Influenza AM2 Channel Oligomerization Is Sensitive to Its Chemical Environment
Julia A Townsend1, Henry M Sanders1, Amber D Rolland2,3
1Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721, United States.
Abstract:
Viroporins are small viral ion channels that play important roles in the viral infection cycle and are proven antiviral drug targets. Matrix protein 2 from influenza A (AM2) is the best-characterized viroporin, and the current paradigm is that AM2 forms monodisperse tetramers. Here, we used native mass spectrometry and other techniques to characterize the oligomeric state of both the full-length and transmembrane (TM) domain of AM2 in a variety of different pH and detergent conditions. Unexpectedly, we discovered that AM2 formed a range of different oligomeric complexes that were strongly influenced by the local chemical environment. Native mass spectrometry of AM2 in nanodiscs with different lipids showed that lipids also affected the oligomeric states of AM2. Finally, nanodiscs uniquely enabled the measurement of amantadine binding stoichiometries to AM2 in the intact lipid bilayer. These unexpected results reveal that AM2 can form a wider range of oligomeric states than previously thought possible, which may provide new potential mechanisms of influenza pathology and pharmacology.
Insights
Influenza A matrix protein 2 (AM2) forms diverse oligomers, not just tetramers, influenced by its environment. This finding impacts understanding of influenza virus pathology and drug development.
Area of Science:
- Virology
- Structural Biology
- Biophysics
Background:
- Viroporins are viral ion channels crucial for infection and are established antiviral drug targets.
- Influenza A matrix protein 2 (AM2) is a well-studied viroporin, previously thought to form only tetrameric structures.
Purpose of the Study:
- To investigate the oligomeric state of the full-length and transmembrane (TM) domain of AM2.
- To determine how environmental factors, including pH, detergents, and lipids, influence AM2 oligomerization.
- To measure amantadine binding to AM2 within a lipid bilayer environment.
Main Methods:
- Native mass spectrometry was employed to characterize AM2 oligomeric complexes.
- AM2 was studied in various pH and detergent conditions, as well as within nanodiscs containing different lipids.
- Amantadine binding stoichiometry was measured using nanodiscs.
Main Results:
- AM2 forms a spectrum of oligomeric complexes, deviating from the established tetramer model.
- Oligomeric states are significantly modulated by the local chemical environment, including lipids within nanodiscs.
- Nanodiscs facilitated direct measurement of amantadine binding to AM2 in a native-like lipid bilayer.
Conclusions:
- The oligomeric plasticity of AM2 is broader than previously understood, challenging existing paradigms.
- Environmental factors critically influence AM2 structure and function, suggesting new avenues for antiviral strategies.
- These findings offer novel insights into influenza virus pathology and potential drug development targets.
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