Characterization of Serotype CD Mosaic Botulinum Neurotoxin in Comparison with Serotype C and A.

Botulinum neurotoxin (BoNT), produced by , cleaves proteins involved in neurotransmitter release, thereby triggering flaccid paralyses, which are responsible for botulism. BoNT is classified into seven serotypes (BoNT/A-G); BoNT/A and BoNT/B are used as medical therapeutics and anti-wrinkle reagents. In this study, we investigated the efficacy of BoNT/CD, a mosaic toxin of BoNT/C and BoNT/D, to assess its potential as a therapeutic alternative for BoNT/A.

Functional Deimmunization of Botulinum Neurotoxin Protease Domain via Computationally Driven Library Design and Ultrahigh-Throughput Screening.

Botulinum neurotoxin serotype A (BoNT/A) is a widely used cosmetic agent that also has diverse therapeutic applications; however, adverse antidrug immune responses and associated loss of efficacy have been reported in clinical uses. Here, we describe computational design and ultrahigh-throughput screening of a massive BoNT/A light-chain (BoNT/A-LC) library optimized for reduced T cell epitope content and thereby dampened immunogenicity. We developed a functional assay based on bacterial co-expression of BoNT/A-LC library members with a Förster resonance energy transfer (FRET) sensor for BoNT/A-LC enzymatic activity, and we employed high-speed fluorescence-activated cell sorting (FACS) to identify numerous computationally designed variants having wild-type-like enzyme kinetics.

Species-specific gene duplication in Clostridia produces variations of cholesterol-dependent cytolysin with different cytotoxicity.

Cholesterol-dependent cytolysin (CDC) is a bacterial toxin that binds to eukaryotic cholesterol-containing membranes, forms oligomeric complexes, and is inserted into the bilayer to create large aqueous pores. Recently, we reported a species-specific duplication of the hemolysin gene in group III Clostridium botulinum. The duplicated genes (bly1 and bly2) encoded two separate CDC proteins (botulinolysins; BLY1 and BLY2).

Complete subunit structure of serotype C and D botulinum progenitor toxin complex induces vacuolation in the specific epithelial cell line.

Clostridium botulinum produces seven botulinum neurotoxin (BoNT) serotypes. In nature, BoNT exists as a part of the progenitor toxin complex (PTC) through associations with neurotoxin associated proteins (NAPs), including nontoxic nonhemagglutinin and hemagglutinin (HA) complex, consists of HA-70, HA-17 and HA-33. Because PTC displays higher oral toxicity than pure BoNTs, NAPs play a critical role in food poisoning.

Knockin mouse models demonstrate differential contributions of synaptotagmin-1 and -2 as receptors for botulinum neurotoxins.

Botulinum neurotoxins (BoNTs) are the most potent toxins known and are also utilized to treat a wide range of disorders including muscle spasm, overactive bladder, and pain. BoNTs' ability to target neurons determines their specificity, potency, and therapeutic efficacy. Homologous synaptic vesicle membrane proteins synaptotagmin-1 (Syt1) and synaptotagmin-2 (Syt2) have been identified as receptors for BoNT family members including BoNT/B, DC, and G, but their contributions at physiologically relevant toxin concentrations in vivo have yet to be validated and established.

Delivery of single-domain antibodies into neurons using a chimeric toxin-based platform is therapeutic in mouse models of botulism.

Efficient penetration of cell membranes and specific targeting of a cell type represent major challenges for developing therapeutics toward intracellular targets. One example facing these hurdles is to develop post-exposure treatment for botulinum neurotoxins (BoNTs), a group of bacterial toxins (BoNT/A to BoNT/G) that are major potential bioterrorism agents. BoNTs enter motor neurons, block neurotransmitter release, and cause a paralytic disease botulism.

Characterization of a membrane binding loop leads to engineering botulinum neurotoxin B with improved therapeutic efficacy.

Botulinum neurotoxins (BoNTs) are a family of bacterial toxins with seven major serotypes (BoNT/A-G). The ability of these toxins to target and bind to motor nerve terminals is a key factor determining their potency and efficacy. Among these toxins, BoNT/B is one of the two types approved for medical and cosmetic uses.

Atomic force microscopic image data of botulinum neurotoxin complexes with different molecular sizes.

This data article provides atomic force microscopy (AFM) amplitude images of botulinum toxin complex (TC) molecules produced by serotype D strain. produces different-sized TC molecules, such as a complex of botulinum neurotoxin and nontoxic nonhemagglutinin proteins (M-TC) and complex of M-TC and hemagglutinin subcomplex (L-TC). In this data article, the M and L-TC produced by serotype D strain 4947 were imaged by AFM.

Sulfated glycosaminoglycans and low-density lipoprotein receptor contribute to Clostridium difficile toxin A entry into cells.

Clostridium difficile toxin A (TcdA) is a major exotoxin contributing to disruption of the colonic epithelium during C. difficile infection. TcdA contains a carbohydrate-binding combined repetitive oligopeptides (CROPs) domain that mediates its attachment to cell surfaces, but recent data suggest the existence of CROPs-independent receptors.

Genetically encoded fluorescent indicators for imaging intracellular potassium ion concentration.

Potassium ion (K) homeostasis and dynamics play critical roles in biological activities. Here we describe three genetically encoded K indicators. KIRIN1 (potassium (K) ion ratiometric indicator) and KIRIN1-GR are Förster resonance energy transfer (FRET)-based indicators with a bacterial K binding protein (Kbp) inserting between the fluorescent protein FRET pairs mCerulean3/cp173Venus and Clover/mRuby2, respectively.

Covalent Modifiers of Botulinum Neurotoxin Counteract Toxin Persistence.

Botulinum neurotoxins (BoNTs) are the most potent toxins known to man and a significant threat as weapons of bioterrorism. BoNTs contain a metalloprotease domain that blocks neurotransmitter release in nerve terminals, resulting in a descending, flaccid paralysis with a 5-10% mortality rate. Existing treatment options cannot access or neutralize the toxin following its endocytosis, so there is a clear need to develop novel therapies.

Identification of a Botulinum Neurotoxin-like Toxin in a Commensal Strain of Enterococcus faecium.

Botulinum neurotoxins (BoNTs), produced by various Clostridium strains, are a family of potent bacterial toxins and potential bioterrorism agents. Here we report that an Enterococcus faecium strain isolated from cow feces carries a BoNT-like toxin, designated BoNT/En. It cleaves both VAMP2 and SNAP-25, proteins that mediate synaptic vesicle exocytosis in neurons, at sites distinct from known BoNT cleavage sites on these two proteins.

Massively parallel de novo protein design for targeted therapeutics.

De novo protein design holds promise for creating small stable proteins with shapes customized to bind therapeutic targets. We describe a massively parallel approach for designing, manufacturing and screening mini-protein binders, integrating large-scale computational design, oligonucleotide synthesis, yeast display screening and next-generation sequencing. We designed and tested 22,660 mini-proteins of 37-43 residues that target influenza haemagglutinin and botulinum neurotoxin B, along with 6,286 control sequences to probe contributions to folding and binding, and identified 2,618 high-affinity binders.

Identification and characterization of a novel botulinum neurotoxin.

Botulinum neurotoxins are known to have seven serotypes (BoNT/A-G). Here we report a new BoNT serotype, tentatively named BoNT/X, which has the lowest sequence identity with other BoNTs and is not recognized by antisera against known BoNTs. Similar to BoNT/B/D/F/G, BoNT/X cleaves vesicle-associated membrane proteins (VAMP) 1, 2 and 3, but at a novel site (Arg66-Ala67 in VAMP2).

Reversible Association of the Hemagglutinin Subcomplex, HA-33/HA-17 Trimer, with the Botulinum Toxin Complex.

Botulinum neurotoxin (BoNT) associates with nontoxic proteins, either a nontoxic nonhemagglutinin (NTNHA) or the complex of NTNHA and hemagglutinin (HA), to form M- or L-toxin complexes (TCs). Single BoNT and NTNHA molecules are associated and form M-TC. A trimer of the 70-kDa HA protein (HA-70) attaches to the M-TC to form M-TC/HA-70.

"Non-Toxic" Proteins of the Botulinum Toxin Complex Exert In-vivo Toxicity.

The botulinum neurotoxin (BoNT) causes muscle paralysis and is the most potent toxin in nature. BoNT is associated with a complex of auxiliary "Non-Toxic" proteins, which constitute a large-sized toxin complex (L-TC). However, here we report that the "Non-Toxic" complex of serotype D botulinum L-TC, when administered to rats, exerts in-vivo toxicity on small-intestinal villi.

Hemagglutinin gene shuffling among Clostridium botulinum serotypes C and D yields distinct sugar recognition of the botulinum toxin complex.

Clostridium botulinum strains produce a large-sized toxin complex (TC) that is composed of botulinum neurotoxin (BoNT), non-toxic non-hemagglutinin and three different hemagglutinins (HA-70, HA-33 and HA-17). HA components enhance toxin delivery across the intestinal cell wall in a sugar chain-dependent manner. Here we characterized the sugar recognition of serotype D strain 1873 (D-1873) botulinum L-TC.

Host-cell specificity and transcytosis of nontoxic nonhemagglutinin protein of botulinum neurotoxin serotype D.

Serotype D botulinum toxin (BoNT) complex (TC), a causative agent of foodborne botulism in animals, traverses the gastrointestinal tract and circulation, eventually becoming localized in neuromuscular junctions, where the serotype D BoNT cleaves SNARE substrate synaptobrevin II involved in neurotransmitter release. During this process, BoNT must pass through cells, thus from the intestinal lumen to the cells of the intestinal tract and blood vessels. The botulinum TC is formed by association of the BoNT with at least one nontoxic protein, which may be a nontoxic nonhemagglutinin (NTNHA).

Crystallization and preliminary X-ray analysis of a novel haemagglutinin component of the toxin complex of serotype C Clostridium botulinum.

The botulinum toxin complex, the causative agent of botulism, passes through the intestinal wall via sugar-chain-dependent cell binding of a haemagglutinin of 33 kDa molecular weight (HA-33). The amino-acid sequence of the C-terminal half of HA-33 of the serotype C strain Yoichi (C-Yoichi) shares only 46% identity with those of the major serotype C strains. Additionally, C-Yoichi HA-33 exhibits a unique sugar-binding specificity.

Identification of the interaction region between hemagglutinin components of the botulinum toxin complex.

The large toxin complex (L-TC) produced by Clostridium botulinum is formed from the M-TC (BoNT/NTNHA complex) by conjugation of M-TC with HA-33/HA-17 trimer consists of two HA-33 proteins and a single HA-17 protein. This association is mediated by HA-70, which interacts with HA-17. The current study aims to identify the regions of the HA-70 molecule that adhere to the HA-33/HA-17 complex.

Sugar-induced conformational change found in the HA-33/HA-17 trimer of the botulinum toxin complex.

Large-sized botulinum toxin complex (L-TC) is formed by conjugation of neurotoxin, nontoxic nonhemagglutinin and hemagglutinin (HA) complex. The HA complex is formed by association of three HA-70 molecules and three HA-33/HA-17 trimers, comprised of a single HA-17 and two HA-33 proteins. The HA-33/HA-17 trimer isolated from serotype D L-TC has the ability to bind to and penetrate through the intestinal epithelial cell monolayer in a sialic acid-dependent manner, and thus it plays an important role in toxin delivery through the intestinal cell wall.

Botulinum toxin complex increases paracellular permeability in intestinal epithelial cells via activation of p38 mitogen-activated protein kinase.

Clostridium botulinum produces a large toxin complex (L-TC) that increases paracellular permeability in intestinal epithelial cells by a mechanism that remains unclear. Here, we show that mitogen-activated protein kinases (MAPKs) are involved in this permeability increase. Paracellular permeability was measured by FITC-dextran flux through a monolayer of rat intestinal epithelial IEC-6 cells, and MAPK activation was estimated from western blots.

Transport of the botulinum neurotoxin-associating protein, nontoxic nonhemagglutinin, across the rat small intestinal epithelial cell monolayer.

Botulinum neurotoxin (BoNT) associates with nontoxic nonhemagglutinin (NTNHA) yielding a complex in culture. BoNT and NTNHA have similar domain organizations, implying that they share common functions, although this remains unclear. Here, we examined cell monolayer transport of serotype D NTNHA in the rat intestinal epithelial cell line IEC-6.

Random phage display-based screening of peptides that bind to botulinum neurotoxin binding protein, nontoxic nonhemagglutinin.

Botulinum neurotoxin (BoNT) binds to nontoxic nonhemagglutinin (NTNHA) protein in a pH-dependent manner, and yields the protease-resistant BoNT/NTNHA complex. Here, we screened short peptides that bind to the serotype D NTNHA (NTNHA-D) using random phage display technique. NTNHA was fixed onto electrode of quartz crystal microbalance (QCM) apparatus, and then the phages displaying random heptapeptides were exposed to the NTNHA-D under the acidic condition.

Small-angle X-ray scattering reveals structural dynamics of the botulinum neurotoxin associating protein, nontoxic nonhemagglutinin.

In cell culture supernatants, the botulinum neurotoxin (BoNT) exists as part of a toxin complex (TC) in which nontoxic nonhemagglutinin (NTNHA) and/or hemagglutinins (HAs) are assembled onto the BoNT. A series of investigations indicated that formation of the TC is vital for delivery of the toxin to nerve cells through the digestive tract. In the assembly process, BoNT binds to NTNHA yielding M-TC, and it then matures into L-TC by further association with the HAs via NTNHA in the M-TC.