Screening of a Drug Library Identifies Inhibitors of Cell Intoxication by CNF1

Abstract

Cytotoxic necrotizing factor 1 (CNF1) is a toxin produced by pathogenic strains of Escherichia coli responsible for extra-intestinal infections. CNF1 deamidates Rac1, thereby triggering its permanent activation and worsening inflammatory reactions. Activated Rac1 is prone to proteasomal degradation. There is no targeted therapy against CNF1, despite its clinical relevance. In this work we developed a fluorescent cell-based immunoassay to screen for inhibitors of CNF1-induced Rac1 degradation among 1120 mostly approved drugs. Eleven compounds were found to prevent CNF1-induced Rac1 degradation, and five also showed a protective effect against CNF1-induced multinucleation. Finally, lasalocid, monensin, bepridil, and amodiaquine protected cells from both diphtheria toxin and CNF1 challenges. These data highlight the potential for drug repurposing to fight several bacterial infections and Rac1-based diseases.

Revisiting Old Ionophore Lasalocid as a Novel Inhibitor of Multiple Toxins

“…Altogether, our results show that lasalocid, a widely used veterinary drug, protects cells from Stx1, ETA and TcdB, in addition to DT and CNF1 [14]. This antitoxin effect occurs at low micromolar concentrations that do not exhibit any cytotoxicity.…”

“…After normalization of the data, we observed a better tolerance of HUVECs, and more than 80% of viability for lasalocid concentrations ≤ 20 μM. Since we showed previously that lasalocid protects cells from CNF1 and DT cytotoxicity [14], we investigated whether it might give a broader antitoxin protection of cells by acting against TcdB. The latter is an unrelated toxin trafficking through the endo-lysosomal pathway, that is produced by Since we showed previously that lasalocid protects cells from CNF1 and DT cytotoxicity [14], we investigated whether it might give a broader antitoxin protection of cells by acting against TcdB.…”

“…Since we showed previously that lasalocid protects cells from CNF1 and DT cytotoxicity [14], we investigated whether it might give a broader antitoxin protection of cells by acting against TcdB. The latter is an unrelated toxin trafficking through the endo-lysosomal pathway, that is produced by Since we showed previously that lasalocid protects cells from CNF1 and DT cytotoxicity [14], we investigated whether it might give a broader antitoxin protection of cells by acting against TcdB. The latter is an unrelated toxin trafficking through the endo-lysosomal pathway, that is produced by the pathogen C. difficile responsible for nosocomial pseudomembranous colitis.…”

“…Sandvig and colleagues have shown in 1982 that a brominated analog of lasalocid (BrX-537A) can protect cells from DT [13], and previous work in our laboratory showed that lasalocid hinders cell intoxication by DT and the cytotoxic necrotizing factor-1 (CNF1) from extraintestinal strains of pathogenic E. coli [14]. However, cell biology effects following cell exposure to this compound are poorly described.…”

A screening pipeline identifies a broad-spectrum inhibitor of bacterial AB toxins with cross protection against influenza A virus H1N1 and SARS-CoV-2

“…Nevertheless, the identified compounds did not allow further development in the clinic. Indeed, their antitoxin activities required concentrations higher than their safety range, and in some instances, they had effects on multiple cellular organelles (58,59).…”