Intoxication of mammalian cells with binary clostridial enterotoxins is inhibited by the combination of pharmacological
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ORIGINAL ARTICLE
Intoxication of mammalian cells with binary clostridial enterotoxins is inhibited by the combination of pharmacological chaperone inhibitors Katharina Ernst 1
&
Judith Sailer 1 & Maria Braune 1 & Holger Barth 1
Received: 7 May 2020 / Accepted: 18 November 2020 # The Author(s) 2020
Abstract Binary enterotoxins Clostridioides difficile CDT toxin, Clostridium botulinum C2 toxin, and Clostridium perfringens iota toxin consist of two separate protein components. The B-components facilitate receptor-mediated uptake into mammalian cells and form pores into endosomal membranes through which the enzymatic active A-components translocate into the cytosol. Here, the A-components ADP-ribosylate G-actin which leads to F-actin depolymerization followed by rounding of cells which causes clinical symptoms. The protein folding helper enzymes Hsp90, Hsp70, and peptidyl-prolyl cis/trans isomerases of the cyclophilin (Cyp) and FK506 binding protein (FKBP) families are required for translocation of A-components of CDT, C2, and iota toxins from endosomes to the cytosol. Here, we demonstrated that simultaneous inhibition of these folding helpers by specific pharmacological inhibitors protects mammalian, including human, cells from intoxication with CDT, C2, and iota toxins, and that the inhibitor combination displayed an enhanced effect compared to application of the individual inhibitors. Moreover, combination of inhibitors allowed a concentration reduction of the individual compounds as well as decreasing of the incubation time with inhibitors to achieve a protective effect. These results potentially have implications for possible future therapeutic applications to relieve clinical symptoms caused by bacterial toxins that depend on Hsp90, Hsp70, Cyps, and FKBPs for their membrane translocation into the cytosol of target cells. Keywords Bacterial protein toxins . Pharmacological inhibitors . Chaperones . Cellular uptake . Clostridioides difficile . CDT toxin
Introduction Clostridioides difficile toxin CDT, Clostridium botulinum C2 toxin, and Clostridium perfringens iota toxin are members of the family of binary actin-ADP-ribosylating toxins that cause enterotoxicity in humans and animals (Ohishi 1983; Songer 1996; Papatheodorou et al. 2018). These protein toxins consist of two separate proteins that are secreted by the bacteria and Katharina Ernst and Judith Sailer contributed equally to this work. * Katharina Ernst [email protected] * Holger Barth [email protected] 1
Institute of Pharmacology and Toxicology, Ulm University Medical Center, 89081 Ulm, Germany
share a widely common cellular uptake mechanism and mode of action. The binding/translocation (B) component mediates the transport of the enzymatically active (A) component into the cytosol of target cells. Here, the A-component monoADP-ribosylates G-actin (Aktories et al. 1986; Schering et al. 1988; Popoff et al. 1988). This leads to depolymerization and destruction of actin filaments and causes rounding of adherent cells (Reuner et al. 1987;
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