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Pseudomonas aeruginosa is an opportunistic pathogen that causes major healthcare concerns due to its virulence and high intrinsic resistance to antimicrobial agents. Therefore, new treatments are highly needed. An interesting approach is to target quorum sensing (QS). QS regulates the production of a wide variety of virulence factors and biofilm formation in P. aeruginosa. This study describes the identification of paecilomycone as inhibitor of QS in both C. violaceum and P. aeruginosa. Paecilomycone strongly inhibited the production of virulence factors, including various phenazines, and biofilm formation. In search of the working mechanism, we found that paecilomycone inhibited the production of 4-hydroxy-2-heptylquinoline (HHQ) and 3,4- dihydroxy-2-heptylquinoline (PQS), but not 2’-aminoacetophenone (2-AA). We suggest that paecilomycone affects QS in P. aeruginosa by targeting the PqsBC complex and alternative targets, or alters processes that influence the enzymatic activity of the PqsBC complex. The toxicity of paecilomycone towards eukaryotic cells and organisms was low, making it an interesting lead for further clinical research.ImportanceAntibiotics are becoming less effective against bacterial infections due to the evolution of resistance among bacteria. Pseudomonas aeruginosa is a Gram-negative pathogen that causes major healthcare concerns and is difficult to treat due to its high intrinsic resistance to antimicrobial agents. Therefore, new targets are needed and an interesting approach is to target quorum sensing (QS). QS is the communication system in bacteria that regulates multiple pathways including the production of virulence factors and biofilm formation, which leads to high toxicity in the host and low sensitivity to antibiotics, respectively. We found a compound, named paecilomycone, which inhibited biofilm formation and the production of various virulence factors in P. aeruginosa. The toxicity of paecilomycone towards eukaryotic cells and organisms was low, making it an interesting lead for further clinical research.

We developed a new class of inhibitors of protein-protein interactions of the SHP2 phosphatase, which is pivotal in multiple signaling pathways and a central target in the therapy of cancer and rare diseases. Currently available SHP2 inhibitors target the catalytic site or an allosteric pocket but lack specificity or are ineffective on disease-associated SHP2 mutants. Based on the consideration that pathogenic lesions cause signaling hyperactivation due to increased SHP2 association with cognate proteins, we developed peptide-based molecules with low nM affinity for the N-terminal Src homology domain of SHP2, good selectivity, stability to degradation and an affinity for pathogenic variants of SHP2 up to 20 times higher than for the wild-type protein. The best peptide reverted the effects of a pathogenic variant (D61G) in zebrafish embryos. Our results provide a novel route for SHP2-targeted therapies and a tool to investigate the role of protein-protein interactions in the function of SHP2.

Zebrafish models are well-established tools for investigating the underlying mechanisms of diseases. Here, we identified cercosporamide, a metabolite from the fungus Ascochyta aquiliqiae, as a potent bone morphogenetic protein receptor (BMPR) type I kinase inhibitor through a zebrafish embryo phenotypic screen. The developmental defects in zebrafish, including lack of the ventral fin, induced by cercosporamide were strikingly similar to the phenotypes caused by renowned small-molecule BMPR type I kinase inhibitors and inactivating mutations in zebrafish BMPRs. In mammalian cell-based assays, cercosporamide blocked BMP/SMAD-dependent transcriptional reporter activity and BMP-induced SMAD1/5-phosphorylation. Biochemical assays with a panel of purified recombinant kinases demonstrated that cercosporamide directly inhibited kinase activity of type I BMPRs [also called activin receptor-like kinases (ALKs)]. In mammalian cells, cercosporamide selectively inhibited constitutively active BMPR type I-induced SMAD1/5 phosphorylation. Importantly, cercosporamide rescued the developmental defects caused by constitutively active Alk2 in zebrafish embryos. We believe that cercosporamide could be the first of a new class of molecules with potential to be developed further for clinical use against diseases that are causally linked to overactivation of BMPR signaling, including fibrodysplasia ossificans progressiva and diffuse intrinsic pontine glioma. This article has an associated First Person interview with the first author of the paper., Summary: Cercosporamide, a metabolite from the fungus Ascochyta aquiliqiae, was identified as a potent bone morphogenetic protein receptor (BMPR) type I kinase inhibitor through a zebrafish embryo phenotypic screen.