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The M2 proteins of bat influenza A viruses reveal atypical features compared to conventional M2 proteins

The influenza A virus (IAV) M2 protein has proton channel activity, which plays a role in virus uncoating and may help to preserve the metastable conformation of the IAV hemagglutinin (HA). In contrast to the highly conserved M2 proteins of conventional IAV, the primary sequences of bat IAV H17N10 a...

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Autores principales: Thompson, Danielle, Cismaru, Christiana Victoria, Rougier, Jean-Sebastien, Schwemmle, Martin, Zimmer, Gert
Formato: Online Artículo Texto
Lenguaje:English
Publicado: American Society for Microbiology 2023
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10506471/
https://www.ncbi.nlm.nih.gov/pubmed/37540019
http://dx.doi.org/10.1128/jvi.00388-23
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author Thompson, Danielle
Cismaru, Christiana Victoria
Rougier, Jean-Sebastien
Schwemmle, Martin
Zimmer, Gert
author_facet Thompson, Danielle
Cismaru, Christiana Victoria
Rougier, Jean-Sebastien
Schwemmle, Martin
Zimmer, Gert
author_sort Thompson, Danielle
collection PubMed
description The influenza A virus (IAV) M2 protein has proton channel activity, which plays a role in virus uncoating and may help to preserve the metastable conformation of the IAV hemagglutinin (HA). In contrast to the highly conserved M2 proteins of conventional IAV, the primary sequences of bat IAV H17N10 and H18N11 M2 proteins show remarkable divergence, suggesting that these proteins may differ in their biological function. We, therefore, assessed the proton channel activity of bat IAV M2 proteins and investigated its role in virus replication. Here, we show that the M2 proteins of bat IAV did not fully protect acid-sensitive HA of classical IAV from low pH-induced conformational change, indicating low proton channel activity. Interestingly, the N31S substitution not only rendered bat IAV M2 proteins sensitive to inhibition by amantadine but also preserved the metastable conformation of acid-sensitive HA to a greater extent. In contrast, the acid-stable HA of H18N11 did not rely on such support by M2 protein. When mutant M2(N31S) protein was expressed in the context of chimeric H18N11/H5N1(6:2) encoding HA and NA of avian IAV H5N1, amantadine significantly inhibited virus entry, suggesting that ion channel activity supported virus uncoating. Finally, the cytoplasmic domain of the H18N11 M2 protein mediated rapid internalization of the protein from the plasma membrane leading to low-level expression at the cell surface. However, cell surface levels of H18N11 M2 protein were significantly enhanced in cells infected with the chimeric H18N11/H5N1(6:2) virus. The potential role of the N1 sialidase in arresting M2 internalization is discussed. IMPORTANCE: Bat IAV M2 proteins not only differ from the homologous proteins of classical IAV by their divergent primary sequence but are also unable to preserve the metastable conformation of acid-sensitive HA, indicating low proton channel activity. This unusual feature may help to avoid M2-mediated cytotoxic effects and inflammation in bats infected with H17N10 or H18N11. Unlike classical M2 proteins, bat IAV M2 proteins with the N31S substitution mediated increased protection of HA from acid-induced conformational change. This remarkable gain of function may help to understand how single point mutations can modulate proton channel activity. In addition, the cytoplasmic domain was found to be responsible for the low cell surface expression level of bat IAV M2 proteins. Given that the M2 cytoplasmic domain of conventional IAV is well known to participate in virus assembly at the plasma membrane, this atypical feature might have consequences for bat IAV budding and egress.
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spelling pubmed-105064712023-09-19 The M2 proteins of bat influenza A viruses reveal atypical features compared to conventional M2 proteins Thompson, Danielle Cismaru, Christiana Victoria Rougier, Jean-Sebastien Schwemmle, Martin Zimmer, Gert J Virol Virus-Cell Interactions The influenza A virus (IAV) M2 protein has proton channel activity, which plays a role in virus uncoating and may help to preserve the metastable conformation of the IAV hemagglutinin (HA). In contrast to the highly conserved M2 proteins of conventional IAV, the primary sequences of bat IAV H17N10 and H18N11 M2 proteins show remarkable divergence, suggesting that these proteins may differ in their biological function. We, therefore, assessed the proton channel activity of bat IAV M2 proteins and investigated its role in virus replication. Here, we show that the M2 proteins of bat IAV did not fully protect acid-sensitive HA of classical IAV from low pH-induced conformational change, indicating low proton channel activity. Interestingly, the N31S substitution not only rendered bat IAV M2 proteins sensitive to inhibition by amantadine but also preserved the metastable conformation of acid-sensitive HA to a greater extent. In contrast, the acid-stable HA of H18N11 did not rely on such support by M2 protein. When mutant M2(N31S) protein was expressed in the context of chimeric H18N11/H5N1(6:2) encoding HA and NA of avian IAV H5N1, amantadine significantly inhibited virus entry, suggesting that ion channel activity supported virus uncoating. Finally, the cytoplasmic domain of the H18N11 M2 protein mediated rapid internalization of the protein from the plasma membrane leading to low-level expression at the cell surface. However, cell surface levels of H18N11 M2 protein were significantly enhanced in cells infected with the chimeric H18N11/H5N1(6:2) virus. The potential role of the N1 sialidase in arresting M2 internalization is discussed. IMPORTANCE: Bat IAV M2 proteins not only differ from the homologous proteins of classical IAV by their divergent primary sequence but are also unable to preserve the metastable conformation of acid-sensitive HA, indicating low proton channel activity. This unusual feature may help to avoid M2-mediated cytotoxic effects and inflammation in bats infected with H17N10 or H18N11. Unlike classical M2 proteins, bat IAV M2 proteins with the N31S substitution mediated increased protection of HA from acid-induced conformational change. This remarkable gain of function may help to understand how single point mutations can modulate proton channel activity. In addition, the cytoplasmic domain was found to be responsible for the low cell surface expression level of bat IAV M2 proteins. Given that the M2 cytoplasmic domain of conventional IAV is well known to participate in virus assembly at the plasma membrane, this atypical feature might have consequences for bat IAV budding and egress. American Society for Microbiology 2023-08-04 /pmc/articles/PMC10506471/ /pubmed/37540019 http://dx.doi.org/10.1128/jvi.00388-23 Text en Copyright © 2023 Thompson et al. https://creativecommons.org/licenses/by/4.0/This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0/) .
spellingShingle Virus-Cell Interactions
Thompson, Danielle
Cismaru, Christiana Victoria
Rougier, Jean-Sebastien
Schwemmle, Martin
Zimmer, Gert
The M2 proteins of bat influenza A viruses reveal atypical features compared to conventional M2 proteins
title The M2 proteins of bat influenza A viruses reveal atypical features compared to conventional M2 proteins
title_full The M2 proteins of bat influenza A viruses reveal atypical features compared to conventional M2 proteins
title_fullStr The M2 proteins of bat influenza A viruses reveal atypical features compared to conventional M2 proteins
title_full_unstemmed The M2 proteins of bat influenza A viruses reveal atypical features compared to conventional M2 proteins
title_short The M2 proteins of bat influenza A viruses reveal atypical features compared to conventional M2 proteins
title_sort m2 proteins of bat influenza a viruses reveal atypical features compared to conventional m2 proteins
topic Virus-Cell Interactions
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10506471/
https://www.ncbi.nlm.nih.gov/pubmed/37540019
http://dx.doi.org/10.1128/jvi.00388-23
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