Various bacterial protein toxins, including Clostridium difficile toxins A (TcdA) and B (TcdB), attack intracellular target proteins of host cells by glucosylation. After receptor binding and endocytosis, the toxins are translocated into the cytosol, where they modify target proteins (e.g., Rho proteins). Here we report that the activity of translocated glucosylating toxins depends on the chaperonin TRiC/CCT. The chaperonin subunits CCT4/5 directly interact with the toxins and enhance the refolding and restoration of the glucosyltransferase activities of toxins after heat treatment. Knockdown of CCT5 by siRNA and HSF1A, an inhibitor of TRiC/CCT, blocks the cytotoxic effects of TcdA and TcdB. In contrast, HSP90, which is involved in the translocation and uptake of ADP ribosylating toxins, is not involved in uptake of the glucosylating toxins. We show that the actions of numerous glycosylating toxins from various toxin types and different species depend on TRiC/CCT. Our data indicate that the TRiC/CCT chaperonin system is specifically involved in toxin uptake and essential for the action of various glucosylating protein toxins acting intracellularly on target proteins.

各种细菌蛋白毒素，包括艰难梭菌毒素A（TcdA）和B（TcdB）通过糖基化攻击宿主细胞的细胞内靶蛋白。在受体结合和内吞作用之后，毒素被转移到胞质溶胶中，在那里它们修饰靶蛋白（例如Rho蛋白）。在这里，我们报告转位的糖基化毒素的活性取决于伴侣蛋白TRiC / CCT。伴侣蛋白亚基CCT4 / 5直接与毒素相互作用，并在热处理后增强毒素的葡糖基转移酶活性的重折叠和恢复。siRNA和HSF1A（TRiC / CCT的抑制剂）抑制CCT5可以阻断TcdA和TcdB的细胞毒性作用。相反，参与ADP核糖基化毒素的转运和摄取的HSP90不参与糖基化毒素的摄取。我们表明，来自各种毒素类型和不同物种的众多糖基化毒素的作用取决于TRiC / CCT。我们的数据表明，TRiC / CCT伴侣蛋白系统特别参与毒素的摄取，并且是细胞内作用于靶蛋白的各种糖基化蛋白毒素的作用所必需的。