Chloroquine derivatives block the translocation pores and inhibit cellular entry of Clostridium botulinum C2 toxin and Bacillus anthracis lethal toxin.
The pathogenic bacteria Clostridium botulinum and Bacillus anthracis produce the binary protein toxins C2 and lethal toxin (LT), respectively. These toxins consist of a binding/transport (B7) component that delivers the separate enzyme (A) component into the cytosol of target cells where it modifies its specific substrate and causes cell death. The B7components of C2 toxin and LT, C2IIa and PA63, respectively, are ring-shaped heptamers that bind to their cellular receptors and form complexes with their A components C2I and lethal factor (LF), respectively. After receptor-mediated endocytosis of the toxin complexes, C2IIa and PA63insert into the membranes of acidified endosomes and form trans-membrane pores through which C2I and LF translocate across endosomal membranes into the cytosol. C2IIa and PA63also form channels in planar bilayer membranes, and we used this approach earlier to identify chloroquine as a potent blocker of C2IIa and PA63pores. Here, a series of chloroquine derivatives was investigated to identify more efficient toxin inhibitors with less toxic side effects. Chloroquine, primaquine, quinacrine, and fluphenazine blocked C2IIa and PA63pores in planar lipid bilayers and in membranes of living epithelial cells and macrophages, thereby preventing the pH-dependent membrane transport of the A components into the cytosol and protecting cells from intoxication with C2 toxin and LT. These potent inhibitors of toxin entry underline the central role of the translocation pores for cellular uptake of binary bacterial toxins and as relevant drug targets, and might be lead compounds for novel pharmacological strategies against severe enteric diseases and anthrax.
Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Albert-Einstein-Allee 11, 89081, Ulm, Germany.
Anna-Maria
AM
Kreidler
Department of Life Sciences and Chemistry, Jacobs University Bremen, Campusring 1, 28759, Bremen, Germany. r.benz@jacobs-university.de.
Roland
R
Benz
Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Albert-Einstein-Allee 11, 89081, Ulm, Germany. holger.barth@uni-ulm.de.
Holger
H
Barth
D000942:Antigens, Bacterial; D001427:Bacterial Toxins / Q000493:pharmacokinetics*; D001692:Biological Transport / Q000187:drug effects; D001905:Botulinum Toxins / Q000493:pharmacokinetics*; D002462:Cell Membrane / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D002738:Chloroquine / Q000494:pharmacology*; D005476:Fluphenazine / Q000494:pharmacology; D006367:HeLa Cells / Q000187:drug effects; D006801:Humans; D008051:Lipid Bilayers; D011319:Primaquine / Q000494:pharmacology; D011796:Quinacrine / Q000494:pharmacology
D000942:Antigens, Bacterial; D001427:Bacterial Toxins; D008051:Lipid Bilayers; C030325:anthrax toxin; D002738:Chloroquine; D001905:Botulinum Toxins; C096324:botulinum toxin type C; D011796:Quinacrine; D011319:Primaquine; D005476:Fluphenazine
Anthrax lethal toxin; Binary protein toxin; Clostridium botulinum C2 toxin; Membrane transport; Pore blocker