MECHANISM OF BOTULINUM NEUROTOXIN ACTION

肉毒杆菌神经毒素的七个血清型是一组大蛋白(150 Kda)具有作用于其上的轻(50 KDa)和重(100 KDa)链亚基 神经肌肉接头的突触前神经细胞。神经毒素 作用于细胞内阻断乙酰胆碱神经递质释放 可怕的肉毒杆菌中毒导致肌肉松弛瘫痪。在……里面 一般情况下，肉毒杆菌病是由摄入食物引起的 厌氧细菌肉毒梭菌已经生长并产生了 神经毒素。一种更常见的肉毒杆菌中毒形式，婴儿肉毒杆菌中毒，发生在 摄取肉毒梭菌随处可见的孢子，产生 婴儿肠道中的神经毒素。生物医学的意义 肉毒杆菌神经毒素不仅限于肉毒杆菌中毒疾病；因为 由于它们在神经肌肉接头上的高度效力和特异性， 神经毒素正被用作治疗多种神经性疾病的药物。 眼睑痉挛、斜视、斜颈等肌肉疾病， 并有可能用于更多的神经肌肉疾病。 在它们的作用模式中，肉毒杆菌神经毒素结合到细胞表面， 并通过内吞作用内化。至少是轻链(有毒) 亚基被转移到细胞质中，在那里它阻止 神经递质的释放通过干扰生化和 胞吐作用的生物物理事件。尽管最近有报道称 肉毒杆菌神经毒素在构成物上作为锌蛋白水解酶 囊泡胞吐作用的组成、分子基础和确切的 它们的毒性作用的生化机制还不完全清楚。 我们研究的长期目标是研究(A)分子 肉毒杆菌神经毒素的毒性活性的基础，以及(B) 神经毒素介导的细胞内机制(S) 神经递质的释放。下一步要解决的具体目标 五年是(一)调查金属结合对土壤的作用 用波谱方法研究神经毒素的结构和功能 神经递质释放试验；(Ii)鉴定 使用合成肽形成有毒部位的神经毒素轻链 作为拮抗剂；及。(Iii)研究 烟酰胺腺嘌呤二核苷酸到轻链的本征使用 荧光猝灭法和平衡透析法。

Seven serotypes of botulinum neurotoxin are a group of large proteins (150 kDa) with light (50 kDa) and heavy (100 kDa) chain subunits that act on the presynaptic nerve cells of the neuromuscular junctions. Neurotoxins act intracellulary to block acetylcholine neurotransmitter release leading to the flaccid muscle paralysis in the dreaded botulism disease. In general, the botulism disease results from ingestion of food where anaerobic bacterium, Clostridium botulinum, has grown and produced the neurotoxin. A more frequent form of botulism, infant botulism, occurs from the ingestion of ubiquitous spores of Clostridium botulinum which produces the neurotoxin in the intestinal tract of infants. Biomedical implications of botulinum neurotoxins are not limited to only botulism disease; because of their high potency and specificity at the neuro-muscular junctions, the neurotoxins are being used as therapeutic agents to treat several neuro- muscular diseases such as blepharospasm, strabismus, torticollis, etc., and have potential to be used for many more neuro-muscular disorders. In their mode of action, botulinum neurotoxins bind to the cell surface, and are internalized through endocytosis. At least the light chain (toxic) subunit is translocated into the cytosol, where it blocks the neurotransmitter release through interference with the biochemical and biophysical events of exocytosis. Although it has recently been reported that botulinum neurotoxins act as Zn2+ proteases on the constitutive components of the vesicular exocytosis, the molecular basis and the exact biochemical mechanism of their toxic action is not fully understood. The long-term goals of our study are to investigate (a) the molecular basis of the toxic activity of botulinum neurotoxins, and (b) the intracellular mechanism(s) involved in the neurotoxin-mediated blockage of the neurotransmitter release. Specific aims to be addressed in the next five years are (i) to investigate the role of metal binding on the structure and function of the neurotoxin using spectroscopic methods and neurotransmitter release assay; (ii) to identify peptide segments of neurotoxin light chain that form the toxic site using synthetic peptides as antagonists; and (iii) to investigate the possibility of binding of nicotinamide adenine dinucleotide to the light chain using intrinsic fluorescence quenching and equilibrium dialysis methods.