Department of Chemistry and Biochemistry, The Botulinum Research Center, University of Massachusetts Dartmouth, North Dartmouth, MA 02747, United States.
Biochem Biophys Res Commun. 2012 Jan 13;417(2):726-31. doi: 10.1016/j.bbrc.2011.12.020. Epub 2011 Dec 11.
Botulinum neurotoxins (BoNTs), produced by Clostridium botulinum are the most toxic substances known to the mankind. BoNTs (seven serotypes, A-G) are produced along with a group of neurotoxin associated proteins (NAPs) in a physiologically coordinated manner, regulated by a common transcription factor for the gene cluster that encodes for the BoNT and NAPs. Hemagglutinin-33 (Hn-33) is a 33 kDa subcomponent of NAPs, which is resistant to protease digestion, and accounts for about half of the NAPs molecules in the BoNT/A complex. Natural exposures to BoNT in food poisoning cases as well as in the medical applications of BoNT as a therapeutic agent, humans are exposed to the BoNT/A complex. The toxin itself is known to block neurotransmitter release from presynaptic nerves, but the effect of NAPs is unexplored. In this article, we report an important observation of the anti-apoptotic effect of Hn-33 in Hn-33-preincubated human neuroblastoma SH-SY5Y cells. Activity of caspases, which are the central executioners of apoptosis, was substantially (78%) reduced by Hn-33. Degradation of chromosomal DNA, another biochemical hallmark of apoptosis, was blocked in Hn-33 incubated SH-SY5Y cells. Interestingly, purified BoNT/A also showed substantial anti-apoptotic activity. These findings may have significant implications to the use of BoNT as a therapeutic agent, and to devise counter measures to botulinum poisoning.
肉毒杆菌神经毒素（BoNTs）由肉毒梭菌产生，是人类已知的最毒物质。BoNTs（七种血清型，A-G）与一组神经毒素相关蛋白（NAPs）一起以生理协调的方式产生，由编码 BoNT 和 NAPs 的基因簇的共同转录因子调节。血凝素-33（Hn-33）是 NAPs 的一个 33kDa 亚组分，对蛋白酶消化具有抗性，并且占 BoNT/A 复合物中 NAPs 分子的约一半。在食物中毒病例中以及作为治疗剂的 BoNT 的医学应用中，人类自然会接触到 BoNT/A 复合物。已知毒素本身可阻断来自突触前神经的神经递质释放，但 NAPs 的作用尚未探索。在本文中，我们报告了 Hn-33 在预先孵育的人神经母细胞瘤 SH-SY5Y 细胞中具有抗细胞凋亡作用的重要观察结果。Hn-33 可使半胱天冬酶（细胞凋亡的中心执行者）的活性大大（78％）降低。另一种细胞凋亡的生化标志是染色体 DNA 的降解，在孵育有 Hn-33 的 SH-SY5Y 细胞中被阻断。有趣的是，纯化的 BoNT/A 也表现出显著的抗细胞凋亡活性。这些发现可能对 BoNT 作为治疗剂的使用以及制定抗肉毒中毒的对策具有重要意义。
