Virtual Screening Identifies Chebulagic Acid as an Inhibitor of the M2(S31N) Viral Ion Channel and Influenza A Virus.

Michel Roberge,Maggie C. Duncan,Pascal Amoa Onguéné,David E. Williams,Aruna D. Balgi,Raymond J. Andersen,Kerstin Andrae-Marobela,Ian Tietjen,Masahiro Niikura,Ibuki Kihara,Maya E. Naidu,Fidele Ntie-Kang,Derrick N. Nebangwa

doi:10.3390/molecules25122903

Abstract

The increasing prevalence of drug-resistant influenza viruses emphasizes the need for new antiviral countermeasures. The M2 protein of influenza A is a proton-gated, proton-selective ion channel, which is essential for influenza replication and an established antiviral target. However, all currently circulating influenza A virus strains are now resistant to licensed M2-targeting adamantane drugs, primarily due to the widespread prevalence of an M2 variant encoding a serine to asparagine 31 mutation (S31N). To identify new chemical leads that may target M2(S31N), we performed a virtual screen of molecules from two natural product libraries and identified chebulagic acid as a candidate M2(S31N) inhibitor and influenza antiviral. Chebulagic acid selectively restores growth of M2(S31N)-expressing yeast. Molecular modeling also suggests that chebulagic acid hydrolysis fragments preferentially interact with the highly-conserved histidine residue within the pore of M2(S31N) but not adamantane-sensitive M2(S31). In contrast, chebulagic acid inhibits in vitro influenza A replication regardless of M2 sequence, suggesting that it also acts on other influenza targets. Taken together, results implicate chebulagic acid and/or its hydrolysis fragments as new chemical leads for M2(S31N) and influenza-directed antiviral development.

Highlights

Influenza A virus is responsible for recurring seasonal and pandemic outbreaks that cause significant morbidity and mortality worldwide
Three compounds restored at least 10% yeast growth at 25 μg/mL including compounds 10/agathisflavone (20.9 ± 4.4%), 13/thiocillin I (16.9 ± 9.2%), and 16/chebulagic acid (29.5 ± 4.4%) (Figure 3C). These results suggest that a subset of compounds identified by virtual screening (VS) might counteract the detrimental effects of M2(S31N) expression on yeast growth, where the activity of 25 μg/mL (~26.2 μM) chebulagic acid is on par with the activity of 30 μM M2WJ352
These results suggest that chebulagic acid hydrolysis fragments selectively interact with M2(S31N) and its histidine residue at position 37 (H37) residue to occlude the M2(S31N) pore

Summary

Introduction

Influenza A virus is responsible for recurring seasonal and pandemic outbreaks that cause significant morbidity and mortality worldwide. The discovery and development of new antivirals against influenza A remain needed. M2 of influenza A virus is a 97 amino acid, type I transmembrane protein that forms a tetrameric ion channel that is proton-gated and proton-selective [2,3,4]. M2 ion channel activity is essential for influenza A virus replication, and the licensed M2 inhibitors amantadine (1) and rimantadine (2; Figure 1A), which target and occlude the M2 channel pore, were historically used as antivirals. More than 95% of adamantane-resistant influenza A virus strains contain a serine to asparagine mutation at position 31 in M2 (S31N) [7]; this mutation distorts interactions of adamantanes with M2 pore-lining residues without affecting M2 ion channel activity or viral fitness [4].

Methods

Results

Conclusion