Antiviral agents. 2. Structure-activity relations of compounds related to 1-adamantanamine

Aldrich, Paul E.; Hermann, E. C.; Meier, W.; Paulshock, Marvin; Prichard, W. W.; Snyder, James A.; Watts, John

doi:10.1021/jm00288a019

Cited by 103 publications

(71 citation statements)

References 2 publications

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“…Second, functional experiments show that mutating residues of the lipid-facing pocket to Alanines dramatically lowers sensitivity to drug, whereas mutating Ser-31 inside the pore to Ala has almost no effect. Third, although the prevalence of the S31N resistance mutation might suggest that a drug can bind at this position, neither the known structure-activity relationship (SAR) of adamantane drugs (8), nor the properties of the S31A mutant, nor the structure of S31N itself support this view. Indeed, naturally-occurring drug-resistance mutations have been observed in many positions, which together span Ͼ3 alpha-helical turns, a region much larger than the dimensions of the drug.…”

Section: Discussionmentioning

confidence: 99%

“…1 A). Because the rimantadine amine group is essential for adamantane inhibition (8), and because it interacts directly with the carboxyl group of Asp-44, we tested the drug resistance of the D44A mutation. We found that D44A(18-60) is tetrameric, as indicated by chemical cross-linking (Fig.…”

Section: Functional Relevance Of the 2 Proposed Drug Binding Sitesmentioning

confidence: 99%

“…In this model, the hydrophobic adamantyl cage is coordinated to the hydroxyls of Ser-31 (Fig. 1B), making the model difficult to reconcile with the chemical properties of the drug (8,9).…”

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Mechanism of drug inhibition and drug resistance of influenza A M2 channel

Pielak

Schnell

Chou³

2009

Proc. Natl. Acad. Sci. U.S.A.

278

292

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The influenza A virus M2 proton channel equilibrates pH across the viral membrane during entry and across the trans-Golgi membrane of infected cells during viral maturation. It is an important target of adamantane-family antiviral drugs, but drug resistance has become a critical problem. Two different sites for drug interaction have been proposed. One is a lipid-facing pocket between 2 adjacent transmembrane helices (around Asp-44), at which the drug binds and inhibits proton conductance allosterically. The other is inside the pore (around Ser-31), at which the drug directly blocks proton passage. Here, we describe structural and functional experiments on the mechanism of drug inhibition and resistance. The solution structure of the S31N drug-resistant mutant of M2, a mutant of the highly pathogenic avian influenza subtype H5N1, shows that replacing Ser-31 with Asn has little effect on the structure of the channel pore, but dramatically reduces drug binding to the allosteric site. Mutagenesis and liposomal proton flux assays show that replacing the key residue (Asp-44) in the lipid-facing binding pocket with Ala has a dramatic effect on drug sensitivity, but that the channel remains fully drug sensitive when replacing Ser-31 with Ala. Chemical cross-linking studies indicate an inverse correlation between channel stability and drug resistance. The lipid-facing pocket contains residues from 2 adjacent channel-forming helices. Therefore, it is present only when the helices are tightly packed in the closed conformation. Thus, drug-resistant mutants impair drug binding by destabilizing helix–helix assembly.

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Section: Discussionmentioning

confidence: 99%

Section: Functional Relevance Of the 2 Proposed Drug Binding Sitesmentioning

confidence: 99%

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Mechanism of drug inhibition and drug resistance of influenza A M2 channel

Pielak

Schnell

Chou³

2009

Proc. Natl. Acad. Sci. U.S.A.

278

292

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“…The binding affinity of each enantiomer results from chiral interactions with the binding area inside the 4-fold symmetric M2 protein. Based on differences in isotropic chemical shift changes measured using ssNMR and MD simulations results, it has been recently suggested that 2-R and 2-S have a strong but differential binding to full length M2, i.e., that 2-R binds more tightly than 2-S. 23 This was the first state of the art ssNMR study of the full M2 protein and analysis of the rimantadine enantiomers binding by ssNMR, but this conclusion appears to be puzzling because: (1) 2-R and 2-S have similar in vivo antiviral activity in protecting mice from lethal influenza; 24 (2) rimantadine was developed prior to the 1992 FDA guidance on the development of stereoisomers. It was approved as commercial drug in the US in 1993 containing both enantiomers.…”

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confidence: 99%

Affinity of Rimantadine Enantiomers against Influenza A/M2 Protein Revisited

Drakopoulos

Tzitzoglaki

et al. 2017

ACS Med. Chem. Lett.

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Recent findings from solid state NMR (ssNMR) studies suggested that the (R)-enantiomer of rimantadine binds to the full M2 protein with higher affinity than the (S)-enantiomer. Intrigued by these findings, we applied functional assays, such as antiviral assay and electrophysiology (EP), to evaluate the binding affinity of rimantadine enantiomers to the M2 protein channel. Unexpectedly, no significant difference was found between the two enantiomers. Our experimental data based on the full M2 protein function were further supported by alchemical free energy calculations and isothermal titration calorimetry (ITC) allowing an evaluation of the binding affinity of rimantadine enantiomers to the M2TM pore. Both enantiomers have similar channel blockage, affinity, and antiviral potency.KEYWORDS: Rimantadine enantiomers, isothermal titration calorimetry, free energy perturbation, Bennett's acceptance ratio, electrophysiology, synthesis, antiviral assay, membrane protein, influenza M2 pore A mantadine (1) and rimantadine (2) (Scheme 1) are channel blockers of proton transit by the influenza virus M2 proton channel 1,2 and long used prophylactics and therapeutics against influenza A viruses. 3 The primary binding site of 1 and 2 is the lumen of the transmembrane domain of a tetrameric M2 protein (M2TM: amino acids 22−46) that forms the proton transit path. 4 Although 1 and 2 have been used as antivirals for decades, it was only after 2008 that high resolution structures from X-ray and ssNMR experiments unveiled the structures of M2TM in complex with 1 or 2. 5−9 According to these findings, the M2TM protein channel is blocked by 1 or 2 via a pore-binding mechanism. 6−10 The adamantane cage in 1 or 2, as well as in other aminoadamantane analogues, 11−13 is tightly contacted on all sides by V27 and A30 side chains, producing a steric occlusion of proton transit 6−9 and thereby preventing the viral replication. The ssNMR results for 2 also demonstrated that the ammonium group of the drug is pointing toward the four H37 residues at the C-terminus. 9 This orientation can be stabilized either through hydrogen bonds between the ammonium group of the aminoadamantane ligand and water molecules in the channel lumen which exist between the imidazoles of H37 and the ligand, 13 and/or with A30 carbonyls in the vicinity, 14 according to experimental 9,14−16 and MD simulations data. 13,17−22 Provided that M2TM is a minimal model for M2 binding, 10 these high resolution structures can be used for the development of new ligands which may bind more effectively to the M2TM pore.The effect of ligand's chirality in its binding with a chiral receptor is of outstanding significance and the characterization of protein−ligand interactions for each enantiomer separately may identify potential stereospecific binding interactions to the receptor. While rimantadine analogues are known antiviral drugs for more than four decades, the relative potency of rimantadine enantiomers has not been studied at the molecular level. The binding affinity...

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“…3B). An intriguing aspect of this binding mechanism is that the amantadine amino group, which has been shown by structure activity relationship (SAR) experiments to be critical for inhibition (Aldrich et al, 1971), does not appear to interact specifically with any of the polar groups within the channel pore. It is tempting to propose longrange polar interactions (~7 Å, Fig.…”

Section: Drug Inhibition and Ongoing Controversymentioning

confidence: 99%

Flu channel drug resistance: a tale of two sites

Pielak

Chou

2010

Protein Cell

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The M2 proteins of influenza A and B virus, AM2 and BM2, respectively, are transmembrane proteins that oligomerize in the viral membrane to form proton-selective channels. Proton conductance of the M2 proteins is required for viral replication; it is believed to equilibrate pH across the viral membrane during cell entry and across the trans-Golgi membrane of infected cells during viral maturation. In addition to the role of M2 in proton conductance, recent mutagenesis and structural studies suggest that the cytoplasmic domains of the M2 proteins also play a role in recruiting the matrix proteins to the cell surface during virus budding. As viral ion channels of minimalist architecture, the membrane-embedded channel domain of M2 has been a model system for investigating the mechanism of proton conduction. Moreover, as a proven drug target for the treatment of influenza A infection, M2 has been the subject of intense research for developing new anti-flu therapeutics. AM2 is the target of two anti-influenza A drugs, amantadine and rimantadine, both belonging to the adamantane class of compounds. However, resistance of influenza A to adamantane is now widespread due to mutations in the channel domain of AM2. This review summarizes the structure and function of both AM2 and BM2 channels, the mechanism of drug inhibition and drug resistance of AM2, as well as the development of new M2 inhibitors as potential anti-flu drugs.

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Antiviral agents. 2. Structure-activity relations of compounds related to 1-adamantanamine

Cited by 103 publications

References 2 publications

Mechanism of drug inhibition and drug resistance of influenza A M2 channel

Mechanism of drug inhibition and drug resistance of influenza A M2 channel

Affinity of Rimantadine Enantiomers against Influenza A/M2 Protein Revisited

Flu channel drug resistance: a tale of two sites

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