Novel compounds targeting the enterohemorrhagic Escherichia coli type three secretion system reveal insights into mechanisms of secretion inhibition

Abstract

SummaryAnti‐virulence (AV) compounds are a promising alternative to traditional antibiotics for fighting bacterial infections. The Type Three Secretion System (T3SS) is a well‐studied and attractive AV target, given that it is widespread in more than 25 species of Gram‐negative bacteria, including enterohemorrhagic E. coli (EHEC), and as it is essential for host colonization by many pathogens. In this work, we designed, synthesized and tested a new series of compounds that block the functionality of the T3SS of EHEC. Affinity chromatography experiments identified the primary target of the compounds as the T3SS needle pore protein EspD, which is essential for effector protein translocation into host cells. These data were supported by mechanistic studies that determined the coiled‐coil domain 1 of EspD as a key compound‐binding site, thereby preventing correct assembly of the T3SS complex on the cell surface. However, binding of inhibitors to EspD or deletion of EspD itself did not result in transcriptional down‐regulation of effector proteins. Instead, we found the compounds to exhibit dual‐functionality by also down‐regulating transcription of the entire chromosomal locus encoding the T3SS, further demonstrating their desirability and effectiveness.

Thinking Outside the Box—Novel Antibacterials To Tackle the Resistance Crisis

“…[222][223][224] Salicylidene acylhydrazides (SAHs) represent aw ell-known class of T3SS inhibitors that have been extensively studied in various pathogens including P. aeruginosa and Salmonella typhimurium. [225][226][227][228][229] However, these SAHs seem to function through several mechanisms which need further elucidation. [225][226][227][228][229] However, these SAHs seem to function through several mechanisms which need further elucidation.…”

“…[224] Diverse SAH derivatives such as INP0341 have been synthesized and were found to attenuate bacterial pathogenesis. [225][226][227][228][229] However, these SAHs seem to function through several mechanisms which need further elucidation. [230] In ad ifferent approach, screening of compound libraries with acellular reporter assay revealed phenoxyacetamide MBX 1641 to be ap otent inhibitor of P. aeruginosa T3SS (IC 50 % 10 mm)w ith al ow toxicity against eukaryotic cells ( Figure 16).…”

Über bisherige Denkweisen hinaus – neue Wirkstoffe zur Überwindung der Antibiotika‐Krise

“…[221] Es wurde eine Reihe von T3SS-Inhibitoren entdeckt, welche die Regulation der Expression des T3SS,d ie Synthese der nadelartigen Struktur sowie die Sekretion und Tr anslokation von Effektorproteinen beeinflussen (Abbildung 16). [225][226][227][228][229] Diese SAHs scheinen über verschiedene Mechanismen zu wirken, welche noch genauer aufgeklärt werden müssen. [224] Vielfältige SAH-Derivate,wie INP0341, wurden synthetisiert und führten zu einer Verringerung der bakteriellen Pathogenität.…”

“…[224] Vielfältige SAH-Derivate,wie INP0341, wurden synthetisiert und führten zu einer Verringerung der bakteriellen Pathogenität. [225][226][227][228][229] Diese SAHs scheinen über verschiedene Mechanismen zu wirken, welche noch genauer aufgeklärt werden müssen. [230] In einem weiteren Ansatz konnte durch ein Screening von Substanzbibliotheken in einem zellulären Reporter-Assay das Phenoxyacetamid MBX 1641 als wirksamer Inhibitor gegen das T3SS in P. aeruginosa (IC 50 % 10 mm)i dentifiziert werden (Abbildung 16).…”

Anti-virulence activities of biflavonoids from <i>Mesua ferrea</i> L. flower

“…During infection, pathogens use the T3SS to inject effector proteins into target host cells, disrupting host defense mechanisms and allowing invasion. Therefore, to reduce virulence or inhibit specialized secretion systems are an obvious aim for us to develop drugs (6,7), and T3ss is a wellstudied and attractive anti-virulence target (6). The whole plant of M. ferrea is wildly used as medicinal plant in tropical Asia and India.…”