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Phosphorylation of the M2 protein of influenza A virus is not essential for virus viability

J M Thomas1, M P Stevens, N Percy

  • 1School of Animal and Microbial Sciences, University of Reading, Whiteknights, UK.

Virology
|January 6, 1999
PubMed

Insights

Phosphorylation of the M2 protein

Area of Science:

  • Virology
  • Molecular Biology
  • Cell Biology

Background:

  • The M2 protein is a minor component of the influenza A virus envelope.
  • Its cytoplasmic tail undergoes posttranslational modifications, including phosphorylation.
  • Serine 64 is a primary phosphorylation site, conserved but not essential for M2 ion channel activity.

Purpose of the Study:

  • To investigate the role of M2 cytoplasmic tail phosphorylation in influenza A virus replication.
  • To determine if phosphorylation is necessary for M2 incorporation into virus particles.
  • To assess the impact of non-phosphorylatable M2 on viral growth and infectivity in vitro and in vivo.

Main Methods:

  • Exogenous incorporation assay to study M2 incorporation into virus particles.
  • Analysis of M2 transport in polarized Madin-Darby canine kidney (MDCK) cells.
  • Reverse genetics and reassortment to generate a virus with a non-phosphorylatable M2 cytoplasmic tail (Ra).
  • Growth and stability assays in tissue culture, eggs, and in vivo mouse models.

Main Results:

  • M2 incorporation into virus particles is type-specific and independent of cytoplasmic tail phosphorylation.
  • Phosphorylation is not required for directional transport of M2 in polarized cells.
  • The generated Ra virus, lacking M2 tail phosphorylation, replicated as well as wild-type virus in tissue culture and eggs.
  • Ra virus exhibited comparable replication in Balb/c mice to the parent strain.

Conclusions:

  • Phosphorylation of the M2 cytoplasmic tail is not essential for influenza A virus replication.
  • The conserved serine 64 phosphorylation site does not play a critical role in viral infectivity or propagation.
  • These findings clarify the functional significance of M2 protein modifications in the viral life cycle.

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