Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA, 92697, USA.
Department of Urology, Boston Children's Hospital, Boston, MA, 02115, USA.
Nat Commun. 2023 Apr 24;14(1):2338. doi: 10.1038/s41467-023-37860-8.
Botulinum neurotoxin E (BoNT/E) is one of the major causes of human botulism and paradoxically also a promising therapeutic agent. Here we determined the co-crystal structures of the receptor-binding domain of BoNT/E (HE) in complex with its neuronal receptor synaptic vesicle glycoprotein 2A (SV2A) and a nanobody that serves as a ganglioside surrogate. These structures reveal that the protein-protein interactions between HE and SV2 provide the crucial location and specificity information for HE to recognize SV2A and SV2B, but not the closely related SV2C. At the same time, HE exploits a separated sialic acid-binding pocket to mediate recognition of an N-glycan of SV2. Structure-based mutagenesis and functional studies demonstrate that both the protein-protein and protein-glycan associations are essential for SV2A-mediated cell entry of BoNT/E and for its potent neurotoxicity. Our studies establish the structural basis to understand the receptor-specificity of BoNT/E and to engineer BoNT/E variants for new clinical applications.
肉毒神经毒素 E（BoNT/E）是人类肉毒中毒的主要原因之一，但其也是一种很有前途的治疗药物。在这里，我们确定了 BoNT/E（HE）受体结合结构域与神经元受体突触小泡糖蛋白 2A（SV2A）以及作为神经节苷脂替代物的纳米抗体的复合物的共晶结构。这些结构揭示了 HE 与 SV2 之间的蛋白-蛋白相互作用为 HE 提供了识别 SV2A 和 SV2B 的关键位置和特异性信息，但不能识别密切相关的 SV2C。同时，HE 利用一个分离的唾液酸结合口袋来介导对 SV2 的 N-糖链的识别。基于结构的诱变和功能研究表明，SV2A 介导的 BoNT/E 细胞进入和其强大的神经毒性都需要蛋白-蛋白和蛋白-聚糖的相互作用。我们的研究确立了理解 BoNT/E 受体特异性的结构基础，并为新型临床应用工程改造 BoNT/E 变体。
