Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Albert-Ludwigs-Universität Freiburg, D-79104 Freiburg, Germany.
Proc Natl Acad Sci U S A. 2014 Apr 29;111(17):6431-6. doi: 10.1073/pnas.1323790111. Epub 2014 Apr 15.
Large glycosylating toxins are major virulence factors of various species of pathogenic Clostridia. Prototypes are Clostridium difficile toxins A and B, which cause antibiotics-associated diarrhea and pseudomembranous colitis. The current model of the toxins' action suggests that receptor binding is mediated by a C-terminal domain of combined repetitive oligopeptides (CROP). This model is challenged by the glycosylating Clostridium perfringens large cytotoxin (TpeL toxin) that is devoid of the CROP domain but still intoxicates cells. Using a haploid genetic screen, we identified LDL receptor-related protein 1 (LRP1) as a host cell receptor for the TpeL toxin. LRP1-deficient cells are not able to take up TpeL and are not intoxicated. Expression of cluster IV of LRP1 is sufficient to rescue toxin uptake in these cells. By plasmon resonance spectroscopy, a KD value of 23 nM was determined for binding of TpeL to LRP1 cluster IV. The C terminus of TpeL (residues 1335-1779) represents the receptor-binding domain (RBD) of the toxin. RBD-like regions are conserved in all other clostridial glycosylating toxins preceding their CROP domain. CROP-deficient C. difficile toxin B is toxic to cells, depending on the RBD-like region (residues 1349-1811) but does not interact with LRP1. Our data indicate the presence of a second, CROP-independent receptor-binding domain in clostridial glycosylating toxins and suggest a two-receptor model for the cellular uptake of clostridial glycosylating toxins.
大糖基化毒素是各种致病性梭菌的主要毒力因子。原型是艰难梭菌毒素 A 和 B，它们引起抗生素相关性腹泻和伪膜性结肠炎。目前毒素作用的模型表明，受体结合是由组合重复寡肽（CROP）的 C 末端结构域介导的。这种模型受到缺乏 CROP 结构域但仍能使细胞中毒的糖基化梭状芽孢杆菌大细胞毒素（TpeL 毒素）的挑战。使用单倍体遗传筛选，我们鉴定出 LDL 受体相关蛋白 1（LRP1）是 TpeL 毒素的宿主细胞受体。LRP1 缺陷细胞不能摄取 TpeL 也不会中毒。LRP1 簇 IV 的表达足以挽救这些细胞中的毒素摄取。通过等离子体共振光谱法，确定 TpeL 与 LRP1 簇 IV 结合的 KD 值为 23 nM。TpeL 的 C 端（残基 1335-1779）代表毒素的受体结合域（RBD）。所有其他梭状芽孢杆菌糖基化毒素在其 CROP 结构域之前都保守有 RBD 样区域。缺乏 CROP 的艰难梭菌毒素 B 对细胞有毒性，取决于 RBD 样区域（残基 1349-1811），但不与 LRP1 相互作用。我们的数据表明，在梭状芽孢杆菌糖基化毒素中存在第二个、CROP 非依赖的受体结合域，并提出了一个用于梭状芽孢杆菌糖基化毒素细胞摄取的双受体模型。
