title: An NF-κB-based high-throughput screen identifies piericidins as inhibitors of the Yersinia pseudotuberculosis type III secretion system.
abstract: The type III secretion system (T3SS) is a bacterial appendage used by dozens of Gram-negative pathogens to subvert host defenses and cause disease, making it an ideal target for pathogen-specific antimicrobials. Here, we report the discovery and initial characterization of two related natural products with T3SS-inhibitory activity that were derived from a marine actinobacterium. Bacterial extracts containing piericidin A1 and the piericidin derivative Mer-A 2026B inhibited Yersinia pseudotuberculosis from triggering T3SS-dependent activation of the host transcription factor NF-κB in HEK293T cells but were not toxic to mammalian cells. As the Yersinia T3SS must be functional in order to trigger NF-κB activation, these data indicate that piericidin A1 and Mer-A 2026B block T3SS function. Consistent with this, purified piericidin A1 and Mer-A 2026B dose-dependently inhibited translocation of the Y. pseudotuberculosis T3SS effector protein YopM inside CHO cells. In contrast, neither compound perturbed bacterial growth in vitro, indicating that piericidin A1 and Mer-A 2026B do not function as general antibiotics in Yersinia. In addition, when Yersinia was incubated under T3SS-inducing culture conditions in the absence of host cells, Mer-A 2026B and piericidin A1 inhibited secretion of T3SS cargo as effectively as or better than several previously described T3SS inhibitors, such as MBX-1641 and aurodox. This suggests that Mer-A 2026B and piericidin A1 do not block type III secretion by blocking the bacterium-host cell interaction, but rather inhibit an earlier stage, such as T3SS needle assembly. In summary, the marine-derived natural products Mer-A 2026B and piericidin A1 possess previously uncharacterized activity against the bacterial T3SS.
authors.affiliation: Department of Microbiology and Environmental Toxicology, University of California Santa Cruz, Santa Cruz, California, USA.
authors.forename: Miles C
authors.initials: MC
authors.lastname: Duncan
authors.forename: Weng Ruh
authors.initials: WR
authors.lastname: Wong
authors.forename: Allison J
authors.initials: AJ
authors.lastname: Dupzyk
authors.forename: Walter M
authors.initials: WM
authors.lastname: Bray
authors.forename: Roger G
authors.initials: RG
authors.lastname: Linington
authors.forename: Victoria
authors.initials: V
authors.lastname: Auerbuch
mesh_terms: D000192:Actinomycetales / Q000737:chemistry; D000818:Animals; D000900:Anti-Bacterial Agents / Q000302:isolation & purification / Q000494:pharmacology*; D000899:Aurodox / Q000494:pharmacology; D001425:Bacterial Outer Membrane Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D058947:Bacterial Secretion Systems / Q000187:drug effects*; D016466:CHO Cells; D003412:Cricetulus; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation; D057809:HEK293 Cells; D057166:High-Throughput Screening Assays; D006801:Humans; D016328:NF-kappa B / Q000235:genetics* / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D011725:Pyridines / Q000302:isolation & purification / Q000494:pharmacology*; D015011:Yersinia pseudotuberculosis / Q000187:drug effects* / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; D058947:Bacterial Secretion Systems; C092866:Mer A2026B; D016328:NF-kappa B; D011725:Pyridines; C060772:yopM protein, Yersinia; D000899:Aurodox; C100213:piericidin A