehniella gut juice, protoxin proteolysis generated a major band corresponding to the active toxin and another band of about 22kDa, whereas the activation of Vip3Aa16 by S. littoralis …