Structural and functional studies of botulinum neurotoxin

描述（由申请人提供）：肉毒神经毒素（BoNT）是人类已知的毒性最大的物质之一，在小鼠中的半数致死剂量（LD 50）为1 ng/kg。因此，BoNT代表了主要的生物恐怖主义威胁（Arnon等人，2001; Gill，1982）。特别是，含有肉毒杆菌毒素的药物和化妆品，如肉毒杆菌毒素、Dysport、Xeomin、CBTXA、Myobloc和NeuroBloc，已成功用于治疗各种神经、耳鼻喉科、眼科、泌尿、皮肤和胃肠道疾病（Jankovic，2004; Truong和Jost，2006）。2010年10月，FDA批准Botox（R）治疗慢性偏头痛。BoNT的毒性和治疗功能都依赖于一种共同的机制，即进入神经元，切割介导关键神经递质胞吐作用的蛋白质，随后麻痹受影响的肌肉。BoNT由肉毒梭菌产生为大的祖毒素复合物（PTC），其包括称为神经毒素相关蛋白（NAP）的辅助梭菌蛋白（Montecucco和Schiavo，1995）。临床制剂也由BoNT PTC组成。意外BoNT中毒主要通过口服受污染的食品发生。NAP被认为可以保护BoNT免受胃肠道（GI）的恶劣环境的影响，并介导毒素穿过上皮细胞屏障的转运，这是中毒的第一步。然而，控制这些过程的潜在分子机制知之甚少。该提案的目标是阐明BoNT PTC的结构和功能，包括NAP保护BoNT的机制，PTC组装的调控机制，以及NAP调节BoNT与宿主细胞之间相互作用的结构基础。该提案的重点是BoNT的血清型A（BoNT/A），因为它是生物恐怖主义的主要关注点，并且是所有BoNT血清型中最常用的药物。我们将使用各种技术的组合，包括X射线晶体学，以及生物化学，生物物理学，细胞生物学，毒理学和生物信息学。如果成功，拟议的工作将指导设计新的治疗和/或预防肉毒杆菌中毒的疗法。我们的工作还可能为Botox（R）和Dysport（R）等药物的活性和副作用提供新的见解，这可能有助于提高其临床疗效并提出新的临床应用。 公共卫生相关性：肉毒杆菌神经毒素（BoNT）既是致命的毒素，也是有效的药物。我们建议研究BoNT祖毒素复合物的结构和功能，该复合物由细菌肉毒梭菌产生，并作为复杂的毒素保护和递送机制。我们目标的实现将有助于提高我们对潜在生物恐怖武器的防御能力，并可能提高BoNTs的临床应用。

DESCRIPTION (provided by applicant): Botulinum neurotoxins (BoNTs) are among the most poisonous substances known to man, with a 50% lethal dose (LD50) of 1 ng/kg in mice. BoNTs therefore represent a major bioterrorist threat (Arnon et al., 2001; Gill, 1982). Paradoxically, BoNT-containing medicines and cosmetics, such as Botox(R), Dysport(R), Xeomin(R), CBTXA(R), Myobloc(R) and NeuroBloc(R), have been used with great success to treat a variety of neurological, otolaryngological, ophthalmological, urological, dermatological and gastrointestinal disorders (Jankovic, 2004; Truong and Jost, 2006). In October 2010, FDA approved Botox(R) to treat chronic migraine. Both the toxic and therapeutic functions of BoNTs rely on a common mechanism to enter neurons, cleave proteins that mediate exocytosis of key neurotransmitters, and subsequently paralyze the affected muscles. BoNTs are produced by Clostridium botulinum as large progenitor toxin complexes (PTCs) that include auxiliary clostridial proteins known as neurotoxin-associated proteins (NAPs) (Montecucco and Schiavo, 1995). Clinical formulations are also composed of BoNT PTCs. Accidental BoNT poisoning mainly occurs through oral ingestion of tainted food products. NAPs are thought to protect BoNTs against the hostile environment of the gastrointestinal (GI) tract, and to mediate toxin transport across the epithelial cell barriers, the first step of intoxication. However the underlying molecular mechanisms that control these processes are poorly understood. The goal of this proposal is to elucidate the structure and function of BoNT PTCs, including the mechanism by which NAPs protect BoNTs, the regulatory mechanism underlying PTC assembly, and the structural basis by which NAPs regulate the interaction between BoNTs and host cells. The focus of this proposal is on the serotype A of BoNT (BoNT/A), because it is a major concern for bioterrorism and is the most commonly used medicine among all BoNT serotypes. We will use a combination of techniques, including X-ray crystallography, together with biochemistry, biophysics, cell biology, toxicology and bioinformatics. If successful, the proposed wok will guide the design of novel therapeutics for the treatment and/or prevention of botulism. Our work may also provide new insights into the activity and side effects of drugs such as Botox(R) and Dysport(R), which may help improve their clinical efficacy and suggest novel clinical applications. PUBLIC HEALTH RELEVANCE: Botulinum neurotoxins (BoNTs) are both deadly toxins and effective medicines. We propose to study the structure and function of BoNT progenitor toxin complexes, which are produced by the bacterium Clostridium botulinum and serve as sophisticated toxin protection and delivery machinery. The accomplishment of our goal will help to improve our defense against potential bioterrorist weapons, and will potentially improve the clinical applications of BoNTs.