Department of Physiology and Biophysics, University of California, Irvine, CA 92697, USA.
Department of Microbiology and Immunobiology, Harvard Medical School, Division of Neuroscience, New England Primate Research Center, Southborough, MA 01772, USA.
Science. 2014 Jun 20;344(6190):1405-10. doi: 10.1126/science.1253823.
How botulinum neurotoxins (BoNTs) cross the host intestinal epithelial barrier in foodborne botulism is poorly understood. Here, we present the crystal structure of a clostridial hemagglutinin (HA) complex of serotype BoNT/A bound to the cell adhesion protein E-cadherin at 2.4 angstroms. The HA complex recognizes E-cadherin with high specificity involving extensive intermolecular interactions and also binds to carbohydrates on the cell surface. Binding of the HA complex sequesters E-cadherin in the monomeric state, compromising the E-cadherin-mediated intercellular barrier and facilitating paracellular absorption of BoNT/A. We reconstituted the complete 14-subunit BoNT/A complex using recombinantly produced components and demonstrated that abolishing either E-cadherin- or carbohydrate-binding of the HA complex drastically reduces oral toxicity of BoNT/A complex in vivo. Together, these studies establish the molecular mechanism of how HAs contribute to the oral toxicity of BoNT/A.
肉毒梭菌神经毒素（BoNTs）如何穿过食源性肉毒中毒宿主的肠道上皮屏障尚不清楚。在这里，我们呈现了 2.4 埃分辨率的结合型 A 型 BoNT 的梭菌血凝素（HA）复合物与细胞黏附蛋白 E-钙黏蛋白的晶体结构。该 HA 复合物通过广泛的分子间相互作用特异性识别 E-钙黏蛋白，同时也与细胞表面的碳水化合物结合。HA 复合物的结合将 E-钙黏蛋白隔离在单体状态，破坏 E-钙黏蛋白介导的细胞间屏障，促进 A 型 BoNT 的细胞旁吸收。我们使用重组产生的成分重新构建了完整的 14 亚基 A 型 BoNT 复合物，并证明了 HA 复合物对 E-钙黏蛋白或碳水化合物结合的阻断极大地降低了 A 型 BoNT 复合物在体内的口服毒性。总之，这些研究确立了 HAs 如何促进 A 型 BoNT 口服毒性的分子机制。
