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The M2 ectodomain is important for its incorporation into influenza A virions
E K Park1, M R Castrucci, A Portner
1Department of Virology and Molecular Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.
Abstract:
M2 is an integral protein of influenza A virus that functions as an ion channel. The ratio of M2 to HA in influenza A virions differs from that found on the cell surface, suggesting selective incorporation of M2 and HA into influenza virions. To examine the sequences that are important for M2 incorporation into virions, we used an incorporation assay that involves expressing M2 from a plasmid, transfecting the plasmid into recipient cells, and then infecting those cells with influenza virus. To test the importance of the different regions of the protein (extracellular, transmembrane, and cytoplasmic) in determining M2 incorporation, we created chimeric mutants of M2 and Sendai virus F proteins, exchanging corresponding extracellular, transmembrane, and cytoplasmic domains. Of the six possible chimeric mutants, only three were expressed on the cell surface. Of these three chimeric proteins, only one mutant (with the extracellular domain from M2 and the rest from F) was incorporated into influenza virions. These results suggest that the extracellular domain of M2 is important for its incorporation into virions.
Insights
The M2 protein
Area of Science:
- Virology
- Molecular Biology
Background:
- Influenza A virus M2 protein is an ion channel.
- M2 and HA ratios differ between virions and cell surfaces, indicating selective virion incorporation.
- Understanding M2 incorporation is crucial for influenza virus assembly.
Purpose of the Study:
- To identify the M2 protein regions critical for its selective incorporation into influenza A virions.
Main Methods:
- Developed an M2 incorporation assay using plasmid expression, cell transfection, and viral infection.
- Constructed chimeric M2-Sendai virus F protein mutants, swapping extracellular, transmembrane, and cytoplasmic domains.
- Assessed cell surface expression and virion incorporation of chimeric proteins.
Main Results:
- Three of six chimeric mutants showed cell surface expression.
- Only one mutant, featuring the M2 extracellular domain, was incorporated into influenza virions.
- The extracellular domain of M2 is critical for its selective incorporation.
Conclusions:
- The extracellular domain of the M2 protein plays a key role in its selective incorporation into influenza A virions.
- This finding provides insights into the mechanisms of influenza virus assembly and protein sorting.