小中大PNAS：改造肉毒杆菌神经毒素
通过改造一种导致肉毒中毒的神经毒素的基本组成部分，科学家有可能扩展这种毒素的治疗用途。目前，A型肉毒杆菌神经毒素(商标名是Botox)被用于化妆品和治疗神经肌肉疾病，诸如眼睑痉挛和过度出汗。这种毒素分裂仅见于神经元的信使酶，这阻止了细胞之间的相互通信并最终导致了麻痹。
Joseph Barbieri 和Sheng Chen修改了E型肉毒杆菌神经毒素的一个氨基酸基本单元，这可以让它分裂一种称为SNAP23的蛋白质，该蛋白质与神经元信使酶非常接近。这组作者把这种神经毒素基因插入到了人类细胞中，结果发现它分裂了自然产生的SNAP23，因此阻止了非神经细胞之间的通信。通过使用一种催化剂向培养的人类细胞中提供这种修改后的蛋白质，这组作者还能够分裂这些细胞中的SNAP23。含有修改后的肉毒杆菌毒素基因或蛋白质的细胞分泌更少的粘液和更少量的一种免疫系统信号传导分子。这组作者得出结论说，利用一种经过修改的肉毒杆菌神经毒素瞄准SNAP23可能有助于医生治疗其他疾病。
Engineering botulinum neurotoxin to extend therapeutic intervention
Sheng Chen and Joseph T. Barbieri,1
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(K224D) 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(K224D) 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.
