Budding of filamentous and non-filamentous influenza A virus occurs via a VPS4 and VPS28-independent pathway.
The mechanism of membrane scission during influenza A virus budding has been the subject of controversy. We confirm that influenza M1 binds VPS28, a subunit of the ESCRT-1 complex. However, confocal microscopy of infected cells showed no marked colocalisation between M1 and VPS28 or VPS4 ESCRT proteins, or relocalisation of the cellular proteins. Trafficking of HA and M1 appeared normal when endosomal sorting was impaired by expression of inactive VPS4. Overexpression of either isoform of VPS28 or wildtype or dominant negative VPS4 proteins did not alter production of filamentous virions. SiRNA depletion of endogenous VPS28 had no significant effect on influenza virus replication. Furthermore, cells expressing wildtype or dominant-negative VPS4 replicated filamentous and non-filamentous strains of influenza to similar titres, indicating that influenza release is VPS4-independent. Overall, we see no role for the ESCRT pathway in influenza virus budding and the significance of the M1-VPS28 interaction remains to be determined.
Bruce
Emily A
EA
Division of Virology, Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK.
Medcalf
Liz
L
Crump
Colin M
CM
Noton
Sarah L
SL
Stuart
Amanda D
AD
Wise
Helen M
HM
Elton
Debra
D
Bowers
Katherine
K
Digard
Paul
P
D000074183:ATPases Associated with Diverse Cellular Activities; D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D002522:Chlorocebus aethiops; D004285:Dogs; D056827:Endosomal Sorting Complexes Required for Transport; D020868:Gene Silencing; D006389:Hemagglutinins, Viral / Q000378:metabolism; D006801:Humans; D009980:Influenza A virus / Q000502:physiology*; D011485:Protein Binding; D025262:Vacuolar Proton-Translocating ATPases; D033921:Vesicular Transport Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014763:Viral Matrix Proteins / Q000378:metabolism; D019065:Virus Assembly
D056827:Endosomal Sorting Complexes Required for Transport; D006389:Hemagglutinins, Viral; C488936:M1 protein, Influenza A virus; C476409:VPS28 protein, human; D033921:Vesicular Transport Proteins; D014763:Viral Matrix Proteins; C458881:hemagglutinin fusogenic peptide, influenza virus; D000251:Adenosine Triphosphatases; D025262:Vacuolar Proton-Translocating ATPases; D000074183:ATPases Associated with Diverse Cellular Activities; C490305:VPS4A protein, human; C490304:VPS4B protein, human