The biological effects of flavonoids on mammal cells are diverse, ranging from scavenging free radicals and anti-cancer activity to anti-influenza activity. Despite appreciable effort to understand the anti-influenza activity of flavonoids, there is no clear consensus about their precise mode-of-action at a cellular level. Here, we report the development and validation of a screening assay based on AlphaScreen technology and illustrate its application for determination of the inhibitory potency of a large set of polyols against PA N-terminal domain (PA-Nter) of influenza RNA-dependent RNA polymerase featuring endonuclease activity. The most potent inhibitors we identified were luteolin with an IC50 of 72 ± 2 nM and its 8-C-glucoside orientin with an IC50 of 43 ± 2 nM. Submicromolar inhibitors were also evaluated by an in vitro endonuclease activity assay using single-stranded DNA, and the results were in full agreement with data from the competitive AlphaScreen assay. Using X-ray crystallography, we analyzed structures of the PA-Nter in complex with luteolin at 2.0 Å resolution and quambalarine B at 2.5 Å resolution, which clearly revealed the binding pose of these polyols coordinated to two manganese ions in the endonuclease active site. Using two distinct assays along with the structural work, we have presumably identified and characterized the molecular mode-of-action of flavonoids in influenza-infected cells.
- MeSH
- antivirové látky chemie metabolismus MeSH
- endonukleasy antagonisté a inhibitory chemie metabolismus MeSH
- enzymatické testy metody MeSH
- flavonoidy chemie metabolismus MeSH
- inhibitory enzymů chemie metabolismus MeSH
- krystalografie rentgenová MeSH
- mikrobiální testy citlivosti MeSH
- molekulární struktura MeSH
- preklinické hodnocení léčiv MeSH
- proteinové domény MeSH
- RNA-dependentní RNA-polymerasa antagonisté a inhibitory chemie metabolismus MeSH
- vazba proteinů MeSH
- virové proteiny antagonisté a inhibitory chemie metabolismus MeSH
- virus chřipky A enzymologie MeSH
- vztahy mezi strukturou a aktivitou MeSH
- Publikační typ
- časopisecké články MeSH
Neuraminidase is the main target for current influenza drugs. Reduced susceptibility to oseltamivir, the most widely prescribed neuraminidase inhibitor, has been repeatedly reported. The resistance substitutions I223V and S247N, alone or in combination with the major oseltamivir-resistance mutation H275Y, have been observed in 2009 pandemic H1N1 viruses. We overexpressed and purified the ectodomain of wild-type neuraminidase from the A/California/07/2009 (H1N1) influenza virus, as well as variants containing H275Y, I223V, and S247N single mutations and H275Y/I223V and H275Y/S247N double mutations. We performed enzymological and thermodynamic analyses and structurally examined the resistance mechanism. Our results reveal that the I223V or S247N substitution alone confers only a moderate reduction in oseltamivir affinity. In contrast, the major oseltamivir resistance mutation H275Y causes a significant decrease in the enzyme’s ability to bind this drug. Combination of H275Y with an I223V or S247N mutation results in extreme impairment of oseltamivir’s inhibition potency. Our structural analyses revealed that the H275Y substitution has a major effect on the oseltamivir binding pose within the active site while the influence of other studied mutations is much less prominent. Our crystal structures also helped explain the augmenting effect on resistance of combining H275Y with both substitutions.
- MeSH
- antivirové látky farmakologie MeSH
- chřipka lidská virologie MeSH
- inhibitory enzymů farmakologie MeSH
- kalorimetrie MeSH
- kinetika MeSH
- krystalizace MeSH
- lidé MeSH
- missense mutace MeSH
- neuraminidasa chemie genetika MeSH
- oseltamivir farmakologie MeSH
- replikace viru MeSH
- substituce aminokyselin MeSH
- termodynamika MeSH
- virová léková rezistence genetika MeSH
- virové proteiny chemie genetika MeSH
- virus chřipky A, podtyp H1N1 účinky léků enzymologie genetika MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH