Protein folding activity of ribosomal rna is a selective target of two unrelated antiprion drugs

Background: 6-Aminophenanthridine (6AP) and Guanabenz (GA, a drug currently in use for the treatment of hypertension) were isolated as antiprion drugs using a yeast-based assay. These structurally unrelated molecules are also active against mammalian prion in several cell-based assays and in vivo in a mouse model for prion-based diseases.Methodology/Principal Findings: Here we report the identification of cellular targets of these drugs. Using affinity chromatography matrices for both drugs, we demonstrate an RNA-dependent interaction of 6AP and GA with the ribosome. These specific interactions have no effect on the peptidyl transferase activity of the ribosome or on global translation. In contrast, 6AP and GA specifically inhibit the ribosomal RNA-mediated protein folding activity of the ribosome.Conclusion/Significance: 6AP and GA are therefore the first compounds to selectively inhibit the protein folding activity of the ribosome. They thus constitute precious tools to study the yet largely unexplored biological role of this protein folding activity

Protein Folding Activity of Ribosomal RNA Is a Selective Target of Two Unrelated Antiprion Drugs

International audienceBACKGROUND: 6-Aminophenanthridine (6AP) and Guanabenz (GA, a drug currently in use for the treatment of hypertension) were isolated as antiprion drugs using a yeast-based assay. These structurally unrelated molecules are also active against mammalian prion in several cell-based assays and in vivo in a mouse model for prion-based diseases. METHODOLOGY/PRINCIPAL FINDINGS: Here we report the identification of cellular targets of these drugs. Using affinity chromatography matrices for both drugs, we demonstrate an RNA-dependent interaction of 6AP and GA with the ribosome. These specific interactions have no effect on the peptidyl transferase activity of the ribosome or on global translation. In contrast, 6AP and GA specifically inhibit the ribosomal RNA-mediated protein folding activity of the ribosome. CONCLUSION/SIGNIFICANCE: 6AP and GA are therefore the first compounds to selectively inhibit the protein folding activity of the ribosome. They thus constitute precious tools to study the yet largely unexplored biological role of this protein folding activity

Antihypertensive Drug Guanabenz Is Active In Vivo against both Yeast and Mammalian Prions

Background: Prion-based diseases are incurable transmissible neurodegenerative disorders affecting animals and humans. [br/] Methodology/Principal Findings: Here we report the discovery of the in vivo antiprion activity of Guanabenz (GA), an agonist of a2-adrenergic receptors routinely used in human medicine as an antihypertensive drug. We isolated GA in a screen for drugs active in vivo against two different yeast prions using a previously described yeast-based two steps assay. GA was then shown to promote ovine PrPSc clearance in a cell-based assay. These effects are very specific as evidenced by the lack of activity of some GA analogues that we generated. GA antiprion activity does not involve its agonist activity on a2-adrenergic receptors as other chemically close anti-hypertensive agents possessing related mechanism of action were found inactive against prions. Finally, GA showed activity in a transgenic mouse-based in vivo assay for ovine prion propagation, prolonging slightly but significantly the survival of treated animals. [br/] Conclusion/Significance: GA thus adds to the short list of compounds active in vivo in animal models for the treatment of prion-based diseases. Because it has been administrated for many years to treat hypertension on a daily basis, without major side-effects, our results suggest that it could be evaluated in human as a potential treatment for prion-based diseases

A yeast-based assay to isolate drugs active against mammalian prions

International audienceRecently, we have developped a yeast-based (Saccharomyces cerevisiae) assay to isolate drugs active against mammalian prions. The initial assumption was that mechanisms controlling prion appearance and/or propagation could be conserved from yeast to human, as it is the case for most of the major cell biology regulatory mechanisms. Indeed, the vast majority of drugs we isolated as active against both [PSI+] and [URE3] budding yeast prions turned out to be also active against mammalian prion in three different mammalian cell-based assays. These results strongly argue in favour of common prion controlling mechanisms conserved in eukaryotes, thus validating our yeast-based assay and also the use of budding yeast to identify antiprion compounds and to study the prion world

Evaluation of the antiprion activity of 6-aminophenanthridines and related heterocycles

International audienceSeries of 6-aminophenanthridines and related heterocyclic compounds such as benzonaphtyridines were prepared. Reduction of one of the three aromatic rings was also performed. The compounds were first tested for their antiprion activity in a previously described yeast-based colourimetric prion assay. The most potent derivatives were then assayed ex vivo against the mammalian prion PrP(Sc) in a cell-based assay. Several of the new compounds were found more potent than the parent lead 6-aminophenanthridine. The most promising compounds against yeast and mammalian prions were 8-azido-6-aminophenanthridine (3m), and 7,10-dihydrophenanthridin-6-amine (14). In the mammalian cell-based assay, the IC50 of these two compounds were around 5 μM and 1.8 μM, respectively

Using budding yeast to screen for anti-prion drugs

International audiencePrions are misfolded proteins capable of propagating their altered conformation which are commonly considered as the causative agent of transmissible spongiform encephalopathies, a class of fatal neurodegenerative diseases. Currently, no treatment for prion-based diseases is available. Recently we have developed a rapid, yeast-based, two-step assay to screen for anti-prion drugs [1]. This new method allowed us to identify several compounds that are effective in vivo against budding yeast [PSI+] and [URE3] prions but also able to promote mammalian prion clearance in three different cell culture-based assays. Taken together, these results validate our method as an economic and efficient high-throughput screening approach to identify novel prion inhibitors or to carry on comprehensive structure-activity studies for already isolated anti-mammalian prion drugs. These results suggest furthermore that biochemical pathways controlling prion formation and/or maintenance are conserved from yeast to human and thus amenable to pharmacological and genetic analysis. Finally, it would be very interesting to test active drugs isolated using the yeast-based assay in models for other diseases (neurodegenerative or not) involving amyloid fibers like Huntington’s, Parkinson’s or Alzheimer’s diseases

The Toll-Like Receptor Agonist Imiquimod Is Active against Prions

Using a yeast-based assay, a previously unsuspected antiprion activity was found for imiquimod (IQ), a potent Toll-like receptor 7 (TLR7) agonist already used for clinical applications. The antiprion activity of IQ was first detected against yeast prions [PSI+] and [URE3], and then against mammalian prion both ex vivo in a cell-based assay and in vivo in a transgenic mouse model for prion diseases. In order to facilitate structure-activity relationship studies, we conducted a new synthetic pathway which provides a more efficient means of producing new IQ chemical derivatives, the activity of which was tested against both yeast and mammalian prions. The comparable antiprion activity of IQ and its chemical derivatives in the above life forms further emphasizes the conservation of prion controlling mechanisms throughout evolution. Interestingly, this study also demonstrated that the antiprion activity of IQ and IQ-derived compounds is independent from their ability to stimulate TLRs. Furthermore, we found that IQ and its active chemical derivatives inhibit the protein folding activity of the ribosome (PFAR) in vitro

Design of new disubstituted imidazo[1,2- b ]pyridazine derivatives as selective Haspin inhibitors. Synthesis, binding mode and anticancer biological evaluation

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Design of new disubstituted imidazo[1,2- b ]pyridazine derivatives as selective Haspin inhibitors. Synthesis, binding mode and anticancer biological evaluation

International audienc