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Engineering botulinum neurotoxin to extend therapeutic intervention.

ABSTRACT: Clostridium botulinum neurotoxins (BoNTs) are effective therapeutics for a variety of neurological disorders, such as strabismus, blepharospam, hemificial spasm, and cervical dystonia, because of the toxin's tropism for neurons and specific cleavage of neuronal soluble N-ethylmaleimide-sensitive fusion protein-attachment protein receptors (SNARE) proteins. Modifying BoNT to bind nonneuronal cells has been attempted to extend therapeutic applications. However, prerequisite to develop nonneuronal therapies requires the retargeting the catalytic activity of BoNTs to nonneuronal SNARE isoforms. Here, we reported the engineering of a BoNT derivative that cleaves SNAP23, a nonneuronal SNARE protein. SNAP23 mediates vesicle-plasma membrane fusion processes, including secretion of airway mucus, antibody, insulin, gastric acids, and ions. This mutated BoNT/E light chain LC/E(K(224)D) showed extended substrate specificity to cleave SNAP23, and the natural substrate, SNAP25, but not SNAP29 or SNAP47. Upon direct protein delivery into cultured human epithelial cells, LC/E(K(224)D) cleaved endogenous SNAP23, which inhibited secretion of mucin and IL-8. These studies show the feasibility of genetically modifying LCs to target a nonneuronal SNARE protein that extends therapeutic potential for treatment of human hypersecretion diseases.

SUBMITTER: Chen S

PROVIDER: S-EPMC2695098 | biostudies-literature | 2009 Jun

REPOSITORIES: biostudies-literature

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Engineering botulinum neurotoxin to extend therapeutic intervention.

Chen Sheng S Barbieri Joseph T JT

Proceedings of the National Academy of Sciences of the United States of America 20090601 23

Clostridium botulinum neurotoxins (BoNTs) are effective therapeutics for a variety of neurological disorders, such as strabismus, blepharospam, hemificial spasm, and cervical dystonia, because of the toxin's tropism for neurons and specific cleavage of neuronal soluble N-ethylmaleimide-sensitive fusion protein-attachment protein receptors (SNARE) proteins. Modifying BoNT to bind nonneuronal cells has been attempted to extend therapeutic applications. However, prerequisite to develop nonneuronal ...[more]

PMID: 19487672

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Project description: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. Besides binding to well-established receptors, an extended loop in the C-terminal receptor-binding domain (HC) of BoNT/B (HC/B) has been proposed to also contribute to toxin binding to neurons by interacting with lipid membranes (termed lipid-binding loop [LBL]). Analogous loops exist in the HCs of BoNT/C, D, G, and a chimeric toxin DC. However, it has been challenging to detect and characterize binding of LBLs to lipid membranes. Here, using the nanodisc system and biolayer interferometry assays, we find that HC/DC, C, and G, but not HC/B and HC/D, are capable of binding to receptor-free lipids directly, with HC/DC having the highest level of binding. Mutagenesis studies demonstrate the critical role of consecutive aromatic residues at the tip of the LBL for binding of HC/DC to lipid membranes. Taking advantage of this insight, we then create a "gain-of-function" mutant HC/B by replacing two nonaromatic residues at the tip of its LBL with tryptophan. Cocrystallization studies confirm that these two tryptophan residues do not alter the structure of HC/B or the interactions with its receptors. Such a mutated HC/B gains the ability to bind receptor-free lipid membranes and shows enhanced binding to cultured neurons. Finally, full-length BoNT/B containing two tryptophan mutations in its LBL, together with two additional mutations (E1191M/S1199Y) that increase binding to human receptors, is produced and evaluated in mice in vivo using Digit Abduction Score assays. This mutant toxin shows enhanced efficacy in paralyzing local muscles at the injection site and lower systemic diffusion, thus extending both safety range and duration of paralysis compared with the control BoNT/B. These findings establish a mechanistic understanding of LBL-lipid interactions and create a modified BoNT/B with improved therapeutic efficacy.

Project description:Background: Botulinum toxin-A (BoNT-A) injections are first-line treatment for adult spasticity. Prior patient surveys have reported that BoNT-A treatment improves quality of life but that symptoms usually recur before the next injection. We aimed to explore, in-depth, patient perceptions of the impact of spasticity and the waning of BoNT-A therapeutic effects. Methods: An internet-based survey was conducted through Carenity, an online patient community, from May to September 2019 in France, Germany, Italy, UK and USA. Eligible respondents were adult patients with spasticity due to stroke, traumatic brain injury (TBI) or spinal cord injury (SCI) who had ?2 previous BoNT-A injections. Results: Two hundred and ten respondents (mean 47.2 years) met screening criteria and had their responses analyzed. Overall, 43% of respondents had spasticity due to stroke, 30% due to TBI and 27% due to SCI. The mean [95% CI] injection frequency for spasticity management was 3.6 [3.4-3.7] injections/year. Respondents described the time profile of their response to BoNT-A. The mean reported onset of therapeutic effect was 12.9 [12.1-13.7] days and the mean time to peak effect was 5.0 [4.7-5.4] weeks. Symptom re-emergence between injections was common (83%); the time from injection to symptom re-emergence was 89.4 [86.3-92.4] days. Muscle spasms usually re-emerge first (64%), followed by muscle stiffness or rigidity (40%), and limb pain (20%). Over half (52%) of respondents said they had lost their self-confidence, 46% experienced depression and 41% experienced a lack of sleep due to their spasticity symptoms in the past 12 months. Following a report of symptom re-emergence, the most common management approaches were to add adjunctive treatments (36%), increase the BoNT-A dose (28%), and wait for the next injection (26%). Seventy two percentage of respondents said they would like a longer lasting BoNT-A treatment. Conclusions: Patients with spasticity can expect a characteristic profile of BoNT-A effects, namely time lag to onset and peak effect followed by a gradual decline in the symptomatic benefits. Symptom re-emergence is common and has significant impact on quality of life. Greater patient/clinician awareness of this therapeutic profile should lead to better level of overall satisfaction with treatment, informed therapeutic discussions and treatment schedule planning.

Dataset Information

Engineering botulinum neurotoxin to extend therapeutic intervention.

Publications

Engineering botulinum neurotoxin to extend therapeutic intervention.

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